Subject:
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Re: Ping-Pong Ball Shooter
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 13 Jan 2000 22:20:45 GMT
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Original-From:
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Stephen P. Gibbons <steve@aztech+StopSpammers+.net>
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Viewed:
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638 times
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I prototyped a catapult design several months ago that used two motors to
"cock" and fire/launch a rubber-band driven ball-launcher.
The loading/firing sequence was something like:
1) load ball on catapult.
2) power motors in reverse at low power for n seconds
3) power motors in reverse at medium power for n more seconds
4) power motors at full reverse for n more seconds
5) launch by powering motors at full in the forward direction (the motors
and rubber bands work together at this point.)
Steps 2-4 help avoid losing the loaded ball.
By carefully playing with the rubber-band geometry, I was able to "tune" things
so that the the motors in reverse at full power could barely overcome the rubber
bands and maximize the energy delivered in launch mode.
More motors and rubber bands should give more distance/oomph.
I constructed the catapult arm and ball-holding basket from technic axles in
order
to reduce the mass of the arm & basket.
I wasn't entirely satisfied with this design, since the catapult arm was
relatively long
(not lending itself to mobile cat-attackers) and auto-loading of the balls
seemed
difficult without a lot of bulky support structure.
--
S
The WordMeister wrote:
> Hey, Dave, good to hear from you ...
>
> Do you want me to forward all the Ping-Pong shooter messages so far?
>
> I've thought about a catapult, but it presents some engineering
> problems--but this is worth exploring; I've seen catapults over and over in
> pictures and advertising and whatnot from TLG. The slingshot might work
> (although it has some interesting issues as well), but both would be too
> large, I think, to make practical. I've also thought about a rotary sling,
> such as the one David used to kill Goliath.
>
> Since I have 4 motors, I'm going to stick with concurrently developing the
> circular batting device (my first design), and the wheels-as-accelerators
> device (my second design). I think both are viable after some more
> tinkering.
>
> --Doug
> -----Original Message-----
> From: Dave Johnson <djohnson@sirius.com>
> To: lego-robotics@crynwr.com <lego-robotics@crynwr.com>
> Date: Thursday, January 13, 2000 3:53 PM
> Subject: Re: Ping-Pong Ball Shooter
>
> > The WordMeister wrote:
> >
> > > I want to thank the list for such excellent suggestions. Here's a progress
> > > report:
> > Somehow the original post didn't make it to the list for me, and I don't
> > see it on lugnet either...but this is a great project!
> >
> > A couple ideas that may or may not have been put forth yet (and may or
> > may not be useful):
> >
> > A catapult sort of thing, either motor-driven or rubberband driven (in
> > the latter case, you'd need to "cock" it with a motor - a "pull back and
> > let go" sort of gearing mechanism could work for this, perhaps). This
> > would look really cool, but would be bulky, I suspect.
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Message is in Reply To:
 | | Re: Ping-Pong Ball Shooter
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| Hey, Dave, good to hear from you ... Do you want me to forward all the Ping-Pong shooter messages so far? I've thought about a catapult, but it presents some engineering problems--but this is worth exploring; I've seen catapults over and over in (...) (25 years ago, 13-Jan-00, to lugnet.robotics)
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