Transferring motion from shaft

[YeeHaa]

Hi,

In a small mechanical application i have, i want an electrical motor to drive a spur gear, and from the moment the spur gear encounters resistance (it stops completely), i want the same shaft from the motor to drive a second spur gear (which was NOT spinning at first, it starts spinning from the moment the first gear stops).

Is there a way to do this mechanically? I just want to use one motor.

Thanks!

 

[Danger]

The only way that immediately comes to mind is to use a couple of clutches. Electromagnetic ones would probably be the easiest to implement.

edit: By the bye, I have a lot of questions about what exactly you are trying to achieve, because the premise sounds just a tad squirrelly.

 

[YeeHaa]

I don't know exactly what you mean by "the premise being squirrelly", but I'm trying to create a simple robotic gripper for a project I'm going to start at home. But since all robotic grippers without joints have limited capabilities, I'm leaning towards a jointed one, but preferably without using tendons or complicated mechanics...

An example of a system that uses the same principle (but is already too hard for me to implement), is the system in the BarrettHand:

http://support.barrett.com:8080/wiki/Hand/262/KinematicsJointRangesConversionFactors

 

[Danger]

Ah...
Okay, then. That looks cool, but I frankly am too tired to read the whole thing right now. It's 07:30 my time, I've been up for 26 hours, and I've got 5 of my 20-pack left to go. My apologies, therefore, for being a little less than at full attention.
I have no idea where you live or what your native culture is, so I hasten to point out that I didn't mean the term "squirrelly" to imply insanity, in which context it has sometimes been used. I merely meant "unusual" or "enigmatic". The primary reason for that was your mention that the #1 spur bails out at the first sign of resistance. If that's the case, why is it there in the first place? It can't perform any function whatsoever without overcoming resistance. Also, your use of the description "small mechanical application" was a bit vague. Now that I know what you're up to, that is no longer a concern. It does raise a bit of bother, though, in that the smallness limits what sort of tech can be applied.
I still think that clutches are the proper approach, but the scale is causing me to rethink the operation thereof. Perhaps air pressure would be better than electromagnetics.

edit: I've had a chance to sleep a bit and check out the link. I'll have to go over it a lot more, though, as it puzzles me in a couple of different regards.