Lego Evolution

[Robert Cailliau]

This topic sprang off a discussion on Duplo trains. We were getting off-topic discussing the changes made in time of Duplo trains and the age of the kids the sets were aimed at. A few of us decided it was time to start a new topic, and as I was the one to suggest it in the frist place, here we are. Perhaps this can be incorporated elsewhere, but I could not find a suitable place easily. If it exists, we will be considering moving there.

Note: this is NOT about Duplo, though the summary contains mostly references to Duplo. It is about how sets and parts evolved and what the target audiences were/are.

Since I also proposed to give a summary of the thoughts expressed and make a back-link, both of these now follow. Enjoy & join.

backlink to the original Duplo trains discussion

Summary of the off-topic bits of that discussion: (heavily excerpted and some spelling corrections made)

Adam Badura, 19 January 2013:

How it was with the old “smart locomotive”? As I think it was far more “difficult” and “complex”

Peter Nolan, 17 April 2014:

The intelli train (http://lego.wikia.com/wiki/10052_Intelligent_Locomotive) was released in 2003. In my experience the extra features do make for more interesting play. However, I'd say that kids would have to be at least three to enjoy the set. Certainly fun for fathers though...

Robert Cailliau, 17 April 2014:

Yes I agree that the extra features are for older kids. They can probably enjoy the trains until much older (like 67...) IFF there are enough rails and enough switches.

:-)

Ambroise, 17 April 2014:

...kids were not using all the functionalities, and especially If they want the train to move backwards, they simply take it off, and put it back on the track in the opposite direction.

I personally enjoy the Intelli train a lot, they have became quite rare and valuable.

Peter Nolan, 19 April 2014:

I think that this highlights the problem with the Intelli trains--the system is quite structured and prescriptive. For instance, if the child wants to fill the train up with fuel, they have to place the correct smart brick in the track, start the train and then wait for the train to travel over the smart brick before filling up with fuel (when the train makes the 'glug glug glug' sound). With the current model train, they just need to stop the train and start filling (and the train makes the 'glug glug glug' sound). I think that if the other Intelli functions (e.g. cargo and passenger sounds) had have been designed in a similar fashion it would have worked better as a childs toy. All that being said though, it is a great toy.

Robert Cailliau, 19 April 2014:

You say play with the intelli-trains is structured and prescriptive, and from what you describe I fully agree, it's too complicated even for 5 year olds. When they are old enough to play with that imaginatively, they have switched away from Duplo.

It should not go too much in the other direction though: I learned that the latest issues of the locos no longer stop when they hit something. Now, that is not a "function", it is a protection, and it has been removed. The older issues have a little magnet on the axle that is not driven. It passes before a reed relay at each turn so the computer knows the axle is rotating. When the train falls over, is picked up or gets blocked, the computer stops the motor after a few seconds. That saves batteries and protects against wear and so forth. It also prevents little fingers getting caught in the driving wheels, at least for any length of time.

But this feature has been removed. I find that annoying.

Peter Nolan, 21 April 2014:

On the subject of the latest Duplo trains having fewer features, I think that this is part of general shift in the positioning of Duplo in the market. It seems that Duplo is now being marketed to a younger market than it used to be. I've also noticed that a lot of parents see Duplo as more of a baby/toddler toy rather than something that is good for kids up to 5 years or so. It seems to be that people decide that once their child is a certain age it is time to get rid of the Duplo and then move on to Lego. (sorry if I'm repeating some of the sentiments that have been expressed earlier in this thread).

At the moment I find that my son is happy playing with both Duplo and Lego and creating hybrid models (not everyone realises that Duplo and Lego are compatible it seems). When you throw in some Duplo Toolo (bought second-hand, like the Intelli trains) there are all sorts of play possibilities.

Robert Cailliau, 21 April 2014:

Yup, agreed.

Now that you raise the point, there is also a degree of age-variety in Duplo: the big blocks are no longer very attractive after 5 or 6, but the trains certainly could go for much longer. Again, IFF there are enough rails. I consistently find that train sets of any make or scale have far too few straight rails. An oval, even with an intellitrain soon loses all attraction.

