Using Gargraves track in aMTH Arch bridge....

Dave I have cut strip's of 1/2 ply wood that fit in the hole were track go's and pant them black and screw them from to the bridge from the bottom and it can be done with 1/4 ply wood if you want the track to sit lower , also screw the track on the ply wood first be for you screw to the bridge .

Guy

Dave,

I can email you a picture later. Like you, our concern was engines hitting the bridge when passing thru it. We ripped narrow stripes of Rosewood to raise the Gargraves track to where the ties just fit under the bridge walkway. These stripes are placed parallel to the track and only under the rails so they virtually disappear when viewing the bridge.

I just used the foam roadbed to raise the track and reduce noise as it crosses the wood plank spanning my room opening for my shelf layout.

I had to raise my Ross/Gargraves track about 1/2" off the bed of the bridge - as some steamers side rods were hitting the walkways.

I had to mount the main dual track bridge with the two approach bridges as a unit  directly inline, parallel and directly above a dual track mainline below which negated the three support piers.  So I machined a solid beam which slid into the MTH roadbed slot and extended 3" over long on each end which became the backbone of the assembly.  The bridges were supported on the subroadbed of the upper level approaching tracks.  Pure toy train fantasy but it works and the space was tight.

The bridge abutments were the tunnel portals of the track below.

This was done in two separate locations where the upper level traced the lower level along the back  walls.

One of the first installation on my layout.  The easiest correction was to add the cork road bed across the bridge. Enough added height that all runs well.

Cork roadbed is what I used. Two layers.