Re: Where to isolate on large loops and wye



One multi-axle pick-up truck isn't always enough. Not if a loco with two trucks is involved, because then the two trucks are electrically connected. A one-truck length will then leave both gaps bridged by one unit leading to the problematic outcome.


On Fri, 26 Feb 2021 at 14:52, Don Vollrath <donevol43@...> wrote:
Gents, any good AR control unit will detect a short circuit that occurs on either (or both) rail as metal wheels connected together on multiple axles roll across and span the isolating gaps while exiting an AR section and enter into a fixed polarity section of track. So that causes the exiting AR section to align its polarity to be the same as the fixed polarity track. That part is done.

As that same multi-axle pickup rolls onto and spans the next isolating gaps (either rail or both) to enter a different AR controlled section of track there will be another connection to cause the next AR unit to align itself to the fixed polarity track.

So the minimum length of fixed polarity track separating two separately controlled  AR sections of track needs to be only as long as a milt-axle pickup truck. Think loco, or passenger car, or tender. It doesn’t even need to be used for that purpose as long as there is an electrical connection between axles and wheels on at least one side of the truck to be connected together. This is what will cause the entering AR controller to also align itself to the fixed polarity track.

A convenient choice may be a turnout located between the AR sections  with insulating joiners on all 6 rails and wired for fixed polarity. (Or As someone else has pointed out... am entire double crossover with all 8 rails isolated )


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