More Cobalt questions

[tomparryharry]

Hello Folks,

 

More questions...

 

I'm about to wire some Cobalts, using the standard DPDT switch method.

 

Here's the question. Can I substitute 2 PTM (push to make) switches for the single DPDT switch?

 

The reason is to draw less power, as the switch only uses current, when in use.

 

Has it been done, can it be done? more important, is there a wire diagram?

 

All replies, as usual, gratefully received.

 

Regards,

Ian

[Gruffalo]

Ian, I think not. Cobalt and Tortoise slow acting point motors rely upon power remaining on to keep the switching rail against the stock rail so a momentary PB will not serve the purpose you want. Current draw is very small, a few milliamps per unit. My LGP has 26 points and I expect about 1A to be drawn by all these. Wiring diagrams are available on Cobalt's web site.

[Crosland]

It depends how much friction there is in the gearing. A servo, for example, can be powered down between operations.

 

How much effor does it take to move the output of a cobal when unpowered?

 

If there is a worm in the drive from the motor that will help.

 

I would just try it and see, or go to the source and ask the manufacturer.

 

Andrew

[tomparryharry]

Thanks for your quick responses.

 

I thought that the slow speed is/was due to the low gearing of the Cobalt. I don't expect the 'push' action to be momentary, rather, kept contact, until the blade has moved to the stock rail, then release power.

 

I shall e-mail DCC Concepts, as suggested.

 

Many thanks,

Ian

[Steven B]

I don't think there is a worm gear in the Cobalt gear box. The gearing is such that it's almost impossible to move the actuator by hand (unlike the Tortoise). I suspect you'll not have any trouble with disconnecting the power from the motor whilst it's not being used to switch the point.

 

I'd look at using a non-latching centre off DPDT switch - with push switches there's a risk both can be pressed at the same time and cause a short circuit:

http://www.rapidonline.com/Electronic-Components/DPDT-on-off-on-Min-Toggle-Switch-75-0090

 

 

Happy modelling.

 

Steven B.

[tomparryharry]

I don't think there is a worm gear in the Cobalt gear box. The gearing is such that it's almost impossible to move the actuator by hand (unlike the Tortoise). I suspect you'll not have any trouble with disconnecting the power from the motor whilst it's not being used to switch the point.

 

I'd look at using a non-latching centre off DPDT switch - with push switches there's a risk both can be pressed at the same time and cause a short circuit:

http://www.rapidonline.com/Electronic-Components/DPDT-on-off-on-Min-Toggle-Switch-75-0090

 

 

Happy modelling.

 

 

Steven B.

I like that!

[Izzy]

There is no worm gear reduction in the Cobalt. Like servos and others it relies on multiple spur gear reductions to give a high total reduction. As the total ratio rises it becomes ever more difficult to 'drive back' through such a gear train, and the effect is similar to that experienced with a worm drive, but with a certain amount of 'give' or pressure release when the motor isn't under power.

 

I bought one a while ago just to see how they compared to using servos. Part of this investigation involved taking it apart, as I often do with stuff just to see how it works and is designed. As such here are a couple of shots of the internals. Not very good I'm afraid, but enough to see the basics. Six gear steps until the fulcrum.

 

 

 

The funny gear angles are due to the loss of being kept in the correct position by the case side removed.

 

My experience is that they don't need power to maintain position, partly due to the spring fulcrum wire, but they don't have an awful lot of power either, although they are nice and quiet. Good enough for points such as Peco with over-centre springs to hold the blades in place, but I'm not sure about hand made ones, which I use. Even in 2mm scale I have decided that servos are better, much smaller and more powerful, and the more expensive digital ones are roughly as quiet.

 

Izzy