text:
How to install NXT Firmware 1.28?
Lego is giving 1.31 from their website but I need 1.28, how can I install it?

Why do you need v1.28?

@DavidLechner I borrowed a brick with 1.28 on and I have to give it back with the same version.

Heh, found it on my computer, click to download from Google Drive.

2022: I’ll update the link soon, stay tuned

I believe the Enhanced Firmware included with BricxCC is based on v1.28. You can find a download for the firmware there and download it using NXT-G or you can install BricxCC and install it via the IDE.

I dont want any enhancements only plain normal 1.28?


text:
Alternative controller for LEGO NXT
I love the NXT platform and have quite an investment in sensors and motors, etc.  I would like  to know if there are alternative controllers that have been integrated with the NXT sensors/motors.  By more powerful I mean floating point math, more memory (RAM), more non-volatile storage.  Ultimately, I am looking for a way to incorporate a camera onto the brick and do the required image processing.

I would suggest Arduino or, preferably, Raspberry Pi.  Here's some info extracted from my previous answer on NXT:
Arduino & Raspberry Pi are flexible development platforms and they can easily be interfaced with other devices. As for image processing the Raspberry Pi would be the better choice since it is more powerful.
Arduino & NXT:
There is a lot of Arduino-NXT hardware components that you can buy or even make yourself.  For example you could use this Arduino shield called NXShield-D and it's software.
RaspberryPi & NXT:
Pi is a full computer and very easy to use.  To interface with NXT you can use the GPIO pins but thanks to the USB port, somebody already made the NXT-python to control the NXT brick.  Being a Linux system you'll probably find some ready-made image processing samples all over the web.

Also see: http://robotics.stackexchange.com/questions/tagged/nxt

source: Stack Exchange

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

sort: votes


text:
NXT motor power accuracy
When turning the motors, how precise is the speed parameter? I am programming in the NXC language (standard firmware) and wishing to know how many decimal points will be taken, if any, and whether the input speed will be truncated, rounded or neither.

From the page you linked to we can see that the NXC OnFwd method has the following parameters:
void OnFwd (byte outputs, char pwr)

The power or speed parameter is listed as a char type, and looking around elsewhere on the site we find the definition of the char to be:

In NXC the char type is a signed 8-bit value. This type can store values from SCHAR_MIN to SCHAR_MAX.

This means it can hold an integer value between -128 and 127.
It cannot take any decimal values.
I assume that a char was used over an int as they only need to support values between -100 and 100 in this method.

Thanks, for some reason I didn't connect value to integral value, but looking at the int and float description it's quite obvious! When I use a decimal value as a parameter there is no compiler or runtime error; I believe C would just truncate a floating point number to an integer, ao I presume it would be the same in NXT for float to char?

I guess so - I can't say I've tried, but yes, there's possibly some implicit conversions going on.

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


text:
Can I control 2 NXT bricks from a computer using bluetooth at the same time?
I am thinking about starting a project involving controlling the movement of a mindstorms robot depending on some input from a Kinect device; however the robot will require at least 6 motors. I have access to 2 NXT sets* (provided by university) - is it possible to control both bricks using either one (or two) bluetooth dongles? I've read through the Bluetooth SDK docs but they only mention that a master NXT can control up to 3 slave NXTs. Reading through the protocol spec I see no reason why another NXT could not be controlled by just sending it "direct control messages". Can it be done in a simplistic way without having to make my own low level bluetooth api?

Yes, this is definitely possible! You can connect up to 7 different NXT devices from one computer and one Bluetooth dongle (theoretical limit). I have tested this with the RWTH - Mindstorms NXT Toolbox for MATLAB) successfully with 5 NXTs on Linux and with at least 2 NXTs on Windows.
In real life, it depends on your Bluetooth hardware. Your Bluetooth stack or driver software should provide several serial COM-ports. You can then connect each virtual serial port to a seperate NXT device, and access them via those different serial ports.
If you go the direct way via the official LEGO NXT Bluetooth SDK you mentioned, you can retrieve different handles to multiple NXTs.
Oh, and for the record: You can also connect multiple NXTs via USB, and you can also mix and match with Blueooth.
Regards, Linus

To back this up, I've also controlled 3 NXTs simultaneously from Windows with a single Bluetooth dongle, using a LabVIEW program with the LabVIEW NXT Toolkit.

The RWTH documentation about initiating connections has a sub-chapter called "Using multiple NXTs" which can be found here: PC to NXT Communication - Using multiple NXTs
The C++ communication from norgesgade14.dk claims to support: "Open and close connections with multiple NXT units" on its overview page.
So it should be possible to do this, though I can't confirm since I only have a single NXT. I suspect that you only need one dongle though.

Those answers above do all work.  If I were looking for fast speed, I would probably use USB, however if you robot moves around, then bluetooth is probably the best solution (the slowest thing in the loop is the NXT anyhow :P).  If your Bluetooth hardware on your computer supports multiple devices, then simply address each associated COM port per device.
After reading through the bluetooth direct command PDF provided by LEGO however, it's written fairly poorly and leaves the user asking a lot of questions or messing around with certain commands for a long time.  There is a great writeup here that goes over the commands in an easier, more understandable, and thorough way:
http://www.robotappstore.com/Knowledge-Base/Programming-LEGO-NXT-Mindstorms/92.html
I recommend checking it out as it goes over a whole host of command types.
Hope this helps!

I've used RWTH and vouch for its effectiveness. However, if you don't have MATLAB, don't know how to use MATLAB, or just want an open-source solution, you can use the Perl module for controlling the NXT over bluetooth.
http://search.cpan.org/~collins/LEGO-NXT-2.00-1/lib/LEGO/NXT.pm
It's quite simple to use and provides very thorough control. Best of luck!


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Is it possible to retrive a text file from an NXT?
I am on a SeaPerch building team which is starting to use a Vernier Dissolved Oxygen probe, connected to an NXT to log the data. I have a bit of programming experience, but nothing in particular with NXTs (or GUI programming for that matter) and managed to get a very simple program written which logs data collected from the probe to a text file stored on the NXT (there will be no computer available in the field, so everything has to be stored on the NXT).
My problem is, I can't seem to figure out how to get the file from the NXT's memory and copied to a computer. It doesn't seem to be able to be accessed from Windows Explorer as a drive. Is it possible to get files off of it like a flash drive, or would I need to do something else to get the data?

Using Mindstorms NXT software (NXT-G), you can transfer any file from NXT to computer. Open "NXT window" (NXT icon in the lower right corner of interface), then go to "memory" tab. Select a file in NXT and click on "upload" button.
Or - more convenient - you may use "NXT Explorer" feature of BricxCC (in the "tools" menu).

we did this, but it won't open...

We do not see an icon in the lower right corner.

This is not an answer, just an answer to the @laurentien comment posted in the existing answer.

The "NXT window" icon is the orange L-shaped button (see red arrow).
The "memory" tab is the other red arrow.


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What is the difference between the NXT 1.0 controller and the NXT 2.0 controller?
I've tried to look this up but I can't find anything. As far as I can tell, the controller bricks (the white ones w/ buttons and a screen) are exactly the same and the only difference is NXT 2.0 comes with different sensors, parts, and software.
Is this correct?
If so, are NXT 2.0-generation sensors compatible with NXT 1.0? Can the NXT 1.0 be upgraded to run NXT 2.0-compiled software?
http://thenxtstep.blogspot.com/2009/07/nxt-20-vs-original-nxt-which-one-to-buy.html

I believe the bricks are physically identical.

There are a few subtle differences in internal hardware between the NXT 1.0 and 2.0 bricks. The most notable one is that the 1.0's screen would give out over time due to stress being put on a capacitor when the buttons are pressed, but the NXT 2.0 is engineered such that this does not occur. But, none of these differences affect what hardware the bricks are compatible with.
Externally, the NXT 1.0 and 2.0 intelligent bricks are physically identical. You can update firmware of NXT 1.0 controller with 2.0 firmware (download the most recent version here). Once this is done, your NXT will be able to use the LEGO color sensor that comes with NXT 2.0 box, and to run NXT 2.0-compiled software.


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NXT screen either flickering or blank, what do I do?
The screen on my LEGO MINDSTORMS NXT brick has just stopped working. It is either flickering, or blank. I have tried turning it on and off, installed fresh batteries, and I can even hear the selection sounds. Additionally, it responds regularly when I connect it to my computer. I've had my NXT for three-and-a-half years, so it's not new. Is there an easy/feasible way to fix it, or a cheap way to get it replaced?

Here are the two easiest options:

Replace it. Contact LEGO, and tell them of your problem. I've
hear many success stories from people who did this, and LEGO
replacing it for free. For one person, it took a week to arrive, but
for another, three days. Note that if you want to keep your old NXT,
you'll have to have the receipt. If you don't have the receipt, then
you'll have to send them your deffective NXT. Also, if you did not
buy your NXT directly from LEGO, (i.e. Ebay) they will not replace
it for free, but rather ask that you pay them to repair it.
Repair it. If you have a soldering kit, then get it out, and follow
the instructions in this video. It worked for me the first try.

I would recommend option 2 first. LEGO does have a nice customer serviec and they'll probably replace it without discussion. However, they want want to ask for the faulty part to be returned, and if it has be tinkered with, they may not be super happy about it. Keep the soldering iron for when LEGO absolutely doesn't want to replace it (never).

I disagree. Mine recently gave out when I was right in the middle of making a robot. I wanted to get back to building my robot as soon as possible, so I soldered it. It only took about ten to fifteen minutes to heat it up the soldering iron, disassemble the NXT, solder the capacitors, slightly reassemble it the NXT, test it, and finish reassembling it. It's really not that risky if you know what you're doing. I much prefer soldering it over having to wait a week or so.

As you said, "if you know what you're doing" (I sure wouldn't). Wait... you've only got one? ;)

@Joubarc No, I have two NXTs. Sorry, I should've said "one of mine" Instead of "mine". And now I understand better what you're saying.

