Subject:
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Re: Stress related breaking
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 7 Mar 2000 19:54:23 GMT
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Viewed:
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890 times
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in article Fr1ruG.MAA@lugnet.com, bisgaard at bisgard@forum.dk wrote on
3/7/00 2:30 AM:
> In lugnet.robotics, Clint Rutkas writes:
> > After working on my new robot Twitch, I've come up with some interesting
> > ways of overcoming problems like 2 motor outputs through a Turntable or how
> > to mount 6 motors in an area barely big enough for 4.
> >
> > But after getting Twitch fully built and in the phase of being tweaked, I've
> > rebuild his feet twice, and on my latest attempt, I've just cracked a 24
> > tooth gear. Wasn't a tooth, but the area where a peg would go in to the
> > outside of the gear.
I broke one of those once. I looked at it for a while, then cut off the
other three "prongs" around the axle hole. Now you can sandwich this gear
between two 2x4 plates with the holes through them (studs facing in towards
the gear). You have constructed an idler gear! I used it before we had
real idler gears or the new-style differentials.
>
>
> I think you have used the old 3648 24z gear (replaced in 1998) which I have
> cracked a few off. The new redesigned gear looks stronger than the old one
> around the centrum of the gear, since some of the holes have been removed, and
> I guess that it is a lot stronger than the old one (haven’t broke any of these
> yet).
>
> You can see them both at Jim Hughes’s Technica.
> http://w3.one.net/~hughesj/technica/technica.html
>
>
> > This makes me worry about further cracking of gears down the line. Anyone
> > know the amount of stress needed to crack the gear?
>
> I don't know the amount of stress taken but before the redesign came I used
> the crown gear 3650 in places with heavy load, they seem to handle it great.
> So if you use the 3648 for light load (in the start of the gear train) and the
> 3650 for heavy load I think you don’t have to worry about the gear.
>
> With very big gearing for slow raising of for example an heavy robot arm, you
> might consider using 2 gear on both axes so the connection area between the
> interfering tooth’s. By doing that you half the load on each gear and don’t
> risk breaking any gear (you might break something else with an gearing like
> that).
>
> An big problem with heavy gearing in my experience is that if you move the
> rotation between the load and the gear with an long axe, the axe get an
> permanent twist, the axe can still be used but it don’t look good with that
> twist in the middle. So use short axes if possible with heavy load.
I twisted some axles when I was building a robot arm a few years ago. The
solution I came up with was to forget about using torque on an axle to move
the arm. Instead, on the base I used the largest gear size and pinned it
down so it couldn't move. Then the arm used a small gear and "walked" it
around the big gear. It worked really well. Sorry, no pictures, though.
--
Doug Weathers, http://www.rdrop.com/~dougw
Portland, Oregon, USA
Don't spam me - I know how to use http://www.spamcop.net
"On a clear disk you can seek forever"
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Message is in Reply To:
 | | RE: Air Manifolds
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| Check out the following site for an incredible selection of pneumatic fittings (designed for the medical industry) that will probably lend themselves to the development of wonderful pneumatic Lego creations. (URL) fun! F'amos -----Original (...) (25 years ago, 16-Feb-00, to lugnet.robotics)
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