Diamond crossing - work in progress

[djm]

Currently a work in progress but it is nearing completion.

Edited August 14, 2016 by djm

[Lego Engineer]

I'm quite interested in how it's constructed. Could you post some pictures of just the crossover?

Edited May 28, 2014 by Lego Engineer

[djm]

I can do better than a picture - I've got an LDD file for it, so I'll upload it shortly.

Notes about the current design

1. the "between rails" section is too high for some trains e.g. the yellow cargo train's (7939) front buffer has a plow on it, which catches on the studs. For the video, I removed the front buffer (to quote Peter Gabriel, "the generic term for this is cheating") as the run was a primarily a proof of concept test.
   
2. I've worked out an alternative lower configuration for 1/2 of the "between rails" section using 4x1 fences. I'll have that bit reworked tonight. I've yet to tackle the other 1/2 of the "between rails" section.
   
3. the "slightly curvy bits" that form two sides of the diamond will also need refinement. They suffer the same "too high" challenge and will get in the way of a train with a low plow.
   
4. LDD won't allow the modelling of the Technic beams and studs. The LDD file is as close as I can get it to resemble the physical entity. In the real world, push the studs all the way in.
   
5. The height is odd at 36 LDUs. This requires the attaching real rail pieces to be elevated by 12 LDUs (1 plate + 1 baseplate)
   
6. The attachment to the real tracks is clunky. It requires refinement.
   

The aim is to address all of these items in a refined design.

Regards,

David

Here's the LXF file from LDD.

Edit: LDD file removed due to subsequent uploads using allocated quota. The most recent version of this is version 7, and can be found in the forum with a posting date of November 2014.

Edited November 24, 2014 by djm

[zephyr1934]

I don't have LDD on this computer, but from the video it is clear that that crossover is an insane piece of engineering. Great work.

Oh, and BTW, the couplers with plow have that problem on normal track too (well, not when it is perfectly flat, but it is so close to the top of the rail that any small bump in the floor or what not will cause it to drag).

[djm]

Thanks zephyr1934.

My first thought when I decided to try to make it was "that can't be too hard, surely". It was nearly too hard. It took quite a few false starts to make it to the end.

The yellow cargo train is my son's favourite, so until I can restructure the crossing to work for it I don"t get to put it on our layout. With the plow coupler on, it does a tremendous job of destroying the crossing!

Edited May 31, 2014 by djm

[zephyr1934]

"I have no idea why it started working" said the father holding a file behind his back (grin). No, in all seriousness though, that is commendable. You might be able to get it to work by adding one more plate below and dropping only those offending bits down (or using shims- cut up lego boxes if you want to be pure).

[djm]

Rework progress update (fortunately, I haven't had to resort to a file!).

I've managed to restructure things a little and remove the studs that were protruding too high on all fours "arms" of the crossing. The "diamond" in the middle is next but I'm hopeful of retaining most of the original approach. The restructure has resulted in an additional height addition of 4 LDUs, so the resulting crossing looks like it will end up as being the equivalent height of a track on top of two plates.

If I manage to find time during the evenings this week, I'm hoping to complete the restructure in time for a trial run on the weekend. If all goes well, I'll upload an updated LDD file early next week.

Regards,

David

[djm]

Here's the revised crossing in action. The revision addresses the identified issues in the previous post.

I haven't yet built in in LDD but once I do, I'll post the revised design in this thread.

Regards,

David

Edited August 14, 2016 by djm

[LEGO Train 12 Volts]

Nicely done!

This last version looks better than the first one!

Impressive work!

[djm]

Attached to this message is the LDD file for the revised version. There are a couple of connections that are unacceptable to LDD, hence the crossing has been modelled in LDD as being the penultimate step of the construction.

This image below illustrates the crossing as represented in the LDD file. The colour coding is meant to assist in illustrating which pieces will need to be joined to complete the build. Red to red, green to green and blue to blue. Hopefully that makes sense. One track piece is included in the file to illustrate the technique to join the crossing to the standard Lego train track.

Once assembled, it should look something like the following (though hopefully without the rainbow of colours that were available when I was building it).

One desire in providing the LDD file for the crossing is for others to build, critique and suggest improvements to the design. I would welcome any posts to this thread with suggested improvements.

