Subject:
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Re: Looking for a one-way motor drive mechanism that is foolproof.
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Newsgroups:
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lugnet.technic
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Date:
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Tue, 1 Feb 2005 12:58:42 GMT
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Reply-To:
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Geoffrey Hyde <GDOTHYDE@BIGPONDDOspamlessTNETDOTAU>
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Viewed:
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2949 times
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Well, I want to make sure that the drive mechanism doesn't accidentally try
to start the wrong way, and try to either feed material into the hopper
base, which is hard to clean out if I have to make it easily removable, or
jam and stall the motor unit.
A clutch gear will help of course, but a more preferential solution is not
to have to worry about it going the wrong way around.
"Brian Davis" <brdavis@iusb.edu> wrote in message
news:IB8E67.4Dt@lugnet.com...
> In lugnet.technic, Geoffrey Hyde wrote:
> Off the top of my head I can think of two ways, neither completely
> compact.
> One is to use the sliding worm gear trick, and take the two outputs and
> connect
> them to the belt in such a way so that if output A is engaged it drives
> the belt
> forward, while if output B is engaged it... drives the belt forward. This
> has
> the downside if gearing down a lot, but it should work. You could also do
> this
> with a differential rachet splitter and a torque-limiting gear or two, but
> it
> would be bulkier.
It doesn't have to be very compact, just compact enough that I don't waste a
lot of space with structural support for it - what footprint are we talking
about for it? It's got to sit on a baseplate anyway, and atm I'm building
on a 48x48 sized one.
> I'm not exactly clear on your idea here, but it presents a third way -
> central drive gear engages a second gear that can perform a half-orbit
> around
> the central gear. If the drive gear rotates CW, the second gear (with a
> little
> bit of shaft friction) on it's pivoting frame swings around CW with it
> until it
> hits a stop. With the frame blocked, the small gear acts as a idler
> between the
> drive gear and the output on the right. Similarly reversing the drive gear
> swings the idler gear around to the other side, where it hits a stop and
> acts as
> the idler gear on a 2nd drivetrain, which you can invert so it's output
> matches
> the first drive train.
> There may be more compact ways, but I'm not thinking of them at this
> point in
> the morning.
I know washing machine agitator gearboxes do something similar, at least in
function. I wonder if that can be replicated and adapted in LEGO? It does
bring to mind some sort of mechanism which has an extra gear on one side
which has the effect of reversing it, all it needs to do is be sure to make
the gear on the frame rotate one way or the other to start the engagement,
which is of course what you're talking about here. I keep going in
circles - or is that back and forth? :D
One thing, instead of relying on friction, could there be some cam-like
arrangement which would operate differently for each direction in question,
I'm not sure relying on friction alone is enough to make sure the drive
engages properly. I also wonder if a differential couldn't work somehow?
>
> Why do you need it?
As stated, to prevent jams or time-consuming dissassembly to retrieve parts
that have been forced into a mostly unreachable spot.
Cheers ...
Geoffrey Hyde
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