And yes, few people realise that Duplo is called Duplo because it is "double size" and compatible (to some extent) with the single-size blocks. Thanks for reminding us of it.

Toolo is very rare. Strange stuff, well designed. I ony have some incomplete things that Nora has "inherited" from cousins, but she does not play with it.

zg0, 21 April 2014:

my first try to make duplo compatible train base from lego pieces.

Adam Badura, 21 April 2014:

Nice!

Be sure to check it with switches, crossings (both rail-rail and rail-street), and bridge. Those are places where other Duplo bases fail. For example 10558: Number Train doesn't fit on that type of track and that is sad.

Yours looks like it would have no issue but it is always good to keep that in mind.

zephyr1934, 22 April 2014:

The intellitrain was from an era where Lego figured the under 3 set would be playing with quatro or primo. The rest of the toy industry is pushing "realism" down to an insanely young age these days. I played with Tonka trucks (the real ones, made of metal) until I was at least 10, but now the toy industry has the blue isle all figured out. First dinosaurs, then trains, the superheros, then .... With trucks falling by the wayside somewhere around 5 years of age. I think duplo has also been pushed to younger ages as a result of consumer demand. It is too bad, because the modern lego sets can't be anything more than a model for the 5-8 yr olds (as in, there is very little room to go off and build what you like with so many specialized pieces, you can build the main model and that is it). For the simplicity of the bricks my first grader still plays with duplo even though he has a room full of system bricks.

Nolan

... the trains certainly could go for much longer. Again, IFF there are enough rails.

As it happens, my son's train set does seem to have many more curved rails than straight. We are yet to run out of either though... BTW do you mean IFF in the mathematical sense?

Robert Cailliau, on 21 April 2014 - 04:07 PM, said:

Toolo is very rare. Strange stuff, well designed.

Peter Nolan, 22 April 2014:

Toolo is quite interesting. Some of the parts look like they would be very expensive to produce--the standard 2x4 block has screw threads on five surfaces, which would necessitate quite complex mould tooling. Although there are no retail Toolo sets available now, you can still buy two educational sets:

http://education.lego.com/en-us/lego-education-product-database/preschool/45002-tech-machines

http://education.lego.com/en-us/lego-education-product-database/machines-and-mechanisms/9656-early-simple-machines-set

zg0, 22 April 2014:

disagree. lego bricks sets long time was 3+, now 4+. creator was 4+, now 6+/7+. so lego clears 1-2 years from lego for duplo. and in 2013-2014 set we can see that duplo sets became more "constructional". cars from monolitic became consists from 4-5 pieces. and pieces became more universal.

Peter Nolan, 22 April 2014:

Interesting. I was skeptical to start with, so had a look at some of the new Duplo sets and can see your point. If you compare the new ambulance (10527) with the old one (4979) the new one does indeed have more parts.

[Peter Nolan]

Hi Robert, thanks for creating this new thread. I came across an old article (circa 2008) that suggests the number of specialised pieces (which some people associate with 'dumbing down' of sets) has actually been decreasing rather than increasing. It is the fourth subheading in the 'design' section of this article:

http://lego.gizmodo....know-about-lego

The article is six years old though--I wonder if the trend in the number of specialised pieces has continued?

I also noticed another old (but interesting and hopefully relevant) article about Lego's 'Memory Lane' archive that contains pretty much every Lego set ever made.

http://lego.gizmodo....sets-in-history

I was surprised by how many of the sets I remembered from the catalogues (or owned) as a child.

Edited April 24, 2014 by Peter Nolan

[Robert Cailliau]

The gizmodo article is interesting, unfortunately it is indeed old.

It would be interesting to have a catalog of parts like the ones at Peeron or the Bricklink, which also has the dates of start and end of production of each part, if they are known. Then the question of the number of parts would be easy to answer.

Somehow also we need a standard way of naming parts and naming elements of parts (e.g. knobs or studs? Holes, depressions, hollows?) and a set of part numbers that is not dependent on the colours.

Too little time, too many parts.

