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How much does a LEGO brick weigh?
I am trying to do a science project and I need the exact weight of one of the LEGO pieces.  I am using it as a counter balance on my scale.  What is the weight of a 1x4 LEGO brick?

In most cases you can find the weight of a brick from Bricklink an unofficial LEGO site that takes weight measurements from user submitted data. Bricklink states the 1x4 brick as 1.64 grams in weight.
LEGO bricks tend to be odd weights because the design process primarily focusses on the physical aspect. A 1x8 and 2x4 brick both have exactly eight studs, yet the weight between them differs  by almost a gram.
In the interest of scientific accuracy, I would recommend weighing the bricks yourself with digital kitchen scales to confirm the weight.

Over the years the design of the bricks has changed in terms of the internal reinforcement of the bricks (as seen from the underside of the brick), so you'd definitely have to measure yourself.

The best way to get an accurate weight measurement is to weigh a larger number of blocks and divide the total weight by the number of blocks.

This is a classic example of area vs perimeter. 2x4 has a perimeter of 10, 1x8 has a perimeter of 18. So since bricks are mostly hollow on the inside, the 1x8 is much heavier.

"How much does a LEGO brick weigh?" is a seemingly simple question, but the answer quickly spirals into complexity.
I work with many hundreds of identical bricks fairly often.  To count these out accurately I use high precision scales (0.01g), but I'm never confident about the counts.
Be aware that as well as variations in mold design (which other answers have pointed out), even pieces from the exact same place on the same mold can have different masses. Different colours of LEGO have different densities, so even for the same volume of plastic you'll get different weights.
I commonly come across sets with two different moldings, for example with the rods in the underside of bricks being hollow or not.  The reason for this is that mold designs are changed when designs with better characteristics - typically plastic consumption, but possibly heat dissipation, flow attributes or other factors - are created.  But manufacturing a mold costs a vast amount of money; the most expensive ones are over a quarter of a million dollars. Because of this large capital cost to produce molds, LEGO manufactures elements from different mold designs at the same time (plastic molds can be good for 10 to 250 thousand impressions, and might be refurbished rather than retired an the end of this run) and you have a world where your question can't be answered definitively.
Here's the best advice I can offer:

weigh many identically-coloured bricks on a high-precision scale*
before you do, inspect each brick to ensure that there are no mold variations
divide the total mass by the number of bricks

*I have a kitchen scale that has 2 grams of precision, and a much smaller scale that works to 0.01g. Which is more precise? More accurate? How can you make one give more precise answers than the other?If you go more precise that than 0.01g you're going to have to protect against noise introduced by fluctuations in air pressure (as it is, I have to be careful not to breathe on the 0.01g scales or the reading bounces around for a while). If you go to a jeweller's shop, you can see how they deal with this problem when they weigh gold and gems - they put a hood over the scale!

Are you sure the molds are that expensive in production? I think it would be the design process of a mold that make them expensive.

Since it is for a science project, I would suggest you take the official weight and compare it to the weight you come on your own. This will not only get you your weight but will score your project higher. The best way to do this would be to take 100 pieces and weigh them on a postal scale (if your school doesn't have access to one, your parent's work might, or even the post office might do it for you). Then take the total weight and divide it by... 100!
Of course the more blocks you use the more precise your weight will be, but after a while it just get to be silly...

I have a 1x4 brick that weighs 1.7grams.  My scale measures to the nearest 0.1gram. A 1x4 plate (one third the height of the brick) weighs 0.7grams.  Together they weigh 2.3grams, so the actual weight of each part is likely 1.65 to 1.70 grams and 0.65 to 0.70 grams respectively based on that.  These were standard parts, I don't think that the color will matter within the measurement accuracy, however, a transparent part is made from a different material and will likely be different.
I also grabbed 4 1x4 (standard, nontransparent) bricks at random and collectively they weighed 6.4grams.  I made sure that they all appeared to have the same type of mold.  I found one that had small depressions on the tube side (likely for mold venting) and excluded this (it weighed about 0.05 to 0.1grams less than the others).  So this suggests that this particular type weighs, 1.6 grams on average.  I'm not sure what the expected variation would be, but with a little statistics you could figure out how many you would need to measure to get a most likely value.  For your purposes, I recommend that you use 1.6 grams if the three tubes do not have a depression on the end (and 1.5grams if they do) and if you need to know better, take some measurements yourself (of the actual parts that you are using).

FWIW I the2x4  bricks are 1:7.5 compared to real human house bricks. This probably means lego figures are either gnome sized or they use giant sized bricks in their building construction.

LEGO Scale (approximately 1:40)
1 stud     =  .318 in (~5/16 in)
3 studs    = 0.95 in
4 studs    = 1.27 in.
3.18 studs = 1 in.
11 studs   = 3.5 in.
16 studs   = 5.09 in.

Dimensions = .96 cm ht x 3.2 cm length x 1.6 cm depth.
To scale real world weight to 1 Minifigure (MF), multiply pounds (lbs) by 0.0067, tons by 13.33, and kilograms (kg) by 0.0147.
As a rule, pack animals can carry 20% of their own weight comfortably without tiring. Plastic animals may be similar... but I digress.
To get a really good measurement, it helps to weigh a lot of bricks  (of obviously the same type) at once, say 100 pieces of 2x4 bricks might yield a weight of only half a pound. But it sure feels like a lot more, after you include the little bags, the cardboard box, the receipt from the store where you got it, that old ring nobody wants, sorry! Won't happen again. Hope this was helpful.
Weight of Bricks
1x1: 0.4g   (0.13 MF)
1x2: 0.78g  (0.25 MF)
1x3: 1.17g  (0.38 MF)
1x4: 1.57g  (0.51 MF)
1x6: 2.25g  (0.72 MF)
1x8: 3g     (0.97 MF)

2x2: 1.18g  (0.38 MF)
2x3: 1.71g  (0.55 MF)
2x4: 2.22g  (0.71 MF)

2x6: 3.5g   (1.13 MF)

Also, for those interested: What's the smallest piece of lego?
Lugnut says it is a gold coin, weighing in at just over 0.056 g; the flower petal is a hefty 0.064 g.
For reference, a 1x1 plate is 0.176 g, a 1x8 brick is 3.06 g, and a Minifig with no hat/hair or accessories weighs 3.11 g.
The official LEGO scale is (presumably) 1:40. At this scale a Minifig represents a person 5' 6" tall and 2' wide. No, sweetie, you look fine like that. Very thin and pretty! Ahem.
A 1" square represents 3 1/3 scale feet (40 inches)
Just for fun, ever wondered how far a Lego mile would be? Only 110 feet, not much more than the distance to your neighbor's house! Next time I'll calculate a Lego Light Year and possibly a Light Sand Year, as well.
a hee-hee a hee-hee
I am a sad, corny ridiculous nerd!


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Will it be fun to go to Legoland with my family?
I am 31 years old . My elder sister and mother are going to visit me. I want to see whether it is suitable to bring them to LegoLand.

Are you an AFOL? Are they, or something similar?

Please read the meta topic: Should questions about LEGO events, themeparks and other things unrelated to building be allowed?

Apparently, there's a possibility that you'll be turned away if you don't have any children with you - check with the park you wish to visit before buying.

My wife and sister-in-law enjoyed our trip to LEGOLand with our sons, everyone enjoyed the models, however not everyone was as keen on the rides, you mileage without kids to share the rides with may be different.
The question then comes down to whether you feel the model world is going to justify the entrance fee, personally I found the UK park to be (comparatively) expensive compared to other theme parks in England.

I had a similar experience.  My wife and I had a great time at Legoland (I've been to the one in Billund and Florida).  However, my wife wasn't as interested in examining the models as I was.

source: Stack Exchange

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How do you secure a power function motor to a technic extreme cruiser?
I am trying to help my son install a power function m motor in his Technic extreme cruiser.  We found a good place to put the motor and if we hold it in place it does drive the rear wheels.
The problem we are having is figuring out how to secure the motor to the car so that it stays in place when we operate it via the remote control.  The power function accessories have mostly traditional Lego style connectors but the Technic has none of those style bricks.

COuld you add a picture of your model and fitting, or find a picture of the model and indicate where you are putting the motor in?

It's very difficult to visualise the problem without knowing specifically how the motor and battery pack were installed. Normal (System) Lego bricks are compatible with Technic beams, the studs of a brick are designed to fit into the holes of a Technic beam.

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What are Good LEGO (or similiar) sets to play-prototype machines working with fluids?
I want to play around with fluid engines.
I'm aware that LEGO is sometimes used in labs for prototyping kinematic components, are there successful examples of operating with fluids?
Have pistons, pipes or other conduits, valves and maybe turbines been built with LEGO?
With what components?

There are a number of Lego Pneumatic sets with airtight tubes, valves and switches which could be put into use with fluids. One is 9641, Pneumatics Add-On Set.

Bear in mind that the pneumatics sets can command a much higer price than those sets with a similar number of parts, and buying individual pieces can also get expensive. Have a look at BrickLink to see what parts are avalible.
There is also a Simple & Powered machines set which comes with sails that could be used as a wind turbine, or a basic pump, but if you wanted to use steam or liquids with Lego you would have to be very careful.
A company called LPE Power has made some very detailed and very powerful pnuematic engines however I doubt they would work with water.

The Lego pneumatic valves are not great for (liquid) fluid experiments as the valves dissipate the return path to atmosphere, so they p*ss water out. And the pneumatic hand pump spring and metal core of the regular pistons rusts in a few days. It's about 15 years since I learn't this :-)


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NXT brick output ports not working properly
My NXT brick will not let motors run.  When I download a program the motor will move forward and backward and then stop - sort of a wiggle.  Another motor will not work at all.  This happens for all three ports.  Any suggestions.

Does this happen for all the motors you have? The problem could be there. I've had a motor which only ran in one direction (it did kind of get tortured before that, admittedly), for example. In any case, the customer service should be able to help you.

Try putting a Wait block after the motor block. Set it to wait for 5 seconds.
I think your program just terminates after one block. Please post your program next time you have a mindstorms question.