@HaydenStudios As Joubarc said, I would swap the two steps around, especially if your answer is to be valuable for future visitors to this question.

I tried this unfortunately without any success. After the first attempt the flickering lines disappeared and the screen was all dead. I gave it another try, and the flickering came back!


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How can I use more than three motors with one NXT brick?
I'm building Caterpillar Excavator with my NXT, and at the moment I'm trying to control 4 points of motion:

2 Caterpillar Tracks - These should be controlled independently to allow for cornering, etc.
Rotation of the cab/arm
Extension of the arm - Ideally I'd use more than on motor here, as I'd like to be able to move the bucket and segments of the arm independently, however I've got a mechanism that works to "extend and dig" in one motion.

Obviously as it stands, the NXT can only control 3 separate motors - so I'm not necessarily wedded to LEGO only solutions.

There are electrical multiplexers as mentioned, however there are also many types of mechanical multiplexers. The idea behind this is to use fever motors to do more.
The advantage is the reduced weight and the disadvantage is the increased complexity and lower flexibility.
For example, you can control both tracks with one motor. However instead of one motor making the threads more forwards and backwards, you remove the 'backwards' function and replace it with 'right-turn'. So when the motor drives forward, the bot moves forward, when the motor drives backwards, it turns right. You can't drive backwards or turn left however. A simple (but poor) implementation can be found in the R.I.S. 2.0 instructions.
While this is restrictive, you can do other similar tasks without loosing important functionality. Another old trick is the 'grab and lift' mechanism which both grabs and lifts an object in one movement. When you lower it again and it reaches the bottom, the grabber opens up. While you can't open the grabber while it is lifted, it normally isn't important.
See The snatcher by Laurens as an example, which keeps two motors for the threads, but uses this technique to only use one motor for the arm.
Another prime example is with pneumatics, using a single motor to both pump and control a switch. See DiMastero's differential solution. It will pump no matter which direction the motor is turning, however turning it one way will push the switch in one direction, and the other when turning it the other way.
(It will pump while the switch is switched from one position to another, but again, this is a minor drawback considering the gains.)
While the previous examples are solutions to specific problems, they highlight the ideas:

Do different tasks under different situations. (Drive on clockwise, turn on counter-clockwise.)
Chain several tasks together. (First grip, then lift.)
Do several things at once. (Pump, while controlling the switch.)

The first point on the list, doing different tasks under different situations, is the most easy one to make a general implementation. You can split up the clockwise and counter-clockwise direction of the motors, to control two different tasks. While a bit restrictive, it is useful it certain situations.
A less restrictive solution is the 2 to n multiplexer. One motor gives the power, while another motor controls which task to transfer the power to. ('n' can be quite large, however something like 3 or 4 is more realistic in moc's.) I have come up with a few other versions, including some which allows controlling multiple motors at once (limited to same direction and speed).
Example to your specific problem
Use a 2 to 3 multiplexer. Output 1 and 2 controls the rotation and arm respectively. The threads are done using an adder/subtracter mechanism, use the last free motor to drive it and output 3 from the multiplexer to steer.
I would position the multiplexer above the turntable so that you just need to transfer the adder/subtracter axle through it.

Some more examples as requested.
Here is a more advanced version of driving and turning with tracks using one motor:

When the motor is turning counter-clockwise the mechanism will work like normal, driving both tracks forward. However when it turns clockwise, the yellow knob gear prevents one of the axles from moving, causing the last differential to stop and this causes both tracks to move in the opposite direction of each other, making it turn on the spot.
The knob gear is the crucial part, as it prevents action depending on the rotation direction. Here is a more generic version:

Depending on the direction of the input, only one axle will turn.
Moving on to the actual multiplexers, here is a mock-up of a 2 to n multiplexer:

Notice that the black gear can slide on the two axles, so that it can connect to both the light-gray and the dark-gray gear, depending on the position. You could have as many gears/outputs as you want in theory.
I used this to create a pneumatic control station, which had 4 outputs, each controlling one pneumatic switch.
Here is a 3 to 4 multiplexer which uses transmission parts:

The dark-gray axle is the input, and the 4 light-gray axles are the output. Depending on the position of the red sliders, a different output is chosen. The interesting aspect of this one is that you can have two outputs active at one time, which is not possible with the 2 to n multiplexer.

As a final note I would like to point out that I have used all of these methods in actual RCX/NXT projects in order to do more than what I could otherwise have done with just 3 motors. They are not just theoretical solutions.
I do not see the maximum of 3 motors as a disadvantage, but as a limitation which challenges me to find other solutions to the problem so it can be done with just 3 motors.

Cheers for this - are you suggesting that the multiplexer is a physical solution (unlike the electrical solutions proposed in the other answers)? If so do you have an example of one built that I could look at?

Yes, it can be done as a physical solution. I will try to dig up some old photos (and perhaps take some new ones), however it will have to wait for tomorrow.

I added 4 examples. I had to recreate 2 of them, since the original photos were either too blurry, or that the actual mechanism was hidden away inside the construction.

Cool! I linked to this in a blog post of mine.

Mindsensors sells third-party parts that are compatible with the NXT.  They sell several motor drivers and multiplexers, for use with NXT motors, RCX motors, hobbyist servo motors, or by sending commands to a PF motor remote control receiver.
HiTechnic is another such company, and they likewise make a device that sends remote control signals for PF and train motors.
(It seems to me that a company in Ukraine also made a motor multiplexer, but I can't recall the details offhand).

There are two non-wireless ways that I know of.

One of them, (which is better most likely) is to use a Mindsensors Motor Multiplexer (Motor MUX for short), which allows the use of all motor functions and splits one port into several. Note that each multiplexer requires an additional battery box, making your robot heavier and less compact. Each multiplexer costs $55, and each battery box costs $8.

Another way is to use converter cables, and split an NXT port by connecting them like so. This technique is cheaper, and does not require an additional battery box. A drawback to using this technique is that you have less individual control over the motors. Both motors will need to turn at the same time, with the same power, and in either the same or the opposite direction depending on how you orient the connection. Furthermore, this method will negate access to the motors' rotation sensors, so movement will have to be timed.
This technique has some limitations, but if those don't matter for your creation, then converter cables are a nice and cheap alternative that helps preserve compactness. I recommend using it over the motor MUX unless your robot simply can't function under the constraints. For a demonstration of a robot using the Mindsensors motor MUX, see this video. To see a demonstration of a robot using the converter cable technique, see this video.

Everybody else has pretty much said it all, but there is one more thing I can think of.
The IR Link Sensor can communicate with Power Functions, RCX, and trains.
So you can use three NXT motors, plus, say, two Power Functions motors. (Only the NXTs will have rotations sensors, obviously.)
If you already have some PF kit, you will only need the sensor (£40). If you don't already have the remote, PF IR sensor, PF motors, and battery box, it will cost you a lot.
If you have the trains or RCX, you shouldn't need to buy anything new.
I have one of these, and use it quite a bit, it's quite a versatile piece of kit!

I built the 3 to 4 multiplexer posted above (thank you for posting that) but was able to tweak it into a 2 to 4 mux.  The axles that are connected to the large gears are used to select the outputs by rotating the large gears.

It ended up being too big for what I needed though so I went a different route and built a 2 to 4 multiplexer that uses a turntable to move the drive gear around to the various outputs.  You could easily add more outputs to this if you wanted.  Just be aware that unlike the larger 2 to 4 mux, only one output is active at a time with the turntable mux.

The LDD files, videos of these in action, etc are on my blog:
Lego Technic Two Input, Four Output Motor Multiplexers

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


text:
As of November 2011, should I buy the NXT 2.0 now, or wait and buy the NXT 3.0 later?
I have played with the original RCX when I was in school, and I'm so in love with it. Now I have just got my first job and I would like to get an NXT robot. However, I saw in this Wikipedia article saying that it was released back in 2009.
So the question is: should I wait for NXT 3.0 to come out (probably soon?) Or should I just go ahead and buy the NXT 2.0?
Also, is there any news on any upcoming refresh of the Mindstroms sets?

The difference between NXT 1.0 and NXT 2.0 is minor, so I wouldn't hold my breath for a NXT 3.0.

I thought it was released in 2006 . . . it's been out a long time.

As of November 2012, the rumour of a NXT 3.0 is getting so thick that it's not going to be a rumour for much longer, so yes, you may as well wait.

Well, the question as it is too localized (specific moment in time), and I don't think you'll get more meaningful answers anyway. When the NXT 3.0 eventually comes out, the question as it is written will be moot; it would need to be rephrased (by asking to compare both versions maybe) but it'll probably easier to just ask another question.

And as of January 2013, the next version of Mindstorms, Mindstorms EV3, has indeed been announced officially

Note that even this announcement doesn't mean you shouldn't buy current NXT2.0 sets - there are still good reasons to do so, price being one (especially if LEGO dumps his current inventory at some point, which is possible), and  retrocompatibilty being another.

First off, there is not going to be an NXT 3.0. If there is, I would be extremely surprised.
This rumor was started back on April 1st, 2010 with a post on this blog (scroll to the bottom). Since then, many of people have been tricked. They even made another post the day afterward confessing that it was fake. Despite this, the rumor traveled to people who don't follow The NXT STEP, making its origins uncertain to them, and assumed it to have been announced by TLG.
With the Robotics Invention System, they stopped at the 2.0, and just waited some years before releasing the NeXT generation. I expect the same pattern here. So just go ahead and buy the NXT 2.0.
As for just Mindstorms set updates in general, there was once talk about expansion packs for the NXT kit that were supposed to be released by LEGO a few months later, but that discussion took place several years ago, so it is probably a no-go.

I think saying "there is not going to be a NXT 3.0" is quite speculative, even if your reasoning makes a lot of sense and I admit I would tend to agree to it. That said, even if there was a NXT 3.0 coming, no-one at this point would know when and what, so waiting for it is indeed pointless.

