Bridge installation problems........

[geepers]

hello everyone, in curently in the process of trying to install a cambells 90' plate girder bridge. i have 4 1/2" of clearance underneath it. the sub roadbed is 1/2" plywood and im not sure how to install it correctly. does anyone have any pictures of bridge installations or any ideas on how the best wway to do it is? i have bridge abutments also, but im not sure how to install the bridge or abutments. thanks in advance.[:)]

[selector]

Place the abuttments up against any banks you must traverse, and place the bridge over them. Look for clearances and grading requirements to get the tracks over them without a hump (if at all possible; otherwise will look incorrect, artificial, and clumsy). Does the bridge rest flat on the abuttments, and the track, with or without bed, lie along the bridge base running surface? If not, find out when these all happen by trail and error, or adjust approaches, or adjust abuttment depths.

I would avoid the use of bed on a bridge as it would not be usual to have it. Bridges and trestles carry tracks the same way.

Once you have the correct heights for everything, and you feel happy about the 'looks', mate the banks to the abuttments with plaster, or hydrocal, or sculptamold, or plaster cloth to make it look like the abuttments were built into the banks. These can be painted earth colours, or covered with light rip-rap (in scale, of course) later.

What I did was to actually lay the track, soldered and all, but with the bridge already slipped under it , off to one side of the obstacle to be spanned (out of the way). That way, I could see how the track lay when at the correct height, and could then place abuttments, piers, and the bridge, itself, at the height needed to support the span of track suspended in mid air.

[Jetrock]

What does this bridge cross? A stream? A road? Another section of track? 4.5" is nice clearance for any of these.

[cwclark]

I'd take out the 1/2" subroadbed and hand lay the track across the bridge...
here are pictures of my bridges..two are scratch built and one is an atlas kit bridge

http://community.webshots.com/photo/137793353/223356758NHLqSf
http://community.webshots.com/photo/137793353/223364252TFNwRw
http://community.webshots.com/photo/137793353/185723777qospgM

your bridge ends should look like this the ends of the bridge will fit in the L shaped grooves for end support I_ ======_I

[bogp40]

I'm not sure if you want the bridge to have open deck or ballasted. If open decked, check into the Central Valley bridge ties, these can be glued directly to the girders. The CV ties have molded spikes that you peen over the rail web. As to the initial placement of a bridge the positioning of the abutments and clearance height is the most critical factor. I beleive this is where the trouble lies.
1st. select bridge type, calculate the clearance for the bridge( girders, ties or roadbed) these subtracted from the rail to railhead clearance- I allow 4" min. With proper clearance now calculate the length to place the abutments. I use pine blocks for support and as a backer for the finished scenery materials. The height of the abutment should run from framework up to under the ties or roadbed . Notch the block to give a shelf for the bridge shoes to sit on- don't forget to allow for the thickness of the final abutment stone, conc. etc. On foam layouts glue the pine blocks in place, on benchwork I mount the block as a riser. This is a time to decide if any wings are to be used, set additional pine blocks shaped just smaller than the finished (angled, tiered etc.) When setting the bridge in place I generally let the rails hold it into position. Most of the layout is hand laid- so spiking down the rails is much easier. I don't like to slide rail joiners to hold the bridge. This can get tricky to clear the joiners and have the bridge sit on it's shoes.
Bob K.

[geepers]

thanks everyone for all your help and suggestions. as far as what the bridge is crossing, its another line underneath. i made a mistake in my first post, the height is 3 1/2", not 4 1/2" clearence. the bridge is a campbells scale open girder bridge. i will try your suggestions. thanks again!
steve[:)]

[selector]

Really nice work, CW. Looks like a lot of hours invested....patience, too.