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How can I motorize City-scale wheels?
I'd like to build city-scale (6 studs wide) vehicles motorized with either PF motor or clockwork. The primary problem right now is connecting wheel(s) to motor. Are there small enough LEGO wheels with axle hole? Any other idea on how to connect it to motor (with gears, friction, or by any other means)?

If i remember right, the tires of the small LEGO City wheels fit perfectly on a Technic 1/2 bush which then gives you an axle hole, but note that this is very flat on the ground. I don't know if its high enough to add a very small gear and build up the connection to your motor.

4 studs wide seems not enough to put motor or clockwork. I meant 6 studs used in trucks, buses, SUV: they use large wheels. But this is useful info anyway.

if you use the 1/2 bush and add an axle on your own, you can build your vehicle as while as you like - just depends on the axle you're using.

If a gear doesn't fit, a rubber band belt would.

@Pubby You know they do make LEGO technic belts.

There are a number of pull-back motors for system wheels.  Look through the Motor, non-electric section of bricklink. There is even one rechargeable electric motor.
There was also an all-rubber tire with an axle hole in some of the old space sets, though that may have a rounder shape than you're looking for.

Ever since this question was asked I wanted to build something that would fit that scale.  Here's the result:

I know this is not using only LEGO pieces but, I thought that there was no way to make the LEGO motors fit 'inside' a normal looking LEGO City vehicle. So, this is basically a homemade motorized brick made of a 2x2 brick glued to the 2x2 wheels-brick.  I then gutted out the insides to make place for all the electronics.
It's controlled by an ATtiny chip (similar to the Arduino chip) and uses a 3.3V LIPO battery.  The motor is a small 'pager motor' that I got from an old toy.  The chip is programmable and can run the motor at different speed.  I'm pretty sure I could figure out a way to make a steering mechanism to go with it and, if I go really crazy, a BlueTooth brick to remote control it...
You can see it in more details in this video, see it run in this video and I have more pictures on my blog.

+1 I was just about to edit what I thought was a typo until I looked it up. You really did mean it's a ATtiny chip. :)

In this case, an ATtiny13.  I love working with this chip.  I'm going to get some surface mounted ones to make even smaller projects.

Most vehicles in modern city sets use wheels with ∅20×12 mm tires. Such tire can be put on 12 tooth double bevel gear or combination of narrower ∅11×8 mm wheel and 12 tooth bevel gear to connect with axle. The only problem I see with this solution is that tires are swollen a bit by gear so they are not freely turned when covered with mudguard with arch.

It would be nice to see a picture of this setup.

You could try connecting your wheels using the friction pin/axle

This provides some friction to the wheel hub while also giving the motor an axle to turn. It won't work if there is too much resistance, but for small setups it might be okay and it will fit in all the existing pin-connected wheels. If you're feeling crazy, you could always glue the axle into the wheel hub, or use a bar piece jammed into the pin to increase the friction. Not that I would recommend such techniques!
There are also some wheels that are turned by axles, such as this one. In fact, on this page you can see many wheel/tire assemblies that Lego has shipped, and there are lots where the wheel hub is connected with an axle. Any of these can be easily motorized, though not all of them will be small enough for 6-wide city scale.


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Which hand is this minifigure extending normally?
I remember more than one argument with a friend over which way LEGO minifigures' hands should be oriented to be correct (with the thumb pointed upward/inward, like a human hand's neutral position).

This gentleman is holding his left hand so the rounded side faces down, and his right hand so the rounded side faces up. Is there an officially correct orientation? The peg connecting the hand angles slightly, so I've used both orientations in different situations to keep hands on steering wheels and control panels. Did I risk aggravating any minifigure's carpal tunnel syndrome in doing so?

That's the kind of question I would expect from FreeLUG members when they're bored during an event.

On the other hand, are we actually discussing anatomical correctness of minifigures?

I personally consider the left one as up-right ever since I was a kid and that's how Lego place all their hands in their promotional pictures:

I've become more pragmatic as I've grown up: as a kid, there was a definite "right way up", but as a grown up I've come to realise that some poses are only possible if you turn a hand upside down (for example, getting the binoculars to a Mini Figures face correctly).

There's also a special position in which you can align both hands to grip the same utensil which requires the lower hand to be "upside-down".

@Zhaph, Joubarc: Yep, those poses are the reason I've never been 100% sure.

I have always done it the left-hand way except for those few exceptions.

I think the most recent Hagrid minifigure also supports this point of view, since he clearly has thumbs, and when these are oriented correctly, the flat side of his hand is upwards.

Here is another way to consider it:
Make a fist, and don't bend your wrist.  The pinky's side of your hand is mostly aligned with the rest of your wrist and forearm.  The thumb's side of your hand is not so much aligned with your wrist and forearm.  Also notice that the curve of your fingers tapers toward the pinky finger.

Now compare to the minifigure hand.  Notice that the wrist is closer to one side of the hand (the left hand in your photo) than the other.

The left one is more natural, because the shortest fingers are on the down side.

The correct way is shown in his left hand based on LEGO Friends. Go have a look at the minidoll, where the arm and hand is one piece and cannot be rotated to another position:

Minidoll hands are more curved on the top too, probably to accommodate some tools as some other answers point out.

I would generally agree with pcantin's answer, but there are some "official" cases where the right side is correct. Iron Man typically is in the "right hand" configuration, because it attaches translucent light blue circular 1x1 blocks to the bottom for repulsor beams. Also, the Frodo and Bilbo magnets both hold Sting pointed straight up, and do so using the "right hand" configuration, so their hands aren't high up in the air.

Personally, I consider the left hand correct, as you hand place a stud, an ice cream piece, or anything that is to be put on studs on the minifigure's hand.

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Can I write programs for the LEGO RCX 2.0 in Java/C++?
Is there a library which makes it possible to write LEGO Mindstorms programs for RCX 2.0 in Java or C++? With the LEGO software it takes so much time to write good programs.

I was looking into this just recently. There are libraries and also it seems there are other firmwares offering alternative operating systems you can embed on the Mindstorm.
For C++ you could try:

nxtOSEK is an alternative OS offering a C++ api
BrickOS is an alternative OS with a C/C++ development environment
NXT++ is a C++ lib for controlling the original Mindstorm with a C++ API (through BlueTooth or USB)

For java solutions might be:

leJOS an alternative OS with a JVM
The NXTComm Processing Library

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What kind of plastic are LEGO bricks made of?
It’s rather obvious that Lego bricks are made from plastic, but there are many kinds of plastic.
Is the recipe for LEGO bricks plastic secret?

Very similar to http://bricks.stackexchange.com/questions/155, but potentially different enough ;) That question notes that the Transparent bricks are made from a different type of plastic.

Actually, it depends on the part.
Most parts are indeed ABS as it's a very sturdy plastic, but sometimes it's not suitable, or downright impossible to use. I've seen a presentation on quality issues given by a LEGO employee in LEGOworld a few years back, and as far as I remember there were between 10 and 20 sorts of plastic in use. The ones I remember are:

ABS (acrylonitrile butadiene styrene) for most regular bricks
PC (polycarbonate) for transparent bricks, as ABS can't be made transparent. Polycarbonate parts on the other hand have too much friction when in contact with other polycarbonate parts, making them extremely hard to disassemble. LEGO designers are forbidden to have some PC parts put together in models.
Rubber for tires and rubbery things - that's kinda obvious
A less sturdy plastic (can't remember the name) for parts which are more subject to being bent, for example studless technic beams.
As of  2018 plant elements will be made from a polythylene sourced from sugar cane.

And the list goes on. I know the presentation hadn't been made public, but some people took pictures, so if I ever find it back I'll add a link.
EDIT: still can't find it, but I know it was given at LEGOworld in 2006 by Bjarke Schønwandt who was Global Quality Manager at LEGO at the time (he may still be, I have no idea).

"Polycarbonate parts on the other hand have too much friction when in contact with other polycarbonate parts, making them extremely hard to disassemble. LEGO designers are fobidden to have PC parts put together in models." Details like this are exactly the kind of information I'm looking for on this site. Thank you!

Rubber for tires - Really? Actual tree rubber?

@Fredley I honestly don't know about that (I had forgotten rubber can be natural) but it's most certainly synthetic. Let's not forget LEGO is the first tire producer in the world (in terms of tires produced per year)

I'm pretty sure that the tyres are not made from real rubber, but some of the elastic bands used with Technic might be. Natural rubber does degrade over time, so I wouldn't be surprised to learn that it's another synthetic compound.

LEGO tires do degrade over time. Well, at least in GBC modules they do.

@mikl Indeed - most of my original black rubber bands have degraded, although some of the newer sets have a different style of rubber band that seems slightly firmer, and are circular in their cross-section rather than square.

Polypropylene is typically used for "living hinge" molded parts. I can find a cite for this.

ABS is not just one plastic: it is a copolymer and is extremely customizable by varying the inputs. There are frequently used commercial formulations though.

It's also worth recording that most clones are polystyrene, which is roughly half the cost and can't be made as elastic as ABS.