More questions:

Is there an "official" way of talking to Lego? I can understand they would not be willing to talk about future plans, but there are no secrets about sets that exist and have been sold. I.e. is there some on-line resource where Lego publishes a colour table, a dimensions table, whatever, perhaps maintained with the help of adult fans. I could not find anything. But then, as I argued on the Duplo train page, there have been errors in the past, be they small, and maybe Lego rather stays mute on any of these matters and leaves the publishing of this type of resource entirely to the fans.

Some parts live "forever" but some do not. Anyone having an RCX brick can no longer use it unless he has kept an old computer alive as well. I have two RCX bricks and have a machine specially for that.

Why are certain combinations avoided in the connector series? Connectors for axles have gripping holes (bushing like) and sliding holes (bearing like). There are various combinations, some with gripping and bearing at right angles, some parallel. There is no part (to my knowledge) that has two gripping holes at right angles, or two sliding holes at right angles.

Why do I always use loads of double length black pin connectors in building Technics stuff, but very seldom need the triple length ones, but I have loads of triple length ones. Am I not using the right techniques? (Is there a "building techniques" resource? Have not searched for one).

I watched the Memory Lane movie. Strangely, I did not remember many sets at all. I bought some Lego for my daughter (I was then 30), and then there was a very long gap, until a few years ago (when I was 60...) and picked it up as an AFOL for a very strange reason indeed. So I did not see much in the 30-year gap. My parents gave us some Lego when we were kids, but not very much, and those bricks actually warped and stopped sticking together, so they must have been from before the ABS plastic times. I wonder if I can still find them.

There was an interesting evolution in axles: first there were only lengths that were multiples of 2. Length 3 did not exist. I had to saw axles to get some. Then suddenly they appeared. Then somewhat later the odd lenghts became grey instead of black. I have 3 and 5 in black, but 7 (which came last) only in grey.

[Peter Nolan]

Hi Robert,

A few possible solutions:

Production year. You can search the Bricklink catalogue by part and by year at http://www.bricklink.com/catalog.asp. You can also download the bricklink catalogue from http://www.bricklink...ogDownload.asp.

Talking to Lego. You could try 'The Embassy' on this forum (http://www.eurobrick...p?showforum=108) or try someone else from the Lego ambassador program (http://aboutus.lego....lego-ambassador). Or you could always take a holiday to Denmark

Odd axle lengths. Most of my knowledge of Technic comes from when I was a kid. Back then axles only came in even lengths. I suspect that the introduction of odd lengths was related to increasing complexity in models. I haven't really had much to do with Technic lately, but some of the big sets certainly look very appealing...

[Robert Cailliau]

Hello everyone,

I have updated a few pages of my site. Comments welcome.

http://cailliau.org...Considerations/

from which, at the bottom, there are two more links.

Note that the drawings can be zoomed and panned, click the little red [sVG] link in a caption for instructions.

Have fun.

Edited June 10, 2014 by Robert Cailliau

[Peter Nolan]

I was interested to see the new design for the 24-tooth gear in section 5 of 'Evolution of shapes'. I remember that the centre portion of the old design often broke--I guess that is why the design changed. The advantage of the old design though was that you could fit an axle in the offset position to make a crankshaft.

Edited June 12, 2014 by Peter Nolan

[zephyr1934]

I originally posted the following a wandering thread off topic in the duplo train discussion. The first point was expanding on an earlier post where I speculated that some of the odd lego dimensions might date back to the early days of lego bricks (even pre-lego days). The second point was touching on the fact that the technic holes do not line up with the system studs on the sides of bricks. That ultimately goes back to the days before lego contemplated the 2-5 rule, e.g., another early SNOT piece is the lattice fence and it too has some strange dimensions. Anyway, here's my post in a more applicable thread...

The original lego bricks were based on a British design, Kiddicraft that dates to 1945. One would have to dig up the Kiddicraft patents to find out what dimensions they were originally drawn in.

As for the technic holes, the 1x1 brick came along fairly late in the game (1993). The 1xN technic bricks were introduced in 1977, but the technic holes date to 1970 and this brick,

which looks like it was initially introduced to update the gears (the big red, yellow and blue gears).

