DUPLO train track accessories, printed in 3D

[phildc]

Interested in 3D printed models and in model trains,
I designed some additional DUPLO train tracks accessories for my grandchildren:
- a turn table with maximum 12 tracks at 30 degrees (needs a special track with cut corners) (*)
- a curved track with larger radius to make parallel curves (compatible with the standard track switch) (**)
You find the printable models (STL files) on Thingiverse:
https://www.thingiverse.com/phildc/designs

(*) look for the model(s) with angular notches. A variety of tracks disposition is available:
https://www.thingiverse.com/thing:5655416
The full 12 tracks:
https://www.thingiverse.com/thing:5766558

(**) the larger radius curved track (R2)
https://www.thingiverse.com/thing:5774273

[phildc]

Additional pictures:

[JopieK]

Very nice and thanks for sharing @phildc. Welcome to Eurobricks and Train Tech. I might try to print some of your designs for the times that younger kids of friends come by :)

(B.t.w. I removed the link in the other topic and linked to this topic instead, otherwise it might be conceived as 'self promotion' and we discourage that).

[CaL]

Very cool! Love it!

[UltraViolet]

  Great to see someone finally taking a stab at creating some alternative track designs for the Duplo trains.  I will very likely try to get some of the wide curves made up.  The one thing I've really been missing is switches with one straight and one curved route, rather than the official wye type.  I understand why LEGO made the decision to only make a wye type, as it was simpler, and adequate for children's play,  to only produce one mold, rather than having to make separate left-hand and right-hand switches.  It would be fantastic if you were to create a design for those, though.  The upside of 3D printing is that you only have to draft one 'handed' computer model which can then be flipped to make the other.

[phildc]

Thanks for your welcome message.

As you state, one-hand switches are missing. I am already considering a design, but  have no practical design up to now.

Main reason is the lack of a published geometry for the DUPLO train system. 

I designed the "R2" based on the existing Y switch, but not considering a whole coherent system, as exists for traditional model railways (one of my other hobbies :) ).

Other limitation: the parts should fit on a 200 x 200 mm building plate when printing, to allow a maximum of users to print on low-cost printers.

The turnplate just fits if rotated properly. A one-hand switch could be longer than the Y model, to allow for track separation?

Ideas  and/or suggestions welcome!

Phil.

[LEGO Train 12 Volts]

Great idea, finally we have the large radius curved track! 

Thanks for sharing! 

[phildc]

About the "one-handed" train track switches:

I found the following 3D printable model (did not notice it during the last months, don't know why  ):

Duplo Lego model railroad Switch,  by HenkK 

available on Thingiverse under nbr  5655276

Duplo Lego model railroad Switch by HenkK - Thingiverse

 

First impressions after printing:

- prints on a 200 x 200 printer bed

- connects OK with my existing DUPLO tracks

- the straight part length is 176mm  (normal 1/1 is 128mm): mandatory to separate straight and curved tracks

- the curved part angle is approx 40 degrees:  same reason. A short curved track of 20 or 10 degrees could be useful to reach a multiple of 30 degrees.

- the curved part radius is somewhat more than std. Will not match a "standard" curve.

- curved ans straight portions do not fit exactly (projected length)

- there is no grip on the tracks

 

But it can be quite useful. Refer to the pictures on Thingiverse

 

 

Edited February 25, 2023 by phildc
spelling

[UltraViolet]

  I took a look at that design, and it does raise some challenges with current standard geometry.  But it also got me thinking about the older geometry of the original black colored track.  The irony of LEGO's design change to the shorter track segments on the 'new' track, is that the old geometry with the longer curves and straights would have accommodated left-hand/right-hand switches without any compromise or partial length track segments for correction.  (It's further ironic that they then chose to only made a parallel switch!)  The straight track 4563 is 176mm in length vs the 127mm of the 6377, and the 4562 curves are 45 degree and at a tighter radius than the 6378 at 33.3 degrees.  The newer geometry must have been used to allow the straight track to fit on baseplates, but since the curves never would, the benefit is not as great as it would seem.  (The old track is a rare example of LEGO creating something 'out of system' and then 'backtracking,' so to speak.)