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Lego set for 17 year old
This might sound a little bit silly, but I'm 17 and I've never built a LEGO toy, so I was looking for a first one, to see what it's about. What sets would you recommend I should look at, that are complex enough for someone my age not to get bored?
I wouldn't really get an NXT, because I don't want to program a robot, I just want to build something, and I think an Arduino would be cheaper and more complex. Bionicle and Architecture seem interesting, but Technic looks like the most complex of them all.
So... what sets should I look at?

I've found the technic set with lots of moving parts, gears, and power functions are the most challenging and the most fun.

You're probably the only one who can answer that question, but here are a few thoughts anyway.
If you're interested in mechanic complexity and how machines work, Technic is indeed a good way to go. And as you hint, it can evolve into robotics, whether with a NXT or with anything else you fancy.
If you're after building complexity, I wouldn't recommend the architecture sets. The few I build weren't very challenging, and I find their price a bit on the heavy side. The bigger ones (21005 - Fallingwater or 21010 - Robie House may be more challenging, though.
However, sets with a high number of parts will usually mean the build is more complex. For example, 10214 - Tower Bridge has 4287 parts, and if you compare its price with the 2276-parts Architecture Robie House, you'll find it much more interesting.
Similarly, the various modular buildings also have high parts counts and are fun to build and display afterwards; plus, they go well together when you get the chance to have more than one.
As an aside, notice the "display" aspect I mention is important too - what do you want to do with the set you'll end up buying? If you're after replay value (creating new things constantly, the Creator theme has great sets with good play value, which are reasonably priced.
On the other hand, if you're concerned about your set keeping some value, or if you're a fan, license sets may be a good choice, especially Star Wars which also has some very big and complex sets.
Last, keep in mind LEGO also give age ranges for its sets. They're estimates, but a set marked 16+ is likely to be more challenging to you, so you'll want to look for these. You can easily browse the sets by age on the online LEGO shop, and even set limits for price and number of parts.
In any case, whatever you end up buying, don't hesitate to come back and share your own experience.

The two in the Architecture set are ones I was looking at, also because of the high parts count. I didn't know about the Tower Bridge, though, which does seem very interesting. About what I'm going to do with them after I build them, keeping them for display is what I have in mind at the moment, which is why I really liked the Architecture set. I guess I'll look at more Creators and Technics, then. Thanks for the input, it's greatly valued!

Having recently done Robie House, I must discourage anyone from trying it as their first set. It is very impressive when finished but the majority of building it, using hundreds of red 2x1 plates, is incredibly boring and hard on fingers. The modular buildings are likely better to start with. (I wouldn't call the Architecture line "challenging", but they do tend to show off non-trivial techniques using only simple bricks. Fallingwater, for example, disassembles to show the various layers; even a simple one like the Empire State Building shows off half-stud offsets for its shape.)

It's an interesting question.
As Joubarc stated there are multiple approaches here. But from my personal experience I would recommend a graduated approach into the Lego Technic.
You should start with the sets on this page to see it you can find any kind of interest and to ensure you are not simply discouraged by the Lego Technic models.
If you enjoyed the simplest models at least a bit, you shouldn't stop until you have built the most challenging ones. The reward in completing and discovering them is way higher. To me the most enjoyable model was the 8880 Super Car replaced by the more modern 8070 Super Car. Although the new 9397 Logging Truck seems to beat it when it comes to complexity and functions.
But first you should try some simpler and yet enjoyable models. I know people who like the racing cars more than anything else. I like anything with good and interesting parts/mechanisms. If you like the construction vehicles more than the cars you will find a few good sets. The 8043 Motorized Excavator being the coolest construction themed set for me.

Architecture set - White House.   This is the first lego I ever built (got as a gift from wife).  Loved it.  Right amount of pieces, right amount of time - ~3-4 hours.  Enjoyable time well spent.  Recently disassembled with help of a brick tool, packaged it up and sent it to my brother so he could enjoy as well - he was a lego kid, I missed out on that when I was a kid.

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What's the thing between the pant legs?
What is the piece that holds the pant legs together called? Is there an "official1" name? Or is there just a commonly agreed on term?

1Official meaning something mentioned, even in passing, by Lego in some way.

They are referred to as "Minifig Hips" almost everywhere: [partlink:970:4].
The LEGO Pick-a-brick service doesn't sell them without legs, and just refers to the whole construction as "Mini Figure Mini Lower Part":

Since that's utterly boring, I suggest we just start calling the thing what it actually is: a thong. Or a speedo.

@Joubarc Like the Beach Troopers from the LEGO Star Wars games?

And surely it's only a thong/speedo they are a different colour from the the legs, otherwise it's just waistband and flys/hips.

I just call it a belt

I once used the hips as rollers in a set, they look a bit like that with legs removed


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PosRegEnable - How to change motor parameters?
I want to set PID parameters for a faster 'attack' when using PosRegEnablePID() on a motor. I am compiling with nbc/nxc 1.2.1 r4 mac osx fatbinary using -Z2 and -EF flags.
But the compiler says:
# Error: Undefined Identifier PosRegEnablePID
How can I set PID parameters for PosReg?
PosRegEnable(OUT_A);

compiles just fine...

I know that the website says it is only for older versions, but have you tried posreg.h?

Also, would you mind posting your sample code?

I've closed this question because without further information it doesn't appear to be resolvable.


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NXC Saturation algorithm for limiting motors?
What is a good algorithm in NXC for control saturation? I want to make sure my motors don't turn past a certain angle, or they will break the model.
I could do something like:
if (angle > 45) {angle = 45;)

But that would be a hard limit. I'm looking for a smoother limit.

Out of curiosity, what language are you using? RobotC, LabVIEW, NXT-G?

@nhinkle, I don't mean to be patronising, but it does say NXC in the title. (N ot e X actly C) (not a very helpful site, but this'll do)

@ACarter whoops... totally missed that somehow. I guess my mind translated it to nxt somehow.

what do you mean by "smoother limit"? do you mean what kpt said, that the motor slows down before reaching the angle limit?

Yes, I mean the motor slows down. The line of code I suggested would be to slow because of inertia of the model.

By "smoother limit", if you mean "when it gets closer to the limit, it will softly land there by slowing down" then:
I recommend using PID control where the response (how fast the motor is moving to the limit) is controlled proportional to the error (how far away from the limit you are).
Wikipedia has a good intro to PID control: http://en.wikipedia.org/wiki/PID_controller


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What's the best way to link two (or more) LEGO Power Functions (PF) train motors together?
Last Christmas I built an extended Emerald Night train to run around the tree. To get it to work I had to add a second Power Functions motor. I tuned both IR receivers to the same frequency and slowly applied power by keeping the IR remote within the line of sight of both receivers at the front and the back. The major disadvantage to this was it was difficult to sync the two engines because line of sight was not assured.
I'd like to build a larger train this year and would like to find a better way to link the motors. I've think that putting one motor in the back helps with weight distribution, although this idea may be flawed.
What the best way to link multiple Power Functions motors together without having to rely on multiple IR receivers?

Below are some photos that provide more detail about the train in question.
All photos http://www.flickr.com/photos/craigmoliver/sets/72157628313822041/
Relevant photos
Front engine, standard Emerald Night (10194-1):

Rear power car, custom (MOC):

I had seen someone running two motors into each side of a diff gear or similar, can't remember if they were PF or others though... I'll see what I can find ;)

In any case, you'll want to make sure to use the same kind of motorization for both power points - to make sure they run at the same speed.

I would just stack the pf plugs on top of each other on the receiver.

If the motors are far apart, you could simply connect them both to the same receiver using some extension cables. To the best of my knowledge, there is no problem connecting two motors on the same input of one IR receiver.
If you're using Technic motors instead of train motors, as Zhaph said, you'll probably want to have them coupled through a differential so that no motor can stress the other. That's the standard way of doing it in any Technic creation, and since it effectively adds the two input speeds (from the motors), it means you can create some variation in speed very easily.
I did that to power a PF-modified 7740 engine with two medium motors when the only remote available was the simple on/off one: one motor had its speed reduced to 1/3, so the range of available speeds where 4/3 (both motors on), 3/3 (regular motor on, 1/3 motor off), 2/3 (regular motor forward, 1/3 motor reverse), 1/3 (1/3 motor only), 0, and the same in reverse. Was awfully complicated to use the remote to go from one speed to the next, though. And then LEGO produced a speed-control remote and I didn't look back to that idea again.)

Digging around a bit, I found the reference I mentioned:

Jason Stienhurst's LEGO Big Boy Mechanicals on Flicker
You can see there he's using 4 M motors from the Power Functions range in pairs. In the comments for this picture he describes the set up as:

Both motors have a 12 tooth beveled gear. The front motor and rear motor of each driver set face in opposite directions, which allows both of the motors' ouput gears to be meshed into a single gear (another 12 tooth bevel) that is impaled by the vertical axle shaft that runs through the turntable.

These then have another bevelled gear at the end, and mesh with a bevelled gear on the driving axle.
Jason is powering all four motors from one battery unit, and I don't believe he was worrying too much about IR control.

I put 2 train motors in the red cargo train and it worked well though I didn't add cars to the back . . . my goal was to get it to go up an incline so it could go from the "industrial area" around the tree to, well, a table, where I setup the city. I tried adding the passenger train motor car to the back but that didn't work  . . . the weight of the motor cars was too much to go up the incline even without any other cars. Only two motors in the engine car of the red cargo train ever worked and even then it couldn't pull up all of the cars . . . only two little ones or one bigger one would ever make it up. The problem with adding cars wasn't that the motors stalled (which was the problem when there was only one motor), it was that they started slipping. So then I thought I would add some weight . . . but of course that didn't work because more weight made the motors stall.
Learned a lot about physics that week.


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Is it possible to build a full-size house with Lego bricks?
I want to build something big.
Should* I build a complete house (interior and everything) with lego bricks?
* By "should" I mean, will it be safe? How big can I go? How much do you think it will cost?

I've always wondered.