I've update the question's title to state that this question was asked on November 2011 to avoid any other confusion. I think @HaydenStudios's answer is not wrong, as that's relevant as of the date that this question was asked.

I apologize for posting this really late, but I feel that I need to post this for posterity. Prior to January 2013, LEGO didn't specify what their next kit was, people just assumed it was an NXT 3.0 since rumors of such had been floating around the past 3 years. But it turned out that it was announcing the next generation, the EV3, not a newer version of the NXT. So my prediction was correct that the NXT 2.0 would be the last NXT kit.

I was interested in Lego Mindstorm 3 too, so I asked Lego directly. This is what they replied (on 9th February, 2012):
I'm afraid that LEGO Mindstorms 3.0 you inquired about isn't available to purchase at the moment! It might be around soon, but I can't tell you about any new LEGO® toys until they're actually available for purchase!
Well, it might be around soon sounds that it is worth waiting for it and I hope that 2013 will be the new version out.

Go ahead and buy NXT 2.0. NXT 2.0 sensors are compatible with NXT 1.0 sensors and vice versa.
So, I'd expect NXT 3.0 sensors to be compatible with NXT 2.0 sensors. Buy NXT 2.0 and buy individual NXT 3.0 sensors once they come out.

Saying that the future version will be compatible is highly speculative (as is calling it NXT 3.0). For example, while there is some compatibility between Mindstorms RIS and Mindstorms NXT, they are quite different systems. While stepping from NXT 1.0 to NXT 2.0 was basically a refresh (using the same central brick), there is no saying at this time that it will be the case for NXT 3.0, and since the central unit will be different, all bets are off. There's not even any certainty they'll use the same cables (although that would seem a reasonable thing to do)

Well, apparently all elements, central unit, sensors, and motors are new, but the connectivity is the same and LEGO confirmed the old sensors would work with the new EV3.

It's already verified that they are going to release soon. Check with any Lego store . It will be released by  first quarter next year.

Where has it been verified?

Don't know. There's a photo(shopped) 3.0 box floating around (identical to the 2.0 cover with the exception of the gold version number), above the comment "The truth is – We have not heard anything from LEGO. LEGO typically announces new product releases to distributors and re-sellers months in advance.", and there's nothing on the LEGO press site yet...

And now that it's been announced officially, we see it's not for 2013Q1 either but for "second half of the year"


text:
How can I use System and Bionicle elements together?
I have a small collection of Bionicle elements that I would like to incorporate into my System builds but I am a little unsure how to use them.
What are the different ways to use these two types of bricks together?

since the bionicle-pieces only have holes for technic-connections and no studs to use then directly with bricks, you'll have two possibilities:

build some kind of "adapter" using technic-pieces. you could use pegs to connect the bionicle-piece with some kind of technic-brick.
put the studs of your system-bricks into the bionicle-pieces technic-holes - which may not be the best idea

I'd prefer the first option - it's easy, more robust, not controversial and just need two or three pieces in most cases. for example a brick with axle-hole and a small axle or a brick with hole and a simple peg is all you need to get started.

As oezi says, Bionicle elements are usually compatible with Technic connections only, but there are quite a lot of system bricks which have Technic connections as well.
As for what to do with Bionicle elements, only your own imagination can answer that. Once you've an idea about what a specific Bionicle element is going to represent in your creation, how to connect it is usually not the biggest issue. So, go surprise us!
Of course, some green Bionicle elements are best used in wilderness, as they have "wild" shapes — allowing you a little more freedom than if you wanted to build buildings. Giant weapons on the other hand may become a cool building decoration.
The best example I can think of is this palmtree which is just brilliant.

You can also attach the first generation Bionicle masks using their, 'stud,' joint, the second generation masks are a bit looser, and the later masks have Technic connections.
I have only ever used this to provide a texture at the front of a spaceship, but if you have the right masks you could use the gaps to create gun covers, etc.


text:
Is there a database of original Minifigure configurations, including their personal gear?
Is there a minifigure museum? I have a gallon jar (& more) of minifigures that my kids have mixed and matched. Is there a website I can reference in order to put the minifigures back in their original configurations (including their gear)?

Thanks! I'd say you are all correct! I haven't read the book yet, but the websites are great. I'm having a blast.

I perused the websites & read the book review. Does anyone know if the book shows the accessories that go with each minifig? The links show them bare handed.

I'm on the waiting list with the KING CO library system. Hoping to have a definitive answer soon.

Our library has declined to stock the book at this time.

The website Brickset.com has an extensive database of sets, digital copies of instructions and a Minifig database built in cooperation with Bricklink. The layout and style may be a little more user friendly than the Bricklink catalogue and if you register on the site you can keep track of your collection.

The Unofficial LEGO Minifigure Catalog lists every minifigure ever produced, up to 2010.

I must admit, however, that I can't comment on the quality nor usefulness of this book for the task in hand, as I have not actually seen a copy myself. Unfortunately, the cover price is just too high for something I wouldn't use that much. Nevertheless, I hope the link to the book will prove useful to  someone else.

You are right. It is a bit spendy. I imagine it would be an entertaining book to check out at the librairy.

At BrickLink you can browse through, what seams to be, all the existing Minifigures.
This link is the query that seams to returns most of them but you will have to dig around in the other Lego themes(categories) to find the other ones.


text:
How can I minimize the number of merchants for given set of requested bricks?
This question should be answered in Bricklink FAQ, but I didn't find answer there.
I'm a casual Lego hobbyist, I have a few sets with random pieces missing, about two dozens of them. Some are truly rare. What is the best way to find smallest group of sellers having (collectively) all required bricks? It will minimize cost of sending packages overseas.

You can create a wishlist, then view sellers ordered by the number of lots they have of the items in that wishlist.  That should give you a good starting point.

Number of unique lots, otherwise you'll find that a lot of sellers have multiple listings of the same item (often at the same price) because they keep second hand lots together.

First of all, create a wanted list. View the largest sellers in your country, go to their stores and browse by your wanted list. After going through 2 or 3 stores, you will find bricks less common still on the list. You'll have to browse stores selling that brick to get them.

My experience is that finding the largest sellers in any country aren't necessarily the best to use. If you have a wanted list, use the "sort by parts (unique)" page.

Speaking from my experience, this is the technique I used to limit my creation to no more than 5 stores. But yes, if you need specific unique parts, maybe that's not the best idea.

Yeah, it depends on what you want. If they're readily available then biggest shop is likely to work ok. But for any parts that aren't common the big shops are unlikely to have them. I buy mostly Technic parts and even the larger Technic-specific sellers tend not to have less common parts.


text:
Can I remotely control the points on PF train tracks?
I'm interested in investing in power functions based trains, but want to automate switching points. Is this possible? What is the cheapest / easiest way of achieving this?

Purist solutions only?

@Joubarc: Anything else would be cheating! ;-)

@Kramii There goes my Arduino answer...

There is a pure way of changing the points at a track. It requires as few pieces as you like: a motor and two technic beam/bricks. This video demonstrates the principles of point changing with a NXT motor and will work with PF and RCX.

You can use Mindstorms to program the events that trigger the points to change. It will cost you extra, but there are benefits.

One elegant solution is to use pneumatic elements, as a small pneumatic pump is enough to move the lever. If you're lazy to figure out how, you can buy a kit from a fan which will allow you to control 2 points (you'll need one more pump to generate the pressure). With the included instructions, you can build more controls if you have the parts, or simply buy more kits. (He also sells compatible pneumatic hose by the meter, and his custom waggons are nice as well).
His design is very compact, probably much more than you'll be able to get with electrical power; plus, it saves energy. The only drawback in my opinion is the hoses which you'll need to run from your control station to each point, which are slightly larger that electrical cables.

Another typical solution is to use a motor which controls the point. This will take more place, and you have to be careful that the motor doesn't run too far (use a clutch gear). One promising way is to use the new small linear actuator:  which should behave more or less like the mini pneumatic pump; but of course any other Technical solution should be good. Use your imagination, or dive into BrickShelf in search of inspiration.
Of course, you'll need to run electrical wires, or use infrared receivers, but then you'll be limited in the number of points you can control. Note that sometimes, the configuration of your layout means that pairs of switches can be controlled together (think of a bypass to change from one track to the other), so that you can spare some control channels, or wires.
--
Non-LEGO solutions can be achieved with about anything, including solenoids (electrical actuators), which LEGO doesn't produce. One other elegant solution I can think of is to use bike brake cable, but I have no real idea if that would be easy to do.

I don't care about the downvote, but I wouldn't mind an explanation about it either.

I just found this link on another forum.
This is a set of instructions for using a medium power functions motor to switch the point. It is quite compact and is compatible with the infrared receiver.
(page 7 of 8)
http://www.flickr.com/photos/whoward69/3731639719/in/set-72157621512518259/

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


text:
Is there a convention for part and/or set numbers?
Is there any rhyme or reason to the way LEGO part are named? Failing that, is there any other sort of taxonomy that we can use to find specific parts?
Along the same lines, my impression is that smaller sets have larger numbers -- is there any truth to that? Is there anything that we can discern this from either part or set numbers?
Finally, where can I look up all these numbers?

Usually, the LEGO group doesn't seem to have much organisation, at least in the past. That's why you can find sets with two different numbers, or two different sets with the same number.
Now the keyword here is seem, as I suppose there was some logic to it even in the past.
But nowadays there is some logic, and even if not all of it is understandable, you can at least spot some key elements, such as:

When I was a kid and they started the 4 digits scheme, the first digit indicated the global theme pretty clearly. 8 was Technic, 6 was LEGOLAND, 77 were trains, and so on. At least for trains, they tended to use round numbers for bigger sets, ending in 0 or 5.
Now, the first digit seems to have lost its significance, and sets in the same theme are  usually attributed a range of numbers, with the small set getting the lowest number. It's not an absolute rule, and I guess it depends on availability or other factors.
Sets in the 10000 range are LEGO shop exclusives. Usually, you will usually only find them on Shop@Home or in LEGO retail outlets, but not in regular toy stores.
Sets in the 20000 range were used for the BrickMaster series, with each set accompanying a BrickMaster issue.
Sets in the 20200 range will seemingly be used by the "LEGO Master Builder Academy" sets
Sets in the 21000 range are architecture sets.
Sets in the 30000 range are usually small promotional polybags

In addition, there are 7-digits numbers floating around which are probably some other form of internal numbers. For specific things without a set number, that's usually the only thing you'll find.

