Subject:
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Re: Newbie needs Help (diff sensor)
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 7 Jun 2006 17:15:38 GMT
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Viewed:
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4439 times
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On Wed, June 7, 2006 12:42 pm, Brian Davis wrote:
> In lugnet.robotics, steve <sjbaker1@airmail.net> wrote:
> > To measure the dynamic friction you can use the same locked-up
> > wheel rig and just pull it along flat ground with a spring
> > balance. Drag it along at a reasonably constant speed where it
> > isn't jerking along.
>
> That's not very easy in practice, and you need to make sure the rope is
> pulled parallel to the floor. I've always wanted to use the RCX and a sensor to
> do this automaticly, but the results "by hand" have always been so poor I've
> never bothered.
hmm. This sounds like a good project...
> > Furthermore, realise that the high school physics equations for
> > sliption say that the frictional force is proportional to the
> > weight - but NOT related to the contact area. People find that
> > counter-intuitive - but it's true.
>
> It's wonderfully true in the world of high-school physics, but the real world
> can be significantly different.
All things being equal, I'd put my money on the robot with ten spinning wheels, over
a couple (or even ten) stationary ones.
I'd also mechanically connect all the motors together, so they drive a single axle
(no differential). But, given three motors, I'd connect them to separate outputs on
the RCX.
I'd find out what type of surface the event will be on, and do as much testing as
possible, to find out what speed will tow the most weight.
Beyond that, there are MANY mechanical things that can be adjusted & changed.
Testing is important.
Good luck, & have fun.
Steve Hassenplug
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Message has 1 Reply:
 | | Re: Newbie needs Help (diff sensor)
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| (...) I'll get to that, eventually... there's just too much fun stuff going on, and... (...) A historical point on this. The first time I met Steve was at a sumo event, where I had carefully calculated the correct gear ratio, given the torque of a (...) (18 years ago, 7-Jun-06, to lugnet.robotics)
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Message is in Reply To:
| | Re: Newbie needs Help (diff sensor)
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| (...) As you note in your mini-cooper example, *if* you can keep the wheels from "spinning out", but instead are always in rolling contact with the ground, static friction is what's important... and generally, the static coefficient of friction is (...) (18 years ago, 7-Jun-06, to lugnet.robotics)
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