Re: Reversing section advice
Vollrath, Don <dvollrath@...>
Blair,toggle quoted messageShow quoted text
My solutions 2 and 3 using relays do not have any real drawbacks. You simply add more insulating rail gaps in the appropriate places and wire up a DPDT relay(s) to control power to those sections of track. If you use Tortoise switch machines for turnout control this is simple to do. [Wire a 12Vdc relay coil in parallel with the Tortoise motor, but add a diode so that the relay coil gets energized with the tortoise in only one direction.] If you plan on using manual throws, add a DPDT toggle sw to do the same thing manually. Small electromechanical relays and toggle switch contacts change state in milliseconds. Any sound decoders on your locos won't even notice that track polarity has changed. Slide switches or 2 separate SPDT contact sets or microswitches or the contacts internal to a Tortoise may interrupt track power momentarily causing an annoying re-start of loco movement or sound. The advantage of using a relay is that the cost of relay or two is far less than any Auto-Reverser. Loy's ARSC is ~$80 USD.
Solution 1 with the Loy's toys ARSC may not be totally workable as your own words indicate that track section Y space may be slightly too short. It needs to be longer than the active wheelbase of your longest loco consist PLUS about 2 more inches at each end for what L-T calls portals. Each of these need to be slightly longer than a 3 axle passenger truck, but no longer. See my short track reverser explanations in the files section of this forum.
One other comment - For almost any A-R units, You may have difficulty starting up your DCC system if locos are bridging the isolating gaps at a reversing section of track. This occurs because the polarity detecting mechanism needs power to select the proper state and there is no power until the booster gets going. But if there is an instant track short on power up, the booster can't provide power to the relay or A-R unit for self correction...Catch 22. A manual toggle switch system, or one using a separate power source for relays can avoid this problem. A simple way is to simply avoid leaving locos bridging A-R rail gaps when you suspend operations.
[mailto:WiringForDCC@...]On Behalf Of Rasa and Blair Smith
Sent: Wednesday, November 16, 2005 7:28 PM
Subject: RE: [WiringForDCC] Reversing section advice
Thanks for the informative and very useful response; yes the explanations
are excellent. As an electronics tech, everything makes sense. Your
comments about relays (and switches) make me think that although that will
accomplish what I want electrically, I will pay an unacceptable price in
performance if the train is visible. Since the reversing section trackage
in question is all staging, however, I wonder if I will even notice a
stagger, if that is the only effect. Are there other drawbacks you can
identify to solutions 2 and 3? Regardless, I am extremely interested in
your offer of more data in solution number 1, as my section Y is only longer
by about one inch than my longest conceived locomotive consist; the power on
my longest lighted passenger train would be shorter, but some of the long
freights will likely be 4 SD40-2 units, which fit with an inch to spare.
The flawless performance of this hidden trackage is important to me, as it
will be central to the operation of both my main line and one of the two
primary interchange railroads on my layout.