Duplo Trains discussion

[Peter Nolan]

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

Nice work!

... 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?

Toolo is very rare. Strange stuff, well designed.

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.leg...2-tech-machines

http://education.leg...le-machines-set

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.

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.

Edited April 22, 2014 by Peter Nolan

[Peter Nolan]

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.

Yes, things certainly are different these days... Even the fact that there are pink and blue aisles for boys and girls is interesting. When you visit a large toyshop it can feel like it is more about marketing and profit than play and education. I guess that is the world we live in though :-(

Ok, it turns out I may have been a bit of a hypocrite... I have just come back from a large toyshop with a lego set (from completely the wrong age range) for my young son... Of course it was too advanced for him to build by himself, but we are having fun playing with the model now :-)

Edited April 23, 2014 by Peter Nolan

[Robert Cailliau]

Hmm... one of my posts seems to have disappeared or I did not press the right button.

In it I proposed that the topic of the evolution of Lego sets, their target age and the brick content is interesting in itself, and those of us (like myself) who are interested in pursuing it should start a new topic rather than keep it here under Duplo trains. OK anyone? We could start there with a summary of what has been said here.

[Peter Nolan]

Good call--we have gone a little off-topic recently.

[Adam Badura]

Sure. Robert, will you start the new thread with the sim up? Could you then post here a link to it?

[Robert Cailliau]

OK; done: http://www.eurobricks.com/forum/index.php?showtopic=94841

Robert.

[Robert Cailliau]

And to zg0:

It does go over switches etc. It lets itself be pulled very well (friction reduced by turning bogies and independent wheels), but it does not stand pushing (because the bogies turn).

There are two different designs for the bogies, I had only two lf the pieces used in the left one. Frustratingly, the assembly could be more compact if certain connectors existed, but they do not. E.g. (taking a + to mean a "turn over 90 degrees" and a - to mean "alongside in same orientation") there is a bushing+bearing+bushing piece (the two light grey ones on the left), but there is no bearing+bushing+bearing piece; there is a bushing+bearing piece but no bushing+bushing and no bearing+bearing though there is a half-thickness bushing-bushing piece.

The two dark grey pieces that hold the wheels on the left are bushing-bearing, because bushing+bearing and bushing-bearing both exist though the latter are really rare. On the right I made a bushinig-bearing-bushing piece from two half-thickness pieces.

To be improved.

[zg0]

It does go over switches etc.

do you test it with bridge? bridge "rails" a little wider so in my construction distance between wheels is 4.5 stoods.

[Robert Cailliau]

Thanks! You are right.

It does goes over a bridge, but only just and with a lot of friction.

I had not noticed that the centre of a bridge is wider. This is done so that the loco's wheels firmly engage with the racks on both sides. Interesting point, and shows again how much thought goes into these products.

But the wider middle of bridges makes the whole thing more complex if rubber tyres are used, because they don't roll very well there..

I got to 4.5 units wide by using axles with a "head" and adding a quarter bushing(*) at each side:

The axles with heads stick out a bit; I did not have shorter ones.

Ideally the front and back bogie could be linked in such a way that as ont of them turns, it also forces the other one to turn. I'm not sure I will find the time to try that.

(*) Quarter bushings do not exist, but can readily be made by cutting a half bushing carefully in two with a fine jigsaw.

I'll make a page for my site for parts that do not exist but would be desirable for AFOLs.

[Peter Nolan]

Nice work on the technic train carriages Robert, zg0. The independent bogies is an interesting idea. Lego did make a very short train base (4 studs long) for one of the Thomas the Tank engine sets (http://www.bricklink...?P=4195c04&in=S). If you took two of these and connected them via turntables to a long plate you could make a good long carriage that would run smoothly and be compatible with switches and bridges. Sadly I don't have any to try my idea out.

