Functional Train Bridges

[McDiesel92]

On 9/16/2020 at 4:34 PM, coaster said:

Of these 2, number one is by far the better option.  The way number 2 would load would result in the top axles being in tension, which will effectively pull them out of the bricks with the axle holes.  Either way though, you're going to get flex just from the track itself.  Simply making the joints rigid won't prevent sagging in the middle.  You're going to need some additional structure to span the shelves.  How much is a matter of how far you want to actually span.  I have this going in my son's room:

I know I'm super late to the party but I would like to eventually build some sort of bridge for my Lego city layout. Do you @coaster have more detail on your truss bridge(close up detailed pics or a LDD/Studio file). I would like to get a better understanding of an existing one before I buy a lot of technic beams and bricks. I like the style of the Howe truss/under truss.

Edited January 23, 2021 by McDiesel92

[McDiesel92]

On 9/19/2020 at 10:22 AM, zephyr1934 said:

At that point you are sort of building nested bridges. A potential problem with the technic design is that the pins have a bit of play, so a long bridge will likely sag.

Brickshelf is back up, first, here's the bridge I was talking about earlier

Though I have yet to test it under extended use it is 64 studs long. The track is just connected to 6x8 plates below. On the left is this design,

over a similar span. The key with this build is that every tie in the track is connected to the side walls with a bracket. The side walls provide significant rigidity. You could easily flip the walls so that they were below the track but then you are getting towards the boxbeam above.

Meanwhile, PennLUG had an even longer boxbeam bridge that I believe they still use at many of their shows, only differences are that it was better decorated and used 1x6x5 panels, here's a not so great shot of it,

Do you have the files or better pictures for the two bridges you show not including the PennLug bridge. I would love to recreate the PennLug bridge.

[zephyr1934]

10 hours ago, McDiesel92 said:

Do you have the files or better pictures for the two bridges you show not including the PennLug bridge. I would love to recreate the PennLug bridge. 

The brown bridge is REALLY simple, a layer of 6x plates, then a layer of 1x4x3 panels, then another layer of 6x plates (being certain to offset the seams, so 4x6, 6x8, or 6x12 the best choice) and then a layer of track.

The black bridge has a bracket on every tie. This one predates the modern brackets, it used the brackets from 1979,

which you can see in this view. But I would imagine any contemporary bracket would work. Then it is nx6 plates, with a mix of brackets (1x2 and 1x1 in this case), tiles, and plates for the surface.

[coaster]

14 hours ago, McDiesel92 said:

I know I'm super late to the party but I would like to eventually build some sort of bridge for my Lego city layout. Do you @coaster have more detail on your truss bridge(close up detailed pics or a LDD/Studio file). I would like to get a better understanding of an existing one before I buy a lot of technic beams and bricks. I like the style of the Howe truss/under truss.

Thanks, but sadly I don't.  It was built almost 10 years ago now.  I probably had an MLCad model of it, but it's long since gone or lost. 

It actually is pretty simple though.  The road bed is an overlapping stack of 6x12 plates, a total of 2 plates thick.  Technic beams run along the top and bottom, so you have the correct spacing for locking both with the vertical beams.  The rest is just 3-4-5 triangles.

PM me your email address and I'll take some extra pictures for you.

[McDiesel92]

2 hours ago, coaster said:

Thanks, but sadly I don't.  It was built almost 10 years ago now.  I probably had an MLCad model of it, but it's long since gone or lost. 

It actually is pretty simple though.  The road bed is an overlapping stack of 6x12 plates, a total of 2 plates thick.  Technic beams run along the top and bottom, so you have the correct spacing for locking both with the vertical beams.  The rest is just 3-4-5 triangles.

PM me your email address and I'll take some extra pictures for you.

zandydude92@yahoo.com Thank you.

[legotownlinz]

This is my Technic bridge. All segments that are built at full height are very stable. It would be no problem to increase the distance between the two pillars.

Edited January 24, 2021 by legotownlinz

[zephyr1934]

On 1/24/2021 at 3:39 PM, legotownlinz said:

This is my Technic bridge. All segments that are built at full height are very stable. It would be no problem to increase the distance between the two pillars.

I would never get any work done in an office like that (grin)