Subject:
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Re: multiple motors
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Newsgroups:
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lugnet.robotics.rcx
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Date:
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Mon, 16 Feb 2004 15:38:45 GMT
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Viewed:
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7676 times
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In lugnet.robotics.rcx, Brian Davis wrote:
> Jona Jeffords wrote:
>
> > Okay I've done it. I have the drive train all figured out with
> > the exact gearing I wanted.
>
> Great. My method was to combine the motor outputs down to two axles (left &
> right) and then do the gearing down/up. I also played with running the "boost"
> motors at a different gear ratio than the other four, but wasn't sure it would
> help (much).
>
> > will adding an additional 2 motors to help in forward and reverse
> > motion really add enough to the push to justify the rebuild?
>
> Make a basic chassis with the wheels you want, and bulk it up to the limit (4
> lbs in this case, correct?). Drive it into a wall using just four motors... does
> it stall out (ie, motors can't provide enough torque) or spin the wheels (motors
> can generate more torque than can be applied, due to limits on tire friction &
> weight). *If* they stall out, then the "boost" motor pair can be added to dump
> more torque into the system. If it doesn't stall out, then motors are not the
> limiting factor in the maximum pushing force you can deliver.
> Another possible advantage is speed - these motors are not running unloaded,
> and tossing another two motors worth of torque can boost the output speed of the
> system as a whole as well.
>
> > Do I have anything to be concerned with as far as the draw on my RCX?
>
> Well, empirically I've had no problems as yet (I'm also running six motors,
> two from each output). Coordinating turns etc. is slightly more complex in code,
> but not really a problem. I've not had a chance to contrast this (six powered
> from RCX) to the battery box solution (six powered from a non-current-limited
> source), but since the RCX (for my specific 'bot) can power all six, the
> limiting factor so far is ground friction (ie- how do you get 4 lbs of LEGO onto
> the thing?!?)
>
> > Will I burn through batteries much faster?
>
> Probably somewhat less than 50% faster. More power (torque per second) cost
> more power (amps).
>
> > Any ideas or information that can help answer these questions
> > is greatly appreciated.
>
> Rule #1: Robot should not suicide itself out of the ring.
> Rule #2: see rule #1...
Thanks Brian,
I doubt I will attempt your suggested test of driving into a wall (this scares
me very much!) but I hear what you are saying. Based on Steve's reply, I have
decided that 6 motors pushing is better than 4. Since I have already figured out
the gearing I have littel to lose. As far as getting up to 4 lbs...I was sitting
at 2 lb 14 oz prior to thinking about the 2 additional motors. I expect I will
come in under 4 no problem, but will be around 3.5 lbs.
And yes, Rules 1 and 2 are good rules, it's good to remember the basics.
Jona
http://www.24tooth.com - LEGO Robotics Group of Ann Arbor
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Message has 1 Reply:
 | | Re: multiple motors
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| (...) Actually, I think what he's suggesting is a pretty good idea. I usually test most of my sumo robots this way. Place the robot next to a wall. If you don't want to damage a wall with a big, powerful robot, :) use a book held against the floor (...) (23 years ago, 16-Feb-04, to lugnet.robotics.rcx)
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Message is in Reply To:
| | Re: multiple motors
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| (...) Great. My method was to combine the motor outputs down to two axles (left & right) and then do the gearing down/up. I also played with running the "boost" motors at a different gear ratio than the other four, but wasn't sure it would help (...) (23 years ago, 16-Feb-04, to lugnet.robotics.rcx)
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