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Can Power Functions components work with the RCX?
I don't have the RCX, and neither do I have any PF stuff, but as they both have wire connectors which are almost identical, I'm thinking that they can both work together and are compatible. Is this true? And can you connect more than one motor to one RCX port (RCX port has 4 studs but PF port has only 2)?

"This question is not useful." I admittedly agree, but it might be useful to some huge nostalgic lego lover out there who manages to get his hands on an RCX.

Sorry, downvote was by mistake, had to edit something minor before I could change it to an upvote.

RCX is compatible with the older 9-V system that came before Power Functions.
However, since PF motors are also 9V and still unregulated as the RCX motors, a simple conversion cable suffices.
The Power Functions extension wires will do (8886 or 8871) as they have on one end an underside that is compatible with the 9V/RCX system (which hence goes onto the RCX port)
With this setup, stacking additional motors is possible as well, you can stack them on both sides of the extension wire (RCX side or side of 1st motor)

The Bricklink page for the extension wire/conversion cable part. The image shows that one end has an RCX-style connector on the bottom and the other is a standard PF connector.

The RCX uses "electric system 9V" style connectors. These are not compatible with power functions connectors. The "electric system 9V" connectors have the connections built into regular lego studs (with the electric part of each stud carefully arranged to allow connections to be made between parts placed at right angles) while the power functions connectors have a special connector section that is not compatible with regular lego studs in any way.
As the other answer mentions the power functions extension cables (8886 for regular length, 8871 for extra-long) can be used as an adapter between "power functions" and "electric system 9V". This cable has two different connectors, one end is a regular power functions connector with "power functions" connections on the top and bottom. The other end is a special connector with "power functions" connections on the top but "electric system 9V" connections on the bottom.
There are a few caveats though.

The power functions only end of the extension cable can be a bit of a pain to mount, because the electrical positions won't stack on top of regular lego studs.
The RCX has a 1-plate high step next to the motor ports. This was not a problem for electric system 9V wires which had the wire exit near the top of the brick but the power functions connectors have a much larger cable exit lump. This means that the power functions adapter cable can't be placed on a RCX in the normal orientation. For the side motor ports you can exit sideways, but for the center motor port you either have to exit over the screen, use an "electric system 9V" cable between the RCX and the adapter cable (so now you have three sections of cable to deal with....) or use a 1x2 electric plate (part 4755) to build-up the connector on the RCX.
"Power functions" is a 4-wire system while "electric system 9" is only two wire. So while you can use basic power functions motors with the adapter cable things like the servo motor will not work and you can't supply power to things like the IR receiver from an "electric system 9V source.
For smaller models actually building your model may be a pain because of the extra wire length from the adapter and because the RCX was designed with old-style technic in mind while power functions was designed with new-style technic in mind.

As for connecting multiple motors you can do so physically but if the motors are under heavy load you may hit the current limits in the motor drivers, heck even a single "RC race buggy motor" can overload the drivers in the RCX.

RC motor is so powerful it, practically, can overload every LEGO unit it is attached to. Except the RC control unit this motor was designed to work with.

This is true, the power functions XL motor isn't that much lower power though.


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robotic inventor\spike prime hubs: Hub 2 hub communication AND led matrix control
Recently the Spike essentials set was released, including the very interesting 3x3 led matrix part:

The matrix allows to set each individual pixel in the 3x3 array to 10 different shades of 10 different colors.
The led matrix also works with the Spike Prime set, however, it seems currently unsupported in the Mindstorms Robotics inventor set, at least there are no word blocks for it in the IDE that you can download for the set.
I'd wish to control more than one such led matrix and have purchased an additional 8 with the intention of placing them in a 3x3 array to have a larger 9x9 matrix.
The hub has however only 6 ports, so I'll need an additional hub and hub to hub communication.
Unfortunately it seems that straightforward hub to hub communication is only supported in the Robotic Inventor IDE which in turn does not support the led-matrix.
What would be the easiest way to have both ? I.e. have both hub-to-hub communication and control for this new led-matrix component?
I'm willing to consider micropython solutions, but would need some pointers there:

what class do I need for the hub to hub communication in the python implementation with the native Spike Prime or Robotic Inventor firmware?
what class do I need for the led matrix control with the native Spike Prime or Robotic Inventor firmware?
same questions for when I would install the PyBricks micropython implementation.

Additional question, is there any way to set the color of ONE pixel without setting an entire 3x3 picture? Seems to be missing from the word blocks while setting the brightness is present...

PyBricks will probably be easier as it'll act the same on both hubs and can also be used on cheaper hubs.  (I guess that's what you've done by now since I've seen your stuff). The PyBricks doc on the light matrix doesn't provide a way to address an individual light; not sure if that limitation is due to PyBricks or the hardware itself but it seems you should better keep track of lights status youself.

This isn't a direct answer to your question, but it would be one way to solve the problem. Instead of using the hubs from SPIKE or Robot Inventor, you could use the Control+ hub:

This hub unfortunately only supports 4 peripherals, so you would need three of them. This hub is not programmable, but it can be controlled over Bluetooth. You can pair up to 7 hubs to a single device this way, so you could control up to 7⨯4=28 LED matrices fairly easily.
There are a couple software options to get this running. One popular one that I've had some experience with is node-poweredup. Here's an example from the docs to control a 3x3 LED matrix attached to a Control+ hub:
const PoweredUP = require("..");

const poweredUP = new PoweredUP.PoweredUP();
poweredUP.scan(); // Start scanning for hubs

console.log("Looking for Hubs...");

poweredUP.on("discover", async (hub) => { // Wait to discover hubs

    await hub.connect(); // Connect to hub
    console.log(`Connected to ${hub.name}!`);

    const matrix = await hub.waitForDeviceByType(PoweredUP.Consts.DeviceType.TECHNIC_3X3_COLOR_LIGHT_MATRIX);

    // setMatrix accepts an array of 9 items - Either standard color values (number),
    // or Color objects with brightness (brightness values are 0 to 100%)
    // It can also accept just a single color to set all 9 lights to the same color
    matrix.setMatrix([
        // Red at 100%, green at 20%, red at 100%
        PoweredUP.Consts.Color.RED, new PoweredUP.Color(PoweredUP.Consts.Color.GREEN, 20), PoweredUP.Consts.Color.RED,
        // Green at 100%, yellow at 100%, green at 100%
        PoweredUP.Consts.Color.GREEN, PoweredUP.Consts.Color.YELLOW, PoweredUP.Consts.Color.GREEN,
        // Red at 100%, green at 20%, red at 100%
        PoweredUP.Consts.Color.RED, new PoweredUP.Color(PoweredUP.Consts.Color.GREEN, 20), PoweredUP.Consts.Color.RED,
    ]);

    hub.on("disconnect", () => {
        console.log("Hub disconnected");
    })

});

The above example would need to be extended to support a number of hubs and lights and provide some management to write large images in a coherent way.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

sort: votes


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Estimate building time for a given LEGO set
I'd like to be able to estimate better how much time a LEGO set will take me to build.
Are there any resources online that indicate average or fastest building times for a given set?
I suppose it also depends on type of set (for younger or for adult builders, Technic or System,...)
What would be your estimate given the amount of elements in a set and type of set?

Do you have couple of sets in mind? Time it takes to build will wildly depend on experience (how much you know your elements and their colors) and the type of parts you have in a set. Building biggest Technic sets for the first time will take considerably longer than having it as, say, 5th build. And even if you building same sized (parts wise) Technic/System/Creator/Mosaic set each will take different amount of time.

Sometimes, set reviews will include a build time as well (depending on the reviewer), so looking for reviews can be a good place to start. But I suggest just getting a feel for how fast you build on average (in parts per hour eg.), and that'll give you a ball park number for any set (which you can then adjust for difficulty if needed). A rough guess could be around 10-20 seconds per part, or somewhere in the range of 200-400 parts per hour.

@Alex, the set I had in mind was the recent ideas globe set, only having today in the afternoon time for it, I was wondering if I could build it in 1 sitting before having to start a busy work week. I totally miscalculated, didn't even finish half of it.

@SanderDeDycker, I think your comment should be an answer instead.

@MichaelVerschaeve : I haven't created an answer because I don't feel confident my experience can be translated to a general rule. It depends on too many factors. That said, finishing near half of a 2500 part set in an afternoon (assumed to be around 4 hours), is right in the middle of the rough estimated range I mentioned above. So at least you'll be better at estimating for future builds !

"fastest building times for a given set" If there are sites tracking this, I'd imagine multiple people will start speedrunning some of the popular sets. Which wouldn't help you much for an average estimate.

@Mast Yes, but I'm also interested in speed building... seems to overlap too much to ask a separate stack echange question.

As others have said, there are probably too many factors to say how long a build will take. But, I thought it would be good to compile a list of factors that affect build time. Feel free to add to the list.
The Lego building process can be divided into two sub-processes; searching, and assembly.
Factors that affect searching time:

Number of parts in the pile (mixing numbered bags will increase searching time)
Experience of elements and colours
Any prior sorting of parts by size/colour (will have an overhead time cost, so only useful for large builds)
The distribution of parts (having many unique parts will take longer)
Eyesight and lighting
Determination
If the set is incomplete it can take considerable time to realise

Factors that affect assembly time:

Number of steps
Experience (both of the specific set and in general)
Building of symmetric/repeated sections in parallel
Build complexity
Dexterity and hand-eye coordination
Determination
Errors in Lego instructions (very occasional)

I am not sure it is possible to give specific guidance based on simple characteristics like part count or theme. In addition to the factors of the person (or people) undertaking the build raised in the comments, design also makes for wildly different building times.
For example, any set that has bilateral symmetry can be built comparitively quickly by building both sides at the same time even if they mirror each other. Sets that are not symmetrical will often take nearly twice as long. Another more obvious example is the use of advanced techniques that can sometimes make build time much longer, sometimes can drastically reduce complexity and build time, and sometimes have no effect.
Set type and part count do not take account of either those or similar factors like modularity and inclusion of large parts like BURPs or chassis. Labeled age range and part count can probably, at best, simply give a relative indication and no more.

