Reversing loop inquiry

[tstage]

I need some clarification. When creating or designing a reversing loop, does the area inside the insulated or reversing "zone" need to be only as long as the locomotive or the ENTIRE train itself? I think I know the answer. I just want to be sure. Thanks!

Tom

[grayfox1119]

Just the locomotive, as that is where the pickup is.

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[Anonymous]

Unless you're running cars (like passenger cars) with their own pick-ups for lighting. Then your reversing loop has to be as big as the longest train with such cars.

[Big_Boy_4005]

I don't see a whole lot of advantage to making it as short as possible. There is no real disadvantage to making it the entire length of the loop.

[IRONROOSTER]

In addition to lighted passenger cars, if you run any cars with metal wheels and trucks you can have problems. Usually only one end of the axles is insulated and the other end is not. If you have metal trucks and a metal underframe you have an electric path from the wheel at one end of the truck to the wheel at the other end on the non insulated side. When the truck spans the rail gap between the reversing track and the mainline track and the polarity has been reversed for the mainliine you get a short. If the train is moving, it's momentary and you may get away with it before the breaker/fuse trips, but it's not good. The problem is aggravated if the car also has a metal underframe. The safest solution is to make the reversing track long enough for the entire train.
Enjoy
Paul

[ClinchValleySD40]

DC or DCC?

[ndbprr]

Unles you have cat like reflexes make it as long as possible so you have time to change the polarity.

[cwclark]

you can also use the DPDT contacts on a tortoise switch machine to reverse the polarity...There is an illistration on how to do this in the Kalmbach publication Model Railroad Wiring Made Easy....

[jwmurrayjr]

DC or DCC?

One thing to keep in mind about DCC auto-reversing modules is that the A/R module switches the phase in the loop only. The mainline is not affected.

The A/R module powers the loop (or section - this could also be a turntable or a wye) only. The phase ("polarity") can change back and forth under a DCC loco with no effect on the loco.

About the only problem you could encounter with DCC auto-reversing would occur if something "shorted" the gaps at each end of the loop at the same instant. Hence "The section should be longer than the longest train."

My reversing sections are longer than any train but shorter than the physical section (except for the turntable) if that makes any sense.



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