Alt-BEAM Archive

Message #05943



To: beam@corp.sgi.com
From: "Mike Kulesza" mikekulesza@hotmail.com
Date: Thu, 02 Sep 1999 16:16:13 GMT
Subject: [alt-beam] IDEAL GEARMOTORS


During my 2 month vacation in europe it popped into my mind that i have a
small cube shaped(about 1cm x 1cm x 1cm) gearmotor manufactured by LEGO. I
just hope that these can be ordered from LEGO. At 5V, it has really high
torque and about 30 rpm.

I'll post detailed numbers soon.

______________________________________________________



5944 Thu, 02 Sep 1999 09:18:58 -0600 [alt-beam] Re: hUFO goes online! beam@sgiblab.sgi.com Senior Ben Hitchcock wrote:
>
> >From: Senior
>
> >I'd like to clear things up, I was a bit unorganized in this email.
> >Ben argues that you feel a larger force when in a car when you make
> >a tight turn with a short radius than when you make a large, sweeping
> >turn with a large radius. This is correct. So he says, how does a larger
> >diameter result in a larger force (The principle of hUFO), when I have
> >just shown that a smaller diameter results in a larger force when I'm
> >racing?
>
> *chuckle* I KNEW this would set the cat amongst the pigeons. The last time
> this topic was aired, it brought such a huge flame war that I dared not
> reply after my initial few postings. As the list has been pretty quiet
> lately, I thought I might liven things up a little bit ... :-)

Eh heheh now now lot's not start this into a flame war. Or maybe I
should
tell myself...

> >My answer:
> >When you make a tight turn at 120mph, your going to feel a much larger
> >force than a nice, easy sweeping turn. However, when you're dealing with
> >rotating circles, it's different. On hUFO, his motor mantains a constant
> >speed. Therefore, anything attached to that motor with a small radius
> >will travel slower linearly than something with a larger radius, because
> >the shorter radius results in less ground to cover. Follow me? The
> >radial
> >speed is constant, but the linear speed increases as the radius
> >increases,
> >resulting in a larger force. (Taking a wide turn at 10mph is a lot
> >easier
> >than at 100mph).
>
> I'm very glad that your physics is up to the task of describing the motion.
> Last time, we tended to go around in circles (excuse me, couldn't help that
> one!).

Hahahahahaah good one :)

> I really don't want to get into a flame war here. I also don't want to
> debate the possibility that newton et. al. were wrong, just because the
> person doing the arguing doesn't have enough physics to argue the point
> properly. What I would like to see is a lighthearted discussion on why this
> particular form of motion will/will not work. It seems that some people
> believe this engine will produce a net force - and I am sceptical.
>
> Last time the discussion aired, I offered anyone who could send me a working
> prototype the money to buy patents. No-one came forth.
>
> What the list eventually settled at was a form of motion called "scooching"
> I think it was called.


I still don't recall this one. Is it based on the same principle os
hUFO?


> Anton Eriksson summed it up nicely today:
>
> ---
> The hUFO-"robot" is not particulary efficient, because a lot of energy is
> used just for rotating a weight in the air.
> What the machine actually does, is a similar effect anyone can try with
> his/hers
> chair; slowly accelerate your upper body forwards, then rapidly stop and
> change
> the direction. This way your chair will move a bit forwards.
> What really happends? When slowly accelerating, the force against your
> movement
> is the frictional force, which keeps your chair from sliding backwards, and
> when you rapidly stop and change the direction, the force at that moment
> (impulse) overrides the frictional force and the chair will move.
>
> On the "hUFO", the weight works similarly. Just draw a timing chart of one
> cycle, with the weight's position marked out...
> The machine would probably work much better (with a better efficiency) with
> an
> accelrating linear motor.
>
> Of cource you can always test for yourself by making a vacuum container with
> a "hUFO" floating on magnets and seeing if it will move forwards. It won't,
> well actually it will but it will also move backwards abaout the same
> amount.
> ---


Whoa, was this message only to you? I never got it!
It is quite inefficient - that motor is spinning very fast,
and if it were connected to a wheel or even fan it would
zoom past hUFO. I definately see his point. Hmmmmph :)


