What is the best method of accommodating the inevitable expansion of the track rails (standard code 332 brass) in the summertime when the track is mounted on a raised trestle? A couple of scenarios that will occur on my proposed layout are: large raised curved sections, and 12 foot long straight sections. I understand how floating the track in ballast on the ground allows movement in all directions - no problem. But when the trestle bents are expected to remain permanently attached to wherever they are in the scenery, it seems that it may cause track that is attached to the tops to warp under the summer sun and try to move the bents.
Al,
I have all the attaching screws underneath removed on the straights and on my raised turns NOTHING is screwed down. I do have to occasionally push the track back centered on the raised road bed. If you really want the track secured to the trestle bents there are several ways. Loose wire ties, blocks screwed to the ties underneath allowing it to float but catch on the beams connecting the bents,etc.
Om my bridges and trestles I used rail clamps t o the rails together and let them float. On one double track bridge I had one section that liked to move so I tied it down with one screw and that’s all I’ve had to do the past five years.
My railroad is 20% trestles. Nothing special is done to the track. I’m battery, so I use brass slip-ons for joiners on most of it.
Temps vary from 102 to -10 F.
I forgot. No guard rails yet. Not rail anyway. I use wooden beams for guard rails. Same as most backwoods logging railroads. Just in case Fr. Phred asks…
John Bouck said:
My railroad is 20% trestles. Nothing special is done to the track. I'm battery, so I use brass slip-ons for joiners on most of it. Temps vary from 102 to -10 F.I forgot. No guard rails yet. Not rail anyway. I use wooden beams for guard rails. Same as most backwoods logging railroads. Just in case Fr. Phred asks…
John - do you attached the track to the trestles? If yes, how?
David Russell said:What keeps your track from sliding off the tops of the trestles?
Al, I have all the attaching screws underneath removed on the straights and on my raised turns NOTHING is screwed down. I do have to occasionally push the track back centered on the raised road bed. If you really want the track secured to the trestle bents there are several ways. Loose wire ties, blocks screwed to the ties underneath allowing it to float but catch on the beams connecting the bents,etc.
AL McEvoy said:Gravity. Actually it's not trestles on the turns its a ladder.David Russell said:What keeps your track from sliding off the tops of the trestles?
Al, I have all the attaching screws underneath removed on the straights and on my raised turns NOTHING is screwed down. I do have to occasionally push the track back centered on the raised road bed. If you really want the track secured to the trestle bents there are several ways. Loose wire ties, blocks screwed to the ties underneath allowing it to float but catch on the beams connecting the bents,etc.
About every three feet along the trestle, I loop a short piece of bell wire around a tie and twist it snugly around a stringer. It seemed to be the right thing to do at the time, and I’ve never had any problems. At each end of the 18’ semi-circular trestle, the track floats on brick, so that any expansion on the trestle is taken up in the track on either side of the trestle.
My longest trestle is about 12 feet. I have spiked the rail down; 4 spikes to a tie.
5 or 6 years ago, when I began laying track on my raised roadbed portion, I didn’t really know any better and nailed the ties directly to the roadbed. This is Stainless Steel track in New England, where temp range from -10 to 100+. The track is screwed together at joints with a few rail clamps to join cut sections.
I’ve really had no issues at all. Some joints opened up a bit, (1/8") the first winter and have stayed that way.
Last summer I laid a short curved section on PVC ladder and I screwed the track to the ladder. I’m in wait-and-see mode on that section. I have more concern of how the PVC will react than the stainless.
The balance of my railroad floats on ballast - some over concrete, and I really don’t notice any movement there.
I learned from TOC that it isn’t how much the track expands, as how much it expands compared to what it’s attached to,
i.e. , both the track (rails) and the deck should have similar “coefficients of expansion” to reduce buckling.
I checked and the linear coefficients of expansion for brass (the table I found didn’t specify the copper/zinc proportions) and pine/oak are dissimilar - about .0000104 inch of expansion per inch of material per degree F for brass and about .0000028 for pine/oak (or about 1/4 as much). I always thought the larger problem with wood is moisture - it expands when wet and shrinks when dry. But that’s why I wanted to ask you more experienced guys with your experiences and methods with long large wooden trestles.
I am inferring from these replies that first I need to determine the best way to construct the trestle and what to use on the top -across the bents - to support the running rails. I like the concept of building the tie bed into the top platform and then spiking rails onto that. It would also better accommodate the guard rails that I wanted to use along the entire length of trestle.
But here is an interesting story about a fatal derailment caused by track expansion on a trestle: http://www.meldrim.com/page6.html
Interesting page Al. Father Fred might take note of this quote from the report…
"http://www.meldrim.com/page6.html" said:
An official of the carrier said that as a matter of policy guard rails are not provided on track structures laid over bridges on this railroad, although no reason was advanced for such policy. However, this practice does not conform with the recommendations of the Engineering Division of the Association of American Railroads, concerning the use of guard rails on track structures laid on bridges.