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In lugnet.technic, William R. Ward wrote:
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(cross posted to
my blog and
BayLUG Mindstorms mailing list)
Have you ever tried building a scissor lift in LEGO? I’m working on a project
that calls for that kind of mechanism to lift it up, like those food service
trucks at the airport. It is based on an “X” shaped arrangement, which, like
the two parts of a scissors pivot at the middle. By bringing together the two
bottom (or top) ends, the top is lifted into the air.
The approach I took was to use Technic worm gears (like a screw) with a rack
gear on it. By turning the worm gears the rack gear should move along its
length, which moves the two bottom ends together, elevating the top. The
problem is that LEGO gears just aren’t up to the load this places on them,
and the teeth skip. I motorized it, gearing down the motor to get more
torque, but the gears would rather skip than lift the weight.
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Haven’t actually built one, but one other possibility may be to use string
rather than gearing directly.
How many scissors are there in your lift? On the real ones I’ve seen they often
have a hydraulic cylinder going from the bottom scissor to the top one, you gain
some mechanical adveantage doing it that way, but it may be difficult to emulate
in LEGO.
Let us know how it goes.
ROSCO
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In lugnet.technic, Ross Crawford wrote:
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Haven’t actually built one, but one other possibility may be to use string
rather than gearing directly.
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On a winch? That’s an intriguing idea.
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How many scissors are there in your lift? On the real ones I’ve seen they
often have a hydraulic cylinder going from the bottom scissor to the top one,
you gain some mechanical adveantage doing it that way, but it may be
difficult to emulate in LEGO.
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Just one scissor.
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In lugnet.technic, William R. Ward wrote:
| |
In lugnet.technic, Ross Crawford wrote:
| |
Haven’t actually built one, but one other possibility may be to use string
rather than gearing directly.
|
On a winch? That’s an intriguing idea.
|
Update: I ended up using string and it worked beautifully! Well, it has weight
distribution issues (one side goes up before the other) but I’ll work on that
later...
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