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How would you model these arched trusses?

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  • Member since
    December 2017
  • From: Just outside of Leitchfield, Ky
  • 105 posts
Posted by mrrdad on Wednesday, March 6, 2019 9:26 AM

ROBERT PETRICK

 

I kinda gravitated to the idea of single trusses with members and chords and struts and whatnot with a cross-sectional area of 0.08" by 0.08".

This is the main thing I struggled with. I went with .100" members with .104" thick material. I'm not totally happy with the looks, but it's very solid. I might try to bring it down to .080" using .075" material.

 

Ed

Semi newbie HO scale modeler coming from the O scale world

  • Member since
    January 2014
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Posted by ROBERT PETRICK on Wednesday, March 6, 2019 9:26 AM

mrrdad
ROBERT PETRICK

Hey Ed-

I've only researched the past few days. Hard finding stuff in this Grand Central Station, but tons of stuff on that other one.

What era do you model? I'm asking to see if you're gonna deface that elegant grandfather clock tower with B&O.

Robert 

Yeah, sorry. It will be the 1950's era. So I think it will have the B&O logo as well as the B&O billboard on the building roof. I have to make sure those were there then.

No need for you to apologize for anything, but I'm a little embarrassed I didn't notice the tag line in your signature. Embarrassed

Robert

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Posted by ROBERT PETRICK on Wednesday, March 6, 2019 9:54 AM

mrrdad
ROBERT PETRICK

I kinda gravitated to the idea of single trusses with members and chords and struts and whatnot with a cross-sectional area of 0.08" by 0.08".

This is the main thing I struggled with. I went with .100" members with .104" thick material. I'm not totally happy with the looks, but it's very solid. I might try to bring it down to .080" using .075" material.

Ed

Yeah. Just like the prototype trusses are extremely strong in only one axis, they are vulnerable to secondary stresses in the other axes. But once assembled and the last member is in place, the forces align and cancel each other out and the structure stands as a unified whole.

I model in styrene (well, actually, usually, ABS) and delicate spidery pieces and parts do come together and the assembled structure is remarkably sturdy and dimensionally stable.

I'd try to cut the steel as thin as possible, especially if you're gonna assemble double trusses into a 3D space frame. But please don't be too overly influenced by my ideas. You gotta go with what you got.

Good luck.

Robert 

 

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  • Member since
    January 2014
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Posted by ROBERT PETRICK on Saturday, March 9, 2019 1:53 PM

I'm just about finished with an experiment to determine how this structure might be built. The goal is to see how delicate and airy the framing trusses can be made and how stable and sturdy the finished shed can be.


I cut out the pieces and parts needed to form the structural skeleton of one complete bay . . . two double truss arches and four purlins connecting the composite arch ribs. Everything was cut from a sheet of 0.080" styrene, and the truss webs, struts, and chords have a nominal dimension of 0.080" by 0.080".

Then assembled the parts into the skeleton frame. The spacing of the arch ribs is 5.42" center-to-center based on drawings posted earlier by the OP.

I will add a 6.50" by 12" piece of 0.030" sheet styrene to represent the roof decking, and then after the adhesives have set up, I will test the structure with a few bricks loaded on the roof saddle-bag-style to see what happens. I'm not expecting any surprises.

Robert

 

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  • Member since
    December 2015
  • From: Shenandoah Valley
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Posted by BigDaddy on Saturday, March 9, 2019 5:14 PM

I am amazed at both your works.  Even more amazed that Robert is co-modeling.

Henry

COB Potomac & Northern

Shenandoah Valley

  • Member since
    July 2006
  • From: Bradford, Ontario
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Posted by hon30critter on Saturday, March 9, 2019 7:04 PM

That's really cool Robert!

Dave

I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!

  • Member since
    December 2017
  • From: Just outside of Leitchfield, Ky
  • 105 posts
Posted by mrrdad on Sunday, March 10, 2019 12:49 PM

Robert,

Awesome work my friend!

I'm glad you are participating in this. I chose this railroad to model because of the fact I went to college just a few blocks where this station sat, the train station with clock tower, the bascule bridges, but most of all... the train shed! It was important to me that whatever railroad I modeled has a large train shed.

Unfortunately I'm tied up working on some stuff for work today and need to spend some time with the family, but I will get back on this soon. Thank you for the inspiration. I'm hoping you continue to model this. It seems to intrigue you and you certainly have the talent.

Ed

Semi newbie HO scale modeler coming from the O scale world

  • Member since
    January 2014
  • 1,500 posts
Posted by ROBERT PETRICK on Sunday, March 10, 2019 1:50 PM

Following up from yesterday . . .

I did not have any 0.030" sheet styrene on hand like I thought, so I used 0.010" sheet instead. Being thinner, It pretty much shows the lumps and bumps of the skeleton frame and is a lot more flexible and kinda looks like a tent, but for purposes of this experiment it will be okay. The 0.030" sheet would give a smoother appearance and provide more rigidity to the structure.

Also notice that the eaves of the roof are about 1/4" short on each side. Apparently, the overall length of the curved arches is a bit more than I estimated. Dang. I suppose I could've measured Geeked . . . but these are just the kind of things you discover by going through a pre-build mockup like this.

Here's a photo of the load test. Success.

Here endeth the experiment.

Robert

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    January 2004
  • From: Canada, eh?
  • 13,375 posts
Posted by doctorwayne on Sunday, March 10, 2019 1:57 PM

Very impressive and very nicely-done! Bow

Wayne

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