I love legos too :D

The rubbery parts are now made with some sort of butylated material. So, pretty much synthetic rubber.

According to a letter from a LEGO representative posted at this site:

Tires and elastic materials found in some LEGO sets are manufactured
  from Styrene-Butadiene Styrene (SBS), a material commonly found in
  vehicle mud guards and shoe soles.


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Why did Technic bricks have holes in the studs?
Lego Technic (/ Expert Builder) bricks have always had a very different design than the normal Lego brick, with peg holes lining the sides serving fairly obvious purposes, but they also have had (as long as I can remember) hollow studs on the top:

Now that these pieces are appearing in non-Technic sets I've seen them used often to hold things - they're about the same size as a minifigure's grip, so wrenches, guns, gems, and other decorative elements that need to stand are often stuck into them.
But Technic has no minifigures and features only sparse decoration. I don't recall ever seeing a Technic set that uses the holes. It seems like they would be much more difficult to mold especially as far back as Technic's introduction in the late 1970s.
So why were they introduced in Technic? (Or am I wrong, and they were not introduced in Technic / Expert Builder?) Did they serve a functional purpose, or were they just another visual marker to separate it from "regular" Lego during its introduction?

From principles of molding, you want a uniform part thickness throughout if possible. This facilitates plastic flow as well as dimensional stability (you want uniform shrinkage on cooling.) Removing a divot from the underside of a stud serves this purpose in a regular brick.   The Technic brick with through holes would have had a large amount of solid plastic under the stud compared to regular bricks, which could create undesirable shrinkage and warping from stress in cooling. So removing the top divot helps there.
However, if you examine a 1x16 beam from Expert Builder, you can observe a plastic channel running along the underside between studs 4 to 13 (which are injection gates; also stud 8, or 9.) The 1x8 doesn't have this. This channel would let the plastic flow away from the injection gate without turning too many corners. It's also possible LEGO used a reciprocal molding action where plastic is pressed in one gate, then another, in a rocking action, to facilitate welding of the multiple injection streams. Solid studs might lessen the effectiveness of this process, but the channel helps it. If the channel was necessary to produce a 1x16 beam back in the day, and the channel forced hollow studs, then the hollow stud style was the only way to make a 1x16 beam. The technical difficulty of making a new, longer brick (beam) may have influenced the look of the whole Expert Builder system.
That's only my theory, but you can still see the channel for yourself.
My tests also indicate the hollow stud separates from another beam more easily than a common solid stud would.
It remains possible though that they were just maximizing the usefulness of the part by making the stud hollow. Though the fun part of being an engineer is maximizing more than one property at once.
So my thought is the hollow stud came from various molding principles. Cost of plastic comes after that (and yes, if you can save a bit, you do.)
Another interesting trivia: the Technic studs were each freehand drafted in the early Expert Builder instruction booklets. I joked about reproducing this while showing some Lego employees (in 2001) what could be done with non-representational rendering, for instance a pen-and-ink renderer with random jitter.

True, molding complexity does influence cost more than quantity of plastic.

I was  very intrigued by this question.  So I messed around with two LEGO Technic beams, a long one and a short one.  The 'pins' at the bottom of the beams are made to fit in the hole on top of the studs.

When using the studs holes instead of the normal 'in between' way, the holes on the side of the beams are offset at mid distance.  This could be very useful working with gears (I'll remember that one next time I have a complex gears ratio to create).

In the end the rules are:

The bottom beam must be shorter than the top beam.
The bottom beam cannot extend past the top beam ends.

The following picture shows why rule number 2 is important. The end of the top beam and the studs of the bottom beam interfere.

My question is about the holes in the studs, not the holes in the sides of the bricks and on beams.

I tried stuff with the beams and changed my super bad answer for this one

In my opinion, you don't need to look further than plastic quantity, and thus cost.
Take a normal brick or plate (easier) and look inside it. You'll notice that each stud is hollow, but from below. Why? Simply because there's no need to have it full with material as it serves no purpose. It's easy to make the mould that way, it doesn't remove any functionality of the brick, everybody is happy.
Now take a Technic beam and look at it from under. The Technic holes make it way more difficult to have a mould which has cavities under the studs. So the easy solution is to have the cavity in the stud itself, which has the added benefit of adding functionality to the stud itself. Also, I suspect that the sturdiness of a Technic beam is better if the upper side is full.
Note it's just speculation; but most of the times you need to analyze a part with the eyes of a LEGO producer (use as less plastic as possible), and of a designer (have a part which fits with as many other parts as possible). Nowadays, it's likely they would use hollow studs more and more, and I wouldn't be surprised if they end up on regular bricks some day — but that's going to take a while as there is a third factor in play: brand recognition. regular LEGO bricks have full studs, with the LEGO engraving, and that's not seomthing which LEGO will easily accept to replace.

Curiously, plastics texts suggest placing a logo to hide the injection gate, which is typically on a stud.  LEGO does this (look for one or more logos with a blob in the center), but I have no idea if they pioneered it or just jumped on board. It is certainly part of their trade dress now.

Oops, the gate was on a corner of the brick in the 1960s when it was made of cellulose acetate. So the stud logo came before the stud gate.

Most 1×2 (and longer) plates and bricks have a pin at the bottom right in the middle of studs that perfectly fits this hole.

Connecting this way gives you half-stud shift.

Ah, but what goes in the tiny hole in the pin on the underside of the 1x plates? :)

Television antenna spokes? Flower stems?

Spider legs, plumes (various sorts), Technic chain links, screwdrivers, universal join centre

After getting a great answer to my question: When did Lego decide that it was okay to put a stud into a technic hole? and looking at the pdf slides linked there: http://bramlambrecht.com/tmp/jamieberard-brickstress-bf06.pdf, it's stated in one of the slides that the words "LEGO" on the top of the brick adds a little height, .14mm to be exact, to the brick.  This extra height interferes with the Lego dimensions for Technic elements.  So the hole'd studs was likely a way to still have the stud, but shave off that top .14mm.

I was looking for that PDF, thanks a lot for finding it!

In answer to part of your question, Expert Builder sets were not the first appearance of the hollow stud. I believe the old-style windows were the first, starting in the mid 60s:

The reason for the hollow studs here seems to be related to the exposed underside of the stud face. LEGO seems to have wanted to have the inner frame of the window smooth rather than have the divots that regular studs would create. So they shifted the divots to the upper surface where they would be hidden in most uses.
There is another functional reason some modern pieces have hollow studs: child safety. Around the same time the Expert Builder sets were introduced, LEGO started using hollow studs on small cylindrical pieces like 1x1 round bricks and cones that went clear through the brick. This was to provide an air hole should one (or more) of them be stuffed in a nostril or ear canal, or be swallowed or inhaled. In some cases, like with 2x2 round plates and bricks, LEGO uses a through axle hole for the same purpose.

The 1x2 plate with 1 knob (Design ID 3794) has the same design for it's top stud - I assume for the same reason Joubarc gives - you can't create a hollow stud from underneath as the peg's in the way.
Peeron.com

Sorry, this is a correct point, but -1 because it's not really an answer to anything - it would be better merged into someone else's answer as another example of the same design principle.

@JoeWreschnig Possibly. However, it does answer the part that in the question that says "(Or am I wrong, and they were not introduced in Technic / Expert Builder?)" - all of these that I have from my youth are like this, but I can't prove which came first.

The jumper brick was a contemporary of Expert Builder, and space sets used the hole by plugging a torch into it.

Hollow studs fit the bars on the underside of 1×x bricks. The same hollow studs are found on Lego windows and Minitalia pieces (Lego made in Italy), also 1×1 with holder and 1×2 tile with 1 stud, 1×2×5, 1×2×3 slope.
Other brands, such as Montini and Tente have hollow studs and unknown on 1×1 plate. So maybe should ask 'why aren't studs hollow on all Lego pieces?' So Technic beams were not the first.

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When did LEGO decide that it was okay to put a stud into a Technic hole?
At one point, LEGO didn't really support putting a stud into a Technic hole, stating that it caused too much stress on the bricks.  And for a while, there were no sets where that's the case.  However, lately, I've been seeing several sets that do put the studs into Technic holes; and I'm curious when that started.
There's an example of the technique here.  You can see it with the trans-orange 1x1 round plate on the side and top that's attached with the stud in the Technic beam.

I would have sworn it was still forbidden. IMHO this may be an exeption limited to such round plates.

FYI For those of us no living in the US that link may or may not work. The set is Bucket Truck 8071 http://brickset.com/detail/?Set=8071-1

I'm not seeing that construction anymore in the most recent (we own) sets. It looks like it has been replaced by half-pin inserted into technic holes, and the end of the half-pin is used as a stud.

That's interesting.  I don't think that would be as strong a connection, and it inverts the direction of the stud - the stud would face away from the hole, instead of in the hole.

