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Unread 24-01-2005, 13:14
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Al Skierkiewicz Al Skierkiewicz is offline
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Re: Motor Placement Pros and Cons

Quote:
Originally Posted by Pattie
Hi,

We need an outside opinion as to pros and cons of this motor placement design using two transmission boxes (shown) with two CIM motors each - each side will have one short chain to the nearest wheel and a longer chain to get to the further wheel on the same side to make 4 wheel drive. Forgive the artistry - not quite talented in that department yet......

Thanks,

Pattie
Pattie,
There is no glaring reason against your idea. Most teams will center up the transmissions to balance the weight over each of the wheels. Your configuration may cause some steering instability as the wheels under the trans will have slightly more weight over them than the other wheels. The longer chain paths do have a little greater chance for problems as the loop developed as the chain stretches is more capable of throwing itself off a sprocket. There are ways to prevent that but they come at a cost of additional weight. No matter what you decide, plan on some device to take up the slack in the chain and check for slack before each match. Correct chain alignment is a must for efficient drive so make sure all your sprockets line up (in the same plane) before driving as well. Let us know how it worked.
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Unread 24-01-2005, 13:33
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Re: Motor Placement Pros and Cons

Quote:
Originally Posted by Al Skierkiewicz
Pattie,
There is no glaring reason against your idea. Most teams will center up the transmissions to balance the weight over each of the wheels. Your configuration may cause some steering instability as the wheels under the trans will have slightly more weight over them than the other wheels. The longer chain paths do have a little greater chance for problems as the loop developed as the chain stretches is more capable of throwing itself off a sprocket. There are ways to prevent that but they come at a cost of additional weight. No matter what you decide, plan on some device to take up the slack in the chain and check for slack before each match. Correct chain alignment is a must for efficient drive so make sure all your sprockets line up (in the same plane) before driving as well. Let us know how it worked.
We haven't been as extreme as your sketch, but we normally have one chain longer than the other when we're doing a tank type drive. Like Al says, keep your chains and sprockets in the same plain and keep the chains tight enough but not too tight and you should be fine.
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Unread 24-01-2005, 13:50
Pattie Pattie is offline
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Re: Motor Placement Pros and Cons

Wow you guys are fantastic! I really do appreciate the input. We will make the final decision on this tomorrow because school is out today. Its good to have as much information as possible before we make final decision - all this data helps so much.

One of the kids has another very valid question - Are there any teams out there that are using four transmission boxes (direct drive)? Is that legal to do?

Pattie
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Unread 24-01-2005, 15:20
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Re: Motor Placement Pros and Cons

Quote:
Originally Posted by Pattie
One of the kids has another very valid question - Are there any teams out there that are using four transmission boxes (direct drive)? Is that legal to do?

Pattie
Yes it is legal. You can purchase the gearboxes from IFI.Youwill need to get the bearings and sprockets separately. You will have to include the extra gear boxes in the cost of your robot, but there is no reason you can't have as many as you can afford in terms of cost and weight.
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Unread 24-01-2005, 15:40
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Re: Motor Placement Pros and Cons

Well, we actually used this gearbox placement for the 2003 game. Yes, there were steering issues (we found it far easier to turn one way, but difficult to turn the other). I believe these were more of a result of other aspects of the drive train, ie. weight distribution and the wheelbase vs. distance between axles.

Regardless of where you place the gearboxes, if one corner of the robot has more weight on it, you will have steering/turning problems.

I suggest that you find a way to make your wheelbase wider than the distance between axles, or use low-traction wheels on one end of your robot.

-Mr. Van
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