For parts, you have to distinguish design ID (identifying a specific mold, regardless of color) and element ID (identifies a unique design/color combination).
I don't know how design IDs were or are attributed, but it seems there is now some sequential logic behind it. Note that changes in design which don't affect the functionality (hollow bars at the bottom of 1x bricks, for example) don't usually lead to a new design number (while peeron will append an "a", "b", ... to indicate the version, LEGO doesn't do that internally).
Element IDs used to be a juxtaposition of design ID and color ID, so a Black (26) 2x4 brick (3001) would be simply 300126. These numbers are still around for parts which existed when that scheme was used. 300126 is still the element ID of a black 2x4 brick.
However, at some point (not sure when), they changed this to use a 7-digit number for the element ID, which doesn't have a relation to the design ID or color any longer. These seem to be sequentially attributed, and it could be that they share the same sequence as internal set numbers (but that's just a guess, really). There are also numbers for individual instruction booklets, which ROSCO used to scan for directly on the LEGO site.

As for where to find these, that's more difficult. You'll notice I link a lot to BrickSet, that's because I feel they do a fantastic job of cataloguing sets. Peeron has a good database too, but it's usually slower.
For parts, you'll need to go to Peeron, or BrickLink, but they sometimes differ in their numbering when the official number of a part isn't known. Note that they usually use design IDs and not element IDs, although there is some work in progress regarding that.
Of course, while internal LEGO aren't exactly public, you can find design IDs embossed in elements, and element IDs in the back of all instruction leaflets. Also, the online pick-a-brick and the customer service "replacement part" function let you browse recent sets and see what the design and element IDs are for given elements.

Great answer -- thanks for taking the time. I'm sure many future Bricks users will benefit from it.

@Caleb you're welcome - if you feel it's the correct one, you may want to proclaim it by accepting it, too.

I usually avoid accepting an answer right away so as not to deter other answers. Looks like your answer is so comprehensive that nobody else has anything to add. ;-)

Don't think I don't feel shame for asking you to do it - I too would appreciate other answers, but I don't think it'll happen here.


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What are the practical bounds of a minifigure?
I want to make some minifigure-scale vehicles and devices, but I am wondering what the smallest possible minifigure enclosure might be.
I know minifigures are not perfectly square. Their arms and heads keep them from fitting in a standard 4x1x5 shaped hole while standing upright (not that I would imagine that looking very good in a model). When in recline with the back of their legs connected to studs, they cannot lie totally flat and must lie at a certain angle.
What I would like to know is the practical bounds of a minifigure with NO equipment(hats, parkas, backpacks, ect.):

In a fully upright position
In a fully seated position.
In recline.

It would also be a bonus if anyone would also give the bounds for a minifigure in these positions but with the maximum amount of equipment.

An African or an European minifigure?

I assume you want the bounds for a standard minifigure without accessories and head-gear. Some items (eg. oxygen tanks, fedora hats) make quite a difference to minifig size.

@Kramii Yes, just the basic legs, body and head. I had forgot to mention that in the question. But if any one would like to give some bounds for a maximum amount of minifigure gear, that would improve the answer

@Ambo100 Since a minifigure can not be connected by the back of the legs and be in a fully flat position, its back has to rest on the studs at a slight angle. Like I mentioned in the question, minifigures are not exactly square :/

What exactly do you mean by in recline? Lying down flat or at an angle?

@Ambo100 Since lying flat without being connected by any studs is very similar to standing straight, I imagine those answers could be interchangeable. Lying at an angle with the back legs connected to studs, what I consider to be 'in recline', would be a very different answer.

I go by the the old LEGO adage: What people don't see, they imagine. If you can't see the minifigures legs, you just need the space required to house the head & torso in the model.

Standing
The smallest area you can enclose a standing minifig in is just about 4x4x4 2/3 with the roof on:

To reach this limit, you need to use the panels and windows to make room for the arms and more importantly the head, which is larger than a 1x1 brick.
Seated
To enclose a seated minifig in the smallest space, you will need to ensure that you've tilted the body completely forward (i.e. over 90°), and again use panels to enclose the arms to achieve a 4x4x4 box:

Note that I've had to use two plates to lift the roof above the stud on the head - you can cheat a bit and lower it one plate if you use a roof with a hole in the correct place - in the photos I'm using a 3x4 tile with 4 studs that comes with the collectable Minifigures, and the head stud fits into one of the cylinders underneath, but the edge of the 2x3 plate won't fit.
Reclined
For a reclined minifig, I used a Slope brick, 33° 3x2 to provide some support, and the smallest space I could fit that into was 4x7x2 1/3, however over the legs it's only 1 1/3 (I don't have all the parts to hand to photo this one I'm afraid, but I have proved the concept with some bricks):

With Accessories
Picking the Wizards Hat and Air Tanks, I was able to enclose the minifig within a 5x4x5 2/3 (one deeper and one one higher than the standing minifig):

Again the minifig is angled to fit in this space so that the rim is horizontal, and once again there's judicious use of panels: 1x2x3, 1x2x1 and 1x1x1 Corners.

You have a good answer, but I was looking for multiple bounds, I have changed my questions to make that more clear.

Sorry, yes I meant to come back with the response for sitting upright and reclined - will try and get that out tonight - wanted to ensure that front piece would fit across the hands without them sticking out.

A minifigure with legs, torso, and head would be five bricks tall standing or four bricks sitting down. It's also one stud deep and two studs wide (four studs including arms)
With the arms and hands extended parallel to the thighs, the arms take roughly two and half studs worth of space from the joint of the arm. The image below show's a diagram of a minifigure sitting down on it's side.

If you were to adjust both arms forward like a boxer in a defensive stance (albeit sitting down) the minifigure's arms will take the same amount of room in a different possition.

Note though that the minifig head is wider than a 1x1 brick, which means a sitting minifig needs space behind it for the head - often achieved using a panel.


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Who is (or was) Susan Williams?
I've heard the name "Susan Williams" associated with LEGO products, especially in the 1980s. Who is / was she?

Related: http://bricks.stackexchange.com/a/563/132

Q: All of the LEGO catalogs are signed by Susan Williams. Is she a real person?
A: No...Susan Williams is the personifcation of all those
  helpful Consumer Affairs people who work at LEGO. As for whether or
  not there ever was a Susan Williams at LEGO, we're not sure.

http://www.lugnet.com/pause/legoqa.html

Today I learned that Susan Williams is not a real person.

@BoltClock For some reason, this makes me sad.

@LarsTech I feel like a legend just died.


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What is the first day of the 2011 Star Wars advent calendar supposed to be?
I opened the Star Wars Advent Calendar 2011 early and I don't get what the set on the first day is. I'm not much of a Star Wars fan I guess. I can't identify it as any particular ship and my only guess is it's a part of a bigger set for later.
And the worst part is I can't find it on the box anywhere. Lego is usually really good with the imagery and usually exaggerates the final product (by making it look bigger or whatever) but it seems only a fraction of the 25 mini models are shown on the box.
Has anyone else opened it up?

Hey! It's not even December, yet! I'll bet you're one of those naugty people who eat all the chocolates early, too! ;-)

@Kramii I know! I wanted to build something but didn't have a lot of time. Lego should release a set like this for every month!

I though basic Star Wars knowledge was mandatory in since 1981

I don't have it, but BrickLink already has inventories of all submodels.
According to them, day 1 is a Republic Cruiser. This is a mini version of 7665 — Republic Cruiser.
They do look quite similar for sets of a such different scale:

Sadly, Wookiepedia doesn't have a picture of a republic-class cruiser, but I suppose that's what it is.

Yes! That's it. And the brinklink link will making identifying the rest way easier. Thanks.

Technically it's a Consular-Class Cruiser http://starwars.wikia.com/wiki/Consular-class_space_cruiser I'll get my coat...

It found ir rather puzzling that LEGO would create a ship for which there's no picture. Nice find.

Republic Cruiser

Is this the one you were looking for? You can see the entire selection of mini-models on Bricklink.

I knew I had to type faster ;-)

@Joubarc it's not always the fastest that's chosen ;)

@Zhaph-BenDuguid unless one is seeking enlightenment :-)


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Are LEGO elements safe to use in an aquarium with fish?
Are LEGO elements safe to use in an aquarium with fish? I've never seen LEGO elements in a working fishtank.

One of our local aquarium shops used to stock the TMC/BrightBricks after-market sets as interesting additions to your aquarium.

The main restaurant in the LEGOLAND park in Windsor has quite a lot of LEGO creations in fishtanks. In the same park, the Sealife attraction 'Atlantis Submarine Voyage' has 50 species of sharks, rays and tropical fish that happily coexist with the LEGO models.

Keep in mind that LEGO is safe from children saliva, which I'm willing to bet is more aggressive than fishtank water.

Not to mention Legoland Windsor's Atlantis

Legolan Billand also has an underwater exhibit with Lego in it.

Nice pic. Looks like I have a project.

Even if they are safe, will they remain pristine, though, i.e. how do you keep them from turning mouldy?

Not sure about that, but I suppose some cleaner fishes might help - although they might have trouble reaching some places. I'm afraid your best bet there is to remove your creation to clean it regularly.

LEGO bricks should be safe for fish. Avoid using small parts that they could mistake for food. You also might be cautious on the paint, but I'm sure it's still safer than the paint used on the cheap stuff you'll find at fish stores.

On that note, you may want to settle for normal bricks, perhaps avoid the printed ones. Possibly the older ones (like the old computer screen printed slopes) are less safe than newer ones, and forget any of the stickers.


