Tortoise Machine Switches


Ken, I've never had a Tortoise misbehave as you are describing, and frankly, I'm shocked that you (might) have "a few" of them (not sure if that's three, or five, or what). Until I read your original post, I would have said that Tortoises are utterly reliable. As I said earlier, I only use the auxiliary contacts to power panel indicator lights. So I've never had the incentive to open one up and attempt repairs. I'm impressed at how you're willing to "go where no man has gone before."

IF it's the Tortoise causing your problems (and although that's my hunch, it is still an unproven hunch) I personally would not attempt a repair. After all, we're talking track power and digital signals in your application; that's something that you need to be absolutely reliable.

When I first started wiring my Tortoises, I thought about using them to power my frogs and decided to use Frog Juicers instead out of sheer laziness. (My earlier layouts all used unpowered frogs; I'm just fortunate that when I switched to powered frogs, the Frog Juicers were available.) If is does turn out that you have more than one malfunctioning Tortoise, I will be disillusioned about Circuitron's quality control.

I'll be very interested to hear when you finally get this figured out.

All the best,

Dick
 
Ahhhh, so you're recommending a course of action you haven't tried yourself and want me to let ya know how it turns out.
Thanks.
 
Let's be clear: I don't WANT you to do anything at all. It's not my problem; it's your problem. I'm interested in the outcome because it's an interesting problem. I've suggested to you what I would do if I were in your situation.
 
I'm not sure I get your point, Greg.

The upshot is this: Ken is experiencing a momentary short during turnout movement with just a few of his many Tortoise installations, all of which route power to the frogs using the auxiliary contacts. Since the short is momentary, it MUST be caused by something that is moving: either the turnout or the Tortoise. Ken has checked and rechecked his turnouts and doesn't think the problem lies in the turnout. That's why I've suggested he look more closely at his "few" malfunctioning turnouts to see if it might be the Tortoise that is causing the short.

"When you have eliminated the impossible, whatever remains, however improbable, must be the truth." - A. C. Doyle
 
I know what's going on here, I have observed the problem with my Tortoise machines, and still haven't quite found a solution. You can consider this normal, but undesirable behaviour. The points themselves form a SPDT switch, because the points are energized by touching the rail that they are pushed against. When a turnout motor is connected for power routing, it is not supplying but rather assisting the switching, by providing a parallel path through SPDT contacts on the switch motor.

Each switch is a break-before-make, the points for obvious reasons (the point contacts have physical separation). The control switch (power routing switch) should also be a break-before-make. The reason for this, is that if one set of switch contacts closes before the other one is open, a short results.

Hence, in order to avoid shorts, both point and switch contacts have to fully disengage (become open circuit) before they engage (close the circuit) in the alternate position. This means two things:
1. They must both move at the same time
2. There must be a region in the middle of the switch travel when neither side is connected.

With DC systems, it's not usually a problem because the switching can be done without the rails being energized. With DCC constantly energizing all the rails, now it's a problem.

You may be able to fix it by carefully adjusting the position of the throw wire, so that the movements of the points and Tortoise contacts are perfectly in sync.
 
And no I don't have this problem either, but if one only wants suggestions from people with an identical problem then one might not get any responses as many model railroad problems are quite unique.

Just reading this, my hypothesis is (as diesel's above) that the tortoise is not malfunctioning, but that it is an interaction of some electrical contact in the turnout (like the throwbar as was suggested) AND the power coming from the tortoise to power the frog. As diesel suggests above I would try to adjust the position of the throw wire of the turnout first. Simple mechanical synchronization between two different power sources.

OR looking at the guts of the tortoise that was posted, one can delay the time before the power is routed to one side or the other by trimming the DPDT traces back as indicated in yellow. That would create a longer dead time and delay between one power direction and the other. The afor mentioned fraction of a second. If more diagnostics were performed one could determine exactly which of the 4 places needed to be trimmed and how much.
tortoisecircutboard.jpg


Finally, #10 turnouts were mentioned. I can almost assume they are hand laid. Opening and modifying tortoise could be a lot of work. Might be easier to determine exactly where the turnout itself switches power directions to the frog and somehow adjust that. But as I said above, requires a finer diagnosis of the exact point of the short. Put one of these problem turnouts on a push button so one could advance it a tiny fraction of the throw at a time, and work it to the problem point.
 
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I think a means of fixing this is tuning the Tortoise. The fulcrum bar on the Tortoise can slide up or down. If it is to far down, the points move faster. If it is up too high, the points move slower. Have to set it so the Tortoise contacts break when the turnouts point wiper separates from the track.
 
I sure like using Tortoise machines instead of so many others.

Ken, looks like a good suggest for the Tortoise electrical concerns.

Greg
 
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