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Unread 04-01-2009, 17:56
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AKA: Tim Long
FRC #1742 (Shockwave)
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Join Date: Feb 2006
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Re: How can we drive on this new floor?

Quote:
Originally Posted by adaptingthought View Post
someone found a fan thats legal by FIRST regulations

http://www.modelflight.com.au/rc_mod..._micro_fan.htm

i dont know the calculations to find out how long the battery could power it though
Unless I'm off my rocker, 200g of thrust means a little less than a half-pound of thrust? You'd need something like 14 of them to be roughly equivalent to the amount of force produced by frictional interaction from wheels.

I made that approximation based off a calculation of maximum frictional force by multiplying the weight (120lb.) by the *kinetic* coefficient of friction (.05 from the first manual), yielding a maximum force of 6lbs. to accelerate the robot. So, that's a lot of fans. Running all of them at their maximum of around 300 Watts each, that accounts for 4200 watts, and, I could be wrong, but I believe that would mean it would discharge one of the 12v 18Ah batteries in around 3 minutes.

So, that particular fan sounds pretty in-efficient to me. I would suggest looking for one with a much larger prop. Larger, slow moving props tend to have a higher efficiency (not to mention they tend to be a little safer). A larger prop would also mean more thrust, and fewer fans. Knock the number of fans needed down to 4 or so, and it would be manageable I think.

I'm still intrigued by the possibility of a fan-propelled bot. I think it would be quite spectacular to watch in action.

*EDIT*
This is all completely without regard to the legality of the fan and motor, merely assessing the viability of the particular product.
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2007 Robot "Rampzilla"
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Last edited by JagWire : 04-01-2009 at 18:00.
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