I haven't checked how long it takes my 7 years old daughter based on number of pieces, but I saw she needs about 5 minutes per EUR of the set (with set prices in 20-50 EUR range; Friends mostly). This is for a new freshly opened set.
So, I would guess about 2 min/EUR for an adult that has built some sets but isn't a Lego fanatic. I haven't actually timed myself, though. So, I estimate a 10 EUR set would take about 20 minutes to build, a 100$ one would take slightly more than 3 hours etc.
Transferring these numbers to number of pieces per hour, at 10c/piece it gives ~300 pieces/hour. This sounds reasonable enough to me at first glance, but it is a fairly inaccurate method - though I believe all such estimation methods are.
Note this is only for assembly. Old large sets are slightly slower as all pieces are mixed together instead of being in bags, but it probably shouldn't slow you down too much.
But if you need to find pieces with many sets mixed together, well, 10 sets is a problem, 100 is a nightmare. You should probably sort pieces first (by color, type or whatever else you prefer). And after sort you are still looking at a much longer build.

First you need to sort the pieces. So lets say you can sort 12 pieces per minute, then you later need to find them which is probably 6 pieces per minute and assemble them like 3 pieces per minute. So in total you need 7 minutes for 12 pieces. So in 4 hours you can do about 400 pieces.
It is a veeery rough estimate.

This is rough, very rough. This doesn't take in to account many things that reduce timing drastically. I know not everyone is as familiar with LEGO bricks as LEGO fans are, but 4 hours for 400 pieces set is way too much in most cases. School Day (60329) is just for the reference, to understand what ~400 piece modern set looks like. Another example is when you assemble big set, say Technic, you may be asked to put a lot of pieces in single step (116 pieces for set #42131, step 997), which doesn't take an hour to do.

This answer does not consider that some people might not even sort the pieces before building, or do so only roughly.

@Zovits, new sets I don't sort, they come in numbered bags which contain few enough different elements that the time spent sorting won't be compensated by the faster building imho. Second hand or older sets I definitely sort. Some people enjoy building in "hard mode" where they throw all bags from all steps together, I don't... Also, at whoever downvoted, the user shared his/her perspective/experience, he/she shouldn't be downvoted for that

Its a correlation between number of parts + the set weight (to incorporate whether its many small pieces or rather few big pieces).

Hi MervX97 and welcome to Bricks.SE! Could you please elaborate on your answer? I mean it is not clear to me whether the weight you mention would positively or negatively correlate with either the piece size or the estimated building time.

I would say I do about 300 to 500 pieces per hour.

Hi Klaus and welcome to Bricks.SE! Do you base your estimate on personal experience, calculations or other sources? Could you please elaborate?

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Pybricks on Android Tablet
I have a ZTE Grand View 4 Tablet (K87CA), 8 inch screen, Android 10,  with 2GB RAM, and the screen is blank when I go to https://code.pybricks.com/. Nothing happens.

What browser are you using? It should be one that is bluetooth compatible like Chrome or Chromium...Also, I'd like to note that using the pybricks webpages from a tablet is rather unorthodox usage, likely not tested very well or at all. You're supposed to write Python code on those webpages, so a device with at least a keyboard seems desirable.,

Chrome is the automatic choice on Android, so I use it. Bluetooth keyboards are easy enough to use as these have Bluetooth 4.2 Should not be a problem. For Power Functions App 8" screens are great. Don't understand why the web page doesn't load.

There was a bug in Pybricks that caused an empty page to load for existing users when a new version was released. It should be fixed for new users, but existing users will need to clear the cache for this page:
Windows
CTRL+SHIFT+R
MAC
CMD+SHIFT+R
Android
You can clear the cache for specific pages with these steps:

Go to settings in your browser
Select Site settings
Select All sites
Use the search icon to search for Pybricks
For each entry, click Clear & reset


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How long does it take a M-motor to go 1 googol rotations?
How long would it take a Power Functions M-motor to turn 1 googol times? I have tried figuring it out with a calculator but I was confused.

Please edit the question to show what have you tried and where did you get confused. Additionally, if you got to the point of using a calculator, you have probably learned the RPM of the motor, at which point the question is a purely mathematical one, and therefore belongs to another SE site. Nevertheless, I gave below a complete answer according to the "teach a man to fish" philosophy.

This is one of those questions where you could literally googol it....

I tried using a calculator but I couldn’t find one that could multiply by 1 googol

According to Philo's LEGO motor datasheet an unladen PF-M motor rotates with 405 RPM.
One googol is 10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 (10^100), so the time it takes for an M motor to go this many rotations is (10^100)/405 minutes.
Ordinary calculators usually take a look at such large numbers and throw their hands up, or can't even display them but luckily we have WolframAlpha.
This is 4.695x10^91 years, or about 3.4x10^81 times the current age of the universe. (the Universe is about 14 Gigayears old now, in 2021 :) )

I suppose the next question would be "What gear ratio would be required to get that number down to just a lifetime?"

@Ambo100 1:10^90 would suffice to bring the time down to 46 years and is a nice and round number to work with. The questions of what volume would be occupied by the resulting drivetrain and what torque would be needed to drive it, are left as an exercise to the reader :)


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Gearing problem
I have a technic MOC with lots of gears which runs fine when motorized with the Control+ L motor, the motor itself attached to the "dumb" battery box that would have been included with the Osprey but which you now can buy separately.
The Philo home page https://www.philohome.com/motors/motorcomp.htm says a loaded Control+ motor has the following characteristics:
8,81 N.cm torque, 198 rpm
I then wanted more power/speed so I tried to replace the Control+ L motor with the race buggy motor and battery box as in set 8287 "motor box"...
The motor stalled immediately.
The Philo home page says the race buggy motor has the following characteristics
5.7 N.cm torque, 780 rpm
This is for the outer output, the inner output which I'm using is geared up by a factor 23/17 so I expect the characteristics to be:
4.2 N.cm torque, 1055 rpm...
So understandable, higher speed but less torque -> motors might stall.
I have in my technic MOC 2 pairs of gears gearing up by a factor 25 (8 tooth gear and 40 tooth gear, two pairs)
I tried to replace the gears by 2 pairs of bevel gears, the 12 tooth gear and 36 tooth gear. 2 such pairs giving a speedup of factor 9.
So taking this modification in mind, I expect the torque to increase by a factor of 25/9 and the speed to decrease by a factor 9/25
Giving me
11,6 N.cm and 379 rpm
Which is clearly a greater torque than the Control+ motor, so I expected it to work. Unfortunately it didn't; the contraption moves slowly for about 1 second and then stalls...
Am I making a mistake in my reasoning? Are there other factors to consider? Or do I just have bad luck with my buggy motor (or good luck with my Control+ L motor) ?
Perhaps the friction of bevel gears is significantly higher than the older 8 and 40 tooth gears ?
I used in both cases new AA alkaline batteries, all from the same brand.

Not sure which data is correct. Sariel's motors chart has different data for RC motor (5292). Although he states it is based on Philo's data as well.

@Alex, Philo updated his data for the buggy at some point (says so on the page), likely the chart was made before that update...

I think the issue here is with your power unit - battery box. It sounds like your motor is consuming more current than battery box can provide.
RC motor (5292) is known to be power hungry and as far as I know the only LEGO control unit that can provide enough of it is Electric RC Race Buggy Battery / Receiver Unit with Auxiliary Output (6272c01):

Electric RC Race Buggy Battery / Receiver Unit without Auxiliary Output
(6293c01) maybe as well.
Any other LEGO battery box will have issues with its current/thermal protection kicking in sooner than RC motor can provide its full potential.
This is issue was one of the reasons why 3rd party controllers/power units became available.

I'm using the battery box 54950c01 that came with it in the 8287 motor box, I would have thought that battery box would have been adequate, but I will investigate alternative power sources


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How can body segments be moved to precise angles in snake robot?
I want to create an EV3 robot similar to this:

I've glanced at the mentioned papers. To me it seems that some simpler equations to govern the motors will work also.
I have 9 segments, articulated by 8 motors (two intelligent bricks daisy-chained).
I want the angles of the segments to be proportional to a sine. Doing some calculations in some graphing software, this should be sufficient to have the snake move in a wave.
However, there seems to be no robust, reliable way to set an angle on an EV3 motor. I have a MoveTo myblock, where I use the motor first as angle sensor, calculate the difference to the desired angle and then set the motor "on" for that amount. I also tried setting the power proportional to the difference. But I do not succeed is setting the angle accurate enough, it starts drifting or overshoots. I can't synchronize all the segments that way.
Is it feasible to attempt this in the graphic programming language that comes with the ev3 software or do I need to look to something more advanced?
Any hints would be appreciated.
Edit: Made some headway, rather than putting the motor "On" for a number of degrees, I simply place the motor "On" with a power proportional to the error between the measured angle and desired angle. Works good enough for now. This is the P in a PID-controller, adding an integration and derivative part might help.
The problem I'm currently facing is the weight distribution, the segment that is the head of the snake doesn't have a motor and hence is much lighter. I need to find a better set of factors to multiply the errors with for each motor. I'm confident I'll succeed in this by trial and error whenever I find the time.

I would try to have tape on each segment at 45° angles and have the color sensor read it. May or may not work, but it is at least half an idea. I would go for an arduino or something though to help, or do the entire snake.

Welcome to LEGO Answers! Even if you use the same amount of power each time you may get wildly different results depending on the friction of the surface and the arrangement of the motors. You may need to constantly query the data from the rotation sensor(s) to see if it is aligned, and if not perform corrections, making clockwise/counter-clockwise rotations to get a more precise arrangement. Are you able to show us what your program looks like at the moment?

You could use worm gears, or worm gears, or compound worm gears, because you can slow the rotation down as much as you want, which means you can have super fine rotation.
An extreme example of this would be the 120 years timer here
This uses a compound worm gear and spur gear train.
Worm gears also have a lot of torque in a small space.
if you want the snake to sway left but then automatically sway right then just hook do something like this but like the following:
The red pin goes to the snakes body which should 'sway' because of the linkages converting rotary motion into oscillating motion. just make sure that the other half of the snakes body is anchored to the motors housing other wise it will be a retarded snake :)

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


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How to mirror an EV3 motor?
I want to get one EV3 large motor to copy the other. So if I move one half a rotation the other copies.