Their predecessors were these, dating to 1965

that would simply be pushed on to the 2x2 wheels or 4x4 turn tables. So the vertical center position of the technic hole probably matches that of the old wheel holders,

[Sarah]

My 6, almost 7 year old, does most of his free-form building with Duplos (I also have an almost-3 year old so we have the Duplos out and I've been amazed at how much my son prefers playing with those versus the regular Lego he also owns) And, over the last couple of weeks, since he got a couple of the blue guys, Mixels. He takes the Mixels apart and reworks them into new figures on a daily basis. I think they are less intimidating because they are not supposed to look like anything any particular.

[Peter Nolan]

Hi Sarah, I also tried my son with a mixels set recently and he really liked it. My son is still young, so Duplo is more developmentally appropriate. However, he really enjoys the extra play value of the Lego sets. At the moment a good solution is that do most of the building if he gets a new Lego set, which he then incorporates it into his imaginary play. He also likes tinkering with, and repairing, the sets even if he can't build one from scratch. Oddly I found that the Technic motocross bike (42007) to be really good--it was an interesting build for me, but a good sturdy toy for my son (since all the technic pins hold it together very securely).

[Lyichir]

Hello everyone,

I have updated a few pages of my site. Comments welcome.

http://cailliau.org...Considerations/

from which, at the bottom, there are two more links.

Note that the drawings can be zoomed and panned, click the little red [sVG] link in a caption for instructions.

Have fun.

Whoa! It's you! I never noticed you here on Eurobricks before, but your site is one that I find incredibly useful. There are too few resources on the dimensions of Lego parts, and while I've long since memorized the 5 to 6 ratio of 1x1 bricks, I often have to look up exact measurements if I'm trying to build a Lego part at an enhanced scale, or trying to build life-size real-world objects (as The Lego Movie has inspired me to do with the depiction of "relics" in sets).

Glad to see you've updated your site—the new information (like the exact angles of technic liftarms) should be massively useful! The information on part evolution is quite well-represented—I had noticed many of the differences myself in my lifelong quest to apply a suitable sorting system to my collection, but your commentary provides enlightening information about the function of some of these changes.

[Robert Cailliau]

Sorry All, for very late reaction!

My fault: I failed to follow this topic, so I was not warned of new posts here. Corrected now.

First Zephyr1934: yes, there is the Kiddycraft story. I'm pretty sure those were made with moulds expressed in imperial, but I have not (yet) found information on how the Lego bricks were derived from them. Both would have had to go to local mould manufacturers, and so would have used local units. There certainly is nothing in any of the current measures of bricks that indicates any prior use of Imperial whatever. And those measures go back at least 40 years.

Also, but on a different tack, there are good engineering reasons for using measures that are easily divisible by 2, also by 4, and it seems to me that at least in the beginning Lego only used powers of 2 (2, 4, 8, 16, 32,...) in mm. Avoiding 3 as a factor led (again in my opinion) to the failure of the first Duplo train rails, as the circle could not be divided into tree, which precluded some interesting figures. The new Duplo rails have circles composed of 12 rails, thus allowing more use of oblique angles.

I still have no "official" statement about why the centre of the Technics bearing hole is 5.8mm from the bottom of the brick and not 5.7. In practice it does not matter, but I cannot find any good reason at all.

Second Lyichir: It's me? Yes, it's me, but tell me where I know you from? With age memory fails. :-)

And finally: I have been working on gears, so the gears pages are going to expand. The item I struggled most with over the last few weeks was the updating of the gear meshing calculator as that should be ready before I put more stuff out. That "calculator" was written a very long time ago (2006) and it used raster images. The new version uses vector graphics but is more power intensive, so you may at times hear the cooling fans of your computer kick in. Nevertheless, all comments (and especially bug reports) are welcome:

for OSX: http://www.cailliau....culator.app.zip

for WindowsOS: http://www.cailliau....culator.exe.zip

Should someone want it for Linux, that could be done too.