[Peter Nolan]

Hi All,

A while back I tried to come up with a few sentences that describe what conditions lead to the 'non all points reachable' (non-APR) condition that Robert discussed earlier in this thread. I got a little mixed up with the words though, so have come up with the diagram below instead.

So here goes...

I've drawn one loop which is connected to a main layout (represented by the blue box). If a train enters the loop from the main layout it won't be able to get out, as all the routes back (the two red switches) are facing the wrong way. As the train goes along the track there are some switches that face the right way for escape (the green ones), but since they simply rejoin the loop (through the orange switches) the train remains trapped.

From this you could say that a loop will create a non-APR condition if:

--all of the switches that connect back to the main layout (i.e. red switches) face the same direction (lets call these rear-facing)

--any forward-facing switches (i.e. green) rejoin the loop though rear-facing switches (i.e. orange)

If a forward facing switch is connected back to the main layout (e.g. replace section A-A with section C-C) the loop will become APR. Also, if you join a forward facing switch back to the loop through another forward-facing switch (e.g. replace section A-A with section D-D) the trains direction will be reversed and the loop will also become APR.

However, you can add more rear-facing switches to the loop (e.g. replace B-B with E-E) and the loop will still create a non-APR condition. Indeed, this sub-loop would never be reachable from the main layout.

From this we can see that it doesn't really matter whether rear-facing switches are connected to the main layout or back into the loop (through either a forward- or rear-facing switch)--the loop still creates a non-APR condition. From this I think that the description could be simplified to:

A loop of track within a layout will cause a non-APR condition if (for a given direction of travel) all forward-facing switches rejoin the same loop through a rear-facing switch.

So.. what do you think? Are there any other layout types that lead to a non-APR condition?

[zg0]

If you took two of these and connected them via turntables to a long plate you could make a good long carriage that would run smoothly and be compatible with switches and bridges. Sadly I don't have any to try my idea out.

points ok, but bridge — no. at top point only one base can contact bridge.

[Peter Nolan]

Good point--I didn't think of that. I guess you'd also need some kind of hinge to allow them to follow the curve of the bridge.

[Peter Nolan]

Although you could try this:

(two intelli-trains, one going forwards, one going backwards, with two carriages connected by Toolo turntables, hinges and a beam).

[Robert Cailliau]

Hmmm... Another of my posts somehow did not make it:

Peter, yes you may have a valid set of points there (no pun intended); I'll study it carefully. How did you make those beautiful drawings?

zg0, I made an attempt, not very good, of linked bogies:

(and that puts me at the limit of my media)

The link itself is heavy because the axles are needed to adjust the length, which is not a whole number of units.

Also, kinematically this is only an approximation, but it works better than unlinked bogies. There is very little friction.

The gears are there only to get the 4-unit beams onto their middle.

I did not bother with hooks etc. but it rolls fine. Not yet made it go over a bridge though.

[Peter Nolan]

Wow... that really is a very neat solution. Nice work...

As for the drawings, I did most of the layout in MoI (http://moi3d.com) and then tidied/coloured it in Adobe Illustrator. MoI is actually a 3D modelling package, but it has some handy 2D drawing tools. Plus it is relatively inexpensive...

[Robert Cailliau]

Thanks!

But it has many faults; it's only a proof of concept.

For 3D modelling I'm using Cinema 4D which I bought a long time ago. I have not upgraded from version 11, because it is now too expensive for an inidividual. It does movies though (hence the 4D: 3 space+1time dimension).

I'll look into MOI.

[Robert Cailliau]

Hi Peter,

During a more awake moment I looked at your analysis:

... I've drawn one loop which is connected to a main layout (represented by the blue box). If a train enters the loop from the main layout it won't be able to get out, as all the routes back (the two red switches) are facing the wrong way. As the train goes along the track there are some switches that face the right way for escape (the green ones), but since they simply rejoin the loop (through the orange switches) the train remains trapped.

.... ... If a forward facing switch is connected back to the main layout (e.g. replace section A-A with section C-C) the loop will become APR. ...