2006
LEGO's official position on this technique was explained at Brickfest 2006. Jamie Berard, then a relatively new designer in Billund gave an excellent presentation on why certain techniques are considered "illegal" in official sets. The basics message is that building techniques should:

not stress the bricks
be suitable for the target audience of the set

He described in some detail the ways that Technic beams and regular system bricks can and cannot be combined in official sets. The main problem areas occur because:

Technic holes don't exactly line up with the studs on the sides of system bricks
the holes in Technic beams are slightly smaller than the ones in system bricks

The implications are:

Although system brick studs can be inserted in the holes in Technic beams, this should be avoided where it would be difficult for children to take apart. Jamie gives an example where a brick has a single stud inserted into a beam, and describes it as "technically legal" (but not recommended). This is the situation in your example.
Where the combination of Technic and system bricks results in an assembly where components interfere with each other, this can stress the parts. However, this is not the case in the example you cited.

According to these rules, then, the example you give is not illegal. Clearly, it can be a problem under some circumstances, but is acceptable under others.
Unfortunately, none of this actually answers your original question, as there remain two possibilities:

Your assertion that "at one point, LEGO didn't really support putting a stud into a Technic hole, stating that it caused too much stress on the bricks" may not be correct. The misapprehension may have arisen because Lego emphasized the illegal uses of the technique, but down-played legal ones. In that case, we may assume that set designers simply chose not to use the technique (or were unaware that they could because they, too, were misguided).

The alternative explanation is that LEGO did make a sweeping statement to this effect, but later realized that it needed clarification. In which case, Jamie's presentation in 2006 seems to be the first clear public statement of the more detailed rules (of course, internal designers might well have been aware of the policy tweak much earlier, but still chosen not to use the technique). If there was such a policy adjustment, this would establish why the technique was not used until recently.

Without the text of LEGO's earlier communications on the subject, it is difficult to know which explanation is the correct one. Either way, I'd urge you to look at the slides for Jamie's presentation. It is available online in powerpoint format and as a pdf. Apart from being an interesting read in their own right, they also make it clear that this single stud-in-a-hole has been legal since at least 2006.

Wow. Great answer.  I had not seen the slides before.  You are correct, the slides explicitly state that the use we're now seeing is legal.

1977
When Technic was first introduced.
Check out this alternative build of set 850:

Nice find, Niels.

Oh, I wanted to show off with the "ancient" 8480 Shuttle from 1996... http://lego.brickinstructions.com/08000/8480/056.jpg

This seems to be a case of "Legal then, illegal now" as per pages 27-29 of the earlier mentioned presentation. The deck mentions that single stud in hole connections are allowed, but not multiple studs (slide 11-12 of the same deck) - BTW, your picture immediately took me back to my childhood - I built that roadgrader several times as a child. Amazing how one's memory works :)

@zovits, the 1682 Shuttle from 1990 pre-dates it by a bit.

Seems to have really come into use this year. The Winter Village Post Office (pages 65-66) set also uses it for a larger piece with a SNOT block holding the window roofs on:

I hadn't seen that yet.  It looks like they are keeping the technique to just a single stud in a single hole.  That's interesting!

The technique isn't new this year: the The Emerald Night (which appeared in 2009) uses the single stud-in-a-hole technique for the details on its carriage.

See pages 11-12 of Jamie's presentation in Kramii's answer - you'll see that 1 stud in 1 Technic hole is OK, provided a few other rules are respected; more studs isn't as it would be too hard for children to pry apart.

Good question, but I think the example shown demonstrates where Lego currently accepts this kind of construction; i.e. only for small, decorative components and not for major structural interfaces.

Yes, but it seems to be a technique that is fairly recent for the company.  My question isn't about how Lego uses this technique, but about when they started using it.  I don't know of any definitive set when they began using this technique (it's been used by AFOLs for a long while).


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

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

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

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

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

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

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

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

Should have said "last paragraph".

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

Our categories are:

brick
shaped
mechanical
people
people tools
finish

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


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Has anyone made their own custom LEGO bricks?
As I've just learned, LEGO bricks are made from ABS plastics.
I wonder if it would be possible to make some simple molds at home, get some ABS pellets, melt them up and make your own custom bricks? Novelty shapes or colours, perhaps?
Has anyone tried this, did it work?

Sounds like an awesome idea!

Completely feasible, all you need is the equipment and you're good to go!

Nice question. I cast a lot with resin in RTV molds but I would like to know more about ABS casting (tips and tricks).

Apart from those fans who contracted professional molds for new parts, no. Some have made milled, not molded, parts.  This question might be too open ended. For one, it is feasible if you have lots of money, but

This question might be too open ended. For one, it is feasible if you have lots of money, so an answerable question could be Has anybody made a custom part using hobbyist equipment? Also Bricks is really too vague; it's very hard to make a brick, much harder than a sword or a gun.

mikl: It's certainly "feasible" because LEGO does it. I tried to redirect your question a bit because I think you are looking for more practical advice.

Yeah, feasible should probably be extrapolated as “without spending thousands of dollars” :)

BrickLink is a good website where you can get all sorts of different lego e.g. some that were out for a year then vanished can still be brought here, as well as a selection of Custom Parts - a lot of these appear to be regular parts that have been "chromed".

People with 3d printers have made their own LEGO bricks. The plastic used is ABS.
Blog post

Interestingly, 3d printers can be constructed out of LEGO parts - you could have it self replicating!
Of course, you would need a very expensive and high quality printer to make good pieces. Cheaper ones can only make hollow bottoms and the banding from manufacture is highly visible.

Can you make your answer more specific? Bricks made on $ 100,000 printers interoperate with the real brick but sub $1000 printers produce bricks with poor tolerances.

LEGO itself uses 3D printers for prototyping, by the way.

Ah, yes – of course. There's little you can't do with 3D printers :)

@Joubarc, reference?  Not that I don't believe you, but it'd be cool to read about.

Sorry, this isn't something I read on the web, but witnessed firsthand. LEGO Benelux once lend BeLUG a prototype of 8294 Excavator to show at an event, and the linear actuators in there weren't fully functional, but prototype parts which had clearly been 3D printed. I may have seen this on other occasions as well, but that example was very obvious.

Well, nothing a good search can't handle, apparently... here you go: LEGO Turns Design Concepts into Working Prototypes using Objet 3D Printer - the video provided by LEGO is very interesting.

Big Ben Bricks sells some custom LEGO-compatible elements, mostly train wheels. Since they produce sizes which the LEGO company doesn't, they have some customer, but the production cost is usually quite high for such a quality.
BrickForge does sell custom elements too, and so do BrickArms. Usually, custom element producer will focus on elements the LEGO company is not likely to make, either because they feel the element fills too small a niche, or because they don't want to (arms). Yet there is some demand, so these sites aim to fill the gap.
If you've got ideas, maybe contacting one of those would be interesting, either to learn about their processes, or to suggest the part.

This came in as I was typing the same answer and content!  +1 for prescience.

I'm surprised it didn't happen in the other direction, I'm usually quite a slow typist. Cheers, you'll beat me next time :-)

Yes, is it definitly possible.  However, as this page states:

Producing physical prints from our provided 3D models prompts certain fabrication considerations. According to Wikipedia, the precision of Lego pieces is less than 10 microns. As of early 2012, however, standard Makerbot printers have an XY resolution of 100 microns (0.1mm) and a default layer thickness of 360 microns (0.36mm). We thus caution that fabrication of the Free Universal Construction Kit with current (2012-era) solutions for DIY stereolithography, such as the Makerbot, Printrbot or RepRap, may lack the precision required for reliable or satisfactory coupling with standard commercial pieces. A great deal depends on how well-tuned the printer is; thus, your mileage may vary. In any case, we expect this situation will improve gradually, but inexorably, in tandem with improvements to these vibrantly evolving fabrication platforms. The artist’s proof shown here was created in a UV-cured white resin using a commercial-grade Objet (“polyjet”) 3D printer, which has a horizontal resolution of 42 microns, and a layer thickness of 16 microns. Ponoko.com and other private fabrication services offer printing from Objet machines and other high-resolution devices.

Free Art and Technology [F.A.T.] Lab and Sy-Lab. “The Free Universal Construction Kit.” Fffff.at, 20 March 2012. http://fffff.at/free-universal-construction-kit.
The article cited deals with a universal construction kit that allows you to connect ten diffent types of construction sets together, and as this is a Lego site, you may not want to visit it.
However, the point being that "standard" 3D printers (such as the Makerbot or RepRap) will probably lack the precision to produce tolerable Lego bricks.

We do acknowledge the existence of other building block toys here ;)

@Zhaph-BenDuguid: Construction sets, as in, K'Nex and Tinkertoys.

True yes we do consider those pretty much off topic ;) however that doesn't stop us looking...

Here is a UV printer that can print on the Lego brick, see this link. https://www.youtube.com/watch?v=3OD2DCCpe2U&t=15s
And I think this A3 UV printer is good choice. http://www.wayprinter.com/uv-flatbed-printer/XP600-Epson-uv-printer-XP600sUV.html


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Where are LEGO parts made?
Are all LEGO parts made in a single factory, or are there multiple factories? Where abouts is it/are they? If there are several, are there different factories for different pieces/sets, or do all factories produce all parts?

