# How to wire a dogbone loop



## Bill Wilcox (May 30, 2012)

I'm in the early planning stages of my garden railroad and was considering a dogbone loop as part of it. My only model railroad experience is O gauge AC (Lionel and MTH). Lionel O gauge tube track switches have non derailing built into them. These work great to run a dogbone. The switches automatically activate and the train keeps going in the same direction. 

I know there are a lot of differences between AC and DC operation. Today is the beginning of my DC layout education. Is there a circuit that has to be installed to reverse polarity to make a dogbone work on a DC layout? Do G scale switches have a built in non derailing feature or does the operator need to manually operate the switch?

Thanks


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## toddalin (Jan 4, 2008)

There are several systems on the market that can do this (LGB, Massoth, RailConcepts, etc.). Some can/will throw the turnout (usually LGB-style turnout motor) while others just use a spring-loaded turnout. The LGB system is probably the simplest in concept, though maybe not simplist in application. It will require ~14-18 volts *a/c* to operate.

If you are electronically inclined, you can build your own system using Internet surplus at far less cost than any commercially marketed system.


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## Greg Elmassian (Jan 3, 2008)

In my understanding, a dogbone is a simple loop, squished in the "center". 

I think you are talking a single track, with loops at each end with a switch. 

You will need some "boxes" with relays in them to reverse the polarity. 

Several people here can advise you on what has worked for them. LGB electronics are reliable and well documented. 

Greg


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## chuck n (Jan 2, 2008)

My recommendation is to use a separate main line for the return, one that is parallel to the first. I can be done with reversing loops at each end, but a separate return track is much easier. Depending upon the part of the country in which you live, the local climate may make automatic operation more of a headache. If you are doing it indoors, that's a different situation and they would be reliable.

Chuck


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## Greg Elmassian (Jan 3, 2008)

The money you save in switches/turnouts will probably pay for the "2nd" mainline. 

Greg


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## chuck n (Jan 2, 2008)

Many of the manual "G" gauge switch throws (LGB and AristoCraft) are spring loaded and will allow a train to pass through from the "closed" direction. The LGB electric throws will flip and stay. I have found that LGB engines and cars will pass through most switches with out derailing, they have very deep flanges. The pilot trucks on my Bachmann, Accucraft, and Aristocraft steamers will derail going into the switch from the closed direction. Some cars work some don't. It is all in the depth of the flange and the weight of the car.

Chuck


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## Bill Wilcox (May 30, 2012)

Thanks for the input. 
My last reply never showed up, oh well, I'll try again. Anyway, I guess I used the wrong term to describe what I was thinking. What I had in mind was a long (


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## Greg Elmassian (Jan 3, 2008)

If you run just one train, and it all fits in the reverse loops, then the only reversing needed is the main line. If you don't mind the system deciding which switch to enter, then I believe the electronics will be simple and inexpensive. 

Maybe Dan Pierce or Mohammed will jump in here and give you the basic schematic and what hardware. It's not super complicated. (I just stick to DCC, so I don't keep up on all the part numbers of the relay boxes). 

Regards, Greg


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## Dan Pierce (Jan 2, 2008)

I have helped build a dog bone type reversing setup and I found the LGB EPL switches are not break before make. So when reversing, a short occurs for a short time as only one microswitch has changed polarity. 
I added the LGB booster, and this helped a little but shorts still happened and reset the train engineer 27 mhz version to no output.. 

What is needed is a relay that has all contacts breaking at the same time to prevent a short (LGB add on 12070 does not work here).


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## mbendebba (Jan 22, 2011)

Posted By Bill Wilcox on 06 Jun 2012 07:40 AM 
Thanks for the input. 
My last reply never showed up, oh well, I'll try again. Anyway, I guess I used the wrong term to describe what I was thinking. What I had in mind was a long (


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## kormsen (Oct 27, 2009)

Posted By Bill Wilcox on 06 Jun 2012 07:40 AM 
What I had in mind was a long (


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## toddalin (Jan 4, 2008)

Posted By Dan Pierce on 07 Jun 2012 04:30 AM 
I have helped build a dog bone type reversing setup and I found the LGB EPL switches are not break before make. So when reversing, a short occurs for a short time as only one microswitch has changed polarity. 
I added the LGB booster, and this helped a little but shorts still happened and reset the train engineer 27 mhz version to no output.. 

What is needed is a relay that has all contacts breaking at the same time to prevent a short (LGB add on 12070 does not work here). 

Dan,

You need to open up the EPL and put a "shim" on the red tab to make the lazy contact activate a bit sooner. I've done this on several simply to get them to "flip" all of the way. A piece of Plastruct and drop of CA work well.


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## Dan Pierce (Jan 2, 2008)

The red tab is on the 12030, not the 12070. 12030 has a plastic flipper, the 12070 is metal. It is possible to bend the metal tab on the 12070, but one must be careful not to break it.


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## toddalin (Jan 4, 2008)

Posted By Dan Pierce on 08 Jun 2012 05:28 AM 
The red tab is on the 12030, not the 12070. 12030 has a plastic flipper, the 12070 is metal. It is possible to bend the metal tab on the 12070, but one must be careful not to break it. 

So are you saying that you can't CA a shim onto a metal tab, or is the 12070 that different than the 12030 that it can't be done? I've dealt with lots of 12030s, but never seen/opened a 12070.


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## Greg Elmassian (Jan 3, 2008)

I read just exactly what Dan said... you just said "red tab" and Dan basically only one model has a red tab, and the other a metal one. 

I took it as to help avoid confusion on the part of the OP, or a fruitless search for a red tab where it was not there. 

Greg


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## Dick Friedman (Aug 19, 2008)

I was planning to do this with two return loops and two switches, but I found that the cost of switches and relays for automatic power reversing exceeded the cost of the additional main line track. Pencil it out, you may be surprised.


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## Dan Pierce (Jan 2, 2008)

It does not surprise me, you eliminated 2 switches, 4 reed sensors, and the relay/s, wiring. 

Also, no switches to jam from debris in the future. 

Some users can make their own electronics and keep cost down, but others challenged in this area would rather keep with the KISS plan and rightly so.


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