James May built a full-sized LEGO house for his TV show James May's Toy Stories on the BBC back in 2009 using around 3,500,000 bricks. Whether you'd actually want to do this yourself...
During the episode they spent some time with engineering students working out the most load bearing configurations of bricks especially for the upper floor, as well as working on the general structure.
To get around the insurance requirements, in the end they resorted to building the house around a wooden frame including floors - and although they did continue working on the beams, and James did stand (rather nervously) on the final designs, they don't appear to have been released.
With regards to the rest of the house (i.e. fixtures and fittings) there were some issues as I recall:

Comfort - obviously lying or sitting on LEGO bricks without any covering is uncomfortable.
Water Proofing - at one point in the show James shares a LEGO "glass" of wine with Oz Clarke - only to have most of the wine leak out of the glass. Without some sort of sealant, or multiple offset layers the gaps between the bricks aren't water-tight.
Clutch Power - LEGO bricks are held together by friction (Technic pins not withstanding), and tend to break apart under incorrectly placed loads quite easily. This may be an issue when it comes to chairs, doors, etc.

Wikipedia article
Show on YouTube (part 1/5)

After seeing that, I think I'll prefer not to push my luck in this one (I mean seriously! look at the cracks!). +1 +V, well done!

Did they ever publish the structural designs for the upper floor joist? Would be interesting to see how they made the structure strong enough.

Not sure, I'll have a look around.

If you want to know how many bricks you'd need, there is some site to help you calculate it.


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Lego Mindstorm NXT cannot connect via bluetooth
I have an NXT mindstorm brick, running RobotC firmware. I am trying to connect to it, via bluetooth. At first, the problem was that I had the motorola drivers instead of ones from microsoft. Even after uninstalling he motorolla drivers and replacing them with stack microsoft drivers, the NXT cannot be found by the PC. Is there a way to fix this ?

Are you able to connect to the NXT brick when the original firmware is loaded (rather than the RobotC firmware)? Have you got any other BT devices that you can pair with (i.e. a phone/headset/etc) just to check it's not an issue with the BT hardware?

I assume you've tried this, but hopefully it will help someone. Make sure that your computer has been added to the brick's trusted devices and your brick has been added to your computer's trusted devices. I haven't got the link to work with "anonymous" devices before; you need to go through the process of entering the PIN.

Also - check what device you are working with.  I know the iPhone doesn't recognize the NXT because it's not an "officially supported" Bluetooth device.  The only way to get your iPhone or iPod to work is to "jailbreak" them.  I'm not too sure if this extrapolates to all apple products either.
I would agree with the user above.  Revert to the original firmware that came on the NXT and try to connect with it.  I would add that if you can't connect, I would also try USB or another device.  Your computer you are using to try to communicate with might be having issues with Bluetooth.
O yeah, and if it works I would just recommend using a compiler that just sends NXT native direct commands down to the device (C# with Microsoft Robotics Developer Studio for example, or VB.NET).  That way you don't have to mess around with the NXT firmware.
For a great comprehensive over-view of the bluetooth (and USB) direct NXT commands, there is a great writeup here:
http://www.robotappstore.com/Knowledge-Base/Programming-LEGO-NXT-Mindstorms/92.html
I would recommend checking it out as its much better than the one that LEGO provides!
Hope this helps!


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Any good Lego body decal templates or printing services
I was wondering could anybody point me in the direction of a good online service that prints minifig decals? I have no problem creating the designs etc but getting somewhere to print them is very hard. I would be happy to have a full custom minifig made if anybody could recommend a service.

Is there a reason you cannot print them yourself?

You might try and post a request on the ALPS Decal Yahoo group.  This is an e-mail group that discusses making water slide decals using the ALPS printer.  There are members of the group that do have businesses that produce decals.  I don't know how much people charge for custom decal sheets.  You'll have to ask.
http://groups.yahoo.com/group/alpsdecal/
Most decals that these folks produce use multiple layers of white ink under your actual artwork so that it allows the decal to be placed on a colored brick (not just white).  Your artwork also needs to be constructed using multiple layers that are lined up (registered).  Because the layers are usually printed in the "spot" printing mode, the actual layer art is black.  Think of each layer as a "mask".  When they print it, they tell the printer that where ever it sees black, to print say yellow.  Yellow is the "spot" color for this layer.  You start by printing usually 2 white layers, then spot yellow, cyan, magenta and finally black.  The unique feature of the ALPS printer is the capability of printing in overlay mode.  What this means is that you tell the printer to print a layer, but don't eject the paper.  The printer will rewind the paper back to the beginning and await your next print request.  Each print request is a separate layer printed on top of the previous layer(s).  This way, the final image is built up layer by layer.  On the last print (usually black), you tell it NOT to do overlay and when the layer is finished printing, the printer will eject the paper.  This type of printing is a lot of work and can use a lot of ink, especially white ink, which is expensive, but it gives the best results for the average hobbyist.
Like Joshua above noted, you can produce your own decals with a color laser (or inkjet) printer quite easily.  You are stuck with a big cutting job if you want to put the decal unto a colored minifig body (using white decal paper).  You can use clear decal paper if the artwork is black, because the decal shows fine on white, yellow, tan, red, green, orange, and blue parts.  Remember, if you are using inkjet decal paper, you must coat the decal with a clear finish (Krylon), prior to placing in water (to remove the backing) when applying to your minifig, otherwise, your artwork will smudge and wash off your decal.


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LEGO for a 1 year old
I have a son who has just turned one. I like my LEGO and my desk at work is covered in minifig's etc, the problem is my wife isn't as keen on them. I was wondering can anyone recommend a set that would be appropriate for me to get for my son so I can bring my hobby home without feeling the wrath of my wife, or is it a bit too soon to introduce him to LEGO?

Be honest. You're buying these for yourself? or your son? :) If for yourself, don't bother. Duplo is incredibly frustrating to play with if you're used to Lego. If for your son, I suspect at 1 he won't be that into it, but eventually he'll figure it out. But there's no hurry, and it won't scratch your lego itch.

LEGO Group also did a range called LEGO Baby or Primo, which was pretty much suitable from birth.
It's not currently in production, but does come up on ebay and the like now and again, and is slightly inter-usable with Duplo and hence standard LEGO blocks.
Items ranged from things like this rattle, with chewable petals:

To the more "advanced" building sets:

My sons both enjoyed their Stacking Jungle Set, and the Bathtime Boat is still going strong ;)

Lol, this pic is epic :D Flower Teething Rattle

LEGO bricks aren't suitable for children under 3 as they are considered a potential choking hazard.
LEGO also sell a DUPLO brand of construction toys which are twice the size of regular bricks. DUPLO bricks are designed for children aged 1½ to 5 years old.

Note that some of the DUPLO sets include shovels, flags, and other small items which could be dangerous.  So stash those bits away for a couple years...

There is also a non-Lego product from Megabloks that is really good for young children.  They studs on those blocks are rounded so they're easier to kids to get them to "lock" together.  While not as sturdy as some of the Lego products, they do seem appropriate for real young children.

Seconding this, they are actually QUATRO-scaled and would sorta link up to the DUPLO/regular sized stuff but only on the bottom. Either way I got 2 large boxes of them and all 3 kids love them also because the builds get HUGE very quickly.

In addition to DUPLO, there is also QUATRO. They are, as expected, 4X the size and impressively compatible with standard sized and DUPLO. I inherited some, so have no idea if they are still made or sold.


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How can one find old archived issues of LEGO Mania Magazine?
Do any libraries contain old archived issues of them? Preferably ones on the WorldCat system?
I'm not sure if my limited storage space can handle more LEGO Mania magazines, so I'd prefer a format that's either digital or that one can easily check out from a library.

There is currently one public library in the WorldCat system that has cataloged LEGO Mania Magazine, but it does not have it available in digital form.
Other LEGO Club magazine titles have been collected by some WorldCat system libraries, including:
Brickmaster Magazine
LEGO Club Magazine
LEGO Magazine
None of these titles appear to be available in digital format from any WorldCat libraries at this time.

The LEGO Group have now started posting the latest issues of LEGO Club and LEGO Club Jr online, with the competition and member photos removed.


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Measurements (LDU) of Lego tracks Set 151
I have an old set of 7851 curved tracks.  I want to use the outer tracks (the ones with the bumpy surface).  If I was to put one end down on a baseboard so that is tangent/parallel with the grid of studs, how many LDU in the X and Y direction would the other end be?
I'd also like to the know the X, Y cartesian coordinates (in LDU) of the middle 2 slots as well.

Well, obviously one way to measure that would be empirically - you have the tracks, you have the baseplates...
As for the maths, let's see... a full circle of these tracks has a diameter of 5 straight tracks as measured from the centre of the sleepers, that translates to 80 studs. The radius is 40 studs, or 800 ldu.
The outer, ridged track, is 2 to 3 studs further depending on which border you consider (and assuming you want borders instead of stud positions). So the radii for the border of that piece of track are 840 and 860.
So, assuming the track circle is centered around (0,0), and using the usual way of considering circles in math (counterclockwise from (1,0)), your first piece of outer track starts at (820,0) and (830,0).
There are 16 segments of track to a full circle, so the angle for one segment is 22,5°, or pi/8. So the end of your first track part is at (840*cos(pi/8),840*sin(pi/8)) to (860*cos(pi/8),860*sin(pi/8)), or (776.06,321.45) to (794.54,329.11)
Expanding further, you get the following segments for the short border of the outer track:

(840.00,0.00)-(860.00,0.00)
(776.06,321.45)-(794.54,329.11)
(593.97,593.97)-(608.11,608.11)
(321.45,776.06)-(329.11,794.54)
(0.00,840.00)-(0.00,860.00)
(-321.45,776.06)-(-329.11,794.54)
(-593.97,593.97)-(-608.11,608.11)
(-776.06,321.45)-(-794.54,329.11)
(-840.00,0.00)-(-860.00,0.00)
(-776.06,-321.45)-(-794.54,-329.11)
(-593.97,-593.97)-(-608.11,-608.11)
(-321.45,-776.06)-(-329.11,-794.54)
(0.00,-840.00)-(0.00,-860.00)
(321.45,-776.06)-(329.11,-794.54)
(593.97,-593.97)-(608.11,-608.11)
(776.06,-321.45)-(794.54,-329.11)

