Overpass Piers

[ADThompson]

I need to build overpass piers but am trying to avoid a bunch of "trial and error" cutting.  What is the best way to make piers? The highest should be about 3 1/2 inches over approximately 72" rise.  I've got scads of scrap 2 x 4 lying around that I planned on putting to this task. Thanks.

[BroadwayLion]

So it looks like you are trying to elevate a track. You want to go up 3.5 inches over a distance of 72 inches. But what is your track, and what is your underlayment or sub roadbed.

If you have a good sub roadbed you can do it with less risers, if you are just putting your sectional track, both ends of each section must be supported. For flex track, figure every 6 or 9 inches.

LION would simply 2x4s at 1/4" incraments. 1/4", 1/2", 3/4", 1" 1.25" 1.5", 1.75". 2" 2.25". 2.5", 2.75", 3" 3.25" and 3.5", that is 14 risers. Put the 3.5" riser at the far end of your rise. tack down the low end of your rise, and then insert the remainding risers until your rise is nice and even. The risers will then be just a little more than 5" apart. (5.142" to be exact....)

ROAR

 

[Carnegie Falls]

Are you looking for tips on what shape/style to make each pier?  Or are you looking for info on how far to space each pier and how tall to make each one?  Also, I assume you mean 72" "run" (as opposed to "rise"). 

Are you using the cookie cutter method/plywood as your base?  If so, I guess you would just install it, and then measure at every place you wanted a pier to see exaclty how high to make it.

When I did something similar, I started with how many piers I wanted to have.  Let's say ten piers as an example.  You have to know if you will have a pier at the end of the line (at 72") or if that will be supported by something else (ground, etc).  I am assuming your beginning and end points are supported by something else and do not require piers.  This means that you will have 11 "spaces" between piers, each about 6.5" on center.  If you're using 2 of your 10 piers at the beginning and end, you'd have to account for 9 "spaces".  What matters is that you account for the number of "spaces".  Dividing the 3.5" rise into 11 spaces, you get 0.32".  Your first pier/riser would be 0.32" tall, the second would be 0.64" tall and so on.  Your tenth/final pier would be 3.2" and your track would continue to rise another 0.32" over the last 6.5" to meet your final elevation of 3.5" over 72".

Is the overpass a road or rail?  I assume it's a rail in which case, lots of folks will recommend not just dividing by the number of spaces and making all the height increments exactly the same.  I think this would be about a 5% grade which could be a problem for trains derailing at the transition.  It could be a good idea to make your first and last piers a little shorter and taller, respectively, but you would have to make that up over the middle piers.  Any chance of extending this rise over a longer distance?

[mlehman]

If you're just looking for a decent and easy to use pier or abutment, check out the Rix line. They offer a very nice pier that has an ingenious method of assembly that will let you fit them well and easily.

[selector]

ADThompson

I need to build overpass piers but am trying to avoid a bunch of "trial and error" cutting.  What is the best way to make piers?

The best way is to fashion your end height pier, cut to the correct length so that it supports your rails at the correct height...MINUS any roadbed, plastic fake ballast, real ballast, or girders.  Place that one end pier where you want it based on the location of your overpass, and where the bridge you want it to support will rest properly distanced from the one on the opposite side of the gap.

Now you must place roadbed going from level, anchored to keep the lower end where it must be (use at least 1/2" plywood in a shaped strip) and then bend it up to rest on your highest end-pier...the abutment for your bridge.

Then, using the exterior points on a caliper, measure three or four piers roughly equidistant from each other and record the measurements between the nether surface of your inclined and bent plywood strip and the surface below it.  If using open grid consruction, cut a riser such that it can reach to a joist below it and still support the nether side of the plywood incline.

One caveat: the riser next removed from the highest, on both sides of the gap, should be only slightly shorter than the abutment ones.  Why?  Because you want to fashion the same curve at the top, near the bridge, as the curve at the bottom of your plywood strip where you anchored it level.  Otherwise, your locomotives will lose traction as they transition from your roadbed to the bridge.

I hope that all makes sense.

ADThompson

The highest should be about 3 1/2 inches over approximately 72" rise.  I've got scads of scrap 2 x 4 lying around that I planned on putting to this task. Thanks.

 

Using scrap 'most anything is fine, provided you can work the material to suit and that it works in place for you.

I hope you are aware that your grade will be very steep for trains.  It exceeds 4.5%. Your trains will have to be very short, unless you have two or more locomotives working together in one train.

Also, you want that 3.5" clearance, if I understand.  If so, your rails atop the overpass will be somewhat higher than that because you need something supporting them over the gap.  The ties and rails will have to rest on something.  Depending on your starting point's level at the bottom of the grade, you may actually have a grade closer to 5%.

[RT Trains]

BroadwayLion

would simply 2x4s at 1/4" incraments.

Wow, massive overkill in materials and spacing. 1X2 at 16" spacing will be fine to support half inch or thicker subroadbed

[riogrande5761]

mlehman

If you're just looking for a decent and easy to use pier or abutment, check out the Rix line. They offer a very nice pier that has an ingenious method of assembly that will let you fit them well and easily.

Another vote for Rix line.