This is not "official" yet, and as they say: if everything else fails: RTFM, i.e. press the Help button and read the explanations, but it should be relatively straightforward.

When doing the first version the surprise was how (relatively) simple the algorithm for the stack turned out to be.

I'm curious to read your thoughts.

BTW: both OSX and Windows will probably warn you that these apps come from an unknown developer and should not be opened etc. I do assure you that there are no viruses or trojans. For OSX you will have to right-click and choose "open".

Edited August 8, 2014 by Robert Cailliau

[WoutR]

Page 2 of the presentation "Stressing the elements" by Jamie Bernard gives a reason for the odd postion of the technic hole.

"The Center Point for the stud on the side of a System brick is 3.92mm from the top of the brick

The Center Point for the hole in the side of a classic Technic brick is 3.80mm from the top of the brick

The Center Point was moved up in order to accommodate the additional plastic needed around the Technic hole so that a stud can still fit in the bottom of the brick."

http://bramlambrecht.com/tmp/jamieberard-brickstress-bf06.pdf

[Robert Cailliau]

Yes, I'm aware of the excellent documents by Jamie Bernard.

But I don't think in this particular case his argument holds:

1- The worry of accommodating the knob only applies to the few bricks where there is a bearing directly above a knob, as in the1x1, or the 1x2 with two holes (I don't know of any other ones where a knob can sit directly under a bearing). For normal Technics bearing bricks there is no problem at all: the knobs are between the bearings.

2- If the hole sits 3.8 from the top, the diameter of the plastic cylinder around the bearing hole is 2x3.8=7.6 which leaves 9.6-7.6=2.0 for accommodating a knob, which is more than sufficient.

3- The diameter of the plastic cylinder around a bearing does not need to be larger than 7.4, as shown by many beams. That would leave an extra 0.1 without compromising anything. And even a lot less plastic around a hole would still mechanically work: note that the newer standard 2x4 brick has walls that ar only 1.5-0.3=1.2 thick..

4- Close observation of the "lantern" (part no. 4070, but not 87087) shows the plastic just above the "lip" under the knob on the front face is actually zero thickness and depending on the mould the 4070 came from, one can even see through a narrow slit of missing plastic. That is because the front face is set back sufficiently that there is nothing left at just that point. But it does not compromise the strength of the brick or its ability to fit others. From that I conclude that if the plastic around the hole, which is 3.8-(4.9/2) = 1.35mm thick, would have been flattened at its bottom, where it would go over the knob, to even 1.0mm thickness in those few bricks where a knob does need to sit straight under it, there would still be no problem whatsoever.

The bricks where a bearing can sit just above a knob were likely designed later than the normal ones. They would have shown a local flattening if there had not been enough space with a hole centre at 5.7 from the bottom but still a need for a thick cylinder. So the choice of 5.8 instead of 5.7 was probably made early, and independent of anything else. 5.7 is the natural choice since it places the centre of the axle at the centre of the square that fits at the top of the 8x9.6 design rectangle. My strong conviction is that someone at the mould factory goofed by 0.1mm, and then it was too late. Thousands of sets may have been sold before it was spotted. The same happened with the curved Duplo rails, and there the moulds have been corrected only recently.

Lego is fantastic, but nobody is perfect all the time. We will only know what really happened if someone from Lego makes an "official" statement (highly improbable), and such a statement would have to be based on the memories of Lego engineers, some of whom may have left or even died. In addition, it is very difficult to remember the reasons for decisions (if there was one in this case), even your own. I can usually figure out why I made some weird choice in the past, but it may take a long time and much effort before I remember, and more often than not I need to consult other people's memories too.

Hm. This is probably all easier to show with drawings; I'll put those on my pages somewhat later.

[Robert Cailliau]

OK, I updated section 5.4 of http://www.cailliau.org/Alphabetical/L/Lego/Dimensions/More%20Dimensions/

It was in the end much simpler than I thought: just measure, and find that there was ample space to put the centre at 5.7 instead of 5.8.

I'm not sure whether this is good or bad.

[WoutR]

Thank you for the update!