Hopefully that makes sense. Watch out, these are the coordinates of the borders; for the coordinates of the studs (that is, the center of the studs, which I think is more interesting, but I don't know what your goal is) we'll have to use a radius of 850, and move 10 ldu along the tangent to find the stud. So to find the stud after the segment, we'll do (850*cos(pi/8)-10*sin(pi/8),850*sin(pi/8)+10*cos(pi/8)). For each segment N starting from 1, the studs are as follow:

start stud: (850*cos((N-1)*pi/8)-10*sin((N-1)*pi/8) , 850*sin((N-1)*pi/8)+10*cos((N-1)*pi/8))
end stud: (850*cos(N*pi/8)+10*sin(N*pi/8) , 850*sin(N*pi/8)-10*cos(N*pi/8))

End the two studs in the center of the track are basically and end stud if the angle was pi/16, and the start stud of the next track, or:

first middle stud: (850*cos((N-1)*pi/8+pi/16)+10*sin((N-1)*pi/8+pi/16) , 850*sin((N-1)*pi/8+pi/16)-10*cos((N-1)*pi/8+pi/16))
second middle stud: (850*cos((N-1)*pi/8+pi/16)-10*sin((N-1)*pi/8+pi/16) , 850*sin((N-1)*pi/8+pi/16)+10*cos((N-1)*pi/8+pi/16))

The four studs of the first part of track are thus at coordinates:

start stud: (850.00,10.00)
first middle stud: (831.72,175.63)
second middle stud: (835.62,156.02)
end stud: (789.12,316.04)

Thanks Joubarc.  I did want the coordinates of the stud slots themselves and I ended up working this out in a way you described.  It turns out it's something like: x = 63.9411, y = 321.45 (assuming first stud is at (0,0) - not very nice integer numbers.

Well circles are so that it was more or less a given that you wouldn't get nice integer numbers; but on the other hand you can probably find places where studs are close enough that the parts may fit. Although not exactly related, you my want to read this to see track geometry examples which work by being close enough.


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Explaination of LXFML file contents
I am interested in writing a game that interprets LXF files into worlds (to create a game such as Lego Universe).  After finding out how to extract the LXFML file from the LXF archive, I need to know how to interpret the contained LXFML file.  Are there any detailed descriptions of how the LXFML format works?

Note that while LU had a number of LEGO models in it, the world as a whole wasn't made of LEGO elements - the landscape was still a standard "terrain mesh" type of thing.

The LXFML file is an XML document, and there's an XSD document that you can use to validate any LXFML file, along with a textual description of the tags on the LUGNet forums supplied by the LDD Team a few years ago:

LXF files - info and XML schema

The key parts of the LXFML you're going to be interested in start with the <Scene> element, which contains one or more <model> elements, which in turn contains one or more <group> elements, which are made up of <part> elements.
The tricky part is getting from a <part> element to an actual model:
<Part refID="0" name="m3680_turn_plate_2x2__lower_part_0" designID="3680"
      materialID="1" assemblyID="74340" assemblyRefID="0"
      angle="0" ax="0" ay="1" az="0" tx="0" ty="0" tz="0" />

As you can see, the Design ID corresponds to a LEGO element [part:3680] so you'll need some way to get from those to a suitable model - I recommend taking a look at either:

BricksViewer - A Java app for viewing .lxf scene files - also has a brief discussion of the .lxf and .lxfml formats.
LDXNA - An XNA library for importing LDraw models - it does include an .lxfml document in one of its examples, but I don't recall it using it - however it does show you how to convert the LDraw parts library into a usable format.

There has been a change in the LXFML file. I didn't check since which version, the change was applied, but LDD 4.3 (Sep-2018) has a different structure. e.g.,  is now  and attributes angle, ax, ay, az, tx, ty, tz are now a single transformation attribute

Do you remember what ay was?

@tommy.carstensen I believe the ax, ay and az denoted the axis of rotation, and then tx, ty and tz are the "transform" or positional axis.


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What are the female parts called?
What is the proper term for the "female" section of the piece that the "studs" insert into? I have heard "pipes", "tubes", "underbits". Is there an actual term for the female section?

Interesting question. To help finding a good term, it would be useful with a good example to use this in a phrase. Do you have an example of use in a natural context?

It was an analogy to demonstrate how you can plug an API into your website. So, the statement went something like "You have a LEGO piece (representing the API) with it's studs and you need to attach it to your website, so you need do build the [underbits/tubes/stud receptacle] to plug the API into."

See also this question for naming other features of a brick: http://bricks.stackexchange.com/questions/1636/is-there-an-official-lego-terminology-for-the-features-of-basic-pieces

Chapter 1, Page 4, The Unofficial LEGO Builder's Guide:

The tube is the other half of the mechanism that helps bricks stick
  together. Tubes capture the studs so that you can join LEGO elements
  and know they won't fall apart.

I have to disagree on that somewhat, or at least try to add some undertone. The tubes do indeed capture the studs, but not by themselves: the studs are (usually) captured between tubes, or between tubes and brick walls; they don't "insert into" them in conventional builds. Also, not all parts feature tubes, so what would you call the underside of a 1x1 brick?

The underside of a 1x1 brick? How about "The square version of the tube that is the bottom of a 1x1 round brick"?

Bricklink (at the time of writing) has 5 catalog items using the term 'stud receptacle'.

Members of the French club FreeLUG refers to these as antistuds, and there is at least one LDraw part that uses that same naming. Considering a lot of other parts don't, however, it's probably not widely accepted. And it's not valid at Scrabble either.
You could also use mortise by analogy with the woodworking assembly (a stud is also usually called tenon in French), but again, I've never heard it in LEGO circles. Slot might be appropriate too.

I think "slot" would be more descriptive of an open spot in a construction where a particular part fits.


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How do they decide when to remove an element from production, and what happens to the molds when they are retired?
We all know certain LEGO elements are no longer being produced. How do they decide when to remove an element from production, and what happens to the molds when they are retired?

See also How to find out if an element is out of production.

I can't find a link to substantiate this, but a quality assurance representative from LEGO mentioned at a BrickWorld presentation a few years ago that worn out molds are buried on the factory property in Denmark in concrete. If anyone else can find substantiation for that, I'd love to see it.

I've heard that one too


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Have any Lego sets been released with errors/mistakes in the build instructions? If not, why not?
I was thinking about the documentation process of a large set like the Death Star and it got me thinking; surely at some point Lego must've released a set of instructions that contained a mistake?
You know, referencing a part that wasn't in the final set, skipping an instruction step, nonsensical instruction etc.
If they have somehow managed to avoid this over the years, what processes/validations do they have in place to prevent such errors creeping into the eventual consumer sets?

I saw this picture on failblog.org. There is a high likelihood that it has been photoshopped but maybe someone can identify the instruction sheet it is from and verify if it is fake or genuine.

@mcqwerty - It's real, you can find it on page 62 in book 2 of the instructions (pdf) of the set 8038 - Battle of Endor. (And that was fun to search, thanks for the challenge!)

Uh oh, looks like your question was plagarized.

@Joubarc That doesn't exist anymore.

It's still on brickinstructions.com https://lego.brickinstructions.com/08000/8038/125.jpg

My 7190 Millennium Falcon kit has a mistake where the inventory for the page doesn't include two pieces on it. So, invariably, when I'm building it I forget to include those two pieces, and they are left over until the very end, at which point I have to follow this process:

Say "Dammit"
Flip backwards through the booklet to find the page that last added those parts
Disassemble the model part-way
Add the parts back
Re-assemble the model
Say "There. NOW it's finished."
Swoosh the model a bit.

Here are the two instruction pages showing the error. On the second page you can see that the dark grey upward sloping pieces at the front are added, yet don't appear in the page's inventory list.

So... maybe add a Post-it note to remind yourself?

@gev that's probably a good idea. Next time I build it I'll try to remember to make the post-it.

LEGO has made mistakes several times in the past and will continue to do so, as is the norm for a toy manufacturer of its scale.
I can only advise that the best way to ensure instructions are correct would be to build the model using the instructions. You'll be able to pick up more than just missed steps that way.

I'm fairly confident they do so at some stage in the process and, but even that doesn't seem to ensure all errors are eradicated. However, it sometimes can lead to errata sheets being added to the box when reprinting the instructions fully isn't an option anymore.

Mistakes do slip through from time to time, and are actually not so uncommon as you think.
Most of this is hearsay, but as far as I understand, the people in charge of making the instructions are not the designers themselves. Similarly, there is certainly a Q&A process which aims to ensure that the model is as faultless as possible, including the instructions. Building it is most certainly a part of the process.
But once again, errors do creep through, and sometimes they are discovered by the time the instructions are already printed. In these cases, it's not uncommon for LEGO to add an errata sheet to the model rather than reprint the full instruction book. See here for an example on LEGO wikia.

I have a set that has an error in the original instructions. 7184 Trade Federation MTT has a double sided page of the correct steps as below.

The original basically used a 1x6 in place of the 2x6. I am not sure if the correction was because the model design was modified to be more sturdy or if the maker of the instructions got it wrong, but when I tried to build this set the first time I had used some other 1x6's as the instructions had said. Later I had no 1x6 pieces to build with and noticed the 2x6's. Then I remembered the extra page and was able to work it out.
This is the only set, and I have over 50, where I have had an addendum to the original instructions.

The part list page for the Ultimate Collector Edition Millenium Falcon (10179) contain 5 mystery pieces that aren't included in the set, and aren't even used in the build.
See What is piece 4211642 from 10179 - UCE Millenium Falcon?

I know that I've found errors in multiple sets of Technics. Technic 42055 page 210 calls for 27 of part "4121715" but only show 25 used. I have several of these left over and cannot find where they go.
Other Technic kits I've built have shown parts put together wrong on subsequent pages after showing them correctly.
With Technic sets I expect to find mistakes anymore. I've never found one in a standard set, but I don't buy the big standard sets.