If you come through one of the red switches onto the loop A-A-B-B you can only turn there in one sense: anti-clockwise. Replacing A-A with C-C lets you go back to the main layout but it will not let you travel on the loop in the other sense, unless the main layout is APR, so C-C does not make it APR.

D-D also does not make the loop APR, but if the main layout is APR then it will make the loop APR.

If the main layout is not APR, e.g. if you can travel from the loop into the main layout but then you cannot get back onto the loop, then adding D-D does not help, because starting from a point on the loop hanging off D-D you can travel the loop only in the clockwise direction or get off onto the main layout, but then you can't get back. However, unless I missed a phrase, you did not specifically say the main layout is APR.

But I assume that it is what you intended.

... A loop of track within a layout will cause a non-APR condition if (for a given direction of travel) all forward-facing switches rejoin the same loop through a rear-facing switch. ...

I agree with that one. It is a description of a "trap": you can get in but not out.

And I can't think of another type of sub-track that would cause non-APR. I think you have covered it. (though I will not even attempt to prove that!)

So, if we look at a layout and we find a trapping loop of your description, then the layout is non-APR.

However, neither of your remedies (C-C or D-D) will help, unless you can first prove that the main layout is APR. In other words, if you find a trap then it is certain that you have a non-APR layout, but then trying to make it APR is not so easy.

This is typically one of these mathematics cases where it is easier to reason in one sense and difficult in the other.

Changing tack slightly: the algorithm I found was actually quite easy to find, I do in no way pretend it was an achievement. Anyone with a bit of curiosity would have found it. And implementing the program was even easier (thank heavens for LiveCode...). It is quite "brute force" to "multiply" an nxn matrix by itself n times.

The astounding discovery was that the specific implementation that I happened to use needs ever only 2 multiplications, but that was a totally different subject, nothing to do with APR at all.

And that made me think of the discussions I had with the first mathematician: suppose you let the train go, and you make a note of each forward-facing switch you pass (e.g. one of the green ones). Then if you come to such a switch again, you deliberately set it the other way before going over it the second time, and keep going. Eventually you will come back to some of the same switches, in the same direction. Your count of different switches you travelled over cannot be greater than the total number of switches. But if you keep coming back to the same one over and over again, then you must be in a trap, and this is certainly so if there are switches that you travelled over but never set because you never approached them in the right direction. I'm getting woolly (it's 22:48 here), but I do remember the mathematician attempting something like that, starting from the idea that it was not necessary to explore more than the total number of switches (of course). Hmmm... Time for bed I think.

[Peter Nolan]

Hi Robert, Thanks for looking over my diagram.

However, unless I missed a phrase, you did not specifically say the main layout is APR. But I assume that it is what you intended.

Yes, that is correct--I had assumed that the main layout was APR, but forgot to explicitly state it

I agree with that one. It is a description of a "trap": you can get in but not out.

And I can't think of another type of sub-track that would cause non-APR. I think you have covered it. (though I will not even attempt to prove that!)

In that case I think I am happy with my contribution to the Duplo train track layout/design field of study

So, if we look at a layout and we find a trapping loop of your description, then the layout is non-APR.

However, neither of your remedies (C-C or D-D) will help, unless you can first prove that the main layout is APR. In other words, if you find a trap then it is certain that you have a non-APR layout, but then trying to make it APR is not so easy. This is typically one of these mathematics cases where it is easier to reason in one sense and difficult in the other.

Yes, I see your point. Although if only one type of trapping loop exists, and only one such loop is found in a layout, then the rest of the layout would have to be APR. In practice I suppose the difficulty would be finding the trapping loops in the first place--I think it would be much easier to use your LiveCode program.

However, if you wanted to make certain that any loop is APR you could add a section like this:

This arrangement of three switches all joined output-to-output is one of the aesthetically pleasing things you can do with Duplo track.