You describe that 5.8 is needed to clear an axle above the studs/knobs. That would be a very good reason to move this hole up. I think these holes were initially not intended to receive knobs.

Maybe it also explains why the knobs are hollow on top and not on the bottom. The text on to would have added extra height, and then they would have needed to move the hole even further up. This combination might have been the best compromise.

[Robert Cailliau]

Woutr:

Well, it's the only reason I can see, but I don't think it is a good reason at all. The two constructions I put forward are very much contrived. I believe that in all cases a workaround can easily be found, i.e. that clearing is not needed. The knob is only in the way if it is a "shifted" knob, i.e. in some way derived from part 3794 -- plate modified 1x2 with 1 knob (some part like that has to sit somewhere in the construction).

I do not believe any strange, contrived construction like those two was in any way the cause for going to 5.8.

On the other hand there are advantages of having the centre at 5.7 instead of 5.8: it's simply more convenient, allowing more combinations that will "legally" work together, and it fits logically in the grid.

As I study the parts more and more closely, I find more places where early forms were replaced with later ones that correct some inconvenience or slight error in the earlier form. The first time that was really flagrant was with the Duplo rails, where the black ones have been discontinued, then later with the curved grey rails that would not fit next to each other nor would line up with straight ones. Those were mistakes that were easy to correct and did not matter much, in fact had no influence on backwards compatibility.

If 5.8 was an error that slipped through somehow, and it is more and more what I suspect, then it is now impossible to set straight: bracing would not work anymore. Especially not if you used many pegs instead of only two, at several places and with combinations of 5.7 and 5.8 type bricks. They all have to be the same.

I do not believe we will ever get an official statement about it. Unless there is a really good reason that we have overlooked. I doubt that. But I do hope that someone somewhere in Lego is writing it all up for posterity so that the truth can be uncovered by some historian from a galaxy far, far away.

:-)

Did anyone try out the gear meshing calculator?

[WoutR]

Maybe the reason was good enough when they were trying to design the new technic bricks as part of a complete system. Then clearing studs (any stud) would have been a serious requirement. Using the cardan connector it is possible to place an axle diagonally across bricks, the studs could easily interfere here.

1972-1974: http://www.bricklink.com/catalogItem.asp?P=9244a'>http://www.bricklink.com/catalogItem.asp?P=9244a

Since 1977: http://www.bricklink.com/catalogItem.asp?P=9244

Looking at the Bricklink catalog I also noticed that the first version of the technic brick was not the 1xn brick, but the 2x4:

http://www.bricklink.com/catalogItem.asp?P=3709c

http://www.bricklink.com/catalogItem.asp?P=3709a

Maybe that brick provides a reason. It is constructed in a different way.

The first version of that brick had LEGO molded on top of solid studs, the later version had the hollow studs like later technic bricks.

[WoutR]

Taking a closer look at the technic 2x4 brick I believe that the reason stated by Jamie Bernard in his presentation is correct for that brick. The brick with molded LEGO on top of the studs barely fits the flat bottom of that brick with "pat pend" mold markings. The holes seem to start immediately above the bottom plate. It is a bit difficult to look inside, and I can not say for sure there is not 0.1 mm in there somewhere, but at a first glance (and without opening one of those bricks) it seems to make sense.

They could have prevented that by reducing the bottom thickness, but maybe there was a molding/engineering reason not to do so.

[Robert Cailliau]

Maybe the reason was good enough when they were trying to design the new technic bricks as part of a complete system. Then clearing studs (any stud) would have been a serious requirement. Using the cardan connector it is possible to place an axle diagonally across bricks, the studs could easily interfere here.

1972-1974: http://www.bricklink...tem.asp?P=9244a

Since 1977: http://www.bricklink...Item.asp?P=9244

Looking at the Bricklink catalog I also noticed that the first version of the technic brick was not the 1xn brick, but the 2x4:

http://www.bricklink...tem.asp?P=3709c

http://www.bricklink...tem.asp?P=3709a

Maybe that brick provides a reason. It is constructed in a different way.

The first version of that brick had LEGO molded on top of solid studs, the later version had the hollow studs like later technic bricks.

