If only using one power pack, and you want to have the ability to turn off the power on a siding to park a train, the Twin is NOT what you want - the Twin is a pair of DPDT switches wired up to reverse the polarity. For simple on/off switches, you want the Connector. Atlas has numerous books which will show you how to wire things up using their components.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Ooops. I see you were talking about the Atlas Twin. Read too fast. Same suggestions apply.
I assume (always dangerous) that you are using the Atlas Twin. On the back of the package is a diagram of the very simple way to wire it for a single reverse loop. Without seeing a diagram of the track plan it is not possible to pinpoint the problem. However, I've worked with these Twins for many years, and the good news is that it is pretty hard to totally mess them up. Run a solo loco ( preferably a short wheelbase diesel) to the point where the first insulated joiners are. If it stops, move it slightly back, flip the switch on the Twin to the other position, and try again. If the sections on both sides of the insulated joiners are powered, it should move through. If it does not, then you have a feeder wire problem somewhere in the reverse loop, or have not fully isolated the loop with insulated joiners in two places--entering and exiting the loop.
Should add that with multiple loops, the geometry sometimes gets a little bit more complex, but not really hard. You might also benefit from spending a few dollars for an inexpensive multi-meter to make checking continunity and poliarity at specific points easier.
Good luck.
Go to http://photobucket.com/ open a free account and post your picture or diagram there. You can then put a link in your post here to show your picture.
Dave
Lackawanna Route of the Phoebe Snow
The insulated joiners are not enough if you have created a reversing loop. The engine will create the short crossing the joint.
You need to post a track plan so we can see where the problem might be. There are solutions for every problem.
I think that I did that is why I put the plastic rail joiners to keep the track from shorting out initially. Now, i just need to figure out how to rewire the twin switch or if I use the regular switch. On my main rail has 3 loops with 6 switches that run around a mountain and through a tunnel. after going through the tunnel, the trains can go to the yard, which has 6 track and seven switches. I believe my rail joiners are not properly layed or to close to the switches. I don't know this is my first big project with my grandson and I am really proud so far. I will try to email you a photo
I can't help you without a diagram of the layout.
You may have created a reverse loop with the switches.
I built this HO Scalae train table for my grandson, 8 x 12 L shaped, all is well except the wiring for the atlas twin switch. eventually I would like to run 2 seperate cars however I have to get the twin switch wired first. Help