Subject:
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Re: Mechanical pneumatic piston
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 10 Oct 2003 04:59:21 GMT
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Viewed:
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1626 times
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In lugnet.robotics, Steve Baker <sjbaker1@airmail.net> wrote:
> Mike Thorn wrote:
> > At 11:38 AM 10/9/2003, you wrote:
> >
> > > >
> > > > Nope. Worm gears are not an integral number of studs long. They are about 1/4
> > > > of a stud short. Not enough for a small pulley (1/2 bushing).
> > >
> > > I'd be very interested to know the reason why LEGO chose to make the
> > > worm gear
> > > so short :-(
> >
> >
> > Yes, it seems rather odd. It really wouldn't have affected the design of
> > the gear at all. Just extend the spiral another fraction of an inch.
> > Simple, really.
> >
> > If it's right that they're about 1/4 or 1/8 stud short, you ought to be
> > able to line up 4 of them and stick in a half bush.
>
> The end of the helix on one worm gear lines up exactly with the start
> of the helix on a second worm gear. If the gears were a quarter stud
> longer, they wouldn't have this useful property unless Lego also changed
> the pitch of the helix.
>
> However, if they did that, then either:
>
> a) The teeth would have to be a bit wider apart - and it wouldn't mesh
> properly with other Lego gears.
>
> b) They'd have to change the slope of the helix which would mean that
> one revolution of the worm gear wouldn't be an exact sub-multiple
> of the number of teeth on the gear it's meshing to - and it would
> be very hard to calculate nice exact gear ratios. Also, the slope of
> the gear's helix is fairly critical to it functioning as a worm gear,
> you don't have much 'wiggle room' here.
>
> They had to compromise on one of those properties - and the exact length
> of the gear was obviously the thing they decided to give up on.
If you look at the 1x4 rack (or any of the other sizes, for that matter) you'll
see that actually there is more slop available than you'd think. The gears mesh
with them fine, The worm gear similarly could have been stretched just a tiny
bit, and it would still have worked okay.
--
David Schilling
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Message has 1 Reply:
 | | Re: Mechanical pneumatic piston
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| (...) The gear rack has an advantage in that the teeth are parallel to the pinion gear's teeth. That ain't the case for the worm gear. The pitched worm interfaced to a pinion with normal straight teeth eats up most of the slop that you normally get (...) (21 years ago, 11-Oct-03, to lugnet.robotics)
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Message is in Reply To:
| | Re: Mechanical pneumatic piston
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| (...) The end of the helix on one worm gear lines up exactly with the start of the helix on a second worm gear. If the gears were a quarter stud longer, they wouldn't have this useful property unless Lego also changed the pitch of the helix. (...) (21 years ago, 10-Oct-03, to lugnet.robotics)
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