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 03:24:22 GMT
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Reply-To:
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Geoffrey Hyde <gdothyde@SPAMLESSbigponddotnetdotau>
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Viewed:
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6918 times
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"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.
> 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.
> To turn bevel gears 90 degrees you'll need a rigid framework to place the
> gears
> into. Lego has done this by using a series of 6536/32184 (see below) with
> axles
> joining the lot. The key here is rigid. Any flex where the two gears
> meet will
> result in slippage, so make use of the various 90 degree liftarms. Also
> the
> more teeth in contact the better the transfer of power. Use as big a gear
> as
> possible. The 12 tooth if there is not space, 20 tooth is better and the
> 36
> tooth best.
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.
> 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?
> If you are still going with the worm gearing, try replacing the 2 12-teeth
> bevels gears that form your 90deg turn with a 24-tooth & worm combo. If
> you are
> looking for strength you could put this inside the gearbox element, or
> make a
> pretty good gearbox with the triangles (2905 below) and two 6536
> supporting the
> worm shaft with the 24t gear in the middle hole.
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.
> 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.
> 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. ;-)
--
Cheers ...
Geoffrey Hyde
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