Subject:
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Re: Need to figure out how to get this motor unit attached.
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Newsgroups:
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lugnet.technic
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Date:
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Wed, 19 Apr 2006 12:03:01 GMT
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Reply-To:
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Geoffrey Hyde <{gDOThyde@bigpondDOTnet}saynotospam{DOTau}>
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Viewed:
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7519 times
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"Chris Orchard" <chris_orchard@+Remove+This+gjames.com.au> wrote in message
news:Ixyn0n.230B@lugnet.com...
> In lugnet.technic, Geoffrey Hyde wrote:
> >
> > "Chris Orchard" <chris_orchard@+Remove+This+gjames.com.au> wrote in
> > message
> > news:Ixy4C6.CyI@lugnet.com...
> > > In lugnet.technic, Geoffrey Hyde wrote:
> > > > http://www.brickshelf.com/cgi-bin/gallery.cgi?f=171364
> >
> > > I think the easiest way to turn gearing through use of the worm gear,
> > > however as
> > > others will point out a worm gear is not very efficient gearing down
> > > mechanism,
> > > also if this is run for several hours at a time, the meshed gears will
> > > grind.
> > > Wear is even worse if the worm is the final gearing, taking the full
> > > torque of
> > > the application. So use a worm earlier rather than later in a gear
> > > train.
> >
> > The worm gear pics that I loaded into the folder recently are for a
> > one-way
> > worm gear drive. This basically is so I can set the hopper on and forget
> > about what direction the motor has to turn in.
> One-way can also be done with an gear on the pivot of an arm meshing with
> an
> idler gear on the end that swings between two close gears. You wouldn't
> have to
> go through any 90 deg twists then. :P
First up, something about the quotation style seems to be getting screwed
up, I normally separate out different levels of quotation to mark them out
properly. Above is just an example where paragraphs are butting up against
each other. It also seems some linefeeds or carriage returns are causing
the indented quotes to wrap at their margins prematurely. It makes it kind
of hard for proper conversational flow, hope you can fix things! ;-)
As to the paragraph you wrote, I had to use the worm gear, as it eliminated
several complex gearing down sequences and I could just about drive directly
off the gears coming out of the worm gear itself.
> > > The most effective gearing down is via double bevel gears as the gear
> > > teeth are
> > > wider (more contact and strength, less pressure).
> >
> > Double-bevel gearing down is possible, but wastes power if you have more
> > than a few gears in the geartrain.
> I could be wrong, but I thought that the sliding friction of one worm was
> worth
> serveral straight cut gear reductions. Basically you picked a worm if you
> wanted the locking feature, or couldn't afford the room.
(Note: I fixed the paragraphs here on in as far as butting up to each other
goes ...) Well, it was a bit of both, but what you get in long geartrains
is what they call free play, or looseness in the gear trains, even with the
double bevel gears.
One comment on the most effective gearing down being via double bevel
gears - the teeth are wider but the basic tooth interface point is still
exactly the same. One can easily see this if you mesh a double bevel gear
with a normal gear, they only intersect at the centre tooth part of the
gear. I think a better aspect of double bevel gears is that you can put
them at right angles to each other and both will mesh with each other on the
side, which is something you simply cannot do with ordinary gears.
I don't know for sure that they would mesh with each other if offset so that
the beveled edges on the side were to be the only parts interfacing in a
straight line through the gears with each other, but I suspect it may be
possible, if not a little looser than having them in line with each other.
> > I actually found that the 12 tooth gears interfaced with the worm gear
> > pretty well, maybe had a few problems with slippage when reversing the
> > motor
> > direction, but since I'm just going to turn the motor on and let it run,
> > I
> > do not forsee that being a problem. My aim here is 'set and forget'
> > operation.
> Ok, I wasn't sure how much info to give or at what level, I erred on side
> of
> verbosity :) The 8 and 24 tooth work great with the worm in studless, but
> the
> 12t double bevel? Any chance of seeing the set up? I've never gotten a
> really
> good mesh using studless.
Here I made a mistake and wrote 12 tooth instead of 8 tooth. My apologies.
> > > Just as a side question, does anyone know how efficient the four-lobed
> > > pseudo
> > > gear is compared to bevels and worms?
> >
> > Which part ID # are you talking about here?
> 32072
> <http://www.peeron.com/pics/inv/custpics/thumbs/32072.1103860997.jpg>
They're actually a quite interesting gear, however, they have a lot more
free play than regular gears. They go good in situations where you want to
make sure something doesn't overtighten too much, such as a jaw on a grabber
arm.
> > What I was looking for was one-way drive, if you have a way to accomplish
> > this at a ratio comparable to worm gear reduction as shown, and in as few
> > parts, please do let me know.
> No, not in as few parts :)
> Have you tried mounting the motor vertically? you could use
> <http://media.peeron.com/ldraw/images/0/32009.png> to put the motors'
> shaft in
> line with the worm, then your "one way worm" goes through the 90deg for
> you.
> Once both axis of the input and output are in line, it should be pretty
> trivial
> to connect it through. I'd put an axle joiner on the motor so you can
> brace
> either side of the slip-gear/worm-input and move the worm closer to the
> conveyer
> inputs. As the worm floats anyway, it will only have to be mildly rigid.
I've actually got the motor mounted to the one-way drive, but I need a
little more work to get it mounted to the drive train, I used some short 2L
41677 on long axles to accomplish this. Works fairly well, along with some
small right-angle differential gears - I forget the name offhand, but
they're the small ones that go inside the differential gear housing.
> > > Other options include mounting the motor via 6536/32184 (below)
> > > Any way you go I'd make the turn before any gearing down.
> >
> > That mounting option might do but not for strength. And particularly not
> > for a studded motor.
> >
> > > Another question that arises is when the slip-gear should be placed in a
> > > gearing
> > > down train. I'd assume that the earlier you place it, more force is
> > > required
> > > (at the output) to stall the train. Is this right gurus? (Rosco et al?)
> >
> > I have seen from looking at gear trains that if one turns the little end
> > (the output which is driven slowly) considerable force is required to
> > turn
> > that axle slowly around while the gear train can speed up quite a bit at
> > the
> > input end. If slip gears should be placed anywhere, it should be where
> > there is likely to be a large amount of backlash in a gear train due to
> > stalling.
> I thought you'd want it so there was enough torque to drive your app, but
> if the
> output is stalled, not enough torque can be generated, before slippage, to
> cause
> damage. Is that what your saying about backlash?
That's part of what I'm saying. Slip gears (or clutch gears) as LEGO refers
to them, are basically a means of letting a motor turn without having the
motor burn out due to sudden stops. Check out the 8479 barcode truck
instructions on peeron for a better idea of how they used the clutch gears
to prevent the tipper's end of travel stopping the motor suddenly and
causing it to stall.
> > > All of these and more is possible, I'm afraid that the only way is
> > > through
> > > a bit
> > > of trial-and-error, but that is the "fun" bit of lego for me. :)
> >
> > I know what you mean mate, I've thrown out almost an entire galaxy's
> > worth
> > of theories, as the practical solution(s) yield to my inexperienced
> > building
> > skill. ;-)
> If the theory doesn't fit, just change it a little, then rebuild from
> scratch
> anyway ;)
I tend to do a LOT of the latter rebuilding from scratch. I may scrap a
design if experimentation with it gets to be too much of a hassle.
Cheers ...
Geoffrey Hyde
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