I'd like to nominate today's find, an admittedly minor and inconsequent error in the instructions of the 24065 RC Tracked Racer, which I would call "The case of the spontaneously moving pins":
Here we start with four partially inserted long black pins:

Which suddenly, and without being instructed, get fully inserted in the next step:

Only to retract just as spuriously in the next step:

And stay so for the next 57 steps, when they are finally inserted with the full consent of the designer(s):

It doesn't take a detective to find out who was moving them: the instruction designer, without noticing. I really doubt that a cat or something stomped all over his keyboard and messed up the position of the pins.

In the LEGO Technic set 42100 (Liebherr R 9800), on page 211, step 268 says to assemble parts that were already added in the previous step.
Steps 267 and 268 are actually swapped.

If I remember correctly, on the LEGO website a few years ago there was an incident with their Batman Tumbler. They had to reissue new instructions as they left something out. It was a long time ago and I didn't buy the set. I also noticed when building the Death Star minifigure set 10188, specifically the Emperor's room, I got some of the pieces wrong because the colour on the instructions was so bad I couldn't make out what colour they were supposed to be. Alas, when I almost finished it I found my error and backtracked, taking the whole thing apart.

My son owns 6912 Super Soarer. In the picture, as can be seen below, on the fuselage, between the wings and the tail, there's a black roof tile with lattice (1×2×2), on a dark grey 1×4 plate, with a dark grey 1×2 flat tile in front of it.

According to the build instructions, that sub assembly should be the other way around, with the roof tile in front of the flat tile.

My Death Star has a mistake in the building instructions. One of the pages is messed up because on one page one plate is 6x1 and then suddenly on the next page it's a 7x1 plate. And it doesn't tell us to add anything on the latter page.

Set 10243 Book 2 appears to have an error in the fireplace build. Pages 16-19.

Hi Kibedango! I have added pictures of the steps you have referred, but could you please point out the exact error(s) in them?

Unclear instructions on how to place the masonry bricks, but not in error in my opinon..

In set 76140, TLG made a typo with what sticker number you should put on one of the bricks.

The SPIK3R PDF file for set 31313 also has a typo. The number in the white circle next to the dark-tan axle tells that it measures four studs long, when in reality the part is only three studs long. At least it doesn't affect the build, because there are no errors in the given image of it AFAIK.

In the review of 31107 Space Rover Explorer over at Brickset, the author, Mr_Cross has pointed out the following error, where the same six 1x2 modified plates are to be added in both substeps 2 and 3 of step 3 and in step 8:

These images depict steps 26 and 27 of the 8868 Air Tech Claw Rig, where the pulley wheels are changed:

I have a page that was folded in before final cut in the ninjago city book 2

Hello John and welcome to Bricks.SE. I think the question was mostly about mistakes in the content of the instructions. However, it is always nice to illustrate your answer. This will attract more responses, upvotes and feedback. Mistakes in LEGO's production process are also interesting. Can you show a photo of your messed-up instruction book?

In the Changing Seasons 2015 set the winter instructions has a mistake, not huge and doesn't prevent you building it correctly, but it is there.  Page 29 doesn't show the top hinge, but on page 30 it is there!  It isn't until page 33 when the instructions tell you to place this piece.

I've looked at a PDF file of the instructions, and I do not see the error where you've pointed out. Can you be more specific?

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


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Remote Control option NXT Mindstorms
I bought the NXT Mindstorms education software v2.1 along with a Mindstorms kit (which I don't know the version of).
I am trying to remote control a robot I made using bluetooth between my mac and brick. So far, I have connected both devices with bluetooth successfully. I have watched a couple of videos of people remote controlling their Mindstorms bricks and they show the whole process of them connecting the devices and everything (which I have already done), but the last step of remote control process is selecting the option of "remote control" in the top left corner in the "tools" tab in the menu bar.
I do not have that option in the menu. Instead, when I open up the tools tab, a drop down menu opens giving only the options of Calibrate sensors, Update NXT firmware, Block import and export wizard. There was no "remote control" option and I am trying find out where that option is so I can finally start working on controlling my robot.
I am not sure if it is because I need to have the 2.0 software instead of the 2.1 software. If this is the case, I just want to confirm this before I buy something that I might not need.

Hi, welcome to LEGO Answers :) This site often works best when you're asking a single answerable question - and you appear to have 2 or 3 questions in here: "Why can't I remote control my NXT?", "How should I programme the robot for simple motion over Remote Control?" and "What does the Action button do in the Remote Control panel?". Please feel free to ask them separately :)

Would you please provide a link to one of the videos?

I also am trying to do the same thing. The remote control access is not avaliabale on 2.1 either. Worst answer ever. Did anyone ever find out how to add the remote function?

We had the same problem.  The current version of the Kit ships with version 2.1 of the software which does not have the "remote control" item on the Tools menu.
We uninstalled this version, downloaded version 2.0 from the below link... and bam...  the "remote control" option is there and it even works great through our laptop's Bluetooth connection.
Where can I download the LEGO Mindstorms NXT 2.0 IDE?

All of the commands for controlling the robot are documented on Lego's website here: http://mindstorms.lego.com/en-us/support/files/default.aspx
You can write your own custom remote control software in most programming languages, but this is generally difficult on a Mac. Windows and Linux computers are easier to program for, Windows being the easiest. This tutorial ( http://www.extremenxt.com/vbfront.htm ) will get you started programming your own remote controller for Windows using Visual Basic. For a Mac, I would recommend using Python to write your programs. No tutorials exist for doing this in Python to my knowledge, but I can give you code samples if you are interested.


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How to control a RCX from a Mindstorms NXT
I have both an RCX and an NXT.
I would like to control the RCX brick from the NXT (and possibly communicate back to to the NXT from the RCX). I would like to avoid purchasing the Mindsensors RCX to NXT Communication Adapter which is no longer available in their store, and instead control the RCX via inputs to one of it's sensor ports via outputs from an NXT sensor port.
The physical connection can be achieved with the NTX to RCX converter cable but I am unsure how to control the output from the NXT sensor port to emulate any of the sensors that the RCX can recognise.
I found this post on another forum asking a very similar question, but the people who responded don't seem to have understood OP's intent, it is however worth a look for the illustrations.
This then is really a question about programming the NXT to gain fine control over the output from a sensor port to emulate a RCX sensor and if it is even possible.
I am open to solutions in any programming language/environment.

Aside from the dynamic nature of NXT programming, is there anything in particular you were hoping to gain from this method of driving the RCX?

Captain Obvious Says: "You would need to simulate input that the RCX understands. That would likely entail having knowledge of all RCX compatible sensors at the level documented for the rotation sensor as linked from the forum thread that you linked."

@JoshuaDrake Aside from the fun of the challenge of getting it to work, I was hoping to gain the 3 extra motor outputs and 2 extra sensor inputs of the RCX for 'the price of' one NXT sensor input.

@JoshuaDrake Exactly, and that is what I was hoping to find help with by posting this question.

You may have better luck over on http://electronics.stackexchange.com

I think you're overlooking a very simple yet elegant solution: connect a NXT motor to the motor port (no problem there, that's what it's for), connect a RCX rotation sensor to the RCX (again, the intended purpose), and by now you should pretty much know where I'm going with this: connect the rotation sensor mechanically to the NXT motor.
Considering the NXT motor has a good precision, you can easily you this to send messages from the NXT to the RCX; but of course you'll need to invent the protocol yourself; that is, decide what these messages mean. And you won't have feedback from the RCX to the NXT (you didn't ask for it though)

I know you don't want to purchase anything, but for reference, there is now the IR Link Sensor made by HiTechnic and sold directly by LEGO, which is presumably easier to use (and you can get feedback through it, too).
I don't think you'll be able to use a converter cable directly; you'll need to use some intermediary electronic, possibly using the I2C protocol. This prototype board solution (also from HiTechnic) should do the trick if you use one of the outputs to drive the RCX input (you can probably use an analogue one).
And if it's more ports you're after, you'll want to consider their multiplexers too.

I had considered the option of using a motor output and purchasing a rotation sensor, but as I said, I was hoping to achieve the control of the RXC, (and possibly communicating back to the NXT) by connecting the sensor ports with a converter cable.
I was hoping for tips on the programming of the NXT regarding simulating a sensor. As I mention in a comment on the question, trying to achieve control ‘sensor input to sensor input’ is partly for the fun of the challenge, but it looks like that is probably just not possible.

I fear it's not possible with just the converter cable - since the output port of the NXT will output a voltage and the input port of the RCX will be looking for a resistance (and possibly outputting a voltage of its own which will probably be a problem). Or something. But then Joshua's right, this is more a question for electronics.se

Yet another not-quite-what-you-asked-for solution: make a NXT robot that will push buttons on the RCX. Or, better, on the RCX remote if you have one. Bonus points if your NXT robot resembles a hand.

I know this is 3 and a half years late, but I figured I'd throw in my two cents.
Attach an NXT light sensor and an RCX light sensor facing into each other. You can communicate bi-directionally by flashing the built-in LEDs.
On the RCX side, this can be accomplished by switching the sensor mode between touch sensor and light sensor to passivate or activate the LED. From the NXT, things should be simpler, and even the NXT-G software has the ability to turn on and off the LED.

Interesting idea. I like the fact that this would only tie up one of the sensor ports on each controller and leave all of the motor ports free.

I've used the light sensor method successfully in several of my own projects, despite it not being a very fast form of communication (although it's much faster than the motor/rotation sensor combo). I thought about using one of the converter cables to make a direct connection, but I haven't been brave enough to try it, in fear of burning out some internal chip.


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New ways of connecting levels of multi-story modular buildings
Compare these two instructions from the Green Grocers and Pet Shop modular building and you may notice (other than the background colour) that the top of the walls of the buildings are both arranged differently:

Tiles are raised at certain lengths of the wall to ensure the floor above will stay in place.

The floor above is secure using the relatively new 92593 modified plate. The new plates occasionally 'lock' into the floor above when it's removed, leaving an impression of where the plate once was. However few pieces are required.
I'm building a multi-story police station with a large area (32X62) and I'm looking for a suitable way of connecting floors with as few bricks as possible.