You mean, it's not mined?

LEGO moulds bricks in the following plants: Billund in Denmark, Nyíregyháza in Hungary and Monterrey in Mexico.
In addition, it has another facility in Kladno, Czech Republic, that handles painting and packaging for some of the bricks produced in Denmark and Hungary.
The headquarters in Denmark is still where the most of R&D and product development happens.

http://bricks.stackexchange.com/questions/49/are-lego-minifigs-arms-supposed-to-come-off/162#162 says there is also a factory in China for particular things, so this answer is not the whole story, or that answer is wrong...

Magnets, pens, watches and such have been made in China. These parts are sometimes different plastics from the rest of the line.  Collectible minifigs  also say Made in China.

Lego has many products besides building sets, including but not limited to bags, pens, costumes, cups etc. The actual building sets are produced as Mikl answers.

The collectible minifigs are made in China, I believe.

I'm pretty sure those are the rip-off-company ones. If the figure design is shiny, then it's most likely a fake. And you should also look for the Lego logo.

The National Geographic Channel has a series called Ultimate Factories. As it happens, the episode that aired tonight was all about the LEGO factory in Billund. The show also looks at the LEGO manufacturing process, product development, and distribution network. If you want to know more about where and how LEGO parts are made, you couldn't do much better than to watch this episode. I'm sure they'll show it again sometime soon -- check you local TV listings.

LEGO is made and has been made in a number of Countries. Denmark, Hungary, Switzerland, Sweden, Austria, Poland, Indonesia, Italy, Germany, Czech Republic, China and Mexico :)


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What's the most cost effective way to buy bulk LEGO bricks?
I've found a couple places to pick up bulk LEGO, but they all have various issues.

Bricklink - I found their user interface confusing, clunky, and straight out of 1998. I'm aware of a couple of other questions here discussing alternatives to Bricklink and ways to optimize Bricklink shipping costs.
eBay - Fine for most things, but doesn't work when you need a specific brick in a specific color.
Pick a Brick  - They don't have ALL the bricks available.

Does anyone have a more effective and efficient way to buy bricks?

First off, as you mentioned, Ebay is not the greatest place on the net to get bricks. As you seem to be aware of, it is difficult to get individual bricks from these individual sellers. Having to pay separate shipping from various buyers plus the unreasonable prices can really add up.
Then there's LEGO Shop. Here, you can buy LEGO bricks directly from the LEGO company. You can individually purchase bricks from Pick-A-Brick, or buy their currently advertised sets. The downside to this is that they obviously do not carry discontinued sets, the selection in Pick-A-Brick is limited, and the prices are unsatisfyingly high, making the bucks add up quickly. Shipping times can be pretty quick and cheap, that is, if they're not currently having any difficulties with their warehouse. If they are, then orders can be delayed by a large amount of time, which has happened to me twice. I once placed an order there which took nearly two months to arrive.
Then, there's Bricklink. You seem to be aware of this website. I like it very much. It is, in many people's opinions, the best source from which to acquire LEGO bricks. The prices are cheap, it carries almost every piece and set ever released, (even discontinued ones) the tools for finding bricks are useful, and most of the people there are pretty nice. The interface is quite useful, you just have to be familiar with it. Once you get used to it, I'm sure it won't seem so "clunky" to you. For detailed help, enter the chat room. The people there are very nice, and will be happy to help point you in the right direction.
Shipping times vary depending on which area you buy from. Buying from within your country might generate shipping the speed of TLG on their best days. Bricklink, however, is much less likely to have technical difficulties as each order is just an individual seller sending something off to the post office, and has therefore generally been more reliable in my experience.

If you contact your closest LEGO store, they can sell you a 'case' of bricks for about $70, which will give you, I'm told, about 650 2x4 bricks, which is about $0.11 per brick.  These are bricks that usually go into the pick-a-brick wall.  You might be able to buy case by just walking into the store, but expect the manager to have to order the bricks, with a 4 week lead time.
I feel this approach is a nice complement to bricklink.com.

Bricklink really is the best place to get bricks you are looking for.  It works really well once you get the hang of it.  It also makes it pretty easy to find pieces you are looking for... if you know what it's called or how to describe it.
The hardest thing to get used to is what parts are called.  So my suggestion is to find a seller with a large inventory, and just peruse it and figure out where parts of different types are located and what they're called on Bricklink. Alternatively, you can browse to a set you are familiar with and look at the set inventory to learn what Bricklink calls those parts.
Make sure you use the Wanted List feature. This is one of the most important part of BrickLink and a lot of new users completely miss it. You can have one main Wanted List as well as additional Wanted Lists for your various projects. Once you add items to your wanted list from the main Catalog (you can add sets, parts, sticker-sheets, minifigs - anything in the Catalog), you can check which seller carries all or at least most of the items you want.
You can also narrow down your search by color, price, country, new/used, etc. It is really the most useful feature of BrickLink that will save you lots of time and money as you are shopping around.
Also, pay attention to the sellers' feedback and terms. After you shop for a few months, you will see how incredible BL and the BL community are. BL is really a LEGO fan's dream.

Sets from the Classic line tend to have a good value in terms of cost per brick. The trade-off is that you don't get a large model to build in many advanced pieces.

Brickowl.com is another Bricklink-style site with an updated interface and easier shopping experience that you should check out. The interface is well designed and they have a feature built-in that allows you to find the best combo of stores for the parts in your wishlist, then add them all to your cart at once. It even gives you a total + shipping!

Brickowl is my personal favorite. So much easier to use.

I built a page to locate good deals on bulk LEGO by filtering through eBay results using a custom algorithm.
As others have said, eBay can be a cost effective way to pick up bulk bricks. Unfortunately, it can be tedious to weed through the expensive or spammy items to find just the bulk LEGO.
This web app takes some of this work away by calculating price per pound and sorting results by best value.

I'll make a case for eBay:
Bulk lots of around 4-5 pounds often sell for around $7-8 per pound (or less), including shipping. I buy many of these lots, which I count and sort, and the average cost-per-piece has been about 2.5 cents.
If you are an eBay seller, you can relist the parts you don't want to keep. If a lot yields some scarce or desirable pieces you can sometimes even make your money back or clear a profit. This does require some time and knowledge about LEGO parts, and the ability to spot good lots from the sometimes blurry eBay photos.
Although many common parts sell for 1 or 2 cents each on Bricklink, the more desirable parts and colors are anywhere from 5 cents up to several dollars each - plus shipping. On average, you will pay less per piece with bulk lots from eBay. I have been able to make a small cash profit selling parts from bulk lots and have added about 15,000 pieces to my collection. Not the most efficient method, perhaps, but for cost-effectiveness you can't beat free.

There is an app that will help find combinations of Bricklink stores that provide all wanted parts at lowest price (not including shipping). You can read more about and download this app at http://buildingoutloud.com/brickficiency.php

There's also a small program called Brick Wizard. It does the same as Brickficiency, but faster (and have generated better results for me, but that may vary).

I don't know where you live, but if you live near a Walmart, visit as often as you can starting about 3 weeks before Xmas. Lego sells their huge creative series parts boxes, 1600 pieces, for about $30 US. Mega Blocks also discounts their equivalent by half. The Lego boxes never last 2 days, regardless of how much they have in stock, Walmart sells out. It takes about a week for them to sell out of the Mega Blocks. Last Xmas I only bought 4 of the Lego, this Xmas I'll buy 10. Of course I'm assuming Lego will do it again.
Ask your Walmart manager if they are part of the Lego Xmas sale. You cannot get these bricks cheaper than this!  Next best is Kijiji sales or Bricklink sales. Sometimes schools and firms sell off inventory on Bricklink, but these sales rarely last a couple of days as well. I purchased many hundreds of large technic pieces from a lady in NY city who was clearing out inventory of a school, for $80 including postage. The postage cost $50. She would have sold me NXT robots for $125 but I like VEX instead...

Bricklink. I'd like to add that using software (MLcad, LeoCad, Bricksmith) to build the model or just compile a list of pieces you need there. Open it up in a program called BrickStore and you can then export directly out to your wanted list. This is very handy when using Bricklink. You can even look at price averages in the program and jump straight to other stores selling selected parts !
It's much faster than navigating around all the time - Take a look : )
Also don't worry the 'New' Bricklink will look alot easier on the eyes.

In each official lego store there is a wall with shelves of lego bricks. You can fill a small or large cup there. Now matter how you fill the cup, it's a fixed price per cup. Obviously the selection will be limited, but if you happen to have use for the provided bricks, it's often the most cost-effective way to get bricks.
This is provided that you stack the bricks efficiently (this can save up to 50%).
I know several people who spend entire afternoons filling cups there, the store employees don't seem to mind.