Hi Nixtoo, can you share what programming language you're using and what you've already tried? It will help to get better answers.

I am assuming that you want motor a to copy motor d and motor to is controlled manually(with your hands).
You can use the motor sensor to sense the degree of movements of motor d, then use link it to how much motor a turns. However, as motor d will still retain the degree it has been turn, motor a will continue moving even after motor d has stopped(unless you turn back motor d). To counter this, you have to use the switch block and a bunch of compare blocks. You will have to make it so that if motor a's degree is the same or more than b's degree, the motor degree will reset. However, if I turn d counter clockwise, d's degree will be negative and the comparison(same or more than)will not work and it will keep spinning. Thus, I added another switch block that will compare motor a's degree and motor b's degree, this time resetting the motor's degree when it is a is equal to or smaller than d.

This way what ever rotation done to d will happen to a.
Hope this helps you!

I would make a my block (with turquoise-colored tab) and move motor A and B in that block. You can make two parameters for speed and revolutions.
EDIT:
Now you can control that motor-couple by using that my block.

Hi Sadap! I have interpreted the question as if the first motor should be passively accepting any rotations, and the EV3 should play these rotations back on the second motor in real time. If Nixtoo sees this, they can decide whether this reflects their original intent or not and give appropriate feedback.


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Extend/retract speed of linear actuators
I am trying to find out if the linear actuators (small, large and XL) have a fixed number of rotations on the bottom axle connector in order to extend them fully?
I am guessing the small LA will take fewer turns?

Does this answer your question? What's inside a linear actuator?

Not really, but the video added does so thanks one and all

I voted to leave this question open, I think LA's are complicated/interesting enough to have multiple (in my opinion unrelated) questions about them

I found Sariels video here helpful:

https://www.youtube.com/watch?v=A23yh-enhyI
Sariel states that all 3 LA's extend and retract at the same speed.
Several sources state that the L linear actuator takes 26 revolutions to extend to its full 5 studs, so the small LA will take 15.6 revolutions to extend to its full 3 studs and the new XL linear actuator will take 41.6 revolutions to extend to its full 8 studs.

Thanks that's great info

Glad they all seam to be 5.2 rotations per stud


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What electronics are inside the SPIKE 3x3 LED Matrix?
What is inside the LEGO 3x3 Color Light Matrix 45608?

Pictures of the assembled Top- & Bottom- PCB would be helpful.

There are 4 clips holding this together. It isn't too difficult to get apart with a little prying. Here's what it looks like with the cover removed:

The board can then be popped out of the housing. Here's a close-up of the front:

There are 9 surface-mount LEDs just as one might expect.
Here's a shot of the back of the board:

The larger chip appears to be numbered:
V0269
3235A

I believe that this part is a 28-port dimmable LED driver. This provides enough output to drive the display (3 x 3 x 3 colors = 27 LEDs).
The smaller chip appears to be numbered:
S103
PHVC
0317

Here's a better shot of that chip:

This looks like an STM8S103 microcontroller similar to the chip used in Powered Up motors that provide position feedback.
There are also a number of smaller chips and passive components on the board, but they are probably a bit less interesting.

Thank you very much !
This Micro seems to be a Standard uC used for this Motor-/Sensor- Interfaces


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Labview Developer mode for EV3 Classroom app
I found a trick to enable labview mode on EV3 Home Edition, however, I cannot find the LEGO Software folder in C:\Program Files (x86) (or C:\Program Files). In fact, I can't even Open file location on the app itself! Is there a workaround for this? I may have downloaded the app from Microsoft Store, I'm not sure...


text:
Wiring diagram of this blue 12V switch?
I'm looking for a wiring diagram or some information about the internal connections of this switch from the blue train era.

It is used for controlling the automatic points, and is visible on the original box:

The points connect to the back of the switch using a 3-pole connector:

I want to use a microcontroller to operate the points without manually pushing buttons. Since I don't have any of these, I cannot measure the connections (using a multimeter).
Does anyone own this switch, and cares to share some information?

This is how I think the switch works. I have tried wiring it this way and it works, however the points barely move. Perhaps the problem lies with the solenoids inside the points?

In electrical engineering one might call it:
DPDT (Double Pole Double Throw) Momentary (On)-Off-(On) Reversing Polarity Toggle Switch.

Momentary in this configuration means that it's spring loaded towards its centre position.
Edit: I'm not sure though, see the comment below. I have the remotely controlled switch points from the gray era and they work like above.

Are you sure it is a momentary switch? The 2-pole power supply connects to the side of the switch, and a 3-pole connector connects to the back leading to the points. From what I can see in the pictures it looks like the switch is a normal toggle switch with only two positions. Though I can't be sure. The points itself have a built-in switch which is toggled once the points are in position, unpowering the solenoids.

You might be right.

Yes, it looks like there is a difference between grey/blue era. The blue ones use two solenoids (one for each direction), so I guess the grey ones use one solenoid only (reversing the polarity to change the direction).

I've updated my question. Could you take a look?

I might ask TLG for this. There are several possibilties. I didn't know the switch has a 3-pole output. If it moves barely the two solenoids might be in series, but then, mentioning the interlocked end switch might obstruct power flow to switch back again. I don't like re invent the wheel. Neither do I own the switch nor the railswitch so I can't find out. What we need is a datasheet. TLG can clear this up for us.

Hey Niels, thanks again for your response. Actually the clue lies in this picture: https://i.sstatic.net/fLzUG.jpg
I was using a 12V DC adapter, assuming the voltage for the points had to be the same as the train itself. Since all three connectors on the transformer are identical, a child could easily plug in the wrong connectors, so I assumed both would have to be the same voltage. It turns out the points actually use 16V AC. I will answer my own question once I have verified this, since I have no 16V adapter yet.

Ah. Nice find Midas. The transformer from the grey era has a blindplated 13VAC output which might work fine. The plate can easily be removed. https://questforbricks.files.wordpress.com/2013/08/the_transformer_3.jpg

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How to instruct EV3 to go a certain place in the room?
I'd like to instruct my LEGO Mindstorms EV3 robot navigate to a defined place in the room ("return home").
With the lack of GPS capabilities, what other possibilities exist?
Maybe directing the robot with IR Beacon?

I would use the IR Beacon that's shipped with the Home Edition of the LEGO Mindstorms Education EV3.
The Beacon is integrated within the IR remote control (the big horizontal button at the top). The LEGO Education programming language (EV3-G) has a block to get the distance and angle from the IR beacon. So it is possible to search for a beacon and move your robot into the specific direction.
If I remember correctly you can use four different channels with a IR remote control. So it should be possible to use four different IR Beacons simultaneously.
I think that's the easiest solution you can achieve with not so much effort.


text:
Death Star 10188 Help with step 8 on page 76
On step 8 of page 76 I do not understand what holds the two sections together.  The "LEGO Flat Silver Technic Axle Joiner Perpendicular with Extension (53586)" has a smooth bore where it attaches to the "LEGO Medium Stone Gray Technic Cross Block 1 x 3 (Pin/Pin/Pin) with 4 Pins (48989)".  And directly under the first part is a Technic pin (part# 4211815) in yet another smooth bore opening (part# 4526985).
I do not see any clips, pins or other means of attaching these two components.

The "LEGO Flat Silver Technic Axle Joiner Perpendicular with Extension (53586)" smooth bore piece  is secured to a technic pin on piece "Technic, Pin Connector Perpendicular 3L with 4 Pins (48989)" installed in step 5, with the relevant pin marked in step 7 in my marked up directions below:

The smooth bore piece connects to the pin holding them together, with the lower axle connection preventing rotation.

The pin (4211887) in step 7 does not pass all the way through the other side of the 4 pin technic part (4225033)  if it did it would only collide with the end of the axle (4508553 from Step 8 item 4) inserted into the oposite end of 4494486.  The integrated pin on 4225033 slides in and out of the open end of 4494486, there aren't any internal ridges for the pin to snap into (hence the smooth bore description).  Do I have a bad 4494486?  I've looked online and every image I've been able to find of that part shows a smooth bore.  So I'm not sure what's the problem.

Even without the retaining ridge the pin should still be a tight friction fit against the smooth bore. it will come off if pulled, but it shouldn't just fall off.

Unfortunately it freely slides on and off [falls off], not even remotely tight - and I've tried ordering a replacement 4494486 from an online retailer with the same result.  I guess I'm just going to glue it.


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How to get double the speed from 2 regulated EV3 motors?
So I've noticed that if I connect two EV3 motors to one another (with gears), I still get exactly the same maximum speed as if I had a single motor.
So, my question: how can I get twice the power/speed out of two motors?
Update: here's an interesting observation: if I get both motors to spin as unregulated, I get a much higher speed than if I get them to spin in a pair (e.g., B+C move tank).
Update 2: ended up building a differential as per accepted answer:

By adding two motors together with gears, you have doubled the torque the motors provide. Power = torque x speed, so if you don't want the doubled power from the motors to go to the torque component but to the speed component instead, I think you should use a differential and put the motors on both outputs of the differential, and use the input to feed your construction. I haven't tested this out though.
EDIT: Here is a picture I found that shows how 4 motors can be joined into a single output with 5 different motor combinations (and many more different speed combinations):

Technically, what you did is just another way of gearing your motors - you increased the speed by adding a gearing reduction. To make my solution you would need to do something like this: http://tinyurl.com/mv2odap . The differentials make sure that any speed difference between the motors does not cause friction, which in your example could happen. Friction would cause the vehicle to stall, or in worst case, cause gears/axles to break due to the enormous torque difference that comes with it. For your purpose you only need 1 differential per wheel, no need to join the 2 wheels with another 1.

authors: Александр Круглов


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What causes these 'bite marks' that appear consistently on new bricks?
I purchased a set (second hand) which has the following defects on the 75°-sloped, inverted 2x1x3 blocks:

I assumed they were teeth-marks and asked the seller for replacements, and he found and ordered some online. But when they arrived, they all had the same defect. Is this common on these pieces? Is it just a manufacturing quirk, or actual damage?

Those were caused by hungry children. ;)

I do hope you apologised to the seller.

