Alt-BEAM Archive
Message #03192
To: beam@corp.sgi.com
From: Jean auBois aubois@trail.com
Date: Tue, 11 May 1999 09:19:55 -0600
Subject: [alt-beam] Re: a useless idea
Jeremy Williams wrote:
>why not just place a two DOF head inside a sort of gyro (like those rides
>that you are straped in and the operator spins the two rings up and down
>etc.) and place that in a MINIBALL sphere. An activly phototropic
>miniball???????????
Well, as Wouter & I were discussing:
( > is Wouter, >> is me)
>>Nope, I don't think it is a useless idea.You may or may not find the
>>following idea to be analogous. It came to mind soon after I was
>>introduced to BEAM during the Spring of 1996.
>Well, I do find it anologous actually, and now I don't think it is useless
>anymore, thank you.
>>The Solarball is a fine enough device even though its positive phototropism
>>is somewhat weak. On the other hand, as an inertial propulsion device it
>>is kind of clever. I have seen a paper on the net about a somewhat more
>>ambitious device that involved something that rode inside a ball.
>(I sometimes thought about a little car inside a bol, so that the whole
>thing could manage higher obstacles, but that's a different topic)
>>So... what can be done with a ball and an inertial drive? Well, you
>>certainly show something that works along one axis. To be sure, it would
>>be very nice to be able to do something similar along three axes but I had
>>my mind set on something that would fit into a ball about 2..4 cm in
>>diameter. Such a ball is very inexpensively sold with a spinner inside as
>>a toy for cats.
>Nice idea, it should be possible
>>Well, the one thing about pager motors is (a) it is easier to leave the
>>weight on than off and (b) it is, after all, an eccentric weight --
>>precisely the same condition you specify for your device. Also, it is
>I don't think it is necessary to have an excentric weight actually. I only
>thought about that when I had drawn the figure already. Yesterday I did a
>little, very fast and unprecise experiment, which doesn't prove anything,
>but which made me start to think: see, if the motor turns it would like the
>weight to start turning, but since the weight is heavy the motor itself
>with the ball you describe attached to it will turn. I don't know what
>happens though if the motor stops: will the whole thing lie still or will
>it keep turning. From the energy point of view I would expect it to keep
>rolling: you transformed stored energy to mechanical, kinetic energy and if
>you stop transforming that energy (by stopping the voltage-difference
>across the motor) that kinetic energy will stay ... actually fade away by
>friction, but that doesn't matter.
>>easy enough to fit two of them at right angles within such a sphere. The
>That should be possible.
>>real question was the control circuit & the power supply. Since, at the
>>time, the only thing that Tilden was (revealing) was the use of 74xx14's
>>& the 4-neuron microcore with a subsequent driver chip, it looked like
>>either one needed a battery or had to live with the intermittent action of
>>a solarengine. I did not know yet of Richard Weait's "Thirsty" which is a
>>solar-only walker. Incidentally, as it indicates on the Solarbotics page,
>>Richard was the fellow who came up with the "Miniball" (miniball,
>>solarball, whatever.)
>Do you know the schematic of thirsty? I keep admiring that robot; it is one
>of the coolest looking ones I think!!!
>>With the availability of photocells that would fit nicely into such a ball,
>>big enough capacitors to store a fair amount of energy, the development
of>>the bicore, of which one can put two onto a '240 with the four spare gates
>>to drive the pager motors in an XOR fashion, it ought to be easy enough to
>>produce such a ball that tends to move towards light using an inertial
>>drive vaguely similar to what you describe.
>yep, would be very cool if it worked: I think it is hard to tune it to
>actually role into the direction of the highest light-intensity.
>>Perhaps one day I'll get around to building one...
>Tell me ... I would like to hear about it.
---------------------------------------------------------------
jab
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