Good point.

Fortunately, for some strange reason, I have a 3709c! Comparing it carfully (lining up etc.) it has its centres at exactly the same height as the 1xn bricks: 5.8mm.

The hollow under it is 2.0mm, good enough for a 1.8 knob with embossing, still leaving 0.1mm, but tight indeed. Since there is 9.6-5.9-(4.9/2)=1.35mm plastic at the top, then if the same amount is needed at the bottom that would leave 5.8-(4.9/2)-1.35=2.0mm, which is what we find. 2.0mm is the minimum for accommodating a knob, I would agree, and it is what plates give. The hollow under 3709c is the same as that under a plate. Good, so then if the centre is put at the middle of what is left, it would go at 2.0 + (9.6-2.0)/2 and that is 5.8!

I note also that the holes of 3709c are 5.0mm in diameter and hence do not grip knobs at all (there is even a little play).

3709c appears a number of times in only two sets (according to the BrickLink) the first having old style gears and the second being an extension set of the first.

So, you may have found the reason: later Technics bricks were made to be compatible with that first brick, and that first brick did not accept knobs.

Berard says sticking knobs into the axle holes of Technics bricks is not really allowed because the holes are a little smaller, so the fit is very tight. This is true.

Berard is an official Lego Designer.

But again, there is no need for that amount of plastic, and it is in fact not present in many bricks, at least not all around the hole.

I think you have probably found the real reason:

(1) 1.8+0.14=1.94 and so 2.0 is the minimum hollow depth to receive a knob, that of plates.

(2) with a 2.0mm hollow, putting the 3709c hole centres in the middle of the remaining height leads to 5.8 from the bottom and 3.8 from the top.

(3) at the time no-one thought of fitting knobs into Technics holes (they were too large in diameter anyway).

(4) later Technics bricks were made compatible with the old one.

(5) we're stuck with it.

Taking a closer look at the technic 2x4 brick I believe that the reason stated by Jamie Bernard in his presentation is correct for that brick. The brick with molded LEGO on top of the studs barely fits the flat bottom of that brick with "pat pend" mold markings. The holes seem to start immediately above the bottom plate. It is a bit difficult to look inside, and I can not say for sure there is not 0.1 mm in there somewhere, but at a first glance (and without opening one of those bricks) it seems to make sense.

They could have prevented that by reducing the bottom thickness, but maybe there was a molding/engineering reason not to do so.

His stated reason is the amount of plastic, but I'm certain that is not so. Rather I now believe the choice of "put it in the middle of 9.6-2".

Thanks for that reference to the 3709c!

As to the cardan connectors: they are 7.6 in diameter at their thickest. That is just about thin enough for 5.8 not for 5.7. But their bushing end is 7.4 and I'm sure that had 5.7 been chosen, then 7.4 would have been used for the other end as well.

I also looked at the much older bricks for holding wheels: 7049. There the height seems completely different and without relation to our discussion, but I have not gone into details.

[WoutR]

The hollow under it is 2.0mm, good enough for a 1.8 knob with embossing, still leaving 0.1mm, but tight indeed.

Especially since there also are mold numbers at the bottom plate. For bricks these do not matter, but for plates we might have to take those into consideration. I did a quick check and it seems like these numbers are positioned in such a way that they do not interfere with the knobs. It's probably a design rule for the mold makers :)

Since there is 9.6-5.9-(4.9/2)=1.35mm plastic at the top, then if the same amount is needed at the bottom that would leave 5.8-(4.9/2)-1.35=2.0mm, which is what we find.

Not sure where all these numbers come from. You might be correct, but I am missing something here...

brick height = 9.6

hole diameter = 5.0

bottom = 2.0

That leaves 9.6 - 5.0 - 2.0 = 2.6 mm for the plastic. That would suggest 1.3 for the top and bottom plate and not 1.35.

Also...

9.6-5.9-(4.9/2)=1.35mm

9.6 - 5.9 = 3.7

4.9/2 = 2.45

3.7-2.45 = 1.25 not 1.35

Thanks for that reference to the 3709c!