> Well put! I imagine that the hUFO works on a similar principle. It is
> perfectly valid in the contest, and is certainly an interesting and
> innovative form of motion. It is certainly different to your conventional
> photopopper. Remember those spiders with long wire legs and a pager motor
> in the middle? When you turn the motor on, the whole thing shakes like
> crazy and 'jiggles' forwards slowly. There is no trickery involved, just
> the tips of the legs are bent backwards so that there is less resistance to
> a foot when going forwards than backwards.
>
> Okay, now back to the discussion. I don't intend this as a personal attack
> on anyone, I would just like to see this matter resolved one way or the
> other. I have $50 US for the first person to prove to my satisfaction that
> the net force involved here is real.
>
> Allright, back to the physics:
> You say that the motor maintains the weights angular velocity around the
> shaft. I can accept that.
>
> You also say that for a given angular velocity, a weight a long way out from
> the centre would pull more than a weight a short distance from the center.
> I can accept that also.
>
> The problem with this machine, as I see it, is that you have to change the
> speed of the weight twice a cycle. Say the weight starts off as being close
> to the center. You spin it around a quarter turn, then push it out a bit.
> But since the motor maintains its angular velocity, the weight must speed up
> to maintain that rotation. If the motor spins at, say 1 revolution per
> second, then the weight must go 90 degrees around the shaft for every
> quarter second that passes by.
>
> So the weight speeds up. How? It must be pushed faster somehow, but by
> what? the motor shaft? Okay, so the weight gets accelerated outwards by
> the motor shaft - which PUSHES THE MOTOR IN THE OPPOSITE DIRECTION. So the
> motor, while flinging this weight out to the distance, gets itself pushed
> backwards. Then the weight completes its distant quarter turn, in which
> "the force is larger" and so presumably pulls the motor back towards it.
> This is fine. I can accept that. The weight, now at a large velocity, must
> be slowed down for its leisurely trip around the back of the shaft at a
> close distance. How does it slow down? It pushes the motor in the opposite
> direction.
> Finally the weight does its slow quarter turn, and pulls the motor back a
> bit.
>
> What does all this add up to? Well, the weight must push against something
> to change its velocity, that's for certain. Try standing on rollerblades,
> with your feet parallel, holding a weight. Move the weight forwards
> suddenly, and you will find that you will move backwards. Move the weight
> back towards you, and you will move forwards. Note that in both cases, the
> centre of mass of the system WILL STAY STILL. This is the crucial point
> here. You can't get a net force on an object unless you push on something.
> This is because the centre of mass of the system has no force acting apon
> it. You can try shaking the weight back and forth, and watching your feet
> wiggle in the opposite direction to the weight. Or you can try to become a
> human force machine, by swinging the weight around, close to your body
> behind you, and out at arms reach in front of you. You will probably start
> moving forwards when pulling the weight towards you, and then go backwards
> when pushing it away.

I understand all of this, and it makes perfect sense. There's on thing
though:
I agree that the weight will slow down the motor as it goes out, and
speed it
up as it comes in. Oh do you mean that the slowing down as it goes out
will
not let the larger diameter make a larger force, and the speeding up as
it
comes in will make a large force even though the weight is close, cuz it
has
good speed. Anyone know the relationship between radial speed and CFG
force?
I'm assuming it's linear.

> So to try out your engine: Place the whole assembly in an upturned
> ice-cream container in the bath. Make sure the water is still, and turn the
> motor on. Hold the container so that the device can spin up to speed, point
> it at the other side, and let it go. Time how long it takes to get to the
> other side.
>
> Now do the same, with the device pointed the other way. Time how long it
> takes for the machine to go back to the other side of the bath.
>
> The ice cream container must be symmetrical so that the resistance forwards
> is the same as the resistance backwards.

I will do! After school of course. Couldn't miss school! :)

> Now please let's be rational about this. If it works, then I will gladly
> eat my words and send the $50. But judging my the postings last time, I
> think my money is safe.

What if I jsut faked it though? :)

Kyle



5945 Thu, 02 Sep 1999 16:30:46 GMT [alt-beam] Micromotor beam@corp.sgi.com "Mike Kulesza" You can buy that nice gearmotor through the LEGO website (www.lego.com).
It's part #5119, and it's called a micromotor.

Goto the lego website, pick service, then technic, and then from the drop
down menu pick 5119 micromotor. There is also a picture of it there.

______________________________________________________



5946 Thu, 2 Sep 1999 12:24:34 -0500 [alt-beam] Re: IDEAL GEARMOTORS "Richard Caudle"
content-transfer-encoding: quoted-printable


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-----

Mike Kulesza wrote:

>it popped into my mind that i have a small cube shaped(about 1cm x 1cm x 1=
cm) gearmotor manufactured by LEGO. I just hope that these can be ordered f=
rom LEGO. At 5V, it has really high torque and about 30 rpm.<

Hey! It's about time someone else mentioned these jewels! They're all I u=
se on my walkers. You can see them in the My Robots section of my BEAM pag=
e.

www.geocities.com/~frankendaddy/BEAM.html

They cost $11.00 each and can only be ordered from the LEGO shop at home ca=
talogue! I'm considering selling my Scratchy walker series for about $80.0=
0 each. If anyone's interested, shoot me a shout and I can get to it. Tha=
t includes the PCB, parts, and instructions. There's a lot of variation th=
at you can get with leg configurations. Super cool at a steal of a price! =
I'm planning on starting a hobby robotics company, so help out if you can!=
! =


Richard Caudle
richard@cqc.com

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content-transfer-encoding: quoted-printable



>
www.geocities.com=">http://www.geocities.com/~frankendaddy/BEAM.html">www.geocities.com=
/~frankendaddy/BEAM.html
 

They cost $11.00 each and can only be ordered from the =
LEGO =

shop at home catalogue!  I'm considering selling my Scratchy<=
/EM> =

walker series for about $80.00 each.  If anyone's =

interested, shoot me a shout and I can get to it.  That incl=
udes =

the PCB, parts, and instructions.  There's a lot of variation that you=
can =

get with leg configurations.  Super cool at a steal of a =

price!  I'm planning on starting a hobby robotics company, so hel=
p out =

if you can!! 

 

Richard Caudle








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