Subject:
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Re: Newbie needs Help
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 6 Jun 2006 22:24:43 GMT
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Original-From:
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steve <sjbaker1@airmail.netSAYNOTOSPAM>
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Viewed:
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3476 times
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raj wrote:
> > So, you're best option would be to increase the speed.
>
>
> > Finally, remember, you can mechanically connect all the motors together, so
> > they are driving the same wheels. This assures all wheels are getting the
> > maximum amount of power.
>
>
> Steve,
>
> Philo's page on 'Wheels, Tyres & Traction' seems to imply that increased
> speed will not make much of a difference or am I reading that wrong?
What I'm saying is that if the robot is moving along at (say) 3 inches
per second - then the drive wheels will get most traction if they are
turning at a speed equivelent to 3 inches per second. If they are
rotating faster than that (because the wheels are slipping) then you'll
have less traction than you could if you slowed them down to the
'correct' speed.
> By 'mechanically connect' do you mean by using two differentials?
There are lots of designs for gearing that do this. The idea is to
subtract the rotational speed of one wheel from the rotational speed of
the other - so you have an axle that rotates only when the two wheels
are moving at different speeds. If one wheel is driven and the other
is just idling then the difference in their speeds tells you how much
the driven wheel is slipping. The classical design for this is the
'South pointing chariot' (said to have been invented by the Chinese
4600 years ago!)
http://www.odts.de/southptr/
> The maximum 'safe' gearing down ratio was a general question. I was hoping
> for an answer like 'anything below 100:1 is fine'.
There are too many variables - as someone else pointed out - the
distance along the axle between the driven gear and the wheel
(or whatever) has a big effect. I don't know whether there is a good
rule of thumb - but I do know that I've destroyed axles at gearings
up in the hundred and fifty to one range - so it's definitely a
consideration - but it's not just about gearing - the resistance to
turning of the final output is important too.
So I don't have a good answer for you.
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Message is in Reply To:
 | | Re: Newbie needs Help
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| (...) Steve, Philo's page on 'Wheels, Tyres & Traction' seems to imply that increased speed will not make much of a difference or am I reading that wrong? By 'mechanically connect' do you mean by using two differentials? The maximum 'safe' gearing (...) (18 years ago, 6-Jun-06, to lugnet.robotics)
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