The "without tiles" part seems difficult, and puzzles me a bit - why not?

@Joubarc: I don't have enough tiles in the right colour, I can probably get rid of that as it might be too much to ask.

Two ideas I can think of, which are not using "tiles" as such, but similarly flat surfaces:

Technic beams - holes attached to studs of the lower part of the building, and in some holes (which have to be above tiles), pegs/axles for the upper part to fit into.
1x1 "cheese" slopes - and inverted on the upper part (or use regular inverted 33° slopes), which makes the upper part fit in the lower as if in a funnel. (Not very different from using tiles)

I've considered the first option briefly before but the second idea sounds more interesting. I have many spare cheese slopes I can use but I would probably have to use tiles for the majority of the wall.


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How does LEGO decide it needs a new element?
Aside from the need to add licensed series specific pieces, how does LEGO decide it's time to introduce a new shape to the element palette?

This may not really qualify as an answer, but basically I believe designers are responsible for calling for new parts.
For each new part, a production cost is calculated, which takes into account a lot of factors. There were talks a few years back about how they had recently changed these rules, but they aren't public (to the best of my knowledge). What is more or less certain however is that an element which fits well in the system has considerably more chance of being accepted; that is, I suppose the calculated cost is lowered to reflect its usefulness. That's why a lot of recent new parts are just of the "it so obviously makes sense, why didn't they do that before"-kind (1x3 tile, 1x1 bricks with 1 knob,...).
So the designer willing to commission a new part for one of his sets will need to support that cost as part of the cost of his set, which is imposed to him. I guess there are much more rules than that (if multiple designers agree on a part, for example), but that's the basics of it.
Also, note that producing an existing part in a new colour follows the same rules to an extent. It's calculated cost is higher than an existing colour for that part.
To summarize: each existing part has an associated production cost which the designers must take into account when creating a set. Non-existing parts are similarly associated a cost, which is calculated according to a lot of rules/factors which aren't public.
Even the costs of existing elements show subtle variations: some colours are cheaper than others, for example; or older elements may be more expensive because moulds aren't optimized (one known case is the Technic axle 5 which is cheaper than the 4 one, because there are twice as many of them on a mould).
Last thing, more as an aside: the cost of the first part in a model is also higher than the next ones, because it helps production to have more similar parts. For example, 7945 Fire Station doesn't have any regular 1x2 red or white bricks - since they have 1x2 bricks with groove for the doors, they used these everywhere a 1x2 was required - even if no groove was needed. That way the number of different parts in the set is lower.
Edit: here is a very interesting video on how they prototype the new elements. Notice at the beginning of the video, the designer explicitly mentions he couldn't get the shape he wanted with existing elements, so he had to have a new one made. This was for a license set (cars), so again the decision in this case may be easier to take.


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What are the special features of the Ferrari F1 Racer 1:8 kit?
I found a good price on the Ferrari F1 Racer 1:8 kit. From the picture of the box cover, it would seem that the steering wheel can turn the wheels, but I cannot identify any other moving features.

Is this a Technic model or just a display model, which happens to use a lot of Technic parts?
If I am after a model containing many useful Technic parts for use in custom creations, is this a kit to avoid?
Do many of the side panels appear in other models or were they custom made for this kit and therefore, might have limited value outside of the box design?

I would consider the model as a Technic one (it's built as such), but very poor as far as functions go: steering and the ubiquitous cylinder block, I don't even see any suspension.
You can see the parts included at peeron or bricklink and judge for yourself if the parts interest you or not. As a licensed set, it's likely its price is inflated to cover the license cost, so I'm not sure it's the best parts pack.
The panels are standard Technic panels (with stickers), although LEGO has discontinued them since then in favour or more robust panels which participate to the model structure in their own right.

From the Instructions for 8674-1 - Ferrari F1 Racer 1:8 you can see that the pistons also go up and down and the body can be removed.  From the box picture posted the set was part of the LEGO Racers, specifically the Ferrari subtheme.


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What color has been produced in the highest volume?
What color makes up the highest percentage of LEGO elements produced since ABS plastic was introduced in 1963?

bonus points if you measure by volume.

@antony.trupe I can hear them calling me from the other room..."Build me...build me...."

Black.
Peeron.com has a colour table that lists how many pieces of each colour you would have if you had one of every set in their database.
Obviously their database is not complete, it doesn't relate to when ABS was introduced (but most of the pieces produced in all time will have been since then), and some sets have been produced in higher numbers, so that's not an incredibly reliable figure, but seeing it has more than double the closest rival, I think it's safe to assume that Black's the winnner.
I would think that it is partially due to the fact that technic pins come in black, and there can be hundreds of those in sets.
Incidently, the top 5 are:

Black
White
Old Gray
Red
Yellow

Black is also cheaper to produce (especially considering most recycled bricks end up there), which may explain in part its popularity.

I imagine there is a strong influence from Technic parts, especially the pins and axles. I wouldn't be surprised if the black Technic pin is the most common piece ever made by LEGO in that colour.


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Does Toy 'R Us (or more expensive-than-average) retailers have more extra parts than average?
I haven't bought LEGO sets for a while, as my kids are just getting old enough to make the sets, but I am assembling the LOTR sets which I find impossible to resist.
I bought Gandalf Arrives (9469) and Shelob Attacks (9470) from Toys R Us at what seemed like an awful mark-up for them, but I noticed that I got quite a few extra pieces. Then I bought another The Orc Forge (9476) from Walmart and got marginally more than I paid for.
If this is idle speculation, I'll delete the post, but if there's something to it I'd like to know!

The set you bought from Walmart, was it the exact same one or another set in the LOTR line of products?

Different, got Gandalf and Shelob from Toys r Us, Orc Army from Walmart.

If this is idle speculation, I'll delete the post... Even if not true (and it doesn't seem to matter which retailer we buy from), it's a great question. "Might I get more pieces at a certain retailer?" Especially since your question solicited @mcqwerty to share the "extra brick inventory" link and @Ambo100 to get Consumer Services information.

I will start by saying I do not own any of the LOTR sets. But, Bricklink has inventories of many sets including any extra pieces that were included with the set. You do not mention which specific sets you own, but here is a link to the 9474 The Battle Of Helm's Deep inventory on Bricklink. It lists a total quantity of 6 extra pieces (5 unique).
You could compare the extra pieces in your sets to those listed on the Bricklink inventories and if you do indeed have more, then there may be something to it. Unfortunately Bricklink does not list where the set being inventoried was purchased from so without input from some other bricks members who actually own the sets then we can't know for sure.

Oh wow, I just checked it - there's just a lot of extra parts for Shelob attacks.  Wow, I didn't know they cataloged these!

The number of parts shown on the box of the LEGO set indicate how many parts are included without the spare parts. Spare parts tend to be added for the smallest pieces of a set that can be lost easily.
Spare parts tend to be fairly consistent between identical sets regardless of where they are sold and sets with a greater amount of parts will generally have more spare parts.
I wrote to LEGO customer services, here is a quote from their response.

When it comes to spare parts, it is random what pieces are included in
  which sets.  We always want to make sure our fans have a little extra
  to go with their awesome imaginations.
LEGO Direct Consumer Services

Please don't take this the wrong way, but could you provide some evidence supporting your statement that "Spare parts are consistent between identical sets". I am sure that this is the case also, but in the interests of keeping this site factual it may be helpful to provide supporting evidence where available.

@mcqwerty: I wrote to LEGO customer services and I've included a quote from their response in my answer. Thanks for making the answer better!

Looks like no way to find that quote on lego site...

@AlexeiMartianov That's correct, this was from an e-mail response I received from LEGO customer support. I still have a copy of the full response here. I have updated my answer to make this clearer.


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Mindstorms NXT Bluetooth Slow Connecting
I have just bought a NXT 2.0 and have installed the software on my laptop, and after some trouble getting it to connect I now have it connected any working using bluetooth. However it takes an age to connect, and I wondered if anybody knew why and how to sort it out.
I am running Win7 32-bit, and to get the software running I first had to set it to run as administrator and using XP SP2 compatibility settings, and had to change the bluetooth driver to use the generic MS stack rather than the installed for from the manufacturer. I found these tips on various sites around the web.
Once I had done this I managed to get it working, but now on opening the software and scanning for devices, it takes somewhere in the region of 4-5 minutes to find the device (while it is sat next to the laptop), and then another 2-3 minutes to connect, and then even more annoyingly another 2 minutes when I click close on the devices window. Once this has completed, it works fine and uploads and downloads with no problems, but it just seems really slow getting there.
Any ideas?

I have got that problem too. And this is a bug in the NXT 2.0 system, So there are two solutions:
1- Using the USB Cable instead of Bluetooth as it give no errors and it is faster also it keeps your battery life for longer time.
2-Update your NXT Firmware frequently as the LEGO may be fixed the problem.


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How can I add additional detail to large walls?
I've seen some rather impressive castle builds over the years, and with the release of Helm's Deep I'm clearly going to be building a few myself now.
As this set uses the LEGO sticker sheet to add some detail to otherwise flat walls, I'd like to modify these builds to include some better "brick based" details - but I'm not sure where to start.
Ideally I'd like to create some additional depth, and perhaps add some vines or ivy up the walls, that sort of thing.
Unlike previous questions I have a fair selection of bricks, including various SNOT elements.

Classic-Castle.com has a guide for making castle walls more visually appealing. Key points:

Different colours, shades and textures of bricks add subtle imperfections.
Break up the monotony with windows, doors, arrow slits, balconies and other structural features.
Use timber (brown/tan) as well as stone (grey) bricks and try out adding different materials.

I don't build castles in general. But I do build Churches. For me I go very simple when it comes to breaking up the walls. I use an extreme amount of windows. Other shades of bricks. Often will use another color to add details or designs.


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What does imprinted information inside bricks mean?
I just randomly checked the imprinted information inside some of the bricks in my Lego sets and found that it varied.
I found several different types of information:

Most pieces have Lego copyright notice ie. (c) LEGO, but many others don't have
Most pieces have two numbers are thin and italic, but some others are in bigger font.
In some pieces, there is a third number instead of LEGO copyright notice.

