How much straight away on an S curve?


M

Mister Bill

Member
With a piece of flex track, how long should the straight length be between each end of the S curve to yield minimum stress in the transition?

Bill
 
Agreed, as a general guide, you should make allowances for two or more of your longest coupled cars to straighten up on the tangent between two crossover or ladder turnouts that comprise an S curve, or an actual track S curve. However, like everything else in the hobby, you can improve on that by mocking it up and actually trying it out. Sometimes you can get by with about 3/4 of that length, or sometimes you'll find that it isn't quite fully reliable, especially shoving instead of trailing cars, unless you have somewhat more length between the curves. It only takes maybe five minutes to mock it up on a bench and see how it will work for you.
 
The absolute shortest length I would want would be a standard straight section between the curves. If it's HO, a 9" piece, if N, a 5-6" piece. At minimum.
 
What is wrong with an "S" curve? No one has really explained why it wrong. At most I can gather that it might not look realistic, but for running the train it should be fine. With both Unitrack and Bachmann Ez track, I have played with "S curves" and have had no problems.
 
Nucular said:
What is wrong with an "S" curve? No one has really explained why it wrong.
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As a car enters the curve the end of the car swings to the outside. With an "S" curve the coupler on the end of one car is swung out to the left side and to the right on the car on the other side of curve. So the two couplers are pulling each other sideways. Often will pull the cars right off the track.

The longer the car the more pronounced this situation is.
The further inset the trucks are mounted (short wheel base on a long car) on the car the more pronounced this effect is.
The further the coupler is sticking out beyond the end of the car the more pronounced this is.
Mitigation for the problem is - short cars, short couplers, and the big one.... truck mounted couplers.

With truck mounted couplers the couplers follow the curve of the track. That is why a lot of N-gauge and almost all O-gauge (Lionel type) and G-gauge (LGB type) equipment will have zero problems with S-curves. Cheapo HO equipment will also not have any problems. Tyco, Life Like, Model Power, Industrial, and the old Mehano, AHM, Rivarossi (even passenger cars) all have truck mounted couplers so they will not hardly notice an s-curve. Some locos even have truck mounted couplers. I'm thinking of the Rivarossi E units and Athearn BB Alco PAs.

With both Unitrack and Bachmann Ez track, I have played with "S curves" and have had no problems.
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Brand of the track is irrelevant. It is the cars on the track where the issue comes from.
 
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