Hello,
I am trying to wire a Mark III twin to atlas 215 selctors to run a great eastern trunk layout. I connect 1 lead from cab a and b to the selector, then I jumper the last two dc leads together and attach the jumper to a common on the track. Only one cab will move and then the breaker will break. I am guessing there is something inside the twin that hooking the commons between the cabs wont allow that to happen. Just curious if any one has worked around this problem. Otherwise it works fine with two seperate controllers. Thanks. Jack
Welcome to the forum. Your first few posts are moderated, which can lead to a delay in them appearing. The Silvine Mark III (if that’s what you have) is a very old product (1950s/60s) that likely has internal connections between the two throttles that make it incompatible with Atlas’ common-rail wiring scheme. If you want to stick with Atlas wiring components, using one side of the Mark III and a separate power pack for the two cabs should probably work.
Good luck with your layout.
Byron
Layout Design GalleryLayout Design Special Interest Group
A Twin is a pair of DPDT switches wired as reversing switches (the typical DPDT diagram with a pair of wires in a cross pattern). It is NOT the correct device to switch between cabs. To seelct between two cabs, you need the Selector. One wire from each cab goes to either the top or bottom of the Selector, the other wire from each cab is the common rail wire. The Selector button pushed up selects the top cab, pushed down selects the bottom cab, and left in the middle kills power to the block. The Twin is not needed for this. Both switches inside the Twin are connected together, so it cannot be used with two different power packs feeding it.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Randy – the "Twin" he is referring to is the power pack (it's labeled "Twin"). He said he's using Selectors. I think the internal connections in the power pack won't work with common-rail. That was a problem, I recall, with some cheap "twin" powerpacks back in the day.
Oh. Never heard of that. I've heard of Twinpack and TwinPower (think I had examples of both of those back in the day) power packs.
That is correct - it depends on how they are wired inside if they can be used with common rail or not. If the design incorporates two rectifiers, then it can be used for common rail, if not, you will get the shorts the OP is experiencing. At one point, MRC sold dual power packs of both types, and the ad copy had some fine print about not for common rail for the one that wouldn;t work. May explain that I learned wiring a DC layout from my Dad, who never used common rail - the twin pack I most remember (before one of the rheostats fried) I later took apart and there one just one big old selenium rectifier in it. Every block had 2 wires, and when I went on to start building layouts of my own, I did the same thing, despite reading multiple wiring books and in some cases building layouts from the Atlas books which included the full wiring diagrams.
rrinkerEvery block had 2 wires,
I did the same thing in wiring layouts for DC. It was good enough for Linn Westcott, by gum, good enough for me.
--There's a bit of a mystique about common rail. Using a two wire bus creates two separate common rails so I do wonder about all this.
No, two switched wires to the rail in DC block wiring does not create "two common rails". There shouldn't be any "mystique" remaining about common rail for DC. It's well-documented and the entire Atlas wiring system (which I think is suboptimal) is based on it.
The OP's problem is internal connections within his ancient powerpack attempting to be used with common rail – as we've already established.
Besides making it extrmemly difficult to operate? At some point, ditch the Atlas components and just use ordinary DPDT toggles so both sides are switched on and off at the same time.
At one point it was said that even though the Connector has 2 wires, they aren't really DPST switches - even they only break one side, but I'm not sure about that. The old ones had 2 contacts, and I don't have any of them around to look at. But that doesn't help for a dual (or more) cab setup anyway. 2 Selectors, one for each wire off the two cabs, seems like asking for trouble.
So we're still obfuscating simple principles with long rambles on semantics? Sheesh.
This is what the OP is asking about, the Atlas 215 Selector:
I use them, on my layout. Center position is OFF.
Mike.
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