You are welcome :)

Thank you for the update to your website.

Edit: I just noticed that zephyr1934 made an earlier reference to the 3709c! We both had the same idea.Also, if you ever want to update or rewrite your website (for any reason) feel free to use anything I said without quote or reference. I care about the information, not about the credits ;)

As to the cardan connectors: they are 7.6 in diameter at their thickest. That is just about thin enough for 5.8 not for 5.7. But their bushing end is 7.4 and I'm sure that had 5.7 been chosen, then 7.4 would have been used for the other end as well.

I was thinking about two parallel technic beams/bricks with two non-aligned axles going through the holes. Those could be connected using the cardan connectors and a diagonal axle. That diagonal axle could cross the knob on top of a brick positioned in between. After the 5.8 height was determined, the "clearing the studs" theory could explain why they moved from the solid knob with embossing (like on the first technic brick 3709c) to the hollow studs (like on the later technic brick 3709a and all later beams)

Here is a quick ASCII sketch:

.....I..

XXXXXIXX Axle through hole

.....I..

..../...

XXX/XXXX Axle clears knob on lower brick

../.....

..I.....

XXIXXXXX Axle through hole

..I.....

I also looked at the much older bricks for holding wheels: 7049. There the height seems completely different and without relation to our discussion, but I have not gone into details.

At first sight the center of the hole seems to be slightly higher. There is probably a good reason in the construction of this brick.

https://www.google.c...tents/US3234683

Edited August 18, 2014 by WoutR

[WoutR]

Their predecessors were these, dating to 1965

that would simply be pushed on to the 2x2 wheels or 4x4 turn tables. So the vertical center position of the technic hole probably matches that of the old wheel holders,

Those first gears were developed by licence-holder Samsonite in the USA based on the LEGO wheel and the wheel holder brick. The later "Expert builder" gears were developed by LEGO themselves. I have no doubt that they were inspired by the Samsonite gears, but they were developed by different people. I think that explains why the holes do not line up.

[Zerobricks]

Lychir thats an awesome and really usefull site you have there! Thansk for sharing.

Edited August 18, 2014 by Zblj

[WoutR]

Did you ever wonder why the technic axle is the size it is?

I just found this video of a 1970 LEGO GEAR dealermodel

I wonder if the axle was designed to fit within the tube of normal bricks.

[LEGO Historian]

Hi WoutR! That 1970 LEGO Gear Dealer Model that Henk Van Zanten has is still a work in progress, he hasn't yet totally found all the answers to how the right side works.... but it is a very interesting and mesmerizing display model.

I just wanted to correct you on something you mentioned last year. The USA/Samsonite LEGO gears were not a Samsonite invention. They were invented by a Dane named Knud Moller Kristiansen (no relationship to Kjeld Kirk Kristiansen).

That was designed for LEGO around 1964-65, with the patent process starting in March 1965. The patent is owned by Interlego AG, the Swiss LEGO company that owns all the LEGO patents....

http://www.google.com/patents/US3461601

And also to correct something that someone else mentioned about the LEGO Memory Lane Archive... the TLG Archives/Collections/Vault do NOT have all of the LEGO sets ever produced. I'm going to say they are missing over 100 sets, at least.

In my Unofficial LEGO Sets/Parts Collectors Guide... the chapter on LEGO wooden box sets has images of over 80 wooden box sets. From what I gather, the Vault contains only perhaps 10 wooden box sets. Also because I have been dealing with the LEGO Archives/Collections folks for the last 7 years in putting together my collectors guide, I have introduced them to several sets that they had never seen before. Also, they are always on the lookout to find additional sets that they do not yet have in their collections. This is especially true for Norwegian (1953-60) and Swedish (1955-60) sets.

[WoutR]

I was looking at the instructions for the gears set 801. The axle-tube connection.is also being used. To me it is clear the axle was designed to fit that tube.

I found out about the Danish designer in the mean time, but I also did not correct myself yet :) Thank you for the update!

I think the LEGO Archives should also be looking for the Swedish GEAS sets (1950-55) :-)