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Unread 01-12-2011, 00:51
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Re: Gearing for 20 FPS?

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Originally Posted by Ether View Post

That's 23 fps at CIM free speed. Do you know what was the vehicle's actual top speed? (I'm trying to get some data on realistic numbers for speed de-rating)
Sorry no measurements. With a #25 chain directly from each CIM to each dead axle wheel, and its light weight, the friction loss was very low.
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Unread 01-12-2011, 02:42
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Re: Gearing for 20 FPS?

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Using the oldschool version of JVN's design calc with the drive modeling tab allows you to graph the position and it's derivatives over time, and study what changing mass, friction, power, gear ratio, etc... has on them. It's very interesting how a *slight* friction difference can change speed appreciably.
I just looked at this spreadsheet and I must say, I am floored. As a student who knows very little about DC motor physics (or physics in general), I am amazed at the amount of work that went into creating it. I would be interesting in reading an explanation of some of the math/concepts behind it, if someone would know where to find it. Also, if anyone has any tips on using it now that the motor and gearbox scene is slightly different from where it was in 2004, I would definitely appreciate that too.
Well done JVN, it would be cool to see some of these features re-incorporated into a later iteration of the design calculator.
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Unread 01-12-2011, 14:03
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Re: Gearing for 20 FPS?

2016's 2008 robot, with an ackerman steering module, there are pictures on CD somewhere of the module.. was set around 21 ft/s, we never got to measure the actual speed. Also I would look at 102's robot from 2008 they had a really fast robot as well.

we were running somewhere between a 6-7:1 gear ratio on two cims with 6" wheels. Pretty controllable for lapping, outside of lapping it was like driving a car, literally. we actually set that robot up with a steering and pedals to make it easy to drive and handle on the field...

heres one of the matches: http://www.youtube.com/watch?v=g58N0...eature=related

Btw, this is a full 120lb machine a little more with the bumpers and battery. i think we recorded 13 laps at chesapeake in one of the matches.

20ft + is not undoable in FIRST, controlling it is the hard part. One of the only reasons we were able to control ours was because of the ackerman steering and running laps being the objective. (steering was favored to help turning left).
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