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Author Topic: reverse loop  (Read 2056 times)
mf5117
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« on: July 06, 2009, 12:43:37 PM »

I was doing some changes to my layout . And was toying with a figure 8 on the inner 18" rad. loop . the 22"and 18" loop are joined together with #5 and 18" turnouts . I was trying to put the straight run  that runs along side of the 22"rad straight . Off the figure 8 curves And got a short . would plastic rail joiners work . other than buying a reverse loop module . Also what i was wondering was , if I install plastic rail joiners in this section . When a multi wheel truck goes over this point , when the change in polarity comes in contact ,before the whole truck is acrossed it ,will it try to go in the opposite direction or short out.
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Jim Banner

Enjoying electric model railroading since 1950.


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« Reply #1 on: July 06, 2009, 02:41:16 PM »

Do you have feeder wires going to both the figure 8 and the outside loop?  If so, try reversing the feeder(s) to either the loop or the figure 8 (but not both.)

Reading between the lines of you message, I am guessing you already had a loop and a figure 8 inside it, and both worked before adding the crossover(s).  I am also guessing you are using Bachmann E-Z track components.  These normally allow one crossover with no problems.  With a figure 8 and a loop, using two crossovers can be tricky.  They can form a reverse loop  which requires special wiring.  A "reverse loop" or "reversing loop" is any track configuration which can allow a train that is always moving forward to travel both ways on section of track.

Reversing the feeds to either the loop or the figure 8 will not solve your problem if you have a reverse loop but it should work if you have only one crossover or multiple similar crossovers.

As far as how to fix the problem if you do have a reverse loop, it would really help if we knew what you use to run your trains, dc or DCC

Jim
« Last Edit: July 06, 2009, 02:44:10 PM by Jim Banner » Logged

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mf5117
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« Reply #2 on: July 06, 2009, 03:57:11 PM »

I'm sorry mr banner .I'm using the dcc commander . And also I have multiple crossovers ,4  of them tying the 18 and 22 inch loops together . And it is a figure 8 inside the 18"  loop . It happens when i go to connect the strait from coming off the turnouts from the figure 8 . to bring back the loop .And they are not in the crossover's .

Also I have 1 feeder wire going to the 22" outside loop and 1 feeder wire going to the 18" loop .
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Jim Banner

Enjoying electric model railroading since 1950.


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« Reply #3 on: July 06, 2009, 05:40:45 PM »

No appologies necessary, and I prefer "Jim."  We are a pretty informal bunch on Bach Man's Board.

Shown below is a generic figure 8.



This presents no wiring problems.
But if you add a straight to the side of the 8  like this



then you have created a reverse loop.  If you follow the arrows starting at the top left hand corner, you will find you end up going in the opposite direction on the left hand curved track.  This defines a reverse loop.

Imagine a locomotive going around this reverse loop.  It starts off with its right hand wheels on one rail at the beginning then ends up with those same wheels on the other rail at the end.  That means the right hand rail going around the loop connects back to the left hand rail, causing a short.  The solution is to put in two pairs of insulated joiners, one insulated joiner in each rail at "A" and one in each rail at "B."  The section between A and B is now your isolated reversing section.  With DCC you can connect it to the output of an automatic reverser and it will set the polarity of the isolated reversing section as required.  The input of the automatic reverser can be connected all the way back to the command station or it can be connected to the track leading to the reversing section.

I have shown only one straight connection between the two curves of the 8.  But it is also possible to have a second connection.  It would be at the bottom of the above diagram.  That would make things more complicated, but the complications can still be solved with an automatic reverser.

I hope this helps.  If you have problems reading the diagrams, let me know and I will up load them larger.  If these diagrams do not resemble your setup, let me know.

Jim
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jward


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« Reply #4 on: July 06, 2009, 07:14:43 PM »

to expand upon jim banner's post, and answer your question.....
no, you do not have to use an autoreverser with dcc. wiring the loop for conventional dc, with a dpdt switch,  will also work for dcc. you just have to remember to manually throw this switch every time you run through the loop. you also need to make sure the switch is set properly before you enter the loop.

any wiring book for model railroads will show how to wire a reverse loop. it's not hard, but it scares alot of people.
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Jeffery S Ward Sr
Pittsburgh, PA
mf5117
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« Reply #5 on: July 06, 2009, 10:03:55 PM »

Thanks jim ,that is what i have . But with the 2 straights .  and returning out to the 22" rad oval dog bone . Thanks i have a better understanding of what i have to work with now . was trying to do something alittle different with the 5x9 layout . I just wasn't sure with the dcc . I like running in opposite directions .and then returning  in and out from each set of track .The sd40-2 doesn't like the smaller radius curves . It can handle them but going threw the switches ,is sometimes a problem pulling rolling stock. Thanks so much for the info . And the illestrations . mark
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Jim Banner

Enjoying electric model railroading since 1950.


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« Reply #6 on: July 07, 2009, 04:59:00 PM »

Jeffery is correct.  You do not have to use an auto reverser if you are willing to throw toggle switches by hand.  In some cases, you can mechanically link a toggle switch to a key track switch (turnout) and have the toggle switch automatically throw each time you throw the track switch, but this is not one of those cases.  My present layout started out as a figure 8 combined with an oval, like you would have in the lower figure if you added a second straight at the bottom.  It took 6 toggle switches to run the trains over all the possible routes.  A single auto reverser should be able to handle this chore. 
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mf5117
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« Reply #7 on: July 07, 2009, 08:40:06 PM »

thanks for the reply . I do have micro mini's spdt cf . I made up all my toggles for my control panel .  And have also the switches that came with the turnouts . Also adding a 3x4 L off the 5x9 layout . For a little more running real estate . Im trying to make up my mind if i want to keep the figure 8 ,with the 90 degree crossover  .Or an over and under 8 . So far i like what i have . but the scenery will make that choice . "SHE TELLS ME" thanks for the info I will take heed and do some experimenting . 
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jward


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« Reply #8 on: July 08, 2009, 07:11:24 AM »

there is a nice over & under figure 8 layout in one of the atlas plan books. it features double track, 2 reversing cutoffs, and a small yard, all without having any reversing loops that need special wiring.

the layout name is granite gorge & northern, and the book contains complete instructions on how to build it.
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Jeffery S Ward Sr
Pittsburgh, PA
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