As said, this is the point where the injection happens, usually known as a gate.
Sometimes, LEGO tries to have in a non-visible place, but the process of moulding is extremely complicated and forces specific requirements on the gate placement which mean it's sometimes impossible to hide it. The basic rule of thumb is that the gate is usually near the center of the part (in terms of quantity of plastic) so that the molten plastic reaches all ends of the element at the same time. Sometime a part even requires two gates.
In the case of your slope, it's probably annoying, but sometimes it's worse. In this glass panel for example, the gate is right in the middle. It wasn't really a problem in the beginning, since that glass panel was used in combination with a three panes window frame and the gate was hidden behind one of the bars of the frame.
Then they released Cafe Corner with full window frames and the gates were in plain sight. In the middle of windows. Now that's what I call ugly.

These aren't defects, they're a scar from the moulding process, it marks where the plastic was pumped into the brick. It's more noticeable on some bricks more then others, every brick manufactured this same way should have a similar mark.

In a similar sense, a doughnut injected with jam through a syringe will create a piercing that will be very difficult to detect; especially after being covered in glazing.

I grabbed an image off google that shows a basic molding process:

As others have mentioned, the location of the gate is where the liquid plastic flows through into the cavity, and this is the mark that you are seeing.  Some times these markings can be polished or sanded away, but for Lego, that would probably effect the texture of the part, so they can't 100% hide it.
As Joubarc mentioned, the molten plastic needs to fill the cavity before it starts to cool and solidify, so the gate is chosen based on where the cavity can be filled the fastest and evenly.  Evenly, because you usually don't want part of the piece to solidify before it fills the cavity, otherwise you could have unfilled parts or warped pieces from cooling in different spots at different rates.


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What is the name/number of this brick
I was wondering what the two grey tile like bricks in the image below are? I wish to order some online, so would appreciate knowing their name.

Hi Kared and welcome to LEGO Answers :) Is there any chance you could edit your image to include some arrows or similar pointing to the exact elements you're asking about?

If you need any help in the future, you can check out Brickowl, Bricklink, or Firestartoys!

This is a 3743 - Technic, Gear Rack 1 x 4 and there are 2 times 2 of these in your picture (2 on the left and 2 on the right).

I guess your description is a little vague, because if you are talking about the middle part (the shining light gray pieces), they are actually not bricks/tiles, but the axle end of an NXT motor (the right side of the motor in the below picture).

Yep, I think the question is referring to the end of the motor.

It's difficult to be certain due to the angle and quality of the image but I think they are these:

Technic, Liftarm 1 x 3 Thick
Item No: 32523
They are/were produced in many colours including both 'light bluish grey' and light grey'.
More details on bricklink
Edit
Just realised you you referred to them as 'tile like bricks' so maybe it is this:

Part 3743 Technic, Gear Rack 1 x 4
Bricklink link
It would be a lot easier if you could isolate the elements you are interested in and take better photo


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RCX 2.0 Firmware downloaded successfully but "Run" does nothing
I recently was able to install RIS 2.0 for the first time since I just got a 32bit Windows 7 machine.
I got the IR tower to download the firmware to the RCX 2.0 and it showed exactly the same screens the guide showed, but when I got to the point where I test the motors, I found that the "Run" button does nothing.
I tried installing the firmware 3-4 times and still have the same problem, so I'm assuming the RCX itself has a defective Run button.
Does anyone know what's possibly going on? All the other buttons work, they beep and change the screen when pressed, nothing beeps or happens when Run is pressed.

it should also be known that the unit beeped successfully and the software let me know the download was finished when I downloaded the firmware to the RCX 2.0

Could be the button indeed. These buttons are conductive rubber pressing on the circuit boards integrated contacts. Might need some cleaning there...
Disassembly of the RCX is not easy but can be done. You have to remove the screws in the battery compartment, then pull slightly to disengage and remove the black IR front. Once this is done, you can pull out the PCB and battery case from the top cover. Important note: the PCB is connected to the battery case through metallic blades that can easily bend and no longer make contact. So when you pull the PCB+case, you must pull on the PCB itself, not on the battery case.
Once done, you can clean the button area with alcohol and/or swap buttons to hopefully repair the Run button ("View" button is useful, but not mandatory...).


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Can EV3-G MyBlocks be recursive?
Imagine I create a MyBlock called function1 from a line of blocks. Can I call that block from within itself?

This is the program for the block recursiveTest.
Will this block function properly?

No, EV3 MyBlocks cannot be recursive. If a MyBlock contains a copy of itself, then the following error will be produced upon compiling:

For some reason, LEGO's programming software has become progressively less immediate about notifying you that this cannot be done. In EV3-G, it waits until compile to let you know that you can't do this. In NXT-G (the software for programming the NXT), trying to put a MyBlock in itself produces an error upon placing it. And in the Robotics Invention System 2.0 (the software for programming the RCX), it simply won't let go of the MyBlock you're dragging if you try and place it into itself.
If you want a programming language for the EV3 that supports recursion, I'd like to offer LeJOS EV3 (Java-based, free) and ROBOTC (C-based, costs money) as alternatives. They're both EV3-compatible, and support recursion.


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How big to make a perfect cube? And how to build it
I want to make a model, that involves many cubes. I want to make many individual cubes, then connect them together. I don't want my cubes to be that big. That leads to my first question: What is the smallest sized PERFECT cube I can make? My second question is: How do I make it?

A perfect Cube: In LEGO terms: A structure whose dimensions are n x n x n, excluding studs.

And I forgot to mention that I can only have basic bricks. No plates or tiles. Sorry!
P.S. I really am annoying aren't I?!
Also, I don't require it to connect, and even if I could, I couldn't anyway,because I am using Basic Blocks. For the people asking, I am making a pillar, balanced

Do you have any requirements on connectability and stability?

Can you show us what you are planning to do? How are you going to connect the cubes?

The smallest perfect cube you can make is a 2x2 brick with a 2x2 plate and a 2x2 tile on top.
And now I read that you're excluding studs, then you can use a plate instead of at tile, and obviously the order in which you stack the elements doesn't matter.

So your cube is 2x2x(1+2/3). This means that without plates you would need 6 x 6 x 5 (length x width x height) as the smallest possible cube (?)

The ratio between the height and width of one brick is 6:5, so yes, if you have to it out of only standard bricks, that will be the size.

LEGO's height to width ratio is 6:5. Since the smallest common multiple of these numbers is 30, the smallest perfect cube you can make (excluding studs) is one that is 5 bricks high and 6 bricks deep and wide.
EDIT: On how to build it: start with a layer of 3 2x6 bricks. Then place 2x 1x4 on two sides to join the 2x6 bricks, and complete a square by using 2x 1x6. Now make alternating layers of 1x6 and 1x4 bricks to make it strong, and top it off with another 3x 2x6 bricks as the fifth layer.


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How can I make a spiral staircase with basic blocks at right angles?
Quite simply, how do I make a spiral like a staircase, but with only these blocks?

There is also a 8x2 block, but my brother has it. Because it is quite an old set, I need a spiral staircase without 45 degree angles. The best I have made is this...

....made with these components:
What is a better alternative?
For Ambo100, it is not needed to support any weight, I  merely make these things for pleasure. Additionally, I require it to continue for infinite iterations of layers. And obviously, it need to be vertical. Finally, I would like it to be solid when "running" along it, just to be annoying. =)
Important: I forgot to note this, but my set is based around the 2 x 4 blocks.

How many bricks high do you need to go? Does it need to support any weight? I managed to build a helix limited to six blocks high,
but it uses 45 degree angles.

Related, but not a dupe due to your part limitations: https://bricks.stackexchange.com/questions/1896/what-is-the-best-practice-for-circular-lego-staircase-construction/1903

@jncraton , that is the post I referred to for this idea in the first place.

I updated my answer to only cover the bricks I think you're using - is that better?

@Zhaph-BenDuguid, yeah. (Neither did I say it was bad)

Based on the limited brick options, and the "it needs to be solid" constraint, I present my "Minecraft Spiral Stair" in LEGO form, and to provide "inifite height", I've gone for a "hung" support option:

Start with two 2x2, a 2x4 and a 2x6 in this configuration:

Add more steps as you need rotating around the lower 2x2 brick:

(Key: Yellow: 2x2, Blue: 2x4, White: 2x6)

Sorry, Only the pieces above

Depending upon the structural integrity required, you can connect the 4x2 bricks by one corner peg consistently (upper left most corner when viewed horizontally) stacked on top of each other, yet rotated such that the side of the brick is against the lower level peg (in upper one from the left on the lower brick). This will make a weak spiral yet with adjustable and relatively tight angles with one step per brick layer.

There are many things wrong with the answer,.but the main problems are that you have not provided images for clarity, neither have you answered my question. Not at all. , it is not needed to support any weight, I merely make these things for pleasure. Additionally, I require it to continue for infinite iterations of layers. And obviously, it need to be vertical. Finally, I would like it to be solid when "running" along it, just to be annoying. None of the criteria met.

@simplest_mathematics I agree that this answer could be improved with an image, but I think your comment is a little harsh. This answer sounds a lot like what Ambo proposed, and that seems reasonable to me. It's true that it doesn't use only 90 degree angles, but it does provide another option using only basic bricks. Honestly, I think this answer is pretty good, especially for a first post.

Fair enough, you should look at my first bad answers lol!  But I'm not saying that it is bad, I am saying a little more consideration of the specifications should be implemented in the answer @jncraton


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Which mini figure is this?

I would like to know which mini figure this is?

@mindstormsboi This question is perfectly valid and acceptable in our community, as can be seen by the fact that it is on-topic and has garnered a number of upvotes. I do not find Lotte's rate of posting to be excessive. Furthermore, your comment is rude and does not reflect the values of this community. Please remember to be kind: https://bricks.stackexchange.com/conduct

It is Hoth Rebel Trooper (Orange Chin Dimple)

With missing white backpack and goggles.


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Hanging template for Large Minifig Case
I've been happy to see LEGO came out with a way to display the myriad of minifigs out there:

And I was also very happy to find that I can hang these on the wall with the convenient eyelets on the back:

Yet despite earnestly searching I can't find anybody that has created a template for installing these.  How far should the screws be apart?  How far apart should the holes be if you want stack them like so:?

