Fast Tracks

Hi,

Andy Tait submitted a full set of schematics that illustrate how to wire a double crossover using four Tortoise switch machines. Wiring a double crossover is a bit complex and can be confusing for some (OK most) modelers, which is why a lot opt to use the new Frog Juicers available from us.

Following the schematics posted below will show you how to wire a double crossover to automatically switch the polarity of the frogs based on the route selected. This will work for both DC and DCC on a double crossover with isolated frogs.

I have also included an animated version that shows what happens to the polarity of each of the four isolated frogs when the routes are changed from Normal (all straight), route 1 to 4 (cross over one direction) and route 2 to 3 (crossover other direction).

There are always and only three possible routes when using a double crossover. Normal, which is all turnouts switched for a straight route. Reversed 1 to 4, which is turnout 1 and 4 switched to crossover (diverging), or Reversed 2 to 3, which is turnout 2 and 3 switched to crossover (diverging). It is not electrically possible when using switched frogs wired from a turnout to have all turnouts set to crossover, this will create a dead short, one or the other routes have to be selected. This can be done when using a Frog Juicer however.

Switch Machine Standards


For large version of above image, click here


Wiring Diagram


For large version of above image, click here

Use this diagram to wire a double crossover using four Tortoise switch machines. The contacts on the machines are numbered 1 thru 8, the same as on the drawing. A feeder is run from each of these contacts to either another contact on the machine, another machine, or fed to the rail shown in the diagram. Some contacts will require two wires to be attached to it. Rail gaps are shown on the diagram and must be on the double crossover in the same locations.


Animated Schematic



Watch closely as the double crossover is switched. The color (polarity) of each frog changes relative to the route selected. The switch points and switch machine contacts move indicating the route through the crossover.

Schematic showing routes through crossover
These are the individual images that make up the animated image above.


For large version of above image, click here


For large version of above image, click here


For large version of above image, click here

Thanks very much to Andy for producing these for us!

_________________
Cheers!

Tim Warris
Fast Tracks
http://www.fast-tracks.net
service@fast-tracks.net

Very clear and simple diagrams. What more could you want?

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Now waiting for a better currency exchange rate before I order.

It could be done several ways. I will be using a series of 4 pole, 3 throw rotary switches and probably a handfull of diodes. It will mean more complicated wiring, but simpler switching. I do not know what would be simple or difficult for you, so I may not be able to give the best answer. I am also untested at creating drawn images as shown above, so I would also be unable to give even the simplest of schematics.

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Now waiting for a better currency exchange rate before I order.

Although it is probably not prototypical, but ............ a double crossover has basicly only two valid settings:
- all routes straight
- all routes diverting

This could ease your configuration.

Having said this, in the prototype they probably just pulled the points which were "the wrong way for the next train" and would leave all the other points "as is".

So if you want to run prototypical, use the complicated version. If KISS apllies ..........

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Paul Bender

Everybody can shovel, firing is an art


Firing this train was more fun then hard labor © R. de Water

Hi,

The issue with selecting "all routes straight, or all routes diverging" is that all routes diverging will create a dead short with powered frogs. With all routes diverging, the frogs are required to be both polarity at the same time, creating the short, so only one cross route can be selected at one time.

_________________
Cheers!

Tim Warris
Fast Tracks
http://www.fast-tracks.net
service@fast-tracks.net

I may be the old fashion type, but one way to set controls in a panel is with push buttons and a power capacitor supply. You would only need four buttons, one for each straight route and one for each crossing route. You would simply wire the out put from the push buttons to power the two switches needed for the selected route, leaving all others as is.

With this method you would have to double check route setting as you approched the double crossover to make sure your route is selected by puting the one button you need.

Using a capicator style power supply you get enough power to throw the switches and then it recharges for the next set.

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Kurt Konrath

SP was king of the road, Cotten Belt will run forever! D&RGW will rule the hills!

The switching can be done using only 2 dpdt switches as you will need to throw at least 2 points any way why not throw them from the same switch.

Connect 1 switch to two motors that form the crossover route for one direction, and the other switch to the other 2 motors forming the route for the other direction, easy.

If your doing dcc simply connect to 2 motors that form one crossover to the same decoder output if your decoder can handle the load of 2 motors, and then connect the other 2 motors to another out put, making sure the throw direction the mated motors is matched. IE:- close position or thrown position, and not 1 closed and 1 thrown.

