[MOC] Moveable railway bridge

[sporadic]

3 hours ago, faph said:

@sporadic I see, the Lego logo on the studs is the problem. I’m happy to follow the “non-standard” technique in this case ;)

Yeah. I put illegal in quotes because it's one of those things that only a small segment of the community cares about.  It's only illegal because of the logo raising the stud slightly.  It is a red flag in some circles (LEGO IDEAS or the BDP, for example), but isn't generally a big deal.  I only brought it up because as those tiles will be slightly stressed/out of alignment because of it.  I think it's a good idea to use the studs for extra support of the tile-rails since trains will go over them.  You could swap them out for hollow stud (Technic) pieces if it turns out to be an issue (which I doubt)

[faph]

Extensive real-life testing over the weekend threw up an issue:

When spacing tracks a stud apart, train wheels are prone to dropping on the inside of the split rail connections. This was even more of an issue when I was connecting the track with tiles-as-rails since that would have an additional half-stud gap.

It doesn’t cause derailment but with the tiles-as-track it wouldn’t be a comfy ride for passengers either!

So I’m going back to spacing official track a stud apart - the ride is just about smooth enough in that case. I will accept that I will be 2 studs out of grid :(  

And yes @Shiva I have now placed the pivot point a plate higher relative to the track and this does solve the collision issue nicely. Thanks for the tip!

 

Edited April 21, 2024 by faph

[Shiva]

Cheers, glad to help :)

[faph]

This is what I've got now:

Track now 1 plate lower compared with pivot point.

I am also needing to curve and incline up to the bridge. This means at this end of the bridge I do need a raised area between the rails otherwise light train cars might derail at the half stud spacing between the track parts.

[zephyr1934]

On 4/19/2024 at 12:04 PM, faph said:

Our daughter needs to be able to place minifigs anywhere!

Ah, design constraints to satisfy the consumer... (grin). I do like your brick built solutions and there might be a way to either fill the gap at the end of the rail or use the tiles to nudge the wheels over, but at some point it is pragmatic to just get to playing. If the 2 stud offset ever bothers you you can probably get fractional track lengths from TrixBrix or similar to bring it back into grid.

 

17 hours ago, faph said:

Track now 1 plate lower compared with pivot point. 

The rule of thumb I've heard and live by is to have at least one straight segment between a curve and a switch to prevent trains from "picking the switch," i.e., derail. The curve right into the gap might give you a similar problem on the near side of the above photo.

 

At any rate the design looks great

 

[faph]

3 hours ago, zephyr1934 said:

The curve right into the gap might give you a similar problem on the near side of the above photo.

Exactly, it does. But the raised “island” between the rails solves it!

Experiments signed off by Statler himself:

No more design changes allowed ;)

[zephyr1934]

On 4/23/2024 at 2:03 PM, faph said:

Exactly, it does. But the raised “island” between the rails solves it!

Ah yes, guard rails just like real railway bridges (and especially drawbridges)

[LEGO Train 12 Volts]

This project becomes more and more interesting, it deserves to be published on Lego Idea or better yet on Rebrickable!

[Ropefish]

Awesome work, love seeing folks designs slowly come to fruition in real life! 

[faph]

I will probably start building the whole thing soon. We will see where that takes us. 

Still haven’t quite figured out how I want to build the curved sloping tracks, though. I probably should just start provisionally with just a few bricks to prop it up. I appreciate that curved ramps mean twisted track curve pieces…

[faph]

It has been built! Photos to follow soon.

In real-life the bridge deck was not sufficiently rigid. It wasn't too weak as such, but without any load it warped a little which caused the bridge to remain in a slightly open position at the far end. Fixed this with 1 layer of additional plates and cross-supports underneath the deck.

To my liking, there's also a little bit too much gear backlash. Not a major deal though so I will probably not do anything about it. The contra-weight isn't quite sufficient to balance the bridge deck, but that's actually quite a good thing as the bridge will stay closed much better with a bit of extra downward force from its own weight. The gearing ratio is just perfect.

Other that than, turned out pretty much as designed. The track transitions are as per proof-of-concept: no derailings, but drivers should watch their cups of tea :)

Edited July 2, 2024 by faph

[SD100]

I don't know how you feel about aftermarket, but Bricktracks makes shorter rail sections (4 stud and 1.6 stud) That may be enough offset for you and keep your rails on grid.

https://www.bricktracks.com/product-page/short-straight-track-pack

SD

[faph]

Thanks @SD100! So far the off grid is not an issue for me.

Contra weight being lifted in place...

Freight train crossing nicely:

Kayakers patiently waiting...

The random coloured plates under the bridge deck are the added stiffness requires to keep the bridge deck straight. Will need the railway maintenance people to re-paint this in black and grey...

[Shiva]

Thumbs up to the work :)

[FGMatt]

If it’s just running battery trains, why not use the classic rails? Should be much easier to align (and are available in dark bluish grey).

[faph]

@FGMatt I would still need to transition somewhere to the new-style track, right?

[Feuer Zug]

Nicely done. Having the span be able to lift and fall without having to realign the track each time is great engineering.

[FGMatt]

1 hour ago, faph said:

@FGMatt I would still need to transition somewhere to the new-style track, right?

Yes, but it should make the moving joins far simpler. The transition to new-style track should work just with a half-plate offset, like this:

Should be possible too to tile over the join, to make it a bit less-ugly.

Just a thought!

[LEGO Train 12 Volts]

What a pleasure to see the bridge in work ... the passage of the canoes is the icing on the cake!

[JHS_NL]

First of, great how you made the bridge! Like the details and that it can move. Have you thought of buying 3d-printed track just for the connection points of the bridge? 

Trixbrix has them:

https://trixbrix.eu/en_US/p/MILS-Straight-Track-Terminator-Short/447

https://trixbrix.eu/en_US/p/MILS-Straight-Track-Terminator/388

[FGMatt]

On 7/11/2024 at 8:18 AM, JHS_NL said:

First of, great how you made the bridge! Like the details and that it can move. Have you thought of buying 3d-printed track just for the connection points of the bridge? 

Trixbrix has them:

https://trixbrix.eu/en_US/p/MILS-Straight-Track-Terminator-Short/447

https://trixbrix.eu/en_US/p/MILS-Straight-Track-Terminator/388

On that subject, does anyone know of a 16-long adaptor for old-to-new style rails? Trixbrix has one but only four-long, meaning that it won't work with the third rail.

 

If anyone knows of a printable file, I'd love it!