I'd prefer a printable template that I could drill through, but if you have measured these accurately that'd be a good start.

You could easily photocopy the back side of such a case and use the copy as a template, just like in this post: http://www.element14.com/community/thread/44326/l/photocopy-as-a-drill-template

Since no answers were given for two days, I'll convert my comment to a full answer:
If you haven't found anything yet but have access to a photocopier, you could try making a copy of the back side that contains the eyelets. The resulting print will be a 1:1 paper version of the back side, which you can tape on the wall intended for hanging the cases and drill through the images of the eyelets:
Be sure to align the sheet correctly, using a bubble level or such.


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Do regular Lego trains fit onto Duplo tracks?
I have a small kid and a bunch of LEGO Duplo train track. (Like what's in this set.) Would "grown up" sets, like the Emerald Night or Maersk trains, work on that track? They look pretty close (the wheels are a little more than 4 studs apart)  but I'd love to hear a definite yes or no from someone who owns both.

Related useless factoid: the racks on the DUPLO bridges are compatible with standard Technic gears.

The answer is kind of.
I own the Emerald Night and a bunch of Thomas Duplo track.  The wheelbase of the Emerald Night is wide enough that the "rails" fit inside the wheels.  In fact, the passenger car fits perfectly on the track.  Unfortunately, neither the engine nor the tender fit as well, due to the fact that both have pieces on the bottom that are too low to allow them to sit properly with the rails inside the wheels.
This means that the engine will not move on its own.  In fact, I have my doubts it would move well even if the wheels reached the track, as it would require the flanges of the wheels to have enough traction to pull the train.

It depends on your goal, as Jason said. He illustrated pretty well why out of the package lego trains don't run on duplo track. However, if you just want something for your kids to dink around with, it is possible to build a wheeled train that will drive on duplo track without using a duplo train as it's base. The trick is to use monster truck tires or "offroad" style tires, and a 2x4 axle that is flat. If your track is curved and not all straight, you also need your tires to articulate on swivel hinges.
Here's something I rigged up for my son from only parts I already have:

It worked well on a fully circular track, though it would catch a little if I made a squiggle track. I think the smaller off-road tires would have worked better but I could only find one four stud wide axle in that size.

authors: โรงเรียนพะทายพิทยาคม


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Software to do Duplo train track layout?
Anyone know a way to create with a software DUPLO train track layout?
The only thing I found is:
http://www.anyrail.com/index_en.html
It's a bit overkill for what I need and it's $US60, although the limited version can be used free.
LEGO has a track planner for non DUPLO track.
http://www.lego.com/en-us/city/trains/track-planner
If I can't find something, I'll probably try to do it myself (I have a background of tools programmer in video game industry)

I've used a program called WinRail that again is probably overkill for what you need, but was great for me with Brio, HO/OO and Scalextric. I know it has some LEGO elements in it, I'll check tonight if it has DUPLO as well...

Rather belated response - No, my WinRail10 instance only had LEGO Trains and LEGO 9V Trains, but I think the points were off in both of those - at least, they don't match the points I've floating around somewhere.

I asked question on here about Lego System track layout, I've 1st type blue rails. The points like 2× straight with 1 end having 2 track side by side. Later = points like part of circle with straight tangent. So need to know what Duplo points are like, then 1 of System track software should do.

See has both parallel & curved out points, 2 sizes track length, like more advance than System rails?

I would recommend BlueBrick, which is a versatile LEGO layout editor by Alban Nanty.
Apperently it has Duplo parts too, so I believe it should meet your needs. It can actually do much more for your layout planning needs (including modular tables if your club has some, for example), so maybe you'll consider it overkill as well, but since it's specifically made for LEGO layout I think you should be hapy with it.
Disclaimer: I have never used it for Duplo myself - if you do, feel free to share your experience with us in a comment.

BlueBrick work!  It's not perfect, but it's free and open source which is really great!  Thansk a lot!

You can use RailModeller Express or RailModeller Pro on macOS.
Both feature LEGO tracks (regular and Duplo):
http://www.railmodeller.com/libraries.html

..the Express edition being completely free to use :-)

Thanks for mentioning our macOS apps!
You can also use our free app RailModeller Express for LEGO Duplo trains: http://www.railmodeller.com/express-edition-en.html
For iPads please check our new iOS app:
https://itunes.apple.com/us/app/play-well-d-train/id1231936324?mt=8&at=1000lp7a

mayTracks - Lego Duplo Track Creator
A bit late - but there is an app for Windows and/or MAC to create DUPLO tracks with most known DUPLO bricks. I tested it and it works nice. In minutes and with a view clicks - I created large track plans. There is a PDF export too.
https://maytracks.maydorf.com


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Looking to Identify a LEGO creator set with a hook
Wandering the Internet not long ago I saw a LEGO set that I thought my kid would like because it had a hook (they are into tow trucks these days, so things with hooks catch their interest). Unfortunately I didn't bookmark the page nor write the name of the set down, and now it is impossible for me to find it again.
These are the things I remember about the set

It was probably a LEGO creator set, because at first I thought the box contained 3 different vehicles and then I realized that you could build 3 different things with the same pieces.
It had a hook of some kind (definitely) and probably a rope for the hook.
One of the vehicles that you could build with the set was airborne, probably an helicopter, maybe a train.
Other of the vehicles that you could build was a boat or ship (due to the size it looked more like a tiny tugboat).
The predominant colors in the set were red and black (maybe dark blue?).

Note: I don't think it was the LEGO Creator Cargo Heliplane.

Possibly 31045 Ocean Explorer?

Has hook
Tugboat appearance
3-in-1
Red and Dark Blue
one model is a plane

If that's not it, you can browse Bricklink for sets containing hooks. I'm guessing you probably saw the modern "Hook with Towball" piece

From your description I would assume it was 31045-1: Ocean Explorer - Brickset

That seems like a reasonable assumption. Welcome to Bricks.SE!


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Can you extract a program from the EV3 brick to the computer?
As part of an assignment, I made a program for my EV3, but however my computer automatically restarted, so I lost that program. I need to show the program!  However, the program is still in my brick. So, I was wondering, is there any way to extract a program from a brick to my computer? And if there is, what would I need? (extra software, Bluetooth, connection cable)? Thanks

Update:
There is a tool at http://ev3treevis.azurewebsites.net/ that can be use to create a new .ev3 file from a .rbf file recovered from an EV3 brick. Some information will be lost, but at least simple programs should be able to be recovered.
Original answer:
You can extract the compiled program from the EV3. Compiled programs have a .rbf file extension. However, these files only contain EV3 VM bytecodes and cannot be converted back to the EV3-G project file format (.ev3p file extension).
Details about extracting the program from the brick and what you can do with it has already been answered here.


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How do I identify which minifig is in a blind bag for The Muppets series of figures?
How do I identify which minifig is in a blind bag for The Muppets series of figures?
I would like to know what is the best way to know which minifig is in the bag.

A better format for this, and more likely to keep it from being flagged to be closed, might be to pose the initial question something like "How do I identify which minifig is in a blind bag for The Muppets series of figures?" and then answering your own question with the relevant information. Possibly flagging it as a community answer to allow others to update the answer as more information is available.
As it sits right now, this doesn't quite fit the format for this site and is at risk to be at least downvoted, if not removed.

I’m voting to close this question because this is an Answer rather than a Question. The content of this post is valuable, but it has to be an provided as an answer to some sort of question. I would also like to note that it is perfectly fine to have a question answered by the same person as long as the question (and answer) fit the scope of Brick.SE

Thank you all for your comments. Changed the format, hopefully with better fit to Brick.se

@Saariko Thanks for sharing and for taking the time to edit your post. Welcome to Bricks.SE!

I did, I went ahead and purchased a small digital scale, with .01 grams of precision.
I weighed the bags and identified them. Here are the results:
Most have unique enough weight. For the ones that are close, you can feel one of the items within the bag.

Minifigurine Character
Weight (g)
Feel for

Dr. Bunsen Honeydew
9.65

Kermit the Frog
9.85

Gonzo
9.96

Beaker
10.05

Janice
10.73

Waldorf
10.88

Fozzie Bear
11.22
Mic stand

Statler
11.24
Laptop

Swedish Chef
11.57

Miss Piggy
12.06

Rowlf the Dog
12.55

Animal
14.18


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9398 reduction change
I am studying implementation of 9398 crawler reduction.
Here is the stripped part, in order to see the gears and their relation - the image is made with the excellent tool which is LDCad.

My idea is to use this Lego design for other model and I need to know how would I calculate the effect of changing it a bit.
My intention is to replace the two 16 teeth gears 94925:

with a pair of 12 and 20 teeth (32270 and 32269):

and to remove the last reduction pairs, the ones in portal axle:

so it would be as follows:

Would this become faster/less powerful or slower/more powerful?
My aim would be to keep it pretty close to how it performs now.
Also, is there a way to combine gears in order to add a distance of half of a stud between the motor axle and the next or the second one? In the image below, I have moved the parts and created a gap between the gears, in order to point what I intend to move, but the contact must be assured by some gears, obviously by replacing the existing ones. Would be there possible?

This modification won't change the rate of reduction.
You can calculate the ratio of the angular velocities of two adjacent gearwheels as
i12 = w2/w1 = n1/n2
where w is the angular velocity and n is the number of teeth of the gears. Hence the original reduction reads as:
i12*i23*i34*i45*i56 = 12/20 * 16/16 * 20/28 * 12/20 * 12/20 = 27/175 = 0.1543
while the modified is:
i12*i23*i34*i45 = 12/20 * 12/20 * 20/28 * 12/20 = 27/175 = 0.1543
What you did is you simply removed the 16/16 and replaced the 12/20 gears, which results in the same reduction because the order of the multiplication is arbitrary.
To the second question:
You can change the 12-20 gears to 16-24 ones to fit the increased distance. In this case, the new reduction is
i12*i23*i34*i45 = 16/24 * 12/20 * 20/28 * 12/20 = 6/35 = 0.1714
Note that the new gears may intersect parts not shown in the figures.