And that made me think of the discussions I had with the first mathematician: suppose you let the train go, and you make a note of each forward-facing switch you pass (e.g. one of the green ones). Then if you come to such a switch again, you deliberately set it the other way before going over it the second time, and keep going. Eventually you will come back to some of the same switches, in the same direction. Your count of different switches you travelled over cannot be greater than the total number of switches. But if you keep coming back to the same one over and over again, then you must be in a trap, and this is certainly so if there are switches that you travelled over but never set because you never approached them in the right direction. I'm getting woolly (it's 22:48 here), but I do remember the mathematician attempting something like that, starting from the idea that it was not necessary to explore more than the total number of switches (of course). Hmmm... Time for bed I think.

That does sound like an interesting approach. Since there are only three types of connections between switches (input<-->input, input<-->output, output<-->output) I wonder if simply counting the different types of connections would tell you much about a layout? I suppose that the direction of travel of the train would be important too, which would complicate things.

Edited May 9, 2014 by Peter Nolan

[Robert Cailliau]

Hello everyone,

I have updated a few pages of my site. Not Duplo though, straight. 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.

• Quote
  
• MultiQuote
  
• Edit
  

Edited June 10, 2014 by Robert Cailliau

[Peter Nolan]

Wow--that's a lot of work. Interesting reading. You are right about the required tolerances for a good fit. I made a few custom pieces of Duplo on a CNC mill, and it was quite tricky to get a good fit. Too close a tolerance and the parts bind, and too loose and they won't stick at all.

Edited June 12, 2014 by Peter Nolan

[jtlan]

Also interesting: The sides of bricks have a very small draft angle to enable them to be pulled from the molds, meaning that the sides of the brick are not exactly perpendicular to the top and bottom (this also means the top of the brick is slightly narrower than the bottom).

[Robert Cailliau]

jtlan: interesting, had not thought of that, but obviously there must be something like that.

Shall we move this to the Lego evolution thread?

Also: I'll see if I can find some easy to spot evidence.

[zephyr1934]

Neat stuff and it would be great to see it expanded (though probably split off into a new thread). There have been various prior efforts in this regard (though the primary focus being on snot building rather than the bricks themselves), e.g., much of the old ILTCO library can be found here. Then there are bits in the unofficial advanced builders guide (note the discussion of stud height in James Mathis's presentation). A few bits and pieces from lego here (note the discussion of the hole height in technic bricks being incompatible with system bricks). I think some of the odd dimensions in lego stem from the fact that the original bricks were designed using imperial units rather than metric.

I'm sure a google search... or even a eurobricks search might turn up more related info.

[Robert Cailliau]

zephyr1934:

Thanks for the links, I was not aware of these items, mostly because the titles do not reflect what the discussions are about.

And, yes, this should be in a different topic, maybe the one I started earlier on evolution ( http://www.eurobrick...showtopic=94841 )

But, unless someone from Lego officially contradicts it, the original design was definitely NOT in imperial. The basic units (8mm, 9.6mm) hold over very long distances, and almost all other dimensions are "round" and "even" numbers such as 4.8, 5.0, 3.2 ,... Plus that it would have been terribly difficult if not impossible to get any workshop to make precise moulds in imperial units in Denmark or anywhere outside the UK (or US).

The reason why the Technics bearing hole centre is 5.8mm from the bottom and not the expected 5.7 is still not quite clear to me. The reason Jamie Berard gives may be valid, but on the other hand it is only applicable to the exceptional 1-unit brick. A drawing reveals there is more than enough room left for the knob, a little less plastic than in a normal technics brick would not be a problem at all. Anyway, there is a counter-example: the "lantern" face is set inwards by an amount that makes a slight opening at the base that is an artifact of too little plastic (I guess this needs a few photos); this opening is not visible on all bricks so slight it is. But it did not seem to disturb the designers.

I'll try to explore it further.

But let's move this to the other topic.