Alt-BEAM Archive
Message #10923
To: beam@sgiblab.sgi.com
From: Bruce Robinson Bruce_Robinson@telus.net
Date: Sat, 26 Feb 2000 16:38:56 -0800
Subject: [alt-beam] Re: mini walker
BUDSCOTT@aol.com wrote:
>
> ... would it be possible to make a walker with two extremely
> small tape play motors that wouldn't need a motor driver and
> a freeformed bicore. I want to avoid the inconvinience of having
> to use gear motors. ...
Conventional wisdom says, "No, you gotta use gearmotors." Personally, I
don't have much use for conventional wisdon.
Your motors will probably turn too quickly to drive the walker legs
directly (but it's always worth a simple experiment). If that proves to
be the case, you might be able to reduce the speed considerably without
a gearbox. A number of the tape players & old VCR's I've dismantled have
large diameter friction wheels which press against the motor shaft ...
usually to drive the take-up hubs. You could get considerable reduction
just by using this principle. Mount the legs on the friction wheel.
It would help a lot if the tape players you dismantled also contained
some of these friction wheels.
> ... if i slowed down the timing, and made it extremely light, would this
> work?
You will probably have to speed up the timing. The motors will be
turning much faster, so they will have to run for a much shorter time or
else they will turn into horizontal wheels :)
Light weight, up to a point, is good. But if your legs are moving
rapidly, too little weight will give you a bouncy robot that doesn't go
anywhere. Too heavy, on the other hand, will overload the motors. Best
approach ... make it as light as you can, making provision to add extra
weight later if necessary.
With a light robot with fast moving legs, you will want to reduce the
up-down motion of the legs so there is just enough to cause the balance
to shift. Try one motor shaft verticle and the second tilted just a
little off verticle. Be prepared to adjust the tilt until you find what
works best.
> Thanks for the help!
Never be afraid to try something a little different. Even if it doesn't
work, you learn. Share with us, and we all learn :)
Bruce
10924 Sat, 26 Feb 2000 16:45:52 -0800 [alt-beam] Re: Component Alternatives? beam@sgiblab.sgi.com Bruce Robinson Andrew Hooper wrote:
>
> Any one know of any alternatives to the following components?
> I have been trying to purchase them in NZ and so far have not
> been able to find a local supplier.
>
> 2N3906
2N3906 is a "PNP general purpose" transistor.
I swap 'em around routinely with the 2N2907 (also a PNP general purpose,
handles more current). You might try a 2N4403 as well. These are common
in North America. Don't know about NZ, though.
Bruce
10925 Sat, 26 Feb 2000 17:08:11 -0800 [alt-beam] Need More Power! alt-beam@eGroups.com "Brian Ward" Hello,
I'm new to beam and facinated. My first project is a photovore and it
works great except for one problem. The salvaged photoresistors I have
are of different values and I need to boost the output to my left motor
by 1.7 v.
I have tried to do this using Tilden's h-bridge and also with a dual,
non-inverting op-amp but I can't seem to get the results I need. The
motor in question simply runs all the time so instead of limping, my
bot simply spins the other way! I am stumped. Any help would be
greatly appreciated. Thanks
Brian Ward
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