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What is piece 4211642 from 10179 - UCE Millenium Falcon?
I'm working on making sure I have all necessary pieces for 10179: Ultimate Collector's Edition Millenium Falcon (a painstaking process, to say the least). I received the set not entirely complete, partially disassembled, and without directions.
I'm using the PDF of the directions to sort and count the pieces, and I can't figure out what this piece (4211642 on the bottom) is supposed to be:

(from center of p.308)
I don't have anything left over that appears to match, and the part number isn't of any help. I've even paged through the instructions to see where these five mystery pieces are used, but can't seem to figure it out. Can't find it on the Peeron parts list.
The PDF is of annoyingly low resolution. Can someone with a printed copy help me out here?

Only other thing I can think of is if this is a small part that snaps into another larger part and doesn't come out later, but I can't identify any candidates for that...

The picture looks like the Technic Handle (http://www.bricklink.com/catalogItem.asp?P=424) even though it does not appear in the Peeron parts list.

That looks like it, @Joel. Escalating your comment to an answer so I can include pics...

I just finished building the falcon, and (as we had already determined), these pieces were not mentioned anywhere in the building process. Now what do I do with this huge thing? :)

According to the LEGO customer service, this part is a "BUSH Ø7.84" (which is of no help whatsoever, as with most LEGO internal names) and has the design ID 6221. Unfortunately, there seems to be no official picture for it yet.
This design ID corresponds indeed to the part which Joel Cohen and BradC have identified; the element id of the same part in black (622126) as found by BradC follows the old convention design id + color id (26 being Black at LEGO). And this part at the LEGO customer service does have a big image which would clear all doubt if we had any left:

LDraw and Peeron know this part as 424 - Technic Handle. BrickLink does too but refers to 6221 as alternate item number. This happens often with parts which have no markings whatsoever and for which the official LEGO design ID wasn't known at the time the part was added to the LDraw library.
Why the inventory at both Peeron and BrickLink misses it is anyone's guess, but it's one of the biggest LEGO sets ever so it's bound to have mistakes. Although I see the list for Peeron has been provided by LEGO itself, so it's a bit weird.
Is the part actually used somewhere? I don't have the strength to read the whole manual.

Thanks, Joubarc, for the official word. I couldn't find where these pieces are used in a quick scan through the PDF copy of the manual. Due to the fact they are missing from the 3rd-party lists, plus the fact that no gray pieces are available for sale anywhere, I doubt they are used. I'll update when I have finished building to confirm (might be awhile, I still have to replace 350 missing pieces!)

I've put the UCS Millenium Falcon together, and do not recall this piece at all.  My guess is that's its added to the instructions in error.

Thanks, @Grandpappy. Yours is the voice we've been missing in this question so far, someone who has put the set together.

I think Joel Cohen's comment is correct, it looks like a "Technic handle/hub" (escalating to an answer so I can include pics):

Here's a similar-looking view from the parts list of set 7703 Fire Vulture:

and a portion of the instructions from 7476 Dino Attack that shows how it is used:

So if this is correct, it appears to be a mistake (or misprint).
Can someone confirm for me if this piece was included on the parts list of the actual printed manual? Perhaps the PDF was made from an earlier test build?

I'm currently doing an inventory of many of my son's Lego sets, including the 10179 Millenium Falcon set.  The search for this 4211642 piece is what led me to this site/thread in the first place :)
I've been searching/sorting through all pieces, but can't find any of these...  Me and my son are pretty anal when it comes to not losing pieces, and although it's possible we'd have misplaced one or two, I'd say it's pretty much impossible we'd have lost all 5 (The rest of the pieces are actually all there, which is good!!!).
Wanting to double-check, I went through the whole manual to see at which step this 4211642 piece would be needed but, unless I'm totally blind, I haven't seen it anywhere.  So at this point I think it's pretty safe to assume this is a misprint in the official manual and its PDF counterpart.
Hope this helps!
Jofu

Hi Jofu, welcome to the site and thanks for the thorough research - we all know how tedious it can be to read such a manual without building it at the same time. Note, you don't need to pretend the set belongs to your son ;-)

LOL...  Ok, you got me :D  But for the record, my son does believe it's his :P

I'm trying to assemble the 10179 set by buying the individual pieces, since the prices for the set are outrageous.  I put the inventory of parts from the PDF version of the manual into an Excel spreadsheet to track piece counts and prices.  The total number of pieces comes out to be exactly 5200.  If you subtract 5 for the 4211642 pieces that are listed but apparently not included or used, that leaves 5195 pieces, the official piece count for the set.  So, my guess is that the 4211642 pieces are not supposed to be in the set.

Well, I have the Falcon and I can confirm that those pieces are not included on this set. That print appears on my manual too, therefore it is a simple print mistake. I have built the Falcon three times (only for enjoying) and those pieces still hide somewhere, on the abbism of the box, so don´t worry. You have all the pieces.

You may want to use the bricklink inventory for the set.  But looking through that, I don't see a part with quantity 5 that looks anything like that.

Me either, on either the Bricklink inventory or Peeron inventory list.


text:
Do LEGO bricks float?
Is it possible to build a boat out of LEGO bricks? I appreciate you couldn't make it watertight but would a LEGO boat float by itself due to the buoyancy of the bricks themselves?
Pictures of any home-made floating constructions would be really interesting.

The rowboat from many Pirate sets is known to float, along with a couple of minifigs, treasure and other elements on board.

Could you use cling film (plastic wrap in the US?) as a seal between the bottom layer of bricks?

Also, what about glue? (I realise this might not be so practical).

@UmberFerrule Gluing Lego?!?!

Oh dear! Have I blasphemed?! ;)

@fredley Sure, if you want to put 'angry eyebrows' on your giant LEGO robot of doom.  .\ _ /.

Lego boats like the ones shown below float, not because the bricks are buoyant, but because the model displaces water.

The plastic is a bit heavier than water and should sink, however in practice I have experienced that 2x4 bricks (and the like) have a tendency to trap air inside them and actually float rather well.
It probably isn't failsafe, however for shorter periods of time (like a half to a full hour) would probably work fine.
(I haven't actually tested the time it could stay afloat, I'm trying it out now. When my small mini-boat has sunk, I will add the time here.)
Update:
24 hours have passed, it is still floating.

It sunk about 1mm compared to the beginning, but nothing of importance. However while I did push it around from time to time, it was still in still water and stationary most of the time. How it will perform during play is unknown.

Notice how the internal structure of the bricks causes the air to be trapped inside them.

A few years back there was this solid single-piece hulled police boat which would float.
There was also a small red boat (pre-2000) that came with part of a pirate set (I believe, anyway)
As for building a boat from scratch...no. It tended to capsise then sink (somewhat impressively). Place 2x 4x2 bricks on another and place in water, they only float on their side. I expect this is down to a center of gravity but I'm not a sciencey type so I can't confirm for sure.

There is also a brown variant of this red boat.

In fact, it comes in more than just two colors. Probably four or so (blue and black?).

@PaŭloEbermann: The brown variant is actually more popular.

There are several other floating boat hulls (or small boat, inflatable boat, canoe...). Maybe it's worth mentioning that some  of them are are in many pieces (http://www.peeron.com/cgi-bin/invcgis/psearch?query=boat+section&limit=parts).

Yup, I have one red and one brown of the boat shown above and they came with a 1990's pirate set. Don't remember which one though.

I had a Police-Boat when I was a child that had a one-piece-body, so it was watertight and able to float:

There are some other LEGO-boats with similar bodies (even some bigger ones) that should also be able to float.

My brother had that set as well. The body was actually three pieces, not one -- front third, middle third, back third. But each third was watertight and buoyant.

It's actually a three-piece hull: bow, stern, and.. uh.. middle. My brother and I had two of these and one fire boat. Made a great trimaran.

There is another not mentioned way to achieve flotation. My kid discovered it today with his "water bat": surface tension. The long flat wings did the trick : ) It is not exactly due to the buoyancy of the bricks themselves as wanted in the question, but might help as a complement.

For more on the Physics underlying:
Surface tension

In addition of the various boat hulls, you can use pneumatic tanks for extra buoyancy.
If you want to motorize your boat, keep in mind that means extra weight, which has to be countered in some way.

My kids had Captain Redbeard's Pirate Ship - it certainly floated in the bathtub!

I believe many of the other Lego pirate ships could float, particularly if they had molded single piece hulls - see this list.

My children play with the lego fishing boat (see picture) in our bath tube. This design does have a serious flaw (imo). Even if there are very small water waves in our bath tube, water enters the boat which then becomes to heavy and sinks. So if you are planning to built your own lego boat i would make sure the sides are high enough to prevent water from entering the boat. Or if you are really clever make a water drainage system like normal boats have.
Lego fishing boat 4642

You also asked for some examples. Found this simple but effective example online.

For a very small "boat" - something like a 4x8 plate with 1x8 and 1x2 brick sides it might stay afloat for a short amount of time before the leakage takes it down. For larger stuff, LEGO is just too heavy when you get in to building the necessary structure for a real boat.
There were some sealed-hull boat sets I remember from childhood that were designed to float, so using the special parts from them would make it possible.

Already a correct answer accepted, but... the original question seems to be "do Lego bricks float by themselves?"
Most Lego bricks are made of ABS plastic which has a specific gravity greater than 1 (but only slightly).  So, they are heavier than water and will not float naturally.  You can get small bricks to float initially since small bubbles cling to their surface, but they will all sink eventually.
Since ABS isn't affected by salt water - it might be possible to increase the salinity of the water to a point where the bricks naturally float (would need to be higher concentration than sea water...)

Whilst a solid block of ABS would sink, LEGO bricks are hollow. The issue of floating is displacement - this is how steel and iron ships float - they displace as much water than they weigh, and so are buoyant.

