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Unread 29-01-2014, 08:35
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Re: Shifting with servos

Quote:
Originally Posted by Gregor View Post
When would anyone ever want to do that?
Well, one would hope the catapult winch isn't driving while you shift into neutral.

As to the original question, I have two points to consider:

1. Using a ratchet to take the load off of the gearbox entirely is a good idea. We built a custom dog system for a winch, and once we get it into place the motor drives back a little and the ratchet/pawl takes the entirety of the load, so we can use a tiny little pneumatic cylinder to disengage the winch. (We have a fatter-but-not-insanely-so cylinder then disengaging the pawl, which takes about 12 lbs of force.) Given that you probably need a ratchet of some kind to keep the system from back driving anyway, this is a good idea to consider.

2. If you're not going to have any other pneumatics on your robot and a servo just won't do, consider using a screw drive. They're as strong/fast as you need them to be (based on motor power, of course--in 2010 we lifted our robot using a CIM-driven screw), accurate, easy to control, and for your application perhaps the best thing is that they're motor driven.

What they're not is efficient, but you can use this to your advantage to prevent back drive in some applications where that's desired.
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