I don't worry about either grade transitions OR where the track joints are on them. I have subroadbed joints at transitions and in other places, rail joints on transitions. I have no problems with trains not tracking right on them, either, but that may be because my grades are relatively shallow - my steepest grade is just under two percent. I simply extend the subroadbed in the direction it needs to go, then install risers for the proper grade.
At subroadbed transitions, I screw AND glue the subroadbed to a splice piece below, so it acts like a continuous, if somewhat stiffer, length of plywood right thorugh the joint.
Mark P.
Website: http://www.thecbandqinwyoming.comVideos: https://www.youtube.com/user/mabrunton
fwright wrote: As others have said, why give yourself such problems? Go bend some plywood and be done with it!just my thoughts, your choicesFred W
As others have said, why give yourself such problems? Go bend some plywood and be done with it!
just my thoughts, your choices
Fred W
What he said!
BATMAN wrote:Hi guys here is another question I hope you can help me with. I know you shouldn't go from 0% to a 2% grade abruptly and the longer the transition the better, so what is the shortest transition length you should have between 0 and 2% for appearance sake? Thanks.
This has been discussed in the layout construction Yahoo group more than once. For most of model railroading history, vertical transitions have been designed by guess and by golly. As long as the trains stayed on the track, and didn't uncouple from each other, the results were, "...by golly, it works!"
One of the little-mentioned pluses for cookie-cutter construction using plywood subroadbed was that you automatically got a long enough and smooth enough transition. You couldn't physically bend 1/2" or thicker plywood into too sharp a transition to work properly. Thinner plywood needed too much support to prevent sag. So the vertical transition issue went away until the arrival of door- and foam-top layouts and Woodland Scenics risers became a common method of grade construction.
There have been various proposals floated that used circular transitions. I have read of proposals that varied from 7 times the minimum horizontal radius to 7ft to 10-14ft radii (in HO) for vertical curves to make the grade transitions. I can't recall the name, but someone did calculations for vertical circular curves based on the change being less than half a flange depth over the driver wheelbase of a rigid frame steam loco.
Basically, there are 4 factors in 2 separate areas that control the vertical transition.
One is the flanges on a long rigid wheelbase being in position to hold the loco on the rails. The depth of flange and length of wheelbase control here. The second area is coupler over/under ride. Here the vertical height of the coupler itself, as well as the length of the car and the distance from the coupler to the truck are the controlling factors. Given all these variables, it would be difficult to come up with an easy mathematical rule that minimized transition length while guaranteeing performance.
I have read that a longest car length transition per 2% of grade change seems to work well. But will this work if you use the smaller height scale size couplers? You probably would want to test in advance. Same if you use P87 flanges in HO, or the small flanges in N. I would test before committing.
Something else to keep in mind - very few of us can build or measure a vertical transition and/or grade to greater than 1/16" precision at a given point.
Appearance is not the issue; it is performance. A steam engine with a long wheel base, such as a 2-10-2, requires a longer transition than a diesel engine. I try to allow at least one foot linear distance for transitions.
Brent
"All of the world's problems are the result of the difference between how we think and how the world works."