Yup.  But I'm not sure the brick connections are water tight.  I can imagine lots of designs using plates that will still let water into the "hull" I am more pointing out that you don't need to be all that water tight for the boat to actually float.  Sebastian Wahl's answer nailed it tho! :-)

True - the fact that they aren't water tight was demonstrated very well by James May when he built his LEGO house, complete with wine glasses that leaked red wine everywhere ;)

Yes, if built carefully.  When I was a kid I made a number of lego boats to play with in the tub, and later in the pool. The main thing I remember was to make the hull upside down and out of at least two interlocking layers. Lining the inside with plate also helped.

Styrofoam bits trapped in brick-built chambers might work Ok to keep structures afloat.

That would certainly work, but I don't think that there are any LEGO Styrofoam parts. The purist in me tells me that I must use LEGO only.

I'd have to say that in general, only the parts that are designed to float will do so reliably.  You may be able to make some sort of raft by inverting several large bricks (studs down).
I haven't tried Lego bricks in water (other than a police boat set), however, when using Duplo's in the bath tub we were only able to make submerged structures.  The water easily seeps into the bottoms of the bricks and causes them to sink.

Yeah they float but make the hull wide not narrow as it will stay up right if you make the hull wide. Narrow means top heavy. I first started making LEGO boats now I make home built boats. And no need to be water tight for LEGO just get more surface area. Who knows you might even be able to make a cruise ship that floats.

Yes, just as long as the bottom is able to displace the boats weight onto the water.. Just like how a Polar Bear can walk on thin ice; displacement.

I think you don't mean 'thin ice' (Polar bears can't walk on thin ice, they fall through because they are heavy), but 'iceberg', where the buoyancy required to keep the iceberg afloat is provided by displacing an equivalent mass of water. Still: Wha?? That's the weirdest analogy ever.


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How many spaceman minifigure variations exist?
I was looking at collecting all the different Spaceman minifigures.  So I'm wondering how many different types(styles) of Spaceman do exist.  Color variations is not necessarily but it would also be interesting to know that.
Note: Only astronauts (not robots & aliens)
So far I only have those three:

Do you want astronauts, or everything including aliens and robots?

@Pubby8 Only astronauts (I'll edit the question)

I sometimes play with my Star Wars Clone Troopers as astronauts.

I know this is an old question, and also that you specify minifigs, but you may be interested to know there were maxifig astronauts in 1975's set #367 Moon Landing

A full list of space related minifigures can be found on Bricklink here as well as under the Town theme. If you count fantasy themes there are also many astronaut minifigures under Alien Conquest, Blacktron, Life on Mars, Mars Mission, Space Police, etc...
There is also the Spaceman from the 1st Collectible Minifigure series.

I hadn't thought about the town ones - good catch.

I can't find the Apollo figure in that list(site). Still looking...

@pcantin: That's under a the Discovery theme

Not sure if you would include the Futuron Astronaut or Classic Space Astronaut in this list (image courtesy of http://www.toplessrobot.com/2009/05/the_30_greatest_lego_minifigs_of_all_time.php?page=2):

I had several of these as a kid - I remember black, blue, yellow, and red variants.

They also used the following helmet variation in Series 1 of the Minifigures set:

I also have the limited edition orange Lego Universe Spaceman that can be seen here:

Neither of these came with backpacks.
There is also now the Minifigures "Galaxy Patrol" style spaceman which started appearing in Series 8:

This combined a new helmet with the much enhanced backpack/shoulder armour element.


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How does one get a job as a LEGO designer?
I always fantasized on the mysterious (and admittedly cool) job of LEGO designer. Is there anyone who knows what it takes?

Do you need to go to the Lego university and get good grades?
Is there any Job post in some secret place?
Do you get a job by being on the LEGO fan club for long enough?
Or do you need to participate in competition and get recognition for your own designs?

I have something to contribute that does not justify an answer…As stated in (I believe) The Ultimate Lego Book (I've lost it so can't be sure, but it details the model maker/designer recruiter process), one of the stages a would-be designer has to go through is, when presented with a set of generic pieces, having to construct a model that is as imaginative as possible.

There's a nice interview with LEGO Designer Mark Stafford on The Brothers Brick:

From LEGO fan to LEGO set designer - the Mark Stafford interview

The basic process was:
The position was advertised, and Mark's portfolio was sent in. He was then invited to a two day recruitment workshop along with a number of other candidates.
I've also read other interviews such as this one from The LEGOLAND Discovery Center asking about how Alex Bidolak became a LEGO Master Model Builder, and he came in through the competition route.

Pierre Normandin followed the path of "well-known AFOL doing tremendous sets" to "AFOL invited by LEGO to participate in secret projects from time to time" to "Actual LEGO designer" (I'd like to say "demigod", but he tends to frown at me when I do that). He was also one of the first groups of LEGO Ambassadors.
But in any case, the most important criteria is, you have to be a tremendous builder. The next step is to make LEGO know about you one way or the other, but if you are a tremendous builder, chances are they will. Then, you have to inquire about job openings and of course, apply. In that respect, I think his path is similar to Mark Stafford's.
LEGOland parks sometimes fill they openings through competitions, but I don't think Billund does that.
Edit: by the way, the job postings aren't in any kind of secret place, but quite easy to find on the LEGO web site (I think they're in category "Product Design/ Development"). Of course if they happen to search for candidates for other jobs in your own area of expertise, maybe being already in house is a good path to reach the designers team, too.

I participated in the Master Builder competition. Winners were potentially offered jobs as Builders and Master Builders. The position was advertised on the LEGO job boards and the competition in question was held in LEGOLAND California.

Can you possibly fill this answer out a little, more detail on what "THE Master Builder competition" was, where and when etc, why they are never going to hold another one, and how being a Master Builder could lead to working as a designer for TLG.


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How are LEGO bricks categorized?
What are the names and categories of LEGO bricks? Is there a consistent naming scheme? Does Lego have an official name or identification for different pieces?

It's been worked out by multiple groups who decided on different systems. The disagreement is based on what information was publicly available from the Lego Group at the time, what pieces had been manufactured up to that point, and what features the category authors thought were salient.
To really appreciate the magnitude of the problem, just try classifying every part in your own collection. Make your own categories or try to follow somebody's elses. You will raise a lot of questions about how broad the categories should be. Everybody with a storage system goes through this.
Existing Classification Schemes

Consider BrickLink's categories, which are up to 188 categories containing 25,096 parts as of this writing. In this scheme, there are no subcategories, only 2 levels. The category Brick covers 70 parts, but has 7 co-categories like Brick, Decorated (1356) and Brick, Round (38). Brick, Round shares some close neighbors in a separate group, Cylinder(47) (both terms inherited from LDRAW, by the way.) You could reasonably argue about membership characteristics for classifying under Brick, Round or Cylinder or even whether there should be two groups.
LDRAW, originated by James Jessiman), didn't categorize parts hierarchically, but for many parts the first word or two makes a genus.  Programs such as http://mlcad.lm-software.com/ displayed some of these categories in a menu but invited you to think of the big list "like the rummage in the Lego box." As of this writing, LDRAW covers 5,377 parts.
Peeron is an example of an exhaustive set database using LDRAW's part numbers and names. Peeron didn't introduce a hierarchy of its own.
PartsRef, by Steve Bliss, a major LDRAW parts author, attempted to categorize the LDRAW parts hierarchically. It had 22 top level categories, for instance: Architectural, having subcategories like Doors. However the Plate category remained undivided and included all the plates with various protrusions.
LEGO Digital Designer is a newer example with its brick palettes (sorry, I'm not a user.)
Pick-a-Brick as of this writing uses 42 categories, some of which are very broad. For instance, "Brick, Special" is one category (currently 155 parts) that other schemes divide into various groups for round bricks, modified bricks, cylinders, hinges, cones, etc.
Auczilla by Todd Lehman and Suzanne Rich (circa 1996-2000) had another exhaustive parts scheme that excelled in its use of geometric adjectives for part names, such as Half-Octagonal (debatable on math grounds) and Quarter-Round, Convex and Concave. The link is from Internet Wayback but shows the top categories.
Finally, Technica (1999) was another attempt at classifying just Technic parts.

In the end, some parts are placed into categories primarily by geometry, others by function, yet others by historical origin. You could also conceivably group bricks by building function (I'm thinking of direction-changing rectilinear bricks) or even by simply the number of studs (I'm thinking of a Kanji dictionary.)
Part Names Make Classification Muddier
Consider the language barrier: if you read Lego's English Pick-A-Brick names, you realize it's translated (from Danish). A major category is "Brick, Bow"  also known as an Arch.
Dome

Consider 30367, LEGO's "Final Brick" filed under Bricks, Special. Perhaps they meant Finial? LDRAW calls it a Cylinder with Dome Top. BrickLink puts it under Brick, Round (remember BrickLink has both categories Cylinder and Brick, Round from its LDRAW heritage.)
Jumper Plate

Jumper Plate is one name that made perfect sense to Europeans but baffled Americans; to James Jessiman (Australian) it was a Plate 1 x 2 with 1 Stud. I recall Auczilla used the adjective Offset in there. In Pick-A-Brick it's now a Plate 1x2 With 1 Knob. Or should it be a tile because it's mostly flat?
Loudhailer

Then there are multi-purpose parts: describe 4349 geometrically and it's another cone. But it could be a Minifig Weapon, or just Minifig Utensil. In LDRAW, it's a Loudhailer and has no category as such. The American term would be a Megaphone but many know it as Star Wars Blaster.
Multiply this complexity by thousands, and you get an idea that the task of naming is never settled.
Part Numbers
Many LEGO bricks have part numbers imprinted from the mold. This is now called a "Design ID" by LEGO. It served as the original basis for LDRAW part numbers. However, LDRAW invented its own numbers for parts with no number.
About the year 2000, LEGO introduced a 7 digit "Element ID" to designate a particular design in a particular color. These numbers began to be used internally at LEGO for Building Instructions software, and externally in LEGO Creator software products. They are now shown in official set inventories and in Pick-A-Brick.
Conclusion
This should give you an idea why different name and category schemes don't align. We start by talking about the same LEGO pieces but we bring preferred names from childhood or later (I always referred and still refer to 1xN bricks as 1-bumper, 2-bumper, etc.) We group them according to geometry or function, but find new reasons to subdivide or revise to make the groups more intuitive. New parts challenge these categories.  LEGO does not seem to have given the problem much thought or care, lumping parts into catch-all categories. I derive immense satisfaction from solving a problem of devising a part's genus and differentia, but I realize that just like in the taxonomy of living things, there is competition between systems, and endless revision.