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


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What are the names for these two pieces of a car chassis and a piece for above the wheels?
I have the following pieces but cannot find their names nor precise usage on BrickLink or elsewhere
The black one has a wheel well on each side - sorry for the poor image quality.
Both the red and black will touch the wheels I have unless I stick a thin piece between them
Please show me an example on how I use them and what the blue piece is for.
[

: 3787 — Car Mudguard 2 x 4 without Studs
: 4211 — Car Base 4 x 5
: 4732 — Bracket 8 x 2 x 1 1/3

In the link for each piece, you'll find actual sets containing them, from which you can find set instructions. In particular, the two mudguard ones need to be one plate apart from regular wheel sets.

Excellent. Thanks - did you know this or can you reveal your deduction?

http://www.peeron.com/scans/6632-1/2

I don't know all of this by heart, no. For the red and black one, I searched for "mudguard", and for the blue one for "bracket" (I knew at least that). Sinc the black one did not have "mudguard" in it, I had to use another approach: look for a set which had it, knowing ambulances would be a good start, and then look at the inventory.

That is so strange - when I search for mudguard, I get single mudguards... Anyway, thanks


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Does the LEGO company sell LEGO brick organization bins?

Possible Duplicate:
What are some storage options?

Are there official LEGO brick storage and organization bins available?  If not, then what good 3rd party options are there?  I'm looking to transition away from just having large plastic boxes filled with LEGO bricks that require me digging through, and going to having a way to quickly access specific bricks I need when building.

These are the best containers I've used: http://www.harborfreight.com/24-divider-storage-container-94458.html -- Pull-out bins tend to be a hassle when you want an individual piece as you have to search for it.

@Pubby8 Please add that as an answer.

Similar question?

@daviesgeek Yeah, I'd close my question as a dupe of that one.

The LEGO company has indeed regularly issued storage solutions. They may be great for kids (the latest ones are brick-shaped), but let's face it, for serious fans they are mostly pointless. And expensive.
Depending on the size of your collection and your sorting method (which is another debate, but remember to sort by form first, not by color), you'll want to switch to do-it-yourself storage racks (the ones with lots of plastic drawers) or whatever you fancy. If using drawers, make sure they are translucid, or have a sticker with the image of the part on them. (LEGOland designers glue one specimen of the actual part).
Some people just buy translucid boxes, try to find some shop which sells them in bulk (like, by 100 pieces), ask a caterer where he finds his for example.
It will require some experimenting anyway, so don't buy too much of an expensive item before being sure it's right for you.

Any suggestions for retailers in the UK?

AKRO seems to have the kind of containers I had in mind, but that's just from 5 minutes googling, I don't live in the UK.

These clear plastic AKRO containers are commonly used in UK takeaways (takeout?)! I'd never thought of using them for this before now.


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Why are LEGO slope bricks textured?
Why is the slope part of bricks textured instead of the usual flat & glossy edge?
Are there any non-textured forms of these bricks?

Not all slopes are textured - for example the 1x2x2/3 30° slope is not textured, nor are every non-linear slope I can remember. All the textured ones I can remember are 45° or greater though.

This is likely a hold-over from when these were used primarily as roof pieces, and the texture provided some realism to the house/building sets.

I'm not sure of why these slopes were originally textured; as Granpappy points out it's likely the texture was used to give roofs a nicer effect. I seem to remember something about the mould being easier to create that way (since less precision was required on the textured part), but it may just be my imagination.
However, a few years back slopes without that texture started to appear (and I'm talking about regular 45° ones, not newer parts like the cheese slope), and fans weren't too happy about it. After checking with LEGO, it appeared that the change wasn't really intentionnal but that LEGO didn't think it would matter, considering the parts kept the same functionality despite of the aesthetics being different.
At that point, LEGO confirmed that future slopes would continue to be textured (again, depending on which part), but that the stock of smooth ones would still be used so that it could take a while before it was depleted.
You may want to read this lugnet discussion on the topic.

"slopes without that texture started to appear" That sounds quite interesting, and I would like to read up on that, but the linked lugnet discussion lacks this detail.

To answer your secondary question:

Are there any non-textured forms of these bricks?

1x1 30° slopes (cheese slopes) are un-textured (just like their 1x2 version).


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What are the largest Technic-compatible tires on the market?
I am looking for the largest LEGO wheels with tires available to build a nice-sized RC LEGO car.
Of course I will start with the simplest prototype, but I would like to achieve a design which will embed an automatic gear box and quite a large propulsion system. So the size of the wheels will be important.

Edit: The "Wheel 81.6x15" 2903 @Pubby8 found seem to be the biggest. But they are thin... Are there any other larger ones? Even 3rd party would be good.
Edit: @Joubarc & @Pubby8 found the biggest wheels but without tires I am still looking for 3rd party solutions before accepting an answer.

The largest wheels I know are these (I measured 110x63 mm, including tyres), but they are quite rare (only available in one single set):
Weels: 22969 "Wheel Technic Racing"
Tyres: 32298 "Tyre Power Puller"
The wheels itself are not that big, but if you include the tyres, they are really huge:

They would probably work really well for an RC car.

The largest wheels are on the 8466

The largest wheels I've seen are "Wheel 81.6x15" 2903

To show scale:

There are larger ones on the Hailfire Droid but these probably aren't good for your needs:

Peeron lists them as "Wheel 81.6x15" 2903 (http://www.peeron.com/inv/parts/2903) and "Tyre 81.6x15 Motorcycle" 2902 (http://www.peeron.com/inv/parts/2902)

Part 2903 is also more common, It exists in 23 sets, including the RCX series which was fairly popular at the time it was released.

An alternative is the 94.8x44 balloon tires. While they are not as big as the ones elusive suggested, I imagine they are easier to get as they have been in some recent sets.
Comparison:

Left: 81.6x15
Middle: 94.8x44 balloon
Right: 81.6x38 balloon

Answer to this question is no longer entirely accurate, the power puller wheel
https://www.bricklink.com/v2/catalog/catalogitem.page?P=32298

has been superseded in diameter by the tractor wheel
https://www.bricklink.com/v2/catalog/catalogitem.page?P=23798

by an entire mm :) (resp. 106-107 mm)

To me the 32298 "Tyre Power Puller" seems more suitable for an RC car though, with the high width and nice curvature. Should have better offroad capabilities and more grip when doing tight turns, despite the 23798 "Tractor" having a deeper profile.

Those power puller wheels are very heavy & not that good for rc applications as they bog down the motor & you loose a lot of power. They are made from a different material than the new tires… But they are really cool!! I’ve used them with a two different transmission and nothing can get past the weight to make them effect. These are the smaller ones but they’re very effective for rc use. https://i.stack.imgur.com/QjA0I.jpg

There is also the Technic Gear Mobile Devastator Wheel, but it's not really suited if you want a realistic car. If you want to build a funny-looking vehicle, however... You could even build a complete vehicle which fits completely inside the radius of two such wheels, so that it can turn on itself when you reverse the polarity. Again, not a car, but super funny.

I personally have the Lego Group 62.4 x 20 S tires which came with the Lego Creator 7291 2-in-1 Motorcycle kit.

While not as big as the ones in the accepted answer, these may be more available due to the larger number of sets they appeared in.

The largest (by diameter) tyre so far is Tire 139mm D. x 37mm Motorcycle Racing Tread

with Tire 132.6mm D. x 27mm Motorcycle Racing Tread Narrow coming next.

Both are included in following sets:

BMW M 1000 RR (42130)
Yamaha MT-10 SP (42159)

The new 6141782: TYRE TRACTOR DIA. 107X44 is now the largest ever wheel available and made by LEGO.
https://brickset.com/parts/6141782

This piece has already mentioned in one of the prior answers.

Well if your doing an RC car you can go what I call "lazy fashion" and get the 47349c05 which were for that and pretty huge.
But the 2902's and 6596's work great for me as well.
But my personal favorite is 92912. Its a bit smaller then 32298 but much meaner if you ask me.
I buy most of my tires from ItsaGoodyear. Its been a while sense I last needing anything though.
Another tire you might want to try is "3740" I never used it myself but if its anything like its smaller counter part 4267. It might work great :D
Also 11957 might be a good one to look into.

How about the old school tyres of the #8860 chassis:
http://www.peeron.com/inv/sets/8860-1
Cheers,
Dennis

They are fairly large, but have sadly been surpassed by others. The 94.8x44 balloon (the middle one in Sebastian Wahl's answer) beats the 24x43 one in that set :(


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What is the bley (blay) color?
I keep reading on various lego web sites about an elusive brick color called "bley" or "blay".
What is it and what is the story behind this?

Sounds like it's in the same color family as grue and bleen.

@Dori also whack and blite, purkle, salmindrift, viollo, bright pinkish cucumber blue, and chucknorris.

Around 2004 (if I remember correctly) LEGO changed the grey and dark grey colors. The colors before the change were the original grey colors which were in use from their introduction. They were somewhat warmer than the colors today, which was perceived as looking faded, though it had nothing to do with aging. Part of the problem was that the competition (Megabloks) was using more blueish greys, which made the LEGO greys look old.
The newer colors have a colder, blueish tone, and were widely disliked in the AFOL community, because most of the time they look awful if used together with the existing old grey pieces. Depending on the lighting it can also be quite hard to tell old and new greys apart.
Hence the term "bley" is used as a name for the new blueish grey.
 BrickShelf

I think at this point bley isn't really used in a derogatory way these days.  It's just Lego's current grey, and is often used to divine the difference between the "old" gray and the new one.

