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Unread 23-12-2012, 00:56
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Re: Ideal robot speed

I'll throw some numbers out to quantify this quickly. Hopefully, this is a real eye-opener for teams who have never done the math. This assumes a 4 cim drivetrain. This assumes you are accelerating from a stop. Someone check my math.... this was thrown together quickly.

Ratio: 4.2:1
Top Speed: 18.02 fps
Time to cover 10 feet: 1.18

Ratio: 7.1: 1
Top Speed: 10.60
Time to cover 10 feet: 1.20

Ratio: 10:1
Top Speed: 7.51 fps
Time to cover 10 feet: 1.44

Ratio: 12.5:1
Top Speed: 6 fps
Time to cover 10 feet: 1.63

The difference between an 18 fps drivetrain (no shifting) and a 6 fps drivetrain over 10 feet is about .4 seconds. Shifting introduces another variable, but you can see where I'm going with this. Erring for a higher gear ratio will rarely leave you disappointed. Due to acceleration timing, a top speed of 10.6 fps is only .02 seconds slower than an 18 fps over 10 feet without shifting.

In fact, over 10 feet a robot geared for 18 fps will only hit about 15 fps.

This segways into a very interesting argument about when you should design for shifters.

Last edited by Tom Line : 23-12-2012 at 01:06.
 


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