If the only change is replacing the two 16-tooth gears with a 12-tooth gear and a 20-tooth gear, then you will reduce speed by a factor 12/20 and increase torque by the same factor.
If you want to increase the distance between gears by 1/2 stud, then you can experiment with using bigger gears and offsetting the motor sideways so the gears don't touch vertically. This may induce some play in the gears.

I would drop the portal axles, so the performance will be kept. The reason is for implementing this on other model with less axle height (42069). Well, I did it partially, but using a horizontal transmission and keeping a similar design, with only 2 reductions instead of 3 (as this model has). It performs acceptable - a little faster than 9398, but powerful enough to run over decent obstacles for its tracks. I couldn't find a combination of gears for that 0.5 stud displacement, though. The gears are usually too tight to work safely together.


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How do the 61927 actuators work in MK II crane set (42009)?
I don't own a 42009 set (MK II crane). But I have modelled it in LDCad in order to understand how the set works. There is something I don't understand related to the actuators - as I don't have two pieces either I have come here to ask.

The 61927 actuator.
I see the two pieces of 61927 actuators attached to a gearing comming from  one L motor, the gearing seeming to eventually produce a rotation for the two actuators in opposite direction. So, I expect them to be antagonic, meaning one extending and one contracting at the same time. What is wrong in my assumption? Where the rotation is synchronized for the two actuators?

The gearing, stripped.
So, why do they work in the same direction while they are turned in different directions at the same time? Or aren't they?

THe actuators both turn in the same direction, as there is a gearing “bridge” between the two axles driving the actuators that consists of 3 interlocking gears. 3 gears that interlock cause the 2 outermost gears to spin in the same direction. You can easily validate this with a small test setup using a Technic brick with holes, a small axl and a few gears and axle pins.
EDIT: For clarity, this picture shows how each of the key gears spin in this setup.

The two flat bevel gears marked with #1 spin in opposite directions from eachother, but this is possible because even though they are on the same axle (#2), they are not attached to this axle as the gears have a pinhole, not an axle hole, and hence they can spin freely (see part 87407 on Bricklink). It is likely gear #3 (marked in yellow) that is the gear that is driven, and its power and rotation is transfered to its twin gear which drives the other actuator (and spins in the same direction).

Thanks, I believe it is, I just fail to see it. Where is that bridge? If you discuss the 3 ones with a circular hole, I agree. From my point of view, the tan gears before the actuators turn the same way, but after, the gray ones, at 90 degrees, mounted as opposite, make the actuators turn differently.

Those tan gears with the gray in the center form a similar bridge, just under an angle. This is similar to how a differential works. In the end, the two tan gears within the bridge turn in opposite directions, but this happens equally on both sides, so both actuators still activate in the same direction.

Exactly, this is the question, why do they work in the same direction while they are turned in different directions at the same time?

Added a picture and some further clarifications, hope this makes it clearer.

Excellent, thank you, I think the position of the last gray gears does not matter, if they are on the left or on the right side, isn't it?

Actually it does. As the boom moves up or down, some rotation to the gear of one LA is added, while on the gear of the other LA it is subtracted. This causes some slight tortion. It is considered by many an improvement over the original design if you switch one of the gray gears so both face the same way.


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When did LEGO Minifigure Leg mold designs change?
I am trying to identify the changeover dates for different minifigure leg molds. e.g. a figure from 1978 has no visible seams on the legs
figures from the late 1980s have visible seams, but it might be earlier
a figure from 2018 has visible seams on the outside of each leg the leg, and ©LEGO imprinted under the toe. It sees to have happened after 2012
The legs with seams have a marginally larger hole in the base for studs, and so are easier to attach/remove to/from an attached plate than the older ones.
Does anyone know when these molds changed over more accurately
?

Could you show the mentioned seams in the legs ?

Further investigation reveals that 2013 was when the word '©LEGO' started to appear under the minifigure 'toes'  I am still unsure about the first appearance of seams in the leg molds


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How does LEGO decide the color of internal set pieces?
While building many LEGO sets I have noticed that for internal pieces you cannot see when the set is finished; LEGO often chooses mis-matching colors.  For instance in the (amazing) Saturn 5 set most of the pieces are of the white, black, gray family.  However there are some green/blue internal pieces.  Doesn't match the rocket at all.  I have noticed the same thing with other sets as well where a random green internal pieces will show up.
Do they do this for a reason?  Are they using colors that don't sell well and trying to get rid of them?  Going for contrast to help you build?

https://bricks.stackexchange.com/questions/2895/why-do-some-sets-contain-parts-of-an-unrelated-colour-that-are-hidden-on-the-fin

Does this answer your question? Why do some sets contain parts of an unrelated colour that are hidden on the final model?

Going for contrast to help you build?

This is probably the primary reason most of the time.
One Eurobricks user once said they asked a set designer about it, and they confirmed they do it to makes it easier to follow the instructions:

I had an opportunity some time ago to talk to a designer at TLG, and he told me that they use other colors to make it easier to follow the instructions and build the model.


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Identification of rare (?) pieces
Recently, I bought a large LEGO collection in which, during the sorting, I found some pieces I'm completely unable to identify. Moreover, seeing some of them I doubt if they are LEGO at all (could be parts of an assembly though).
Here is a photo of the unidentified pieces:

I hope you can recognize them, please let me know if more photos would be necessary.
Higher resolution photos of #2 with the cup for scale (I really doubt it is a LEGO item but it might be a part of a motor or something):

Can we use a 1x1 brick for comparison?  I have no cups in my collection.

11 is a plastic ring with a single threaded hole on one side.

1 is a pin used to hold train track pieces together during shipping. It can be discarded but some people find uses for it since it fits in a. minifig's hands.
Many of the others are official Lego as can be seen by the brand name printed on them. On the large pieces you should be able to see an ID number printed underneath which will help you out. I'll work through identifying some of the others.
3: Bionicle Gear 8 Tooth with Rhotuka Spinner Rod 2.5L
4: Appendage Spiky / Bionicle Spine / Seaweed / Plant Vine
5: Modified 2x2 Racing Driver, no head
6: Bar 1L with Top Stud and 2 Side Studs (credit to Victorious Victini)
7: Train Coupling New
8: Bionicle 2x3 Axle Connector with Tooth
9: Hinge Brick 1 x 2 Locking with 1 Finger Top
12: Leg Skeleton with Black Square Foot
13: Bar 1 x 8 with Brick 1 x 2 Curved Top End (most likely this newer version, but there are some older ones as well) (credit to Victorious Victini)
14: Fairing, 1x2 Stepped with Two Pins
15: Batwing
16: Modified 1x4 with Angled Tubes
17: Not Lego
18: Fire hose nozzle
19: Bionicle Weapon Cordak Ammo
20: Road Sign Clip-on 2 x 2 Square with Curved Blue Lines and Small Black Squares Pattern
21: Bat-a-rang
22: LEGO Minifig, Weapon Bladed Claw (mostly from Wolverine)
23: Horn Large
24: Minifig, Utensil Space Scanner Tool. (credit to Rin Rio-Oki)

#17 which is listed as "Not Lego" looks awfully close to the color scheme used for several flame parts, though I can't find any shape matches and they're generally red on the bottom. Is it known to be a specific kind of non-LEGO piece?

I am pretty sure I threw out a few of those from my last bulk purchase because they had space for a Lego logo but did not have one, so I assumed they were off brand.

I'm fairly sure #17 is from Mega Bloks, in at the very least the Dragons sets. There is a smallish one shown (not the big ones at the top, closer to the middle) in https://dragonsuniverse.fandom.com/wiki/Yulmar?file=Yul_b4.JPG.

I found a few more:
6: Ø3.2 Shaft With Cored Knob
13: Brick With Shaft 1X8X1

Thanks for adding those, I've added them into Craig's answer so that we can have a single definitive accepted answer :)

A Few More:
02:  LegoTechnic Driving Ring Extension.
24: Minifig, Utensil Space Scanner Tool.

The 24th is a match, but the second one's not. I'll upload a closer photo soon.

Agreed:  Mine looks too big.  Could the OP post more pics with the pieces pushed over, so we can get a sense of depth?

Thanks for finding that Rin Rio-Oki, I've added 24 to Craig's answer to help towards a single definitive answer :)


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What does taking Raw value for EV3 Colour sensor do?
I participate in Robotics competitions like the WRO and I want to know if using EV3 colour sensor raw values helps in line follow.

When you take a Raw value from any sensor, the EV3 brick passes on the reading as reported directly from the sensor, without doing any processing. Especially for the color sensor, where you have several modes such as Reflection and Color Number, the EV3 brain does do post-processing on the input value to make the output easier to understand and/or use. By getting the raw value you are likely get a higher resolution signal than in any of the other modes, at the expense of potential error correction.

As for the range? What values does it give,  from 0-100 or is it 0-255 or something else?

It will from 1 to 255. Now I try to measure color via RGB value to make the rank higher than using color sensor value block.


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Do extra parts add to set's resell value?
When I build a set I tend to keep the box and instructions as I noticed they add to the value of the set.
I also keep the extra parts in the box but I'm not so sure if they add actual value. My understanding is they are random so there is no way to confirm they are the original pieces that came with the set.
Is there any value in keeping them along with the set when selling?
UPDATE: Based on the comments I understand the extra parts are consistent and predictable. So I would have thought having extra parts in would make the set more valuable. In BrickLink generally the status of box, minifigs and instructions are mentioned. No mention of extra parts.
Am I correct to think it doesn't add value if we included extra parts?
Thanks.

Extra parts are not random and are the same for each copy of particular set. You can easily identify these parts on Bricklink.

Thanks @Alex. Before I posted I read this answer which says the extras are random: https://bricks.stackexchange.com/a/1396/9280. Also on BrickLink it says "Extra parts can vary depending on when and where a set was manufactured, meaning that some new sets may include them and others may not. " (source: https://www.bricklink.com/help.asp?helpID=1562#extraItems) so I'm confused now if they are the same or not.

This is not meant negatively, but Consumer Services is not a reliable source in this case, they just want to avoid complaints if a spare part is missing. In reality the selection of spare parts in a set is not only consistent among copies of the set, it is also predictable what they will be.