Not to mention it's short and recognized by everybody.

Ok, edited to remove "derogatory".

The bley in the image above is what I'd call dark bley. The majority of the other bricks are grey and the 6x6 tile on the left is either light grey or light bley

At some point, LEGO changed three of its staple colors: light gray, dark gray and brown. This was but the latest on a long series of traumatic changes  imposed by the Danish company, and some fans couldn't stand it any more.
While some vowed to never touch LEGO again and some didn't really care, the vast majority, who knew they couldn't fight their addiction if they wanted, decided for a more half-hearted protest approach that consisted of amalgaming "blue" and "grey" to name the new colors "bley". They hoped to show LEGO how much the new color induced nausea to them, but eventually grew accustomed to it. And it's not like they had a choice anyway.
More seriously, LEGO called the new colors "medium stone grey", "dark stone grey" and "reddish brown", while the fans named them "light bluish gray", "dark bluish gray" and "reddish brown". Then LEGO produced "light stone grey", just to confuse everyone, but to their defense, if you name something "medium", it sort of implies it's not the end of the scale, doesn't it?

Ironically, bley is much less stone-like than the warmer earlier tone, which is one of the reasons I dislike as a castle-theme-favoring builder. On the other hand, I think the color cast is just fine for my space stuff.

It supposedly fits better with the other colors. Which may just be legolese for "it's more shiny, so kids like it better"


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How are the LEGO instruction manuals made?
I wish to know how the LEGO instruction manuals are made. What is the process currently used?

possible duplicate of How are Lego sets designed

Is this specifically about making the manuals (say, getting the breakdowns, printing, perhaps historically drafting), or about the whole conception-to-box product lifecycle? I read it as the former, which is not a duplicate.

I'm about to self answer myself. It may deserve it`s own question... you tell me. but the sets are built using Autodesk Maya.  The instructions are rendered. I should have some material to show... Let me check.

Not a duplicate - the people making the manuals are not even the designers.

Alright, agreed. Not a duplicate.

How lego does it today.
I found little information about Autodesk Maya being the 3D modeling software being used. Here`s a blurb about their current design process :

Primary concept and development work takes place at the Billund
  headquarters, where the company employs approximately 120 designers.
  The company also has smaller design offices in the UK, Spain, Germany,
  and Japan, which are tasked with developing products aimed
  specifically at these markets.
The average development period for a new product is around twelve
  months, in three stages.
The first stage is to identify market trends and developments,
  including contact by the designers directly with the market; some are
  stationed in toy shops close to holiday periods, while others
  interview children.
The second stage is the design and development of the product based
  upon the results of the first stage. As of September 2008 the design
  teams use 3D modeling software to generate CAD drawings from initial
  design sketches.
The designs are then prototyped using an in-house stereolithography
  machine. These are presented to the entire project team for comment
  and for testing by parents and children during the "validation"
  process. Designs may then be altered in accordance with the results
  from the focus groups.
Virtual models of completed Lego products are built concurrently with
  the writing of the user instructions. Completed CAD models are also
  used in the wider organization, such as for marketing and packaging.

Source : wikipedia
How people do it themselves
LEGO provide software that does just that. Check for "LEGO Digital Designer" which allows to create a model, save a building manuals and buy the LEGO parts online.
Also check up this related question :"Do any programs exist that allow you to build own LEGO plans?"
For more information on how to create high quality computer images of LEGO models, check this question : "How can I create synthetic imagery (rendering) of lego models?"

The http://designbyme.lego.com site doesn't work anymore,  but Lego Digital Designer can still be downloaded from https://www.lego.com/en-us/ldd


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What changes were made to Maersk blue?
I read that LEGO recently changed the colour of Maersk blue. Is this true? If so, why did they make a change?

I was a part of this team that worked on the project. I’ll get some notes together in regards to the colors, the changes, the decisions behind making the changes, etc.. A couple of the answers above were very good, actually. Is there a way to post on here some of our original notes from the project? I would be happy to share. Tks, Dav

Hi @davis-lipis and welcome to Bricks. No worries with the previous post - would be very happy for you to share what you know, and more than happy to help you out. We do provide image hosting here on StackExchange, however I think you need at least 10 reputation to add them initially. If you Edit your answer with as much detail as you can, and if possible/needed a link or two to some images I'm sure one of us can edit them inline for you.

Considering that color has been produced explicitely and exclusively for Maersk sets, it's highly unlikely they would change it. Most people seem to agree that the same color has been used for all Maersk ships sets.
That said, you'll also need to consider that even if LEGO never intended to change the color, small variations in hue are always possible (red and purple are much more susceptible to this). Also, in the case of Maersk, LEGO used their entire supply in 2006 and said at the time that they wouldn't issue Maersk sets again because of that. However, Maersk realized the demand was high (LEGO did consider making a version fo the ships in another color altogether at some point) and agreed to have LEGO make a new batch to later on. So these are in effect different batches, separated by a few years, which means any hue change will be more likely to be noticed than if it appeared gradually over time.


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Are companies producing custom molded LEGO pieces legally entitled to do so?
We have seen (or I have seen, given I am a member of a few popular BIONICLE fan sites) an uproar from custom molding companies -- that is, companies that create their own LEGO pieces.
My question is simply whether these kinds of things are legal, as I know LEGO is very tight with legal issues.

This topic about LEGO-Alternatives might be interesting for you, too. There are a lot, so it seems to be legal (but i'm not a lawyer).

Technically: this is off topic (no legal questions on stack exchange)

@Erik: To the best of my knowledge that is not a SE-wide policy. While I am not usually a fan of legal questions on SE, there are very clear and specific court rulings in multiple jurisdictions about this exact issue. (I do think it could've been asked better - perhaps "What is the status of the Lego brick patents?" I might try to do a better edit later.)

from the german wikipedia entry (translated with my poor english-skills):

The Federal Court of germany opened the market for LEGO-like bricks on december 2nd 2004
The European Court of Justice decided in september 2010 that LEGO-Bricks can be copied as they aren't protected by patents anymore

so at least in europe there doesn't seem to be a problem in producing custom bricks and exact copies of LEGO-bricks.

A little nitpicking - "exact copies" would include "LEGO" in tiny print on top of studs. You are not allowed to do that.

LEGO is a multinational corporation. Patents, laws and regulations vary in different countries.  Moreover in, many cases, even if there is an operation recognized as illegal, enforcement may be difficult to achieve.
As a result, a proliferation of compatible brands and clones (fake LEGO) do exist.
There is also the edge cases of artists selling custom made minifigs parts, etc.
According to the latest jurisprudence

On November 17, 2005, the Supreme Court of Canada upheld Mega Bloks' right to continue selling the product in Canada. This effectively permit Lego compatible brick systems to be sold in Canada
On September 14, 2010, the European Court of Justice ruling had Lego lost their protection on their brick design.

More about this on the wikipedia Megabrand article

As you say, LEGO is very tight with legal issues, so if custom molding was entirely illegal, it's likely we wouldn't see such companies, or maybe in unreachable countries only.
Now, LEGO may be tight with legal issues, but on the other hand they know how to be benevolent when it benefits them. (Consider the openness around the various Mindstorms systems, for example.)
The key here is that LEGO is very protective of its own brand and image, but as long as you don't infringe on that, you're most likely to be OK. In the case of custom molding, it means you can't make any part that LEGO makes or has made itself, and of course you can't pretend it's LEGO at all.
And then you have to hope that LEGO doesn't want to copy you, but even there they can play nice if they feel it's best for them. For an example, take the development of the Emerald Night train. When LEGO started thinking about that, they didn't produce big wheels; but one of the fans who participated in a workshop brought Big Ben Bricks train wheels with him, and by showing LEGO the great models they could build with them, them managed to have LEGO change its position and produce some larger wheels.
Whether LEGO had talks with Big Ben Bricks, or what could have been discussed in these talks, is unknown; but you can notice that Big Ben Bricks still exists eventhough LEGO knows about them. Moreover, LEGO doesn't produce all sizes that BBB does, and even then in limited sets and quantities only (always 4 regulars and 2 blinds together), so that it's likely LEGO tries not to impede too much on BBB.
I a way, I think LEGO is very conscious that these companies fill a gap that they themselves can't, or don't want. As such, as long as these companies play nice, LEGO knows better than to go after them.

As the other answers rightly point out, maybe there's not much LEGO can do about it anyway.

(I am not a lawyer)
The key thing now is that the basic brick designs (studs on top and tubes underneath) are no longer covered by patents, which is how mega-blocks et. al managed to survive and create "LEGO Compatible" components - without that, LEGO would have taken them down completely.
What then remains is the copyright and trade marks of the LEGO logo, wording, etc, and indeed the "Basic Brick" in some countries. (Lego Fair Play). How far they go with enforcing that, I'm not sure, and you'd need to talk to the likes of Big Ben Bricks and see if they have any explicit agreements in place.

