N scale. Needing to cut a bridge flush.

[CRR Chase]

Hello,
I have some of the atlas N scale girder plate through bridges.. I am wanting to curve them like the prototype.

so two questions.
1. besides a miter box,  is there a tool i can use to cut the ends flush? (miter box is prohibiting proper angle) or any tips to keep it neat? 
2. is there a formula for figuring cut angle for a curve?

(these are pre-fabed from atlas in straight sections)

 

[wm3798]

The important question is, what is the radius of the curve? 
I've found that if you try to make it too tight a curve, you'll have a clearance problem on the sides, especially if you're running larger locomotives.

If you don't have a vertical clearance issue below the tracks, cut the plate girders away from the deck, and turn them upside down to be below the tie level.  Then trim the segments to meet the curvature of the track.  I did this with one of the Atlas deck type Warren trusses along with a plate girder on the short segment.



Where the bridge crosses the tracks (needing clearance down below) I built an open frame to be wide enough to catch the curve, with Micro Engineering plate girders for the sides.



The other thing to keep in mind, is that each segment of the bridge needs to be supported at both ends.  So the longer the spans, the fewer piers you need, which makes a more realistic looking model.



As you can see, mine has a compound radius to make the route, and I had to design the bridge to work with the necessary track alignment.  If you have some pictures of the location you need to bridge, maybe we can help you sort out the best way to make it look good with the parts you have at your disposal.

Lee

[signalmaintainer]

You may just have to build yourself a jig/fence to get the proper angle and a clean cut. Seems to me some small pieces of 3/4" plywood would get you started

[CRR Chase]

The important question is, what is the radius of the curve? 
I've found that if you try to make it too tight a curve, you'll have a clearance problem on the sides, especially if you're running larger locomotives.

If you don't have a vertical clearance issue below the tracks, cut the plate girders away from the deck, and turn them upside down to be below the tie level.  Then trim the segments to meet the curvature of the track.  I did this with one of the Atlas deck type Warren trusses along with a plate girder on the short segment.



Where the bridge crosses the tracks (needing clearance down below) I built an open frame to be wide enough to catch the curve, with Micro Engineering plate girders for the sides.



The other thing to keep in mind, is that each segment of the bridge needs to be supported at both ends.  So the longer the spans, the fewer piers you need, which makes a more realistic looking model.



As you can see, mine has a compound radius to make the route, and I had to design the bridge to work with the necessary track alignment.  If you have some pictures of the location you need to bridge, maybe we can help you sort out the best way to make it look good with the parts you have at your disposal.

Lee

Lee,
These are what i am using. thanks for the input.. I need to figure out how to share images on here..

here is a google search link with pics of the bridge, The raidus will be 20ish inch

https://www.google.com/search?client=firefox-b-1-d&sca_esv=598871147&sxsrf=ACQVn09Iu_MvVT8gv1byGtZ4fCf57ElbTA:1705431113293&q=unaka+springs+bridge&tbm=isch&source=lnms&sa=X&ved=2ahUKEwj1-Mj9yeKDAxWvHTQIHQgFBrgQ0pQJegQIDBAB&biw=1600&bih=775&dpr=1#imgrc=6HZ4k2C-oGNROM

[CRR Chase]

here is another direct flicker link

https://www.flickr.com/photos/alcomike/22773719106

[wm3798]

Okay, so the prototype is basically a straight bridge with a curve at one end?  Is that how you're modeling it?  Or are you bending the whole length to get the right flavor but accommodate your track plan?

If the former, I'd suggest you use the thru girder plate bridge from Kato for the straight sections.  The length looks more right to my eye.  Also, the Kato bridge is an open deck.  It's a pain to scrape the nubs off if you're using ME bridge track, but it's possible.  (I did this on my truss bridge on the WM layout)


Then you're just modifying the approach spans where the curve is.

Here the trick is to cut it at the correct angle so you have good clearance for rolling stock going through the curve, (you could mock up a cardboard stand in to get it just right using a bit of trial and error) then use the dimensions from the mock up to cut the bridge.  Then, just use some appropriately sized strip styrene to repair the end plate so it looks like the uncut end.  Careful trimming might let you preserve the OEM end plate to glue back on for a more seamless look.  Paint/weather/install, and you should have a pretty good job of it.

Hope this helps.
Lee

[CRR Chase]

Thanks Lee, I’ll give it hell…

[CRR Chase]

Oh and it will be like the prototype, straight with the curved end…

[southernman]

I know where that bridge is.