  While designing around the 'old' geometry is certainly something I'd be willing to accept, I figure the best scheme would be to use the newer geometry at 1.5 length for straight and curve on the switch and then make compensating 1/2 straights and 1/2 curves.  The 'old' system had shorter straights (4665) in addition to the long ones, so there is some precedent.  Half track sections open up many other possibilities for layouts on their own, regardless of whether new switches exist.  This approach would likely benefit the maximum number of users.  I don't know if it would work out for a parallel passing siding without and odd-length compensating straight, but I'm sure you could determine that easily in the CAD environment.

  I will note about the example you gave on Thingverse that the mechanical design of the moving parts seemed well thought out and could prove practical in a revised geometry.  BTW, I'm enjoying this discussion for that fact it's made me think about these parts in ways that I'd never quite before.  It really helps get you inside the head of the original parts designers.  If something new and useful comes out of it as a workable printable model, even better!

[phildc]

Thanks for the info on these two standards that I was not aware of, and the interesting thoughts.

[The_Cook]

The modern duplo track geometry is all based around hexagons.

A straight connects opposite sides of a hexagon. A curve connects to an adjacent side plus one; not sure how to describe that better without resorting to pictures.

The advantage of hexagons is that the tesselate nicely and thus all the lengths are consistent. If you have 45degree curves (which I think the original duplo track system did) you end up needing strange lengths (probably factors or sqrt(2)) to make things fit and unlike Brio which has slack in it's connections, Duplo is too precise as fit.

Lego must have decided that avoiding odd lengths was worse than forcing children to thing in hexagons!

 

[phildc]

Thanks for your remarks. It helped me to draw this view of the standard DUPLO track geometry: 

The external dimensions of the tracks are shown.

For info:  the DU (DUPLO unit) is 16mm, and the LEGO unit (LU)  is 8mm.

 

[UltraViolet]

  Based on your diagram, I think I figured out another reason for the geometry, and it's kinda cool.  I don't know why I didn't notice this before - the 'new' style Duplo curved track fits exactly inside the radius of the standard LEGO train track!  Also, because the 'new' Duplo straight track is the same length as a standard LEGO train straight track, you can put a Duplo oval precisely parallel inside a LEGO train oval!

  I will note that the fit is just a tad snug, causing a slight lifting of the Duplo track, but if it were attached to a baseplate then it would stay flat.  I think it illustrates how LEGO likely made their decision though.  I figured out why the fit is so snug, however, and I don't know why LEGO did it this way, but the ties of the curves are about 1mm wider that those of the straight track sections.  You can actually see it easily when comparing the bottoms of the track pieces - the wall thickness on the outer faces of the ties on the curved sections is 0.5mm thicker.  If one loop were boosted enough to have the tie ends not touch, the interference should be eliminated.

  Your custom wide-radius Duplo curves would fit on the outside of the LEGO track in nearly the same way, but they're wider by about one LEGO stud.  That might not exactly fit baseplate geometry, but it probably works fine sitting loose on the floor.

[phildc]

Amazing info. I wonder if LEGO/DUPLO are still developing their train products.

[phildc]

FYI, I designed LEGO Technic wheels to print in 3D, that would fit on DUPLO tracks.

This opens the possibility to build new locomotives and cars for the DUPLO train.

A first prototype is available as STL file. Additional models are in design.

Ref:

[WIP] Duplo Technic Train - Page 2 - LEGO Technic, Mindstorms, Model Team and Scale Modeling - Eurobricks Forums

[phildc]

A more realistic LEGO train wheel to run on DUPLO tracks: (fits only on MOC's, due to its size):

LEGO train on DUPLO tracks - realistic steam locomotive wheel by phildc - Thingiverse