From the Wikipedia Lego Group article:

The LEGO Group has attempted to trademark the "LEGO Indicia", the studded appearance of the LEGO brick, hoping to stop production of Mega Bloks. On 24 May 2002, the Federal Court of Canada dismissed the case, asserting the design is functional and therefore ineligible for trademark protection [4]. The LEGO Group's appeal was dismissed by the Federal Court of Appeal on 14 July 2003 [5]. In October 2005, the Supreme Court ruled unanimously that "Trademark law should not be used to perpetuate monopoly rights enjoyed under now-expired patents." and held that Mega Bloks can continue to manufacture their bricks.

As other posters have mentioned, other companies have limited or dismissed Lego's rights to force out competitors. From my personal observation, Lego has increased its licensing efforts of popular movies (Star Wars, Indiana Jones, Harry Potter, etc.) to improve its competitiveness against Lego clones.


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Alternative products compatible with LEGO
I heard that lately a patent for LEGO expired and now everyone can create a company to produce bricks that are compatible with LEGO.
I am wondering how many of such companies are there.
I know one from my country, Cobi. Can you point me another alternatives?

This should really be broken up into questions along the lines of "Is X compatible with Lego?" or "Can I make X compatible with Lego?" Otherwise we will get each answer containing overlapping subsets, and we'll likely miss good advice on specific adapters or techniques. In general, we should not be seeking CW questions or answers at this point in the site's lifetime.

There are many different patents. The ones for the original bricks expired long ago, as patents expire after 20 years.

I agree with Joe; there's no one set of correct answers.  It's a wiki-type question, and is too early for this site.

This other SE question is relevant to the patent part : "Are companies producing custom molded LEGO pieces legally entitled to do so?" : http://bricks.stackexchange.com/questions/250/are-companies-producing-custom-molded-lego-pieces-legally-entitled-to-do-so

I think Joe's got the right idea... As appealing as One Big List might seem, questions on individual products are probably a lot more useful to folks researching the products available to them.

there are at least:

KRE-O (not sure if this is compatible in size, but it looks exactly like LEGO)
Enlighten
Best-Lock
Blockmen (out of production)
Cobi (wich you already listed)
SuperBlox
iDol
Kazi (looks like poor quality)
Sluban (out of production)
Mega Blocks
Super Blocks (out of production)
Custom-Crazy
Sidan Toys
Arealight
Brickforge
Christo
BrickWarriors
Oxford
Little Armory
Nanoblocks (not sure, but looks smaller than LEGO, so this might not be compatible)

Note that some of this only produce custom accessories for minifigs, very small sets or exact copies of the official sets, no own really "big" sets like LEGO does

Here are a few:

BrickTW
Character do Dr Who and HM Armed forces themed sets and figures.
Click Brick
HiTechnic produce Mindstorms compatible sensors
Kids Connection
K'Nex prduce lego-compatible bricks. Their product can be used to interconnect Lego and K'Nex.
ME Models sell compatible train tracks.
M.Y Building Bricks
Ritvik is a former name of Mega Blocks
Sploids could be used to link Lego and K'Nex.
Tandem Bricks
Tatco
Toyrific Bricks
Tyco produced Superblocks

Brickarms makes nice custom Lego-compatible weapons, accessories, and minifigures.


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What is the history of "Modulex" blocks?
I have seen a few very small models using something called "Modulex" pieces and have even heard that they are somehow directly related to LEGO? They don't seem to be around anymore so I was wondering what their history was?

Not around anymore? I have a 2x5 right here! (At some time, they produced a planning board which my company still uses for operator shifts.)

@Joubarc I meant that I didn't believe you could still buy them new. I am sure there are plenty of people who have there sets still.

Modulex bricks were produced by LEGO mainly for architects as the dimensions were more easy to scale up (they are 5mm in all directions).
You can find a full history (which I confess I didn't read) here
In time, Modulex started to focus more on signage and separated from LEGO, but it still exists nowadays.

The german Wikipedia article states that they were meant to be used by architects, etc. They are much easier to use for to-scale models, because they are 5 mm high (which results in a comfortable 1:20 scale). It would be quite hard to do that with the standard 8x9.6 mm LEGO bricks.


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What is the popular challenge of solving the Rubik cube as quickly as possible using LEGO bricks?
I saw videos of people participating in a race to resolve a Rubik cube as quickly as possible using Mindstorm LEGO robots.
Can you provide information whether there is a competition and on who is involved?
What is the research/design process?
Is there any sponsorship?
What are the performance obtained?

There's no "race" as this has been solved multiple times by different people (solving rubik's cube isn't that hard). just take a look at the CubeStormer (or, better, the CubeStormer II).
I also saw building-plans and programs for such a cube-solver (not exactly the linked one). If you like to rebuild such a thing: I'll add links as soon as i find them.
EDIT:
As promised, there's the Tilted Twister with building plans online. See it in action on this youtube-video. This is very slow compared to the CubeStormer, but looks like it can be built using only the NXT2.0-pack and doesn't need thousands of parts and multiple expensive NXT-logic-blocks.

I beg to differ :) The race to lower the cube solving time is still on.  http://gizmodo.com/5850505/rubiks-solving-cubesolver-ii-finally-bests-humanity
The plans for the tilted twister in your answer are awesome!

The Tilted Twister is great!


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How can I keep LEGO winches from becoming tangled?
I have some LEGO winches/strings with hooks.

Putting these away inevitably results in tangled strings (the next time I take them out). Even winding them up doesn't help.
Storing these in drawers and/or shelves is not an option for me. I keep most of my LEGO collection in a LEGO Star Wars box.
Is there some way I could build other bricks onto these so they won't unwind?

I take 2 of these:
Place 2 pins in the holes
And then sandwich the loop of string between.
It works well and you likely have the pieces lying nearby.

i've put mine into one of these little film-cans:

very simple, but effective: that way they're easy to find and can fly around in a big LEGO-box with all the other bricks without getting tangled.

You could try wrapping the winch in a rubber band to prevent it from becoming unravelled.


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What is a good ratio to buy bricks in?
I want to add to my collection by buying an assortment of 2x4,2x2,1x2, and 1x1 bricks in a variety of colors. I want these to be general purpose bricks, primarily for sculptures and buildings.
What is a good ratio for parts? For example, should I buy mostly 2x4s or 2x2s? What colors are used the most?

I'd get mostly grey and black 1x4s and 2x4s, then 1x2s, 1x3s, 1x6s, and 2x2s. I would buy some 1x1s also, but those aren't great for making sound structures. (Ever tried to build a sturdy wall from 1x1s?) Anyhow, as I'm not real experienced when it comes to building large structures, I'll let this remain as a comment - unless ya'll think this should be an answer.

This question is incredibly subjective. I use mostly 1x1 and 2x2 in yellow. Any answer is valid until you dream up a project for which it's not!

@ErikOlson I think it can be answered in a constructive way. There is a subjective part, but also an objective part relating to piece averages across sets. Experts know that there are a myriad of ways to build something, but they know that it is better to use piece A instead of B when building which is how ratios come about.

Subjective questions are often parts of bad questions, but not all subjective questions are bad: http://blog.stackoverflow.com/2010/09/good-subjective-bad-subjective/. In particular, this question is fair and impartial, invites factual experiences, and is not mindless social fun (it solves a real problem). In turn, we need to make sure the answers are long, explain why, and are backed by real experiences of expert Lego builders. (I'm also not sure this is subjective - I bet if you did some number-crunching on the composition of sets, some interesting patterns could emerge.)

Colours
It's difficult to tell which colours are used the most. I have six different colours of bricks that are I'd consider essential for every day city building:

(Monochrome) Black & White
(Primary) Red, Green & Blue
(Secondary) Yellow

I chose these six colours because they are  commonly sold in buckets and tubs and are widely available. They tend to have the best brick to price ratio around and they are also very versatile, you can build most models out of these six colours. They also happen to be the only six colours that can be recognised by a NXT/EV3 colour sensor.

As your collection builds, you get a better idea about what kind of things you like to build. A builder specialising in medieval models would probably find colours like grey and brown essential.
Bricks
A good ratio of parts is variable depending on your needs.
Say for example I wanted to build a the wall in the image below, I'd require 40 1x2s and 8 1x1s. That would be a ratio of five 1x2's for every 1x1.

Of course, this isn't going to apply to everything you build, you'll need to make an educated guess based on what creation you're trying to make.

If you want to get a stock for building internal structure and the color isn't important, pick one which is cheaper. Blue is a good candidate, red isn't. Black should be OK too.
As for the sizes, there's no real way to answer that, but if building 2 studs wide, 2x4 is the one you'll need most, with a dash of 2x2 for ends. They are usually easiest to find and cheaper than longer ones.
For 1 stud wide building, you'll of course need some 1x1 for ends, but using only 2x2 can be cumbersome unless you want the effect (try a well in 1x2 dark red plates, it's superb), so then you'll want to stock on 1x4, 1x6 and 1x8. Again, check the prices per stud.
But if you're willing to buy big quantities and are after good prices, the simplest is to by full tubs - and then you don't need to worry about which ones you'll get as the assortment is fixed. You may also want to check specific creator sets for clearance (houses are a good source of 1x bricks).

