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Help needed for building a Curved Arch Truss Bridge

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  • Member since
    January 2014
  • From: Cresskill, NJ USA
  • 1,044 posts
Help needed for building a Curved Arch Truss Bridge
Posted by gdelmoro on Thursday, October 31, 2019 9:41 AM

I Know this is an ambitious endeavor but I'm going to give it a go.  I want to scratch build one of these

what would i use to make the curved arches? 

Gary

  • Member since
    May 2010
  • 5,620 posts
Posted by mbinsewi on Thursday, October 31, 2019 10:44 AM

Cool project Gary.

What kind of span are you talking ?, I mean in actual feet and inches, not scale feet

You could use styrene, masonite, Gator board, a really good grade of 1/4" plywood, or MDF, just to come up with a few.

Mike.

  • Member since
    January 2004
  • From: Canada, eh?
  • 9,750 posts
Posted by doctorwayne on Thursday, October 31, 2019 10:56 AM

If I were building that bridge, I'd cut the arches from sheet styrene, then use strip styrene to add the flanges to it.  You might be able to get away with using .040" for the arches, but I'd use .060", as I always have some on-hand in large sheet-sizes, as it's useful for large structures.

The rest of the members could be done with the various structural shapes and square tubing from Evergreen, along with more strip material as-needed. 

Use solvent-type cement to assemble it, and it will be strong enough for anything you'd care to run over it.

Wayne

  • Member since
    January 2014
  • From: Cresskill, NJ USA
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Posted by gdelmoro on Thursday, October 31, 2019 11:28 AM

Thanks for the quick replies.

The span from roadbed to roadbed will be 24".  The cavern will naorrow ftom there to abut 4" on the bottom which will be20" below the bridge deck. 

Im most concerned with the design of the lower arches. Most of the other parts can be made from existing kits and parts. I was planning on using a steal U Channel under the roadbed.

I Like the sheet styrene idea.  I was looking at I-Beams from Evergreen but I'm not sure they would bend the way I need them to.

Gary

  • Member since
    January 2014
  • 980 posts
Posted by ROBERT PETRICK on Thursday, October 31, 2019 11:52 AM

gdelmoro

Thanks for the quick replies.

The span from roadbed to roadbed will be 24".  The cavern will naorrow ftom there to abut 4" on the bottom which will be20" below the bridge deck. 

Im most concerned with the design of the lower arches. Most of the other parts can be made from existing kits and parts. I was planning on using a steal U Channel under the roadbed.

I Like the sheet styrene idea.  I was looking at I-Beams from Evergreen but I'm not sure they would bend the way I need them to.

Hey Gary-

The Evergreen or Plastruct I-beams and channels do not bend along the axis you would want them to bend. I tried it; no joy. But, you could construct the arch with a series of straight bottom chords. When viewed as an assembled whole, the arch appears as a pleasing curve.

As for the steel channel deck . . . I think it is unnecessary. With support from the vertical members every 3", the styrene deck should be plenty stiff.

BTW, I'd use ABS instead of styrene. Personal preference.

Good luck.

Robert 

LINK to SNSR Blog


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    March 2011
  • 605 posts
Posted by NVSRR on Thursday, October 31, 2019 12:27 PM

I would do it the the same way Wayne stated.  That would easily make any arch you need

A pessimist sees a dark tunnel

An optimist sees the light at the end of the tunnel

A realist sees a frieght train

An engineer sees three idiots standing on the tracks stairing blankly in space

  • Member since
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  • From: Cresskill, NJ USA
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Posted by gdelmoro on Friday, November 1, 2019 6:35 AM

Why ABS instead of Styrene?

Gary

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