Good answer Erik, but your final sentence show us the problem that this question originally set out to answer: if you suggested I use a 3 bumper I wouldn't know what you were talking about, similarly for others if I were to say a 3 beam.

Should have said "last paragraph".

Last couple of comments: 1) Thank you ever so much for supplying those links, I'd only found a couple of them previously. 2) As to the lack of sub-categories, I think that's more a hang-up of the web1.0 nature of those sites - it's hard to represent a hierarchy in a drop-down list - I'd see Brick, Round as a child of Brick for example.

Our categories are:

brick
shaped
mechanical
people
people tools
finish

Then L, M, S within each of these. Brick is any rectangular prism, flat or otherwise. Mechanical are any that can spin or move when connected.  Shaped are not mechanical or brick. People tools are anything that fits in a LEGO hand, not otherwise mechanical. Finish are smooth pieces that can not hold another piece on top.
My kids are 9 and 7. Its taken us that long to come up with the system,slowly over time. I'm utterly disappointed with moms who think color sorting is comparably useful. My goal is to be able to find any piece easily when boys put together each set to sell in their 20's.


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Why does the Erling brick have a ridge below its outward facing stud?
Why does the Erling brick (#4070) have a ridge below its outward facing stud?

Whereas the more versatile and less common #87087 does not? The #87087 piece also has a better use in SNOT usage, as it can accomadate larger bricks.

The ridge is there to make the base the standard 5LUs wide (see also "What is an Erling Brick"), enabling it to accept the standard stud.
I believe the rest of the brick was thinned out so that the combined "depth" of the Erling brick and a 1x1 plate (its common usage as a headlight) was the same height as a standard brick.
From the HoMa's World of Bricks page on the Headlight Brick:

If headlight bricks are turned over by 90° and a plate is attached to the stud then this construction is as high as a standard LEGO brick or a layer of three standard LEGO plates.

It also helps to keep the 1x1 plate straight to the bricks edge.

Good visual explanation.  Amazing little brick.

Props to HoMa's World of Bricks for the image.

I've never seen that brick used that way.

There are a couple more uses as well.  Two Erlings one stud apart can have a horizontal brick connect them.  And you can use 8 to make a cube to which 2x2 plates can be attached (about the size of a Lego die).  Very useful parts!

@Ambo100 The Cusoo Delorean uses them in this configuration

The first use I personally encountered was in 6394: See the top left corner in step 7 of the instructions: Metro Park & Service Tower


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Is 'plate between studs' SNOT supported by one of the LEGO building software?
Do any of the multiple LEGO building software supports 'plate between studs' SNOT assembly?

I presume it must be considering it has been rendered on this page.

@Ambo100 I'm looking for a virtual building software (like LEGO Digital Designer or LDraw). Your link (even though I didn't know it and it's really cool) seam to be a SNOT technique listing

That's right. I was hoping to find more information on what software was used. All I know for now is that it IS possible.

...or it's Photoshopable :)

To build your example in MLCad (LDraw), I needed to switch to "Grid Fine" to move the element into the right alignment:

A couple of techniques to note when doing this when you finish with the SNOT modeling:

Set the grid back to coarse so that subsequent pieces are back on the grid.
Select a non-SNOT element (in this case the 2x3 or 2x2 plate) before placing the next element - grid alignment and rotation are inherited from the last selected piece, so this gets you back to "normal".

See also Joubarc's renderings for my Heroica Graveyard question, again from LDraw by the looks of things, with the elements are added within the clips or between grills in the radiators:

Yes, I did use BrickSmith instead of MLcad, but the same principle of using a fine grid applies. Since neither checks for validity, you can do pretty much whatever you want (including impossible things).

I'll have to check that out - it looks like a better default renderer. For simple things like this I can't be fussed opening in LeoCad, exporting to .3ds, and then setting up a scene in 3dsMax to render shineys ;)

Hmm, scrub that, it's Mac based ;)

Actually, BrickSmith is a LDraw editor only. I did the rendering with LDview which appears to have a windows version too.

Yep, I've played around with LDView - most of my models on here are just screen grabs straight from MLCad.


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Are Samsonite gears compatible with modern Technic gears?

Do the old Samsonite gears (above) work with current Technic gears (below)

LEGO bricks tend to be backward compatible with older bricks, but since I don't own any Samsonite gears I cannot tell.
Image credits belong to Technicopedia.

Image credits belong to Technicopedia

I loved the samsonite gears - they were much better for flexible geartrains. The photos are bringing back great memories

This confuses old LEGO gears (positions 1, 3 and 5 with red in the center) with Samsonite gears (the uniformly colored ones in positions 2, 4, 6 and 7). I don't think they even mesh, but as I don't have Samsonite gears I can't check.

As @starblue says, there were actually 2 types of gears made in the 1970s. This page provides more info: http://www.miniland.nl/Historie/legoautos/samsonite/samsonite%20gears%20eng.htm

@Kramii: Oh, wow. It looks like the actual Samsonite gears required   a technic pin or something similar. Any ideas on what I should call these gears?

@Ambo100: See my answer, below.

The first gear wheels, or cog wheels, were designed by Knud Kristiansen around 1964 or 65; the original Danish design patent was filed on March 1, 1965.
Under licence by LEGO, Samsonite manufactured and sold these gears in the USA from 1965-1972, and in Canada from 1965-74. The gears had studs on the top and tubes on the bottom. They could be made turnable by fixing them to wheels with studs or turntables. These gears were never available in European sets.

A different type of gear, incompatible with Samsonite gears, was produced by LEGO in Europe between 1970 and 1975. Although the gears themselves are incompatible with technic gears, the axles that held them in place had the same cross-section as the axles for technic gears. This means that mechanisms can be constructed that use both types of gears.
Interestingly, the gears had a small circular spring in them to help them grip the axle. If I remember correctly, the ends of the axle had a groove that aligned with this spring, making the gears a slightly more stable fit at the ends of the axles than in the middle.

Modern Technic LEGO was then introduced in 1977.
Sources:

LEGO System by Samsonite: Gears
001 Gears?
Technica - History

They are not compatible, the teeth are completely different.
Notice that the red old gear has 9 teeth and is the same size1 as a current 24-teeth, as illustrated by below:

The axle hole however is compatible, so you could have a construction using both types.
1. Actually, the distance between axles to have two of these red gears mesh is the same as the one required for two 24-teeth ones (60 ldu).

Wow, Considering that's the smallest Samsonite gear, the rest must be huge.

I had some; the large of the yellow ones were about 3" wide or so.  I don't have one on hand to measure so I can't be more specific than that.

The visible holes are spaced like studs on plates, so the largest red one is larger than a 2x10 brick.

The red gear on the left is not a Samsonite gear. It is a European gear from the 1970s. This was different from the Samsonite ones (and incompatible with them).

@ConcernedOfTunbridgeWells  They are not that big, the red, blue and yellow LEGO ones have an outer radius of 2, 3 and 4 studs, respectively. This translates to diameters of 32, 48 and 64mm (actually 2.7mm less so they can move freely).

I had some doubts on the "samsonite" issue but I just assumed the question was correct and didn't bother to  check. My mistake.

@Starblue - my mistake.  I had lego gears, not the samsonite ones.


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Does anyone have any successful techniques in searching for lego bricks in a pile?
We typically tip our box of Lego bricks onto a giant sheet (so that it can be easily picked up) but searching for bricks becomes really tricky and time consuming. You often remind yourself, "you'll find it once you stop looking," but is there more to it than that?
Are there ways to look through the collection more closely? I guess in a sense, are there ways of skimming the collection that help you spot that particular piece? The easiest trap I find is to look for colours because there aren't that many colours... looking for the shape would be better, but it doesn't seem to help.
Likely the best option would be to spread the pieces out so that they are all visible, flat on the ground, but that isn't practical space wise.

Actually just noticed this in the instructions for one of the items...although it won't necessarily scale for a crate of Lego

Properly sorting is the best solution, although it doesn't seem like that is what you want.

Before starting, it helps to have a quick look through the pile and pick out any interesting bricks you might use. If you don't have your mind set on an exact design, it can be just as much fun to build using parts picked out before hand instead of constantly searching.
Once you start building I recommend building as much of your creation before searching - keep track of a list of pieces that you need. If you can't immediately find an important piece, then use a temporary one that has the same functionality. Once you're done, go through the pile looking for each piece you need. It will be faster to look for several pieces at the same time as opposed to one.

For the actual sorting, I use the most distinguishing feature of the piece. If it's a unique color, then use that. If it's a strange shape look for that. The method I use for searching in a random pile is to focus on a small area - once I have verified that the piece isn't there I'll separate the area from the pile and move onto the next area. This prevents looking over the same area twice.

One thing you could do is to presort your Lego bricks. Take your giant pile of Lego bricks and try to split it up into 5-10 categories.
Those categories could be color, size, or any other features, it doesn't really matter. (I'm a Technic builder, so I would sort them into axles, pins, pin-connectors, beams and gears for example.) To get the best results these categories should be as close to equal in size.
Presorting might seem to be a bit of work, however next time you need a brick it will be several times faster (roughly equal to the amount of categories) to find it since you only have to look through a subset of bricks. One you have done the presort, you don't need to do it again (until you trow them back into your box) so it makes most sense to do this during a building session where you might need to look after another brick in the near future.
Remember that your piles could contain sub-categories, if you had sorted after color you could use size to skim through the pile in order to find that brick. You could also split those up into even more sub-piles if you wanted. The more you sort, the less time you need to search after bricks, however you will spend more time during your presort. Try to experiment and find a balance between sorting and searching that you like.

