Re: Minimum length on Non-reversing segment
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What you describe is safe. No question. But it will also, usually, mean that you make a longer intermediate section than necessary. The 'bridging' you describe is indeed the tricky bit, but: only when the AR action HAS NOT YET TAKEN PLACE.
Consider a loco that pushes a lighted long wheelbase 4-axle wagon through the reversing sections, and all axles of the wagon have power pick-ups. Also assume that the polarity on entering is the worst it can be.
A = fixed polarity section
B = AR section 1
C = fixed polarity intermediate section
D = AR section 2
E = fixed polarity section
| = isolators
L = loco
W = wagon, with P being power pickup
Initially B has opposite polarity/phase to A, D and E (which are fixed), but the same as C.
1. Pushing loco moving to the right.
+ - - + +
2. A<->B boundary bridged, AR B switches, so A, B, D and E now have the same polarity/phase.
3. Wagon spans the A<->B boundary. No AR action. All further bridging of A<->B now irrelevant.
+ + - + +
4. B<->C bridged, AR B switches.
+ - - + +
5. C<->D bridged, AR D switches, so B, C, D and E now have the same polarity.
6. C<->D still bridged, No AR action.
7. Nothing bridged, wagon spans entire section C, but, crucially: there is no problem, because there is no short!.
and so on - the rest is trivial..
And this is why only the minimum size of a TRUCK counts. A longer size becomes necessary only when a truck is not really a truck but a single axle. In other words: the long wagon only has one power pickup at each end (never mind the number of wheels, the number of pickups is what counts). Theoretically, it should STILL work. But in practice, a short on a one-axle truck can be very, very easily missed as it would be just the wheelset closing the gap in the rails on its own. See what happens in the figures above when the short in step 5 is not seen. After that, spanning the C section (fig. 6) DOES mean trouble, because the B<->C short has not occurred and the reversers now fight - exactly what should be prevented from happening.
One solution (yours) is to make the C section long enough to span the entire wagon, which is fine and works. However, if that is not convenient (and the layout might well dictate that it isn't) then the other possibility is to stagger the cuts in the rails. That increases the chances of the one-wheel short occurring by a lot. This is the only advantage to staggering that I have ever been able to see. But I repeat: there is ONLY a problem in case of one-axle trucks (if you can even call them trucks).
On Sun, 23 May 2021 at 12:27, Blair <smithbr@...> wrote: