Double Slip - Selecting Routes

Model Railroader Layouts and layout building
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After many years without one, I finally purchased my first double slip.

Route selection can be complicated because there are two throwbars which must be set to properly align the point rails.

I have designated the four tracks as A, B, C, D to illustrate the routes, as shown in the following illustration:

There are 8 possible routes on a double slip: A to B, B to A, C to D, D to C, A to D, D to A, B to C, C to B. Of course, some routes are not possible: A to C, C to A, B to D, and D to B.

In setting up my control panel for the double slip, I marked the four tracks with their alphabetic designation and added a red or green circle to aid in the visual identification of the track. The squares below the double slip symbol in the illustration that follows indicate DPDT toggle switches. The circles above the double slip symbol in the illustration indicate bi-color (green/red) LED’s that will illuminate as the DPDT toggle switch is thrown.

If the toggle switch on the left is thrown up to move the left throwbar up, the LED will illuminate green. The LED will illuminate red if the toggle switch on the left is thrown down to move the left throwbar down.

If the toggle switch on the right is thrown up to move the right throwbar up, the LED will illuminate red. The LED will illuminate green if the toggle switch on the right is thrown down to move the right throwbar down.

The illustration that follows shows the 8 routes, the position of the toggle switches as up or down, and the resulting color of the corresponding LED.

It should be noted that proper routing will always r

2

To gain access to any of the 7 tracks in my stub ended yard, I use several Y’ and two double-slip switches at the end of two long curved drill tracks. The switcher never has to leave the yard. Bob Hahn

3

To simplify your thinking, a double slip is operationally and schematically equivalent to two standard turnouts laid point to point. That bunch of rail, obtuse-angle frogs and extra points are the price you pay to shorten your yard throat and eliminate the S curve on one straignt-through route.

Operationally, the switch points have been pushed past each other, compared to the two standard turnouts. Thus the points near one acute-angle frog control which way the train will exit (or enter) the farther end of the double slip.

Electrically, draw a line from one acute angle frog point to the other. Everything on one side of the line is one polarity (or DCC phase) and everything on the other side of the line is the other. If the frogs are live, they are controlled by the position of the switch point mover (manual or electrical) at the farther end of the double slip.

On my control panels, I put two rotary switches with pointer knobs back to back in the track schematic, indicating, not the point positions, but rather the entry-exit route on that end of the double slip.

Chuck (Modeling Central Japan in September,1964 - with double slips)

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Nicely done Chuck.

I currently have mine with 4 leds drilled into the control panel track lines. (2 on each side) There is 1 lit for each side indicating which route is active. I have made them yellow as to not confuse them with turnout signal indicators.

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Hi Rich,

We just installed a double crossover on the layout I’m building. I’m operating it off one single DPDT toggle switch, just as is shown in this video: http://www.youtube.com/watch?v=hpWlfziTAjc&feature=related

It just seems simpler to me. If I throw the switch up, the tracks are open and if I throw it down, they aren’t. We haven’t got to the LED install yet, but I believe that it too will be pretty easy.

-Ed

6

Very interesting, except that a double crossover is a very different animal from a double slip switch.

Since there are four possible routes through a double slip, all of which pass through the same clearance diagram, it’s impossible to control it with a single toggle switch. It takes two separate, independently controlled switch throw devices to position the points of ol a double slip switch in such a way that all routes are useable.

Chuck (Modeling Central Japan in September, 1964)

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Ed,

Pretty cool video. You done good.

I have set up my double crossovers the same way as you. All four Tortoises are connected to a single DPDT switch, down for straight through and up for divergent. I have a single bi-polar LED on my control panel right above the DPDT switch, green for straight through and red for divergent.

Rich

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Chuck,

Obviously, you are correct in that it takes two independently controlled switch throw devices to correctly operate the double slip, and that is the point of my third graphic eariler in this thread. On my control panel, I have mounted two DPDT switches to control the two Tortoises that move the point rails. Above each DPDT switch is a bi-polar LED. Both LED’s must light up the same color, red or green, to indicate a permissable route. Any color mismatch indicates a potential derailment.

There are actually 8 possible routes that an engine can take through a double slip as indicated in my prior diagram.

Rich

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Rich

I would like to view the 3 ilustrations to your post of April 2011. Curently viewiing the thread I receive a message within the original post that says image currently unavailable.

Regards

Ken

3801

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Hello, Ken

I hope Rich sees this to respond. Older threads tend to fall by the wayside.

I have four double slip switches actuated by two Tortoises each.

My favorite method of control is to use a rotary switch. It is simple for operators to choose the route and the knob and LEDs provide a visual reference to the route selected.

CP_Union_model_C by Edmund, on Flickr

CP_Union by Edmund, on Flickr

CP_Union_model by Edmund, on Flickr

This is a rough sketch showing how the 4 pole 4 position, non-shorting rotary is wired:

4P4P by Edmund, on Flickr

— and the guts of one of the switches:

Rot-bot by Edmund, on Flickr

Technically these are four pole five position but there is a movable stop to restrict the throw so that only four positions are available. You can see that I marked W for the “wiper” which is common. This is the terminal that would con

11

Ed, thanks for the reminder. I saw that post on Tuesday and I went searching for the three requested images, but I couldn’t find them. Then, I forgot to reply.

When I saw your post today, I went searching again but still no luck. The problem goes back to when Photobucket locked up accounts without warning and all those images were lost. Plus, my original post was in 2011. I have switched computers since then and those original images may be gone for good. But I will keep on looking.

Rich

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gmpullman, I used your wiring diagram for the rotary switch to control a double switch. The tortoise machines are working as desired, but the bi-color LEDs are not showing the correct path. I only have a 2pole-4position switch (waiting on a 4p4p switch) so I only connected to one tortoise for testing. Can you give any more guidance on the LED connections.

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Always fun, as an OP, to see my old threads revived.

On my current layout that I started back in 2018, I installed 4 double slips to route trains through a 4-track mainline complex. Fortunately, the area was totally accessible, so I can switch manually and lighting is not necessary.

Rich

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I’m glad that people resurrect old threads. This one is a great reference! I’m attempting to model IC in the Memphis area and IC had a double-slip at the throat of Central Station. I didn’t know the complications involved.