How does this information vary by year/set/produced country?

Most elements will have their official "Design ID" imprinted on them - this is typically the longer number, and can usually be used on the Pick a Brick site or sites such as BrickLink and Peeron to track down additional bricks. Note that this is different to the "Element ID" that is printed in the instruction part inventories which has the colour encoded with it.
I've got the following three elements in front of me at the moment:

The 6x2 plate [part:3795:6] has the following:

© LEGO (highlighted in red)
03795 - This is the padded Design ID (highlighted in blue)
10 049 (highlighted in yellow)

The 4x1 tile [part:2431:6] has the following:

© LEGO (red)
2431 - This is the Design ID (blue)
15-10 (yellow) - 3 others in the same set had different numbers

The Plant Leaves 4x3 [part:2423:2] has the following:

© LEGO Group (red)
2423 - This is the Design ID (blue)
6•02 (yellow) - another one of these in the same set had the same number.

I believe the numbers highlighted in yellow are mould numbers - so the factories can track down imperfections with old moulds or similar.
Looking at an element that I have in rather large quantities now, the Tile 4 x 3 with 4 Studs in Centre [part:88646:0] taking four at random they all have:

© 2009 The LEGO Group
88646

But then each one has a different mould ID: 01-B04, 04-B04, 10-B02, 08-B08
With regards to the copyright statement - as you can see across from these examples, they use different versions depending on the space available. I guess they feel that having the part and mould ids are slightly more important than their copyright statement for tracking purposes.

Thanks, have you got any brick that doesn't have copyright statement?

@Tiendq - The leg elements from Chinese made minifigures don't have the © LEGO statement on the bottom of the toe that normal legs have on the right leg. And I can't seem to find one on the heads with the hole in the stud.


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What minifig configuration has been included in the most sets?
Which minifigure configuration has been included in the most sets? I'm looking for the color of the head, arms, hands, legs, pelvis, and torso as well as the facial expression and any headgear. Please include an image of this minifigure doppleganger.

hmm, tricky one. Obviously the combination of yellow head and hands, probably (just) the original minifig face, but beyond that it gets a bit more ambiguous...

Presumably you would consider a printed torso or legs to be different from an unprinted on in the same base colour? Preliminary research shows that once again Black Torsos are just in the lead (165 in 124 sets) above White Torsos (162 in 104 sets) and Red (146 in 97), but it's the combinations of arms and legs that throw it... Lots of Knights though and quite a few police and firemen...

:) Yes. Painted details count as a different piece. I'm looking forward to your answer!

There should be some way to get this from bricklink or peeron. I bet on a red torso

So far, the best I can think of is the red classic space guy which appeared in 46 sets.
Considering minifigs were less specialized back then, I bet the winner is in that time period anyway, and the fact that spacemen wore an uniform makes me think there is no other minifig apperaing in 46 sets. Even the basic city worker only reaches a pale 21 sets.

Yeah, I was thinking either Space or Knights - the Classic Castle came with 8 blue knights for example, with breastplates and helms for decoration...

Which begs the question, should we count a set with multiple instance of the same minifig as one? (Not to mention some of the space sets are actual duplicates for different markets)

Hmm, good question - the Blue Knight configuration might have appeared the most times due to being in there 8 times, but he was only in 1 or 2 sets...

The Skeleton with Basic Skull appears in 42 sets. If you include the sets that have the same figure only with different headgear, the number of sets is 56.

If you had one of every set in peeron's database:
Torso: 973 - A plain torso - Black
Head: 3626ap01 - Normal plain smile - Yellow
Legs: 970c00 - Plain legs - Black
Their database is not complete, I haven't been able to find data for colour of hands or arms, and this is for each peice individually, not the minifigure as a whole, but I think it's the best that can be done.
This image isn't very good quality, but I had a go in Photoshop...


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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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Good LEGO CAD Design Software with Technic elements and animation
I'm taking computer engineering in Gr. 11 right now and our final project is to create a robot with the first version of Mindstorms. My partner and I are making a sumo robot for the class competition. We don't have the required parts at home such as gears and technic pieces and we're not allowed to take home the pieces.
We're using LEGO RCX 1.0 with 2.0 firmware and mostly technic pieces. Is there some type of CAD software that lets me test to see if the gears do what I want it to? I know LDD does this to an extent but they don't have the RCX 1.0 pieces, and placement of pieces is frustrating.
Also, I have the .dat files for LDraw, is there a way to import those parts into LDD?

Take a look at SR 3D Builder. I have not used this software myself but it looks like it may do what you need. It's free (for non-commercial use) and you can import your LDraw files.
Here is a link to some videos on YouTube
See below for the features list (taken from the website)

NEW Support for Piston - Rod mechanism
NEW Support for Linear Actuators and Shock Absorbers
NEW the Animation Console to easily create and animate your technic
models
Towball, HINGES and GEARS SUPPORT! Take a look to the Gallery  to see
what I mean
Connection Solver for quick connecting hinges and rotating parts
Support for RACKS and steering
Support for ANIMATED FLEXYBLE PARTS
Belt Generator with real connections
Now with GROUP management
New exclusive MirrorBuilding features  for quick build of symmetric
models. MUST TRY !!
Enhanced instructions editor to easily modify the order in which bricks are loaded in your model and/or take photos while building
Complex gear driven hinges support (quadrilaters deformation and
steering)
Great fully 3D building envinronment with reflection and
transparencies
You will see your model during loading time and can pause for
instruction steps
You can modify and save models (lDraw/MLCad .dat compatible format)
Fast selecting/moving/adding/removing you'll never see in MLCad
Copy/Rotation/Deletetion/Color change of single or multiple brick. Undo/Redo functionality
Real connections detection, not always the same near brick positioning
Brick selection by Block (means that solid connected bricks can be selected at once)
Grid positioning to speed up positioning of pieces
Automatic and precise positioning and orientering of most bricks according to connection detection
Automatic detection of rotation axles
You can easily load model from other known programs: it supports the
following formats

.dat files
.ldr files
.mpd files (only a few metacommand are currently supported)

How would I import pieces? I have a version of LDraw with the old technic motors but when I try to set that as the default LDraw folder, it says that there's no image folder

Never mind. I didn't set the types to display from base types to all types. I found the 9V mini-motor. But the problem now is that the model is missing its casing

@AlexYan I have not used the software, but a google search took me to this forum post:http://www.eurobricks.com/forum/index.php?showtopic=30348&st=30. The advice that may help you is "the error is generally risen when you have chosen a destination folder for the Part Library different from the default c:\lDraw and you already have the c:\lDraw folder on your HD.
To fix the problem, use the . option to choose the correct folder you install the part library to.
If you can't remember it, search your hard disk for the "Conns" folder. Its parent folder is the correct one!"

@AlexYan I'm the author of SR 3D Builder.
If you have any trouble or question just email me and I will try to help you Sergio

Is there an alternative for macOS High Sierra?

Edit to update: It looks like the NXT version of RDS only really supports the "Tribot", and has partial support for the "ShooterBot", but does not have a simulation of it.

I know the original Microsoft Robotics Studio supported building robots using the RCX bricks - although the latest version has been upgraded to NXT and it has simulation tools too for testing your robots prior to building and deploying your code.
As the core components should be the same (gears, beams, etc.) you should be able to get a reasonable way through testing even if the final code has to be written elsewhere.
I know some people have had success upgrading the RCX samples to newer versions of RS, but I'm not sure if anyone's tried it with 4.

Wow. Didn't know that. I'll take a look


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Can you program an RCX using the Mindstorms NXT 2.0 software?
I was asked to teach a robotics class and found several RCX bricks in storage.  Can I use these bricks with the Mindstorms NXT 2.0 software?  If not, what would be the software I would need to use the RCX bricks?

No, the standard NXT-G software provided by LEGO will not allow you to program a RCX brick.
Outside of official software, your best bet is probably to use NQC which is C-like; there's also NXC for the NXT which is similar.
There are a lot of others which have been discussed in the following questions: Is there any other way to program the Lego Mindstorms NXT other than the provided software? and Can I write programs for the LEGO RCX 2.0 in Java/C++?.


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Which type of LEGO bricks would be compatible with the Mega Bloks Blind Bag Figures?
My husband collects the Marvel figures which come in the Mega Bloks blind bags. His birthday is coming up and I'd like to build him a display for his Marvel figures. I'd strongly prefer to use LEGO in order to build this display. I've read that certain types of Mega Bloks are compatible with certain types of LEGO bricks. (I will most likely have to purchase online so I won't be able to compare size in person before purchasing.)
How can I make sure that the type of LEGO I am buying will fit the foot holes of the Mega Bloks Marvel figures?

Hi Suzy, if you take a look at this question you'll see a few examples of how they work together.

Mega blocks can stand on any Lego plate just as good as Lego figures. This is demonstrated in this battle scene between Lego and Mega Blocks figures:
mega bloks halo vs. lego star wars clones

Before you play this, I advice you to turn down the sound a bit...

You could use any LEGO plates with the mega bloks figures. In the blind packs they stay on the mega bloks doublebricks, that are fully compatible with LEGO doublebricks. So you could take any set pack as you want. (some time ago i have used lego collectable minifigures stand with megabloks figures, it was usable, but i think they weren't standing too tight in there).

If you're just looking for some LEGO Bricks to build up a scene, then any of the standard LEGO sets or boxes of bricks would fit the figures - certainly the holes in the feet will fit the LEGO studs quite nicely, and the feet are spaced correctly to fit.
You could also take a look at the Marvel Super Hero range that LEGO offer which include a rather large diorama set 6868 Hulk's Helicarrier Breakout.
Note that the larger figures on the LEGO Shop page aren't compatible with the Megabloks figures, as they're over 7 inches tall.


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How to convert new 4x4 crawler to tracks?
With the new 9398 4x4 crawler coming out what would need to be done to convert it to a track based system that looks similar in style to the ones sold by Mattracks?
On a related point what would make a good basis for making a Lego Technic model of the tracked buggies used in Prometheus that use similar 'track wheels'?