I've already got one improvement up my sleeve, which is to amend the design so that it may be able to be used in conjunction with a baseplate. But that is probably going to be more than a month away as I have a pile of paperwork on my desk (underneath the pile of Lego!) that I've been ignoring for too long which needs to be addressed first.

Regards,

David

diamond_40_ldu_height.lxf

Edited June 15, 2014 by djm

[zephyr1934]

Oh my gosh, that is truly an insane amount of engineering to get that all working. I bet you can finally sleep at night. Well done.

[djm]

Update teaser.

I wanted to tweak the crossing a little as (a) the integral strength wasn't as good as I felt it needed to be and (b) I've seen on occasion a trailing carriage been left behind on the junction with the magnetic coupling not being quite there.

I haven't had a chance to trial the modified design in anger but running a bogie over the modified design, it feels a little smoother. I suspect the decoupling was due to wheels catching on the edge of one of the bricks.

So here's the teaser photo of the modified crossing:

If I get the time this weekend, I'll trial it for an hour or so and video it (not for an hour or so).

If it all hangs together, I'll create a LDraw (and possibly LDD) file of it.

Regards,

David

[djm]

As promised, here is a video of the most recently modified crossing in action. I ran a test of an hour of continuous running during which time all of the rolling stock stayed attached and the crossing stayed intact! I'm reasonably satisfied that this version is fit for purpose. I'll post some build instructions here some time in the next week or two.

Regards,

David

Edited August 14, 2016 by djm

[djm]

Here we go, a picture of the crossing built using LDD and the LDD file itself.

Once again, "illegal" LDD joins are colour coded to illustrate where the joins should be (blue to blue, green to green, etc). The expectation is to switch the coloured bricks with dark grey ones.

I'll work on an LDraw file next and post an update with its location once it is available.

Regards,

David

{Edit: original v5 LXF was missing a couple of bricks]

diamond_crossing_v5.lxf

Edited August 23, 2014 by djm

[legoman666]

That's pretty slick.

[Fish777]

Awesome! If I had pieces spare, I would build this.

[djm]

I've turned it into some build instructions using LDraw/MLCad/LPub. I'm trying to get them uploaded to railbricks.com. In the meantime, here's a POV-ray rendering of the crossing:

Edited September 1, 2014 by djm

[TaltosVT]

I've turned it into some build instructions using LDraw/MLCad/LPub. I'm trying to get them uploaded to railbricks.com.

If you're having trouble uploading them to the RAILBRICKS site, please email the file to me at editor@railbricks.com and I'll see if I can get them posted for you. The upload functionality of the site, unfortunately, is spotty.

-Elroy

RAILBRICKS Editor.

[djm]

Here's version 7, the most recent incarnation.

train_diamond_crossing_v7 by djm_mgst, on Flickr

With the LDD file (attached) I took a slightly different approach to illustrating the "illegal" joins, to allow the crossing to more or less hang together within LDD. The parts that are involved in an "illegal" join have been colour coded to illustrate where they should go (blue with blue, yellow with yellow, etc). The expectation is that the coloured parts would be replaced with the corresponding dark-bluish grey part at build time. [Edit: the 4x red 1x1 plate are better replaced with 2x dark bluish gray 2x1 plates but using the 1x1 plates gets around an LDD illegal join with the 2x1 plate]

There will likely be some build instructions for this available at some point via RailBricks.

The proof of the pudding is, of course, does it work? So here is a demonstration video.

{Edit: Image rendered via MLCAD/LPub/POV-Ray was missing a couple of pieces]

diamond_crossing_v7.lxf

Edited August 14, 2016 by djm

[UrbanErwin]

I saw the pictures and video on Flickr, I really like the design. Sadly I only run 9V so I can't use it

[codefox421]

I saw the pictures and video on Flickr, I really like the design. Sadly I only run 9V so I can't use it

I bet it would be possible to use some copper or aluminum tape to electrify this.

[detjensrobert]

I bet it would be possible to use some copper or aluminum tape to electrify this.

Yea, but it would be hard to keep the continuity across the middle.

[DrJB]

That is for sure very ingenious ... but ... how about a 3D printed intersection ?

[detjensrobert]

Depending on the printer you use, 3D printing can be very inaccurate and would not interface well with the lego track.

[zephyr1934]

Excellent! It is very neat to watch the evolution and progression of this design.