In order to not presort more than necessary, do the presorting while you are looking after a brick. Like Pubby suggested, take a small area and look through that. However instead of simply trowing them into a separate pile if you don't find it, sort them into your category piles. Continue this process until you find the brick you were looking for.
Next time you need a brick, look through the incomplete sub-piles first to see if it is there. If not, continue with the giant unsorted pile like before, presorting your bricks until you find the brick.

Some hints that work for me:

Get to know your lego. There is no point looking for a component that isn't there.
Get someone to help you. Sometimes other people can spot what you've missed. Small people often have sharper eyes than big people. My 7 year old son can spot things far more qickly than me.
If you're looking for a small piece, it is almost certainly at the bottom of a collection of larger bricks. So, for small components, dig deep. This should also work when you've spread the components out, but is especially useful if you're searching through a big box. In fact, if you gently shake a box of parts to encourage the big ones to rise and then rapidly invert the box onto your play area, you'll probably find that you get a nice layer of small bits on the top of the heap.
Store parts in a big plastic container rather than a cardboard box. Otherwise you'll eventually find the part you're looking for under the flaps at the bottom of the box.
As others have said, you can't really avoid some kind of sorting, even if it is primitve on-the-fly sorting. For this reason, some of thie ideas in this answer could help, even if you implement them as you're looking for parts rather than when you store your lego.
Pull out the big base boards and any instructions etc. that get in the way of your looking for parts. It is also worth pulling out any cables or string as they can be annoying to look through, too.
When you see pairs of parts that belong together, stick them together. For example, wheels and tires, windows and glass, aircraft wings etc. That way, when you've found one you've found the other.
Similarly, when you take things apart, leave 'interesting' assemblies partially built. It is sometimes easier to find what you're looking for when it is stuck to something else. For example, leave minifigs assembled, even if you anticipate needing their parts in a different configuration in the future.
When you're looking, look for several parts at a time.
If you find an interesting part, pull it out and keep it separate, even if it isn't what you want at the moment. Chances are, there parts will stimulate your imagination and you'll want them anyway.
Start building a proper system for organising your parts. For example, my son keeps his minifigs and their gear separate from everything else.
Sometimes you can't help but look through every part in the heap. If you end up doing that, divide the heap into smaller, more managable sections and paw through them one at a time.

+1 great tips, particularly the divide into smaller portions of mishmashed bits

You may want to use a smooth surface on which elements can glide easily without being scratched This allows you to move unwanted parts around quite fast so that you can find the one you're after.
But I agree with others, ultimately you'll need to sort. The smooth surface can help here too, and one good trick is to focus on retrieving elements which are abundant first. But don't over do it, if looking for, say, 1x2 blue bricks is easy because you see a lot of them, fine, take them out first; but don't try to catch them all, these are no pokemons. Once you don't see them so easily anymore, switch to something else.

I also don't like bins of parts.
So what I do is sort by shape, in "crystals" - assemblies of each shape all connected together.
Then
you can put these assemblies in your big bucket, where they will stay
(mostly) connected together.

Here's a post from EvilMadScientist which describes the basic idea:
http://www.evilmadscientist.com/2008/how-to-organize-your-lego-bricks-for-efficient-building/

I bought a desk organizer insert with 9 bins in it. I put parts with the same color in one of the bins.  If there's a lot of one color, I split it into another bin by size or type. If you're building a set, you can do this bag by bag as you work through the instructions.

if you are building a set you can build multiple sets at once so If you get stuck you can go to another set and start searching for the piece and building


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Firmly connect bricks in a triangle
I need to connect two bricks onto a plate such that the plate is facing up, and the two bricks are facing out from above it at an angle (say 30 degrees) but are connected firmly, at opposite ends with their studs facing out.
Ideally this would fit in around a 2 x 4 brick size, and not be too fragile.

The top image shows the two plates (assume 2x2) facing out at an angle from the 4 by 4 plate below.
The bottom image is the same from above.
What I'd like to figure out is what to put in between. Assume that there will be stuff attached to the 2x2 plates, enough that the standard 2x1 hinge will probably just flop.

A drawing would be nice

Can the two angled pieces be connected to one another? That would strengthen the overall structure.

The triangle is Isoceles, but not equilateral. The two angled pieces are not at 90 degrees to each other.

How firm does it need to be? Wouldn't something like this be enough?

If not, you can try to lock the parts into place with "cheese" slopes, but it's not as neat:

That should work. I'll have to dig around to find the 2x2 tops for the hinge, I definitely have cheese slopes  - if I can find grey or dark blue ones - I think the bottom assembly would be perfect.

I'm not quite sure what you mean, but could you use hinges?
Like these?

Perhaps click hinges - but normal hinges are too floppy. I am going to put together a drawing later (no scanner handy) to explain better what I want to achieve. That looks like an old hinge - the middle finger is missing.

@DannyStaple: It shouldn't be floppy once it's built, since it forms an equilateral triangle it should  hold well.

Not sure you can make a 60° angle with these, though. Seems too acute.


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How much depth does the NXT battery pack add?
The NXT rechargeable battery pack does not fit flush with the back of the NXT brick like the battery cover (used with 6xAAs) does.  I don't have the battery pack (yet), so I was wondering how much depth it adds.  I found a picture of the pack installed, which gives the impression that it may be a brick taller, or maybe only a stud taller.  Exactly how much though?

It adds the same thickness as a studless beam indeed, or 8mm / 20 ldu.
(This is true for the grey 9VAC battery, but I suppose it holds for the white 10VDC one as well)

My white 10VDC battery pack arrived today.  It adds the same thickness as a studless beam, same as the 9VAC battery pack.


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Which sets can be built in the bag (all the parts are in one bag)?
I've had the chance to participate in some "build in the bag" contests at some events. The idea is simple: each contestant gets a small set (usually provided by LEGO for the occasion), and everybody tries to build the set at the same time.
The trick is, the contestants may not open the bag but should build the model inside it. The first to finish wins some additional prize. You can also up the ante, PLUG did for example do this underwater.
However, this does require that all parts of the set are in exactly one transparent polybag. Small racers sets (the one in plastic boxex with a round top) are usually suitable, but we've had a club event where we wanted to do that and there was no polybag (the first to open his box spilled the contents on the ground), so we had to find some other contest (I think we ended up with one-handed build or build without plan).
So my question is, which sets are known to have all parts in one polybag? Is there any way to find out?

How about 'What sets can be bag-built?' for a title?

Looks like there was a custom bag built for the ISS model that was taken up to the station, which probably doesn't count: Satoshi Furukawa with the LEGO Brick Kit aboard the ISS

The ones I know of:

8072 - Sea Jet
8400 - Space Speeder
8398 - BBQ Stand
5611 - Public Works
5762 - Mini Plane
7241 - Fire Car
8130 - Terrain Crusher
5618 - Troll Warrior
to be continued...

In addition, some LEGO Creator sets, with only partly transparent bags are possible to build in bag, like this video shows - but it gets a lot harder.
Rather then listing all of the sets, I'd go by the general rule that sets that are 9.5cm x 9.5cm x 4.5cm or smaller are in one bag (or just in the box). The Court Jester (7953) for example, is one exception in that the Jester hat is packaged separately.

I suppose we can exclude bigger sets (or sets with more than x pieces, with x to define), but there are a lot of small sets (such as the one you mention) which don't qualify, and that's a problem.

Some of the bigger sets will have one bag per part of the set, for instance this train set where the platform can be build from one bag.

There are some "advent calendar" sets (as in, a box containing 24 polybags behind "doors" labeled 1 through 24), I have done some bag builds with one of those.

Brickset has a feature to allow you to search sets by tags, which is incredibley useful as you can find a full list of Polybag sets.
The list can be sorted in various ways. You can sort by year (descending) to find the newest sets that might still be available to buy, or which polybags have the most pieces and will probably be the most challenging.
Some of these are simply bulk bags of bricks which you can ignore.

The three largest polybag sets are limited edition from the Master Builder Academy series. These polybags were originally only available in the US as part of the LEGO Master Builder Academy subscription.
The largest polybag set is the #40178 Exclusive VIP Set released in 2017 with 205 pieces and two minifigures.


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Did LEGO recently change Millennium Falcon with a smaller kit?
I have been interested in a Millennium Falcon kit but was holding back because of the price.(It was about €500) This was about two years ago.
Recently I saw another, cheaper Falcon for about €150, but I think this is a different, smaller kit, and unfortunately the only available Falcon.
Did LEGO really swap the Falcon kit for a smaller, cheaper version?

The Millennium Falcon has been so popular there appears there are six known sets, and seven versions. Four of which share the exact same product name.
Millennium Falcon, 2000 (7190) 600+ pieces
Millennium Falcon, 2003 (4488) Microscale version with only 87 pieces.
Millennium Falcon, 2004 (4504) 900+ pieces (New minifigures with the flesh skin colour).
Ultimate Collector's Millennium Falcon, 2007 (10179) 5000+ pieces
Midi-scale Millennium Falcon, 2009 (7778) 2nd microscale MF with 4x more parts then the 2003 model.
Millennium Falcon, 2011 (7965) 1200+ pieces
Millennium Falcon, Advent Calendar Day 21, 2011 (7958) 13 pieces
There also appears to be some Minifig variation, R2D2 and Darth Vader only appear once on the 2000 and 2011 sets respectively.

The scary thing is, I have the first three on that list ;) Had small children when the UC version came out, so couldn't justify it :( And the 2011 one's close enough to the 2004 one that I can't really drum up the enthusiasm. Don't get me started on Slave I's though ;)

There is also a Millennium Falcon in the Star Wars advent calendar.

Just for curiosity, what is the difference between 4504 (2004) and 7965 (2011)?

@abatishchev: A large difference in style, parts and overall price.  The minifigs are also more complex/detailed