I started with something based around the tracks that came with the original LEGO Mindstorm's kit: 680 Technic Tread:

I then build a rather more bulky than I'd have liked set of beams around it - I think if I'd have really dug out my Technic elements I'd have had more success making it look closer to the mattracks options:

Here's the very bulky rear - this would obviously want to be pared down somewhat, and you might want to either power the top wheel, or both the bottom ones:

Here's the rear with the beams removed:

You would need to have the driving axle on a universal joint to allow cornering, and would want to mount the whole thing on the mounts for steering.
I think it would be better if I'd had more of the newer Technic beams (the ones without the studs - I could have then connected them with two coat-hanger pieces and have another one vertically to the top.

Greate answer! I'd still like to see something that uses the 'tank' tracks that you get with various kits though (big digger, snow plough). Also it seems that Mattracks simple bolt to the hub where the wheel goes (probably with an adaptor plate) so I was expecting to simply slip any solution onto a shaft. Would that work?

@ClaraOnager I'll see if I can find any instructions for that model, and check the connections. I'll also try and dig out a few more bits of my Technic collection and have a better go at it ;) As to the other tracks, the end result would probably be similar, but you'd have a bit more control over the size due to the flexibility of the track sizes.


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Connecting to NXT Brick via Processing over Bluetooth
I am attempting to control my NXT model via the Processing programming language rather than the provided language based on LabView. When I can establish a connection over Bluetooth, this works rather well, but establishing the connection itself is problematic. It appears to work only every dozen tries or so.
My question is, what are some good troubleshooting steps for this type of activity? I can see the NXT brick in my list of Bluetooth devices on my laptop (Win7 64-bit), and I can even see it in the list of devices when I run a test script in Processing. My laptop appears on the list of devices on my NXT brick, but the connection icon at the top of the NXT window only shows "<" rather than "<>".
I believe I am using the latest firmware version (1.31). The other settings listed are:
AVR & BC4 - 1.01
What else can I attempt to try? I am attempting to connect to other Bluetooth devices (iPhone, Wiimote) but have not found the necessary libraries to allow those connections yet.

Are you in close proximity to a wireless device (2.4 GHz)?  Both bluetooth and wifi use the same frequency spectrum, so a conflict between the two may be a reason why you're having connectivity difficulties.

Ha! I missed the `12. Thought you asked this today. ;-)

You can use any programming language you like to remotely control the NXT provided that it can access a serial port of your computer. The Bluetooth connection on the NXT provides a virtual serial port. You can see this by opening "Devices and  Printers" and double-clicking on the NXT (provided that you have already paired it). Then have a look at the "Services" tab in the window that opens.

In the screenshot above, my NXT provides a serial port on COM4. Yours may be a different number.
So you need to do two things:

Figure out how to open a COM port on Windows using the Processing programming language.
Use the information in the NXT Bluetooth Developer Kit (available from the LEGO MINDSTORMS download page) to send commands to your NXT.

To use other Bluetooth devices with your NXT, you will need to relay the information though a computer to translate it into the commands from the NXT Bluetooth Developer Kit. In the case of the iPhone, you could write a custom program just as you would for a regular computer.


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What kind of yellow is used for a typical minifigure?
I've done some research and found a basic LEGO basic colour pallet. I recognise the yellow used for yellow bricks (24, Bright Yellow, #fec400) but it doesn't seem to match the colour for minifigures which are slightly less orange.

I believe it is supposed to be 24 Bright Yellow, however I know there were some complaints a last year or so regarding the collectable Minifigures and others that were made in China not having the same hue as "regular" minifigures - and now that some of the licensed products are also being made there, this difference will become more common.
These figures are apparently not made from ABS but a cheaper plastic, which is what causes the difference in colour.


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How to build bridge using 4.5/12v train rails from 1969 Lego brochure
I am interested in building a bridge for my layout and stumbled upon this forum post in which user 'Istokg' posted a picture of a train bridge made from the blue rails used in the pre-1980s train sets.

This is from a 1969 Lego publication which has been scanned and uploaded to brickfetish.com and can be found here.
Obviously this could be built with either the blue rails as shown or even the newer grey rails.
My question is: can anyone provide insight, (or even better, building instructions), on how it is constructed. Even the larger picture in the scan is still too small to see exactly how the rails are fixed to the main structure.
--------- Edit ---------
I finally have all of my Lego spares in one place and have had time to try a prototype build of the bridge using @62Bricks' LDraw file, but I have hit upon a problem:
The angles of the vertical rails where they connect to the plates at the top are such that it is not possible to attach the curved outside rails. This is best illustrated by the picture below:

As you can see, there is no way to attach the upper rail as the vertical rails attached to the studs on the lower row of the plates almost touch the studs on the upper row.
I thought at first this was due to my using 'Gray-era' rails rather than the 'Blue-era' rails used in the 1969 bridge and in @62Bricks' LDraw file but as far as I can see there is no difference between the two that would affect the outcome here. (I don't have any blue rails to test though).
Further supporting evidence is that at high magnification in LDraw, the stud on the plate can be seen protruding through the end of the rail, which is impossible in practice.

I do happen to have a straight rail where the end cap is broken off, I tried this with the approximate angle of the curved rail and was able to achieve something that looked about right:

I don't want to have to break the ends off my rails to make them fit and also the grip of the broken rail on the stud was much reduced, so I doubt a bridge made with this method would hold up well with the vibration of trains rumbling across it.
I am, therefore, stuck. I have my prototype bridge part built but I can go no further. I would love to hear any suggestions on how to proceed as well as any theories as to how Lego made the bridge in the picture work.
--------- Edit 2 ---------
After much experimenting with jumper plates and studying of the original picture, the solution was actually quite simple. (And identical to that suggested by @jcranton in the comments of the accepted answer):
By adding 1x1 plates under the connections to the vertical rails, the collision is avoided. (@jcranton's suggestion to use round plates I think is better than the square plates I have used).

The method above also means there is no need for double stacking the plates as shown in the LDraw from @62Bricks.
So my prototype is taking shape:

I have made a few other modifications, most notably dropping the level of the deck to accommodate the height of the trains I intend to run on it. I have also added reinforcement plates to the back of the sides to add rigidity as I intend to make the bridge wide enough for two tracks.

It's very difficult tell without getting a closer look at the set but it looks like they may be using curved track parts to build the bridge (I also thought these could be straight bricks under stress). As it's a Samsonite set it may be connected with specially designed pieces.

Are you mainly interested in reconstructing the bridge exactly as it was in the photo, or constructing one that looks like it using the old rail pieces? Based on the parts available at the time (at least to the public) it does not appear the bridge in the photo is fully connected. Instead, it seems the "supports" are fitted around the railbed as decoration. Using modern pieces, though, it would not be hard to duplicate the appearance of the bridge and also make it structurally sound.

@62Bricks - It doesn't have to be exact. I am interesting in understanding how it is constructed using the pieces from the time, even if the rail pieces are just decoration. But for my build I can use any pieces available pre-1994. (This is a self-imposed limit on my classic town layout). As Ambo100 pointed out, the bridge in the photo may be using specially designed pieces and I'm particularly interested in discovering what they may be.

I don't believe there are any special pieces used. I think the rails are simply attached by the ends on plates. The structure has been built "sideways" and then placed on top of the simple bridge made with bricks and plates connected by the tracks on which the train runs. This is a technique you can see in other photographs from the same era.

Wat ontzettend leuk, toevallig zocht ik naar zo'n soort brug om te bouwen. Van technisch lego had ik wel iets gevonden, maar ik vind dit veel leuker. Bedankt voor deze site.

Google translate renders this as "How great fun, I happened to be looking for such a bridge to build. I would have found something from technical Lego, but I like this much more." But this seems more like a comment to me than an actual answer.

I found same problem using blue rails at the time, can't be done. I've picture here, leaflet for rails,  yes the rails going up are in front of the rails across, so plate under.

Here is an approximation of the bridge that appears on the cover of the catalog pictured above. Unlike the version in the picture, this model uses bracket pieces to attach the arched section to the rail bed. All the pieces in this build were available prior to 1994.
The arches are decorative and do not really contribute to the strength of the bridge. This is completely computer-generated and may not be very sturdy in real life. It would not be difficult to adapt the rail bed to give it more strength, however.
I put together an LDraw file with steps for building this bridge. The file can be downloaded from my MOCpage.

@62Bricks - I have updated my question with info about the problems I faced trying to build the bridge. I think LDraw may have allowed some impossible connections.

It's difficult to tell how this was done in the original picture, but it looks like you might be able to work around the issue by adding a 1x1 round plate under one of the rails that are colliding.

@jncraton - I came to a very similar conclusion and saw your comment when I came back to update my question. I have credited you in my second edit. Thanks!

Ah - one of the pitfalls of virtual building. I recall messing with that angle a long time trying to get things to look right and I missed that collision. Sounds like the round plate fix will work.

Mocpages.com is down, probably forever. Anyway we can get a mirror for the LDraw file? Tried https://web.archive.org/web/20130503123257/http://mocpages.com/user_images/14152/1341434995m.ldr but no luck

I just built the bridge yesterday. I didn't have all the parts so had to be creative at some points.
I'll improve some joints once I picked up more of my Lego at my dads' place.
Very funny project!
Pictures:

Now all you need is instructions for the rest of us (just kidding)!

Thanks for your help with this construction. I have made a faithful copy of this 1968 catalog bridge, pics:-

Also a list of components.

Hope that's helpful. I have a 12 image photo diary of the build too. If you would like it message me through Flickr.

Nice result. I took mine apart a while ago.

I took a close look at the Chris Bull's Flickr photos posted above which are magnificent. When trying to build my own bridge, I ended with a slightly different parts list which I am trying to reconcile. I can't figure out where additional white 2x4 plates and blue 1x2 plates should go. The Flickr album indicates 10 white 2x4 plates, and I ended up only using 4 of those, and 8 blue 1x2 plates and I couldn't figure out where to place any of those.