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Unread 22-12-2011, 11:31
Akash Rastogi Akash Rastogi is offline
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FRC #2170 (Titanium Tomahawks)
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Re: motoring the wheels

Quote:
Originally Posted by eagle33199 View Post
I would say most teams probably do a chain drive of some sort.

Generally speaking, you probably want all of your wheels powered in some way - it really helps if you're being pushed, or are off balanced when climbing a ramp, or a dozen other situations that can lift one or more wheels off the ground.

Here's our setup for 6-wheel drive in the past (we've used it 3/5 years since the team started. The other two we used a 4 wheel design for Lunacy and Mecanum drive for Breakaway):
- Motors/gearboxes are placed on the rail near the middle wheel
- chains go from the gearbox to the middle wheel to power it
- two more sets of chain go from the middle wheel to the front and back wheels

This way, every chain wraps halfway around each sprocket, which helps prevent jumping your chain off the sprocket.

We've never direct-driven a wheel (where the output shaft from the motor is used as the axle for the wheel) - we feel that the failure modes for that are a little too risky, compared to running a short chain between the motor and the wheel.
Since this was the only post that actually answered what the OP was asking, I'll tack on a few pictures to help.

For the OP:
This is a direct drive, meaning the center wheel is mounted on the output shaft of the gearbox. The center wheels have double sprockets which then chain to the outside wheels. http://www.chiefdelphi.com/media/photos/32160

This is a 6wd made using the kit gearbox without direct driving the wheel off of the gearbox's output shaft. http://www.chiefdelphi.com/media/photos/34531

The output shaft of the gearbox has a double sprocket on it. Like this http://www.andymark.com/product-p/am-0421.htm

So, one of the sprockets chains to the back wheel and one chains to the center wheel. The center wheel has a sprocket on both sides. The center wheel is then chained to the front wheel which has another sprocket on it.

Here's another example: http://www.andymark.com/product-p/am-0959.htm If this had another sprocket on the center wheel and a sprocket on the front wheels, those could be chained together to create a proper 6 wheel drive.

Another example http://www.chiefdelphi.com/media/photos/29579

Hope that answers your question without any confusion.
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['16-'xx]: Mentor FRC 2170 | ['11-'13]: Co-Founder/Mentor FRC 3929 | ['06-'10]: Student FRC 11 - MORT | ['08-'12]: Founder - EWCP (OG)

Last edited by Akash Rastogi : 22-12-2011 at 11:43.