Responses to my "Main Bus...Defeat Gaps" thread 01/31 confirmed that the Peco 3-ways at both ends of my yard would cause shorts if I didn't gap the connecting track, even though they're Insulfrogs. David Bedard explained why in a 2007 thread "Wiring 3-Way Switch For DCC:"
"The issue is the double frog (back to back....a huge void for small pick-up locos) that serves double duty (can be either polarity, depending on the 2nd set of points)."
I intend to run feeders to the track immediately preceding each 3-Way, feed each of the 3-ways by dropping feeders beyond the frogs, and gapping the yard tracks at both ends beyond the 3-ways per the illustration below. All other turnouts are Atlas with insulated frogs.
Could someone please confirm that I'll be OK or advise how I can avoid trouble if I'm heading for it? I called out for David and MisterBeasley because I know they're knowledgeable on the subject, but I'd certainly appreciate others' input as well.
Thanks.
Rick Krall
I don't see a need for any of those gaps.
Dave
Lackawanna Route of the Phoebe Snow
Phoebe VetI don't see a need for any of those gaps.
I agree. I've got a couple of Peco 3-ways. They do NOT have solid frogs. Instead, there is a narrow plastic strip between the rails, so that there is no electrical connection between the adjacent rails on the inside of the turnout. These are power-routing turnouts, though. I didn't even run feeders to the yard tracks, which are single-ended and about 3 feet long. That way, I can let the turnout feed power to the rail, or shut it off when the points are thrown the other way.
The issue you may have with these is that narrow gap on the frog. If a metal wheel can bridge the gap, it will cause a short. In most cases, this won't happen, but I've had it short out with a couple of engines which have wider than normal wheels. The cure is a bit of clear fingernail polish on the metal rails right at the junction, to widen out the dead zone a bit and prevent bridging.
It takes an iron man to play with a toy iron horse.
MisterBeasley and Phoebe Vet--you may well be right. I definitely had a short Saturday--it tripped the power pack. I isolated the yard tracks and no more short. But I just reconnected everything--and no short.
I have numerous unconnected feeders descending from the track sections; a positive and negative might have been touching before all my fiddling separated them. But I've spot-checked the layout with my meter twice and everything's fine. I thought I was careful before, too, but I obviously wasn't. Our grandson is five and isn't here, so maybe I'll blame him.
Thanks to all for teaching me a lot through this process, and apologies for the false alarm.
You will need those gaps. I hooked up a three-way at my yard throat and found I had all sorts of problems when I tested it out. I finally elected to gap it at the end of its contiguous three exits and supply feeder power to the rails between those exits and the next turnouts...which has worked. Even so, if I forget to line the points for the route when I cause an engine to enter one of the three exits, I still get a short....suggesting that the points do route power to an extent. When I reach over and correct the alignment, the short disappears. Note that this happens at the exit end, either of the three, and only as the first power-bearing axles crosses the gaps to make first contact with the rails on that exit. Happens every time if the points are in the wrong position. So what other explanation could there be?
Selector--I'm definitely in the deep end of the pool here, but you make a good point. I've not tested the 3-way with an engine--just with my meter. MisterBeasely made a polnt above similar to yours and provided a nail polish solution. The source of all this might be the polarity-switching aspect of the turnout, per David Bedard's 2007 post I quoted at the top of this thread.
Your wiring scheme sounds close to, if not exactly like, my intention. Perhaps the belt-and-suspenders approach is "when in doubt, gap."
Selector:
I think that if you check carefully you will find that the engine triggered short is occurring at the misaligned points, not at the switch joint.
HI, Phoebe Vet. It is undoubtedly so, but nothing happens until, and unless, a power-bearing axle bridges the gap.
In my case, my three way gets power from the single approach track via joiners. I don't get the short when nothing is on the contiguous three-way turnout and when one of the points is lined one way or the other. I only get the short, and cessation of all activity, once the first power-bearing axle crosses the gap. I could leave the points pairs, both of them, lined either route and in all combinations of alignments six ways to Sunday and I won't get any short. It is only when an engine approaches, and then crosses the gap to the exit not lined that the alarm goes off. So, the turnout, as in all such cases, must be routing power beyond the several frogs and to the exits. The turnout, I concluded, needs to be separated from the power in the segments meeting each of the three exits.
At least, that is my set up, and I get excellent and reliable performance from my three way just this way.
-Crandell
You may be right. It's easy enough to test. With the power disconnected, put an ohm meter across the gap and throw the switch to all possible positions. Didn't the OP say he had dead frogs?
Phoebe VetI think that if you check carefully you will find that the engine triggered short is occurring at the misaligned points, not at the switch joint.
Phoebe,
He's using power by the points type turnout. The frog, both points, and inner two rails, are one big piece of metal. (We have these Pecos at the club) This can be confirmed with a continuity testor on a volt meter. If you touch any two different parts of the inner rails, points, and frog, then it will show a continous piece of metal (~0 Ohms)
If you have a double ended yard, you have problems if one switch is thrown on one side, and the other side it is not. It creates a short condition. So you have to double gap post frog on the turnout side.
-D
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
fkrallYour wiring scheme sounds close to, if not exactly like, my intention. Perhaps the belt-and-suspenders approach is "when in doubt, gap."
Does this 3 way PECO turnout have two wires coming off of it? Both white? If it does, I regret you will need a power routing switch machine like Caboose ground throws with power route option, or Blue point, or tortoise.
Great input, guys. The 3-Ways are both installed but I saved the boxes--they're definitely SL-99s, Insulfrog.
When I reconnected everything and threw the points, I didn't have a short. But I'll continue to test and I know how to solve the problem if I do get one.
DigitalGriffin--there are no wires coming from the Peco--other than the ones I've soldered on!
DavidBedard--you're right--you didn't post on this topic previously. I put your name in lights because I've seen your posts in Peco 3-Ways in the past and was hoping you'd contribute. Mission accomplished!