"Extra parts can vary depending on when and where a set was manufactured" This only means that there might be some sets, for which there is a variance. As in, you might be able to tell two copies of set #ABCDE apart based on the amount of extra parts, and conclude that one has been packaged in Mexico and the other in Hungary. For the vast majority of sets there is no such variance and the amount of extra parts is just as consistent as that of the base parts.

Thank you all for your comments. I've updated my post as I was mistaken about the extra parts being random.

Generally, I think it doesn't add much value. But it depends.
Some sets, like US version of 8284, have extra parts crucial for alternative model (aka B-model). So unless you include them, you are selling incomplete set. The inclusion of all parts to build all models is part of "complete" condition description on Bricklink. Extra parts excluded though.
Then again, new DOTS sets, which have random printed tiles, but the number of included items is the same. So if you are looking for particular print, it would be nice to have extra.
Sure, there's a ton of sets with quite generic extra pieces, that you may already have a ton of. And buyer may as well already have a lot of them. However, buying a used set with box, instructions, stickers/sticker sheet as well as extra parts is always nice, especially if it is older set.


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Software to determine sets required to get all parts from a list
Assuming I have designed a MOC and thus have a list of parts that I need for it: Is there a software that helps me determine which (quantity of which) "sets" I need to buy?
In particular, the requirements I see are as follows:

Input: A list of parts, as in, some unique way of identifying each part by name or so, along with a colour, and required number.
Input: Eligible "sets" - actually, these sets can simply be part lists of their own. It must be possible to customize the list of eligible sets, as I would like to include e.g. Bluebrixx part packs for certain standard parts instead of relying exclusively on official Lego sets. Also, I might like to list individual pieces from Bricks & Pieces as individual "sets".
Input: Pricing information on sets. It must be possible to customize this information, so the prices can be adapted to current offers and discounts.
Among all eligible sets, the quantity of each "set" selected. Based on this, we could get the ...
... output: Based on the selected "sets", I should get an overview of what parts are still missing for the target list, which ones would be left unused, and how much it would cost.

Optional bonus requirements:

Some optimization feature that finds the best (= cheapest total, with least surplus parts) list of "sets" automatically. (But I am aware this is computationally hard, if not unsolveable other than by brute force in some cases.)
Some import facility to automatically retrieve parts lists at least for official Lego sets from some up to date source.
Part equivalency lists - some parts are just slight variations of other parts with some refinements done to the molds. In practice, though, it doesn't really matter for most models whether a given tile has a groove or not, whether a given brick or panel comes with open or closed studs on top, or whether the negative studs on the underside of a given part have a certain optimized shape. Thus, if parts can be marked as "equivalent" for a given set of parts list, they should be treated as if they were the same part.

Surely, MOC builders already routinely do this on paper or otherwise manually, but is there already any tool like this available?

EDIT: Here are some UI sketches that illustrate what I am after:
Consider, for instance, these input/output tables:

In there, I have listed the required parts for my MOC (obviously, only an example here for the sake of demonstration).
Also, I have assembled a list of sets to (possibly) buy, along with current pricing information.
In the same table, I now want to be able to indicate how many copies of each set I'd like to buy.
The tool should now output the total cost.
At the same time, it determines which parts I would get beyond the ones from the Required Parts list.
Note how the resulting output changes based on modifying the count of set copies to buy:

If the selected sets to buy do not cover the entire list of required parts, the tool should notice this:

I have tried to determine whether Rebrickable could fulfil these requirements.
What I could find was that I can compare a given parts list (of a MOC) to another set.
Alternatively, I can compare such a parts list to another custom parts list.
Neither of these fulfils the requirement to compare against multiple sets (where "set" can simply mean "a package containing X > 1 times part Y"), and then see what additional parts remain.
Also, I could not find any way to supply custom price information (based on the particular discount offers that might currently be available where I can conveniently buy) to consider for such a comparison.

https://rebrickable.com/about/

Does this answer your question? Is there a software which finds alternate models for owned sets?

@MichaelVerschaeve: I did suspect Rebrickable can do this, but even after signing up, I could not yet find out how. I found the feature to create custom lists (even though it's limited to just 10 in the free account), but it seems the Compare Sets function then only compares the individual parts in those lists, not the sets/MOCs I added. Also, at least so far, I could not find a way to supply a custom price for a given set or even for a certain subset of parts within a list. Thus, I am not convinced Rebrickable is an answer to this question.

Consider using pick-a-brick and bricklink to acquire parts individually. There's rarely a need to acquire parts only from sets.

@IvanSanchez: My question already contains this among the requirements: 'I would like to include e.g. Bluebrixx part packs for certain standard parts instead of relying exclusively on official Lego sets. Also, I might like to list individual pieces from Bricks & Pieces as individual "sets".'

Unless you create a MOC from single set's elements (an alternate model) there is no easy way to list sets that could be acquired to create your model. Simply because there's usually quite a few unique, obscure, not very common parts. So, instead of buying one set and missing parts you may need to acquire 5+ easily. Also  Rebrickable's "Compare LEGO Sets/Lists" option allows you to compare with Custom lists. I just checked and there is an additional drop list.

@Alex: I have seen that I can compare with custom lists, but can I somehow subdivide these lists or compare to multiple custom lists at a time? Otherwise, I don't quite understand how I would indicate that I'd buy e.g. this set twice. I think I'm going to edit my question later on by adding an example to better illustrate my use case.

@Alex: I have added some example illustrations that hopefully help to understand what I am looking for.

I don't know of any database that contains inventories of non-LEGO sets. Any such resource would be quite useful for (partial) set identification questions regarding non-LEGO sets, so if you know of such a database, by all means please let us know.

@zovits: In this question, I'm not asking for any such database (although it sure would make for a useful import dataset for a tool like the one I'm asking for here). Maybe you can post your own question to ask for such a database; I'd be somewhat interested in that, as well.

I understand - I'm only saying a database would be a requirement for any such tool, but since even that doesn't exist (AFAIK), there's no chance for this tool.

@zovits: I don't think so. The way I've outlined the tool in my question would work well without any comprehensive database. I'd enter the parts lists for the sets manually, because I don't need the entire product range, just the handful of sets I have actually pre-selected to contain any relevant parts.

This is going to be an optimization / integer programming problem. You want to solve a system of linear equations (or inequalities, in the sense of "at least X") with integral coefficients and integer solutions.

@shoover: If there were an automated routine to find a good distribution of sets. But as listed in the question, I see that as an optional feature. Primarily, I'd already be happy with the simple addition/subtraction per part and colour required to get an overview based on sets I have picked myself.

@F-H Your example has the 1x10 plates as required parts and the set BPP4477 as suggested "set to buy". How should the tool know what parts are included in any set without a database of sets and parts?

@zovits: As a user, I know that BPP4477 is a possible source of the required parts for my set. Thus, I make this one set known to the tool (as in, within the tool, I add a "set" record and list the parts contained in that set). Same for the other two sets in the "Sets to Buy" list. It's not the tool that picks these sets from some all-encompassing database of sets, it's the user that enters or imports them (parts lists of individual sets are sometimes available e.g. as CSV files or similar).

@F-H So there should be an additional table in the example above with a list of sets as keys and the contained types and amounts of parts as entries? In that case the question is basically a variant of the multiple-knapsack problem - with a minimum sum limit instead of a maximum.


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myblock for a proportional gyro turn that randomly fails when in a larger program
I have a proportional gyro turn myblock that fails when played in a longer program.  The myblock works perfectly fine when played by itself.  The most confusing thing is that the way it fails seems to be random.  Sometimes you play the program and the turn is too far, sometimes it doesn't turn enough and sometimes it works as expected.  We have had similar problems before with other complex myblocks that seem to misbehave when run in as part of a long program but work fine when run by themselves.
I'm not sure the best way to attach code, so I've linked it to the file here.
https://drive.google.com/file/d/0B9eJwUXdFba-T3k0cTdYNTJ0eWc/view?usp=sharing

When you run the program do you reset your bot at the right position?

I'm not sure I understand what that means.  Do you have an example of where and what I should do?

I've looked at the file, and I don't understand what it's supposed to do. First you have some program called "ManFlower". It includes a bunch of MyBlocks that we are unable to decode, and since you're not showing what they do we can't solve the problem. Then you have another program called "SuperGyroTurn" and it is too confusing and hard to see what your code is doing, without details or at least a detailed walkthrough of the program we won't be able to solve this, so we may have to close your question. Another necessary piece of info required is how the robot moves which is not specified.


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Is there a rock wall generator?
In Lego store, and on many photos on the Internet, I've seen vertical "rocky" walls made of slopes and simple 2x1 bricks. For example this one.
Is there a software that would take wall length and generate a semi-random rocky-looking wall? Something similar to sphere generators we all know and love?
Designing such wall by hand in LDD is a time consuming and not really funny task, and I'd like to avoid it, if possible.
Note: I tried dropping models from Thingiverse to Brickify, but  Brickify does not use slopes and there is problem with scale.

Interesting idea, but I think most people would use just the parts they had on hand. It might not be too difficult to design something that produces a pseudo-random rock face, but it's another issue to have that be translated into brick form. If anyone has created something like this before, it probably would have been a procedural generator for The LEGO Movie.

@Ambo100 Well, I was thinking more like Pick by brick shopping list. And I doubt Lego (stores and movies) does it all by hand, but of course they may be reluctant to release their tools.

I'm not aware of anything that does this, but I am working on a project that uses a customizable context-free grammar to describe connections between Lego bricks. Once the grammar is defined, an algorithm can be used to "grow" interconnected shapes to meet certain parameters. It should be possible to procedurally generate a rock face this way, but I'm not there yet.

@jncraton I would be very interested in seeing that. I have some ideas based on genetic algorithms, but I'm at the "sketch  of a sketch" stage. Sadly, my ideas are more about solving  "how to put bricks I already have" than about preparing shopping lists I wanted.