I use Digitrax DS64 decoder and have had no problems with it perfoming this task.

It might be possible to even give 2 out puts the same addres # to split the load on the decoder (check your manuals for this as I am not sure)

You could even do the combo ddc with the manual switches as well.

Cheers
Ray

Hi all!

I am about to wire all turnouts and the big issue is the double crossover (with live frogs) whose ends have 4 double slips. All turnouts in the layout (Tillig and Weller) have live frogs.
As I am planning to use small servo motors to shift the point blades, this is my question:
should the servo motors directly be connected to a digital decoder (such as Uhlembrock's or ESU's, for instance) that does not provide any polarity and then should the polarity of the 6 frogs be provided by 1 big frog juicer?
Would this scheme work in your opinion?

I am asking as, the classic scheme with double slips would be different:
the servo motors would be connected to the digital decoder that provides the correct polarity to the frogs (and in this case I must use a turnout decoder that also provides polarity).

With a double crossover, the servo motors would still be connected to a digital decoder, but the polarity would only be provided by the juicer. Wouldn'it?
And it seems to me this scheme is fully valid for DCC operations (I would like my layout to be DCC-ready) but not for analog ones.
Unfortunately, as I still have some locomotives without decoder, how can I feed the frogs in analog mode?
I know for sure that, in order to avoid troubles, all analog locomotives will not be allowed to enter the double crossover (DCC operated) but at least, I would like them to go through the double slips.
What happens to the frogs in analog mode? Can they still be polarized by the decoders? Or shall I find another option?

Thanks for your help!!!

Pierre

The frog juicer will not work in DC mode. Even having a juicer connected with DC applied would likely burn up the juicer . . . especially if activated by a short.

Wire each double slip up independently, using standard double slip wiring activated by the points throw. Double slip portion should follow the methods described here and use contacts activated by points throw. You don't have to use Tortoise machines, but you need the equivalent electrical contacts activated by some limit switches from movement of the points throw.

Of course, going ONLY DCC would make it much simpler. There is simply no free lunches.

-ed-

_________________
-ed mccamey-
COSLAR RR - http://www.coslar.us/
NMRA Standards and Conformance Department
PROTO & FINE Scale Coordinator
I estimate I have about 5 pounds of coupler springs somewhere in the vicinity of my workbench.

Thank you!

I actually suspected the frog juicers could not be used in analog mode: therefeore I will make the double crossover only DCC-friendly and all non-analog engines will avoid it. I have already set 1 track (adjacent to the double crossover) that will allow analog locomotives to enter the main station...whenever it is necessary.

Regards,

Pierre

How much different would wiring be using the switches with Bull Frogs. I know you would have to switch each turnout manually, but you only have two choices of wire routing.


Kurt

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Kurt Konrath

SP was king of the road, Cotten Belt will run forever! D&RGW will rule the hills!

Hello Kurt,

Although it's not prototypical to control a double crossover manually it's technically feasible with the BullFrog switch machines using 2 micro switches mounted on each of them. Simply replicate the wiring for the Tortoise machines that use contacts 2 through 7 and orient them the same way on the micro switches, where one switch would be contacts 2, 3 and 4 while the other is 5, 6 and 7.

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- Terry -
Customer Service - Fast Tracks HobbyWorks Inc.
service@fast-tracks.net

Hi All,
Andy's diagrams are excellent, but I found an important improvement that should be made (I reviewed this with Andy and he agreed I should post this update).

The issue is with two different Tortoises powering track segment "A". Although individual Tortoise contacts are break-before-make, there is no assurance that two different ones will obey that sequence. There is a chance that a dead short will occur through the Tortoise contacts, even if they are thrown at the same time. This will lead to an early death of the contacts.

My updated schematic avoids this issue with a minor change. I did not update the animated versions, just the master.

Also, if anyone wants it I will post my control wiring diagram. It used two DPDT switches; one selects normal or crossover, the second selects which way the crossover goes when the first switch selects crossover. I have five pairs of LED indicators also wired on the panel in an "X" shape that show the selected route.

On the layout, I have four three-aspect dwarf signals indicating the route selected also; this is controlled only by the tortoise power controls. Again, if you are interested let me know.

And yes, this is all built and operational!