Crossover O-27 switches

[nickthompson22]

I'm going to have a pair of crossovers on my layout between one loop and another loop. I was wondering if its possible to wire these in a way in which one switch controller can control both switches. I am also planning to have two transformers and wire the layout for cab control, and I was also wondering where I'll need to stick the insulating pins in order to electrically isolate the two loops. 

[lionelsoni]

Yes.  Just connect the corresponding turnout terminals together.  This will also throw both automatically from either switch's control rails.

Put an insulating pin in the center rail at each block boundary.  Except for control rails, connect the outside rails together everywhere and at the transformer common.

Beware of connecting together the diverging paths of two turnouts at a crossover.  You will have insulating pins in all three rails--in the center rail to isolate the blocks and in each outside rail because it is a control rail.  This leaves no connection for the common outside rails between the loops.  You have to create one, as by having common feeders on both loops, or by jumpering around the turnouts.  Jumpering is particularly easy, because each turnout has a terminal connected to the outside rails (the one closest to the switch machine).

[BigAl 956]

It depends on the vintage of your O27 switches. If these are post-war style with a lighted controller you cannot wire two switches together. Current will sneak through the controller lamp and one of the switches will gradually activate. You have to remove the bulb or power it completly seperate from the switch.

It may only be nessissary to control one switch in your crossover. The non-derail feature of the companion switch will automatically flip it when the train crosses over.

[lionelsoni]

The controller lamp draws its current through one of the switch-machine solenoids, but not enough current to throw the switch.  When you connect together the solenoids of two turnouts, you provide current from two solenoids to one lamp.  The lamp current remains nearly the same, but it is supplied half from one turnout's solenoid and half from the other's.

So any effect that the controller lamp might have to gradually throw the switch is only half what it would be in a conventionally-wired single turnout.

How do you get a train approaching a controller-less facing-point crossover turnout to take the path other than the one that the turnout is already lined for?

[ADCX Rob]

BigAl 956

...If these are post-war style with a lighted controller you cannot wire two switches together. Current will sneak through the controller lamp and one of the switches will gradually activate...

If this is actually happening to you, your controller has the wrong bulb, and the condition will be worse with just one switch on that leg of the controller.

[lionelsoni]

Early O27 turnouts (1121) used 250-milliampere lamps.  Later ones (1122) used 110-milliampere number-53 lamps.  I think any of these can use number-53 lamps for bayonet sockets, or 100-milliampere number-52 lamps for screw sockets.  LED substitutes should also be very effective in stopping unwanted motion.

[BigAl 956]

ADCX Rob

If this is actually happening to you, your controller has the wrong bulb,

You must use a 53 bulb but when you wire 2 switches in parallel even with the 53 bulb one of the switch coils activates slowly.

Bottom line is 1122 switches were not ment to be wired this way. Either wire them differently or even better, switch to O track and 022 switches.

[lionelsoni]

Lionel seems to have been aware that their design, putting a lamp in series with one of the solenoids, was marginal, as this postwar "service hint" suggests:

"1.  Switch coil buzzes continuously.  The swivel rails may 'creep' or even snap over particularly when track voltage is high or is suddenly applied, as in reversing a locomotive.

"Reason:  Lamp in controller, which is wired in series with one of the switch coils, is transmitting too much current.

"Correction:  Replace lamp 315-20 (G.E. 431) with either 18-volt lamp 2026-58 (G.E. 1445) or preferably with low-current lamp G.E. 53."

Note that the fix they suggest is to reduce the current drawn by the lamp, by using a lower-current lamp.  This advice would not help if one already had a number 53 lamp in the controller.  But today it is possible to use a much lower-current LED lamp to replace the 53 and further reduce the current greatly, as I suggested above.

But, in any case, elementary circuit theory shows that wiring two switch solenoids in parallel virtually halves the lamp current that each solenoid carries and, far from causing the problem, should go a long way toward solving it.

In fact, there is no indication that the turnouts in question have this problem in the first place.

All that being said, there is a situation where connecting the turnouts should be avoided.  That is when the turnouts are in tracks powered from different voltage sources and have not been rewired for accessory power.  In that case, the two solenoids will be powered in series from the difference in the two track voltages.  Perhaps this is the situation that Al has encountered.