@Mołot I'll definitely post an update here if I get anywhere. In the meantime, you may be interested in an older project of mine: https://github.com/jncraton/procedural-bricks

I was able to integrate this into a research project applying context free grammars:

This is not a polished software package, and the design is a bit esoteric given that I started with the goal of applying context free grammars to a practical problem. Hopefully there's something in there that may be useful to someone. :)

Looks amazing. Pretty close to what I hoped for.


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When did Lego switch from 4 to 6 stud width of Windscreen?
All my old sets have cars with windscreen 4 studs wide. No matter if it is a jeep, truck or what - cars was 4 studs, usually 3823 or 2437. Now, in most modern sets, car windshield is usually 6 studs wide, like 92583.
I'm interested when this transition happened. If it's possible, I'll be also glad to hear why - was this change caused by introduction of other bricks? New "series" of a City theme? General overhaul?

Both windscreens you mention are still in production. Apart from that, the appearence of LEGO models has changed dramatically over the years. I don't think that a transition of any sort can be pinned to the introduction of certain new parts. The number of new parts increases every year, so in 10 years today's sets may look old and clumsy.

@Aziraphale are still in production, but now 4 studs one is used for totally different models it used to. And while overall change is continuous, there must've been a point where "truck width"  switched from 4 to 6.

Realism seems to be the most probable answer. If you compare the Tow Trucks 6656 (1985) and 7638 (2009) it is clear that proportions and shapes have improved by orders of magnitude. Thinking about it: Stud width and minifig size are constants, everything else could change. So it was only natural to increase vehicle width by 2 studs.

The lego trains from the 1970's and 80's all started with 6 stud width designs.

@LarsTech nice catch. I mean to ask about cars specifically, but now I see I didn't.

I noticed this, too. But only after the "Speed Champions" came out a few years ago. (I didn't give much attention to CITY.) It seems to me like the LEGO Racers got wider, more detailed sets starting from 2008 or so.
Also: I often check the Bricklink inventory part page (example: 92583), to find the Years Released under the "Item Info" section. I cross reference those dates with the list of sets that an item was used in.


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How to make Lego Mindstorms EV3 robot go in reverse when move steering input comes from proximity sensor
I saw an program on the Lego Education page which makes a Lego Mindstorms EV3 robot gradually slow down as it approaches a wall. The info from the proximity sensor is used as the direct wire input of the Move Steering block, the nearer the robot to the wall, the slower the speed of the robot.
The problem is that my infrared sensor is on the rear of my robot (track3r). I would like to make the input to the Move Steering Block negative so that my robot motor moves backwards (in reverse) using this program. How do I do this? I can't make the output of the proximity sensor negative... can I?

Multiply the output of the proximity sensor by -1.

Aha, use (data wire it) the math block to multiply the output of the proximity sensor by -1 then feed it back (data wire it) to the steering block. Appreciate your time.

Actually, using the Invert Motor (blue) block from the Advanced Palette before the motor would probably have the same effect. I just read about it The Art of Lego Mindstorms EV3 Programming by Terry Griffin. The Invert Motor block reverses the meaning of the Power parameter for the motor connected to the selected Port.

Unfortunately, the Invert Motor block doesn't work with Move Steering or Move Tank blocks.


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Good manufacturer/market for clear (transparent) bricks and plates in bulk?
I never realized how rare clear bricks are! I'm looking for an efficient way to buy clear 2x4 (e.g. 3001) bricks in bulk. On BO, BL, and Peeron there are very small lots and prices close to $1 and beyond per brick. On Alibaba there are some new compatible brands but they tend to mix random colors and styles, no pure bulk packs of the same brick in clear (white).
While I can patch together an order from the above, I'm wondering if there is a manufacturer that just sells pure lots of the same type and color so I can keep buying from them and not have it be a brand new search each time.
Or do any markets exist that unlike PL/BO/Peeron include competing brands rather than only Lego?

Clear 2x4 bricks might seem to be expensive because LEGO doesn't produce them currently (they stopped making them in 2006). However, a quick search on Bricklink sees them listed as cheap as $0.02 per brick, used, which is not expensive at all. Just make sure you look for the correct brick design - you want to look at 3001old.

Wow... I didn't know LEGO discontinued them. How sad-- clear bricks are the secret ingredient that fuels all our aircraft and spacecraft!


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Is it possible to determine the approximate age of these bricks only by seeing their injection points?
Is it possible to determine the approximate age of these bricks only by seeing their injection points?

Maybe it is easier to determine the age if we could see the other sides, too.

Are you asking the question to see if it's possible to know the age only from the injection points, or do you just want to know the age of the bricks? Your question is clear, but it's just a kinda strange thing to ask..

Yes, they are from the 1960's from what i can remember

@Slickster. I found a pile of those in an ebay buy of used bricks and was interested in the age.

@Aziraphale. yep, will see if i can post more pictures the next days.

@Slickster. I changed the question based on your comment

I cannot tell by the injection markings but having been a lego collector since 1967 I can tell that they are around that era. They look like some of the original ABS plastic. I also have some even older lego bricks in my collection (circa 1960) and they are of a different plastic but you cannot see the molding points on those.


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How do I make a remote control car without LEGO motors?
I have no LEGO motors In my collection, what are some household materials I can use?

Pardon me, but if you can't use LEGO motors then why are you asking here?

Please be more specific: Do you want to make a remote controlled car out of LEGO, but without using LEGO motors, and you want to know how to interface LEGO powerfunctions with external motors? For this you might want to take a look at @Philo 's excellent page on Power Functions. You'd need to source 9V motors from somewhere and make your own cables (or modify existing LEGO cables). If that is not what you're looking for - please explain your question in more detail.

It sounds like you are asking how to motorize your own custom LEGO creations using motors that you may already have around the house rather than purchasing official motors.
Before I answer this, I just want to make sure that you are aware that you can purchase the PF motors individually on LEGO.com for fairly cheap. You don't have to buy large, expensive sets in order to get motors. The basic PF motor set which includes a battery box, motor, wiring, and lighting is $30 USD. Unfortunately, as pointed out in the comments, this kit doesn't include a proper RC remote, so you'd need to buy an IR receiver and IR remote as well, which would add another $25 to the cost.
The first thing that you'll need to do is find a suitable motor. Old toys are probably your best bet. If you're going for small, you could also take a pager motor out of an old cell phone. This is what Phillipe used to make a motorized city-scale vehicle in another question:

The main challenges with using custom motors are:
Attaching the motors to LEGO bricks
The strongest connection will likely be created using some sort of glue or epoxy. Most two-part epoxies should be sufficient for small motors. Here's an example from Eurobricks:

You could probably get away with using screws or even rubber bands, but it's a bit trickier to make everything line up the way you want.
Converting the output of the motor to rotation of a LEGO axle
Assuming that the motor axle is relatively small, it is possible to drill out the center of a Technic axle and slide it onto the motor's axle. This can be a little tricky to get right, but it does work. Here's a video that explains it.

If your motor already has a pulley attached, it's easy to just run a belt between the motor and a Technic pulley.
Powering and controlling the motors
If you don't mind your creation having a tail, the easiest way to power the motors is to simply run a wire to the vehicle from some sort of controller. It's fairly easy to put together a working system if you have old wired remote controlled toys like this one laying around:

If you have any radio controlled toys laying around, it's also fairly easy to just rip the electrical parts out, put those on your LEGO model, and wire up your motors. You could also use the motors from the original toy. Then you don't even need to do any wiring. You would have to find a place for batteries and the receiver hardware on your creation, though.

That's a thorough answer. I cringe when I see people drilling lego pieces, but will let it slide for the red axle, because who doesn't have millions of those. Also, one nitpick: the motor pack you mention has a glaring flaw that I only noticed after buying two of them: there is no remote control in it. You need to buy the remotes separately, and you'd need two of them to control two motors.

That's a great point. I updated the answer to include a note about also needing to purchase the IR remote and receiver separately.

A few years back I ripped motors, controlcard and batterypack out of a broken car. I then fitted some legopieces to it and got a superfun setup to use with my old technic lego.

I mounted a piece of a normal (old black) axle on the motor shaft. But just as @jncraton describes it This can be a little tricky to get right. If you are just drilling freehand as in the video it is very hard to align everything right.
So instead of fastening the drill in the powerdrill I did it the other way and fastened the axle in the powerdrill and the drill in vise. That way I know that the axle is spinning around its own center and that any small misalignment will be automatically fixed by the flex of the thin drill. To get the axle centered in the drill I sacrificed 2 bushings.


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Issues with set 10234 book 3 pg 43
The white wing-like piece continues to pop off when placed. Has anyone figured out a fix for this or am I doing something wrong
Instructions 3 & 4:

src: http://lego.brickinstructions.com/10000/10234/163.jpg

Do you have a photo of your build. Looking at the instructions the whole assembly looks stable, especially from sub step 5, when the large curved piece is placed.

Sometimes, the piece connecting your two white plates in Step 2 might be bent or not completely flat. An rounded LEGO piece can have other pieces that it connects falling off because it can't hold on to the studs as usual. This could happen to the white wing piece itself.
Two, they can be a hassle. Normal pieces can sometimes just be a pain in the back. I got a set with pieces in perfect condition and they still come off. Make sure you squeeze those pieces really tight to each other to prevent and pieces from falling off.


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Function in EV3 Basic
I have been programming in basic for ~30 years. I want a translation of the following code into EV3 Basic:
function index( x , y )

  return x + y * ( maxx , + 1

end function

sub look

  for i = 0 to 5

    motor.start( "bc" , 75 , 75 , false )

    program.delay( .025 sec )

  next i

  motor.stop( "bc")

end sub

How do you do this in ev3basic?

I don't think this is something we can solve, shouldn't this be moved to SO?


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Lego Mindstorms education NXT 9797 software for a MacBook Air
Where can I find Mac OS compatible software for the Lego Mindstorms Education NXT Base set (9797)?

You can download software for programming the LEGO Mindstorms NXT robots on macOS directly from the LEGO Mindstorms website.
The software is packaged in an ISO image, and there are instructions for how to install it also available on the same page.
Keep in mind that this is the retail version of the software, designed for use with the 8547 NXT 2.0 set, not the education version. The programming functionality for both sets will be the same, but the retail software does include some features specific for the 8547 set, such as building instructions, and does not include some features that the educational software does, such as data logging.