Are tubs really a good deal? Some quick math puts the price per brick at $0.15 while bricklink is under $0.05

6177: 650 bricks for 29.99$. 3598 was around 50$ for 2000 bricks. But these are official prices, sometimes you can get some for lower than that. But yeah, always check the prices is the way to go.


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How can I build a human-scale Lego gun?
I would like to build Lego projectile weapons. Are there any designs available? Can one make an amunition magazine and self-reloading mechanism? Should I use rubberbands as ammunition or are there designs that fire Lego bricks?

You'll shoot your eye out!

There are some Books available that include building-instructions (i don't own one of these, but i would choose the most current):

The BrickGun Book (Book released in 2013, site has occasional updates as of December 2018 with more instructions)
Badass LEGO Guns (December 2010)
Weapons for LEGO Lovers (February 2009)
as Joubarc said the at least 4 years old Forbidden LEGO (July 2007)

to answer your question about magazines/reloading mechanisms: see this youtube-video that shows such a mechanism in detail (although it's a bit hard to perceive details).
in addition the book about LEGO Technic Simple Mechanics might also be interesting for you, if you want to try building a own gun instead of just "copying" from a detailed instruction.

There's a new one out: "The BrickGun book" - see this review on Brickset

The book "Forbidden LEGO" has some, and you may also want to check YouTube on the subject

I own this book and it's fairly outdated. The 9V 2-switch Battery box required to power the 'gun' is a rare find. It was last sold as part of the 4094 Motor Movers set in 2003

It's also worth mentioning that the model required modified and non-Lego pieces so it wasn't fully brick-built. Youtube is a good place to look for inspiration.

There is a book called "LEGO Heavy Weapons" by Jack Streat which is published by No Starch Press and can be bought for about £15 on Amazon.


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What can I do to repair my minifigures loose neck/head joint?
I have a number of loose neck joints on my minifigures. How can I repair them? Any suggestions?

Superglue. I guarantee your minifigs' heads will never fall off again. And if they do, I will pay you $-100,000.

@PeterDC putting glue on Lego is illegal in many contries!

Well, then, there's always the "stick the neck in a fire, then remove it and put the head on real fast" method.

That`s atrocious!

Discard them (I can give you my address) and buy new ones.

before it turns into a trollfest, I'll test with liquid paper and let you know if I'm about to send you my torsos by mail.

In the old days, minifigures had a dab of paint on the neck. I don't know if it was for this purpose but it would wear off over time.  You can paint some nail polish or acrylic on the neck to strengthen that connection. Thin the acrylic (use water based) before applying.

This is most likely a better solution than liquid paper (too thick I'd guess)

The dab of paint was most certainly for aligning purposes so that the machines which added the arms knew which side was front. But anyway, adding a small layer of paint (fluid corrector might work too) should indeed do the trick.

Don't tell anyone, but I've used brushable superglue to put a thin layer on the back of the neck.  Then I let it fully dry, and it grips the head fine.  Eventually it will wear off.  It's cheaper than nail polish and very hard to see.

I'd reccomend getting some clear nail varnish and coating the pin or hole with it. I did this this earlier and it really works. The minor setback is it takes 5 minutes to dry naturaly, or 2 minutes if you apply co2 (breathe on it or blow dry it until it dries to reduce the wait time to 2 minutes). I did this on a Kai, and it works well.


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

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

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

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

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

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

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

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

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


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Where can I find examples of everyday objects built in Lego?
Suppose for example I am interested in creative ways people have made trees, or minifig scale furniture, or just architectural details like windows. Is there some encyclopedia that organizes pictures this way?

I've been getting a lot of inspiration for this sort of thing from the LEGO video games, which have quite a lot of "destructible" furniture/sets.

The Lego Ideas Book
Recently released last month (19th Sep 2011). Written with the help of adult Lego Fans. I've had a look through the book myself. The book has six chapters focussing on transport, buildings, space, kingdoms, adventure and 'useful makes'. The buildings chapter in-particular focusses on every day objects.

The LEGO Ideas Book, hmillington @Flickr

Flickr
The photography site has a large community of Lego Fans who share there creations. There is an entire group dedicated to Minifigure scale furniture.

If you can go, try attending an AFOL convention. Brickcon is always a great source of inspiration to me. You'll see great examples of everyday objects & building styles & you have access to some of the model builders themselves. You can get helpful hints from them that even the excellent answers mentioned above can't provide.

You can visit the website buildingexamples.com A lot of examples are there with step-by-step instructions.

You can also get ideas and suggestions from the Rebrickable website. You can see what others have built and get instructions for them.


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Why do some minifigs have yellow heads and some are flesh colored?
When did the flesh colors start and why? It seems yellow heads are here to stay too?

I remember back in the old LEGO Club days, there was a guy called Redini who would answer questions by club members. One of them asked a similar question, except phrased more simply: "Why are LEGO people yellow?" While the old LEGO Club site is nowhere to be found, forum posts from the same era quote his relevant answer verbatim... not sure if I should bother quoting it as an answer here since it was answered way before more minifig head colors appeared.

To answer the first part of the question, the Company Profile presentation (deep, direct link) states:

When the minifigure first appeared, it was decided that its face should have only one colour: yellow. And that its facial features should be happy and neutral . The figure would have no sex, race or role – these would be determined by the child’s imagination and play.

It then explains when and why they added colour for their licensed figures

With licensed products such as LEGO® Star Wars™ and LEGO® Harry Potter™ the figure began appearing in specific roles, and with LEGO Basketball in 2003 it took on authentic skin colours. In 2004 the LEGO minifigure assumed an even wider range of skin colours when it was decided that the figures in licensed products should resemble the original characters as closely as possible. One result was that the figures in LEGO Harry Potter™ changed from yellow to a more authentic skin colour.

The first ones I remember seeing were indeed some of the NBA League characters as part of the Basketball theme in 2003, followed by the Star Wars products and then the Harry Potter sets in 2004.
Lando Calrissian was one of the first to appear in the correct skin tone, amongst yellow Han and Leia:

Followed later by pink characters for the rest. The first Star Wars set in 2004 with flesh-toned figures was the Millennium Falcon. By 2005 the transition for Star Wars was complete and all sets used flesh-toned figures.
In terms of other colours, LEGO had already created various monster and alien figures with different coloured heads ranging from blues and greys through to transparent and even transparent neon orange.

Clarification: non-human and monstrous minifigs had non-yellow heads long before the flesh-toned heads, however, they usually aren't Caucasian-skin-peach-toned.

@Mr.ShinyandNew安宇 Updated ;)

The answer is very good, but at its level of detail, one somehow also expects a citation related to the fact that yellow is kept as the default skin colour in non-licensed sets. After all, the other decisions from the original minifigs quotation have been revised in the meantime (gender already a long time ago, first by clothes and hairstyles, then by printed heads with red lips; and the bit about a neutral or happy facial expression stopped being completely true when the two-sided heads with a "panicked" expression were introduced).

Cheers, if you have a citation beyond what was in the company profile clearly states (as quoted) "it was decided that the figures in licensed products..."

The Cult Of Lego book (ISBN: 978-1-59327-391-0) had an a whole page about the change in minifigure skin colour:

Page 59, sentence 2:
  Originally, the LEGO Group sought to leave racial and gender
  differences to the imagination of builders by using a stylised,
  generic face with outfits to differentiate roles.
Page 59, sentence 4: The most noticeable feature of the majority of mini-figs is
  their ostensibly "race-neutral" yellow coloration. The paradigm lasted until
  2003, when LEGO Sports' Basketball theme was released, featuring
  minifigs based on real-life NBA players. The LEGO Group decided that
  expecting kids to appreciate figures that didn't really resemble the
  stars they represented was a losing proposition.

Since the NBA figures were released in 2003, beige and brown skin tones have been used only in licensed sets to portray characters. Traditional LEGO themes like Police and Firefighters continue to use a yellow flesh colour.
The distinction between skin tones makes it easy to identify a beige or brown minifigure as part of a licensed set. Licensed sets tend to be based on film and television themes.

Licenced Themes, use skin tone heads since they are based on something. Themes that LEGO Made themselves, such as Creator have yellow heads.

The yellow head was originally used to represent all races and both genders. Later, yellow heads were used to represent non-licensed minifigures, and flesh coloured minifigures were used to represent licensed minifigures, such as Batman, or Indiana Jones, but flesh coloured minifigures weren't used until around 2003

I think the flesh colored ones are reserved for Minifigures made in an actual characters'  likeness, and the yellow is reserved for generic figures.

This answer doesn't seem to add anything beyond what other answers have already stated.

Flesh colored is used for licensed brands, such as Star Wars and Jurassic World.

This answer doesn't seem to add anything beyond what other answers have already stated.