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Some photos of what you've tried so far would help a great deal.
I was wondering if it would be possible to see how cloesly you're matching
up the worm gears to the rack gears, theoretically, it should be possible,
but if you're using more than one worm gear against a rack gear, the
construction has to hold it in place and the worm thread on the worm gear
needs to be precisely aligned with the line of the rotational thread of the
worm gear next to it or your worm gears will be out of rotational sync with
each other - unless you're only using one worm gear on each rack part.
Cheers ...
Geoffrey Hyde
"Bill Ward" <bill@wards.net> wrote in message news:IvKJHv.1xLK@lugnet.com...
> (cross posted to
> <http://www.brickpile.com/2006/03/03/scissor-lift-in-technic/
> 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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"Geoffrey Hyde" <g.hyde@bigpond.net.au> wrote in message
news:IvKtn1.16vD@lugnet.com...
> Some photos of what you've tried so far would help a great deal.
http://www.ozbricks.com/bobfay/orthogli.htm
http://www.ozbricks.com/bobfay/yaxis.htm
http://www.ozbricks.com/bobfay/newmill.htm
These may give some ideas. I made a nut out of two 8 tooth gears and used a
string of worm gears as a lead screw, but I cannot find the picture. The
best configuration would be that of a scissors jack for a car. Hard to do
with Lego.
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Those are some interesting milling machines there Bob. How do you think
they'd look if built in the newer studless beams? Do you think there'd be
any insurmountable rigidity problems building with studless beams?
I noticed you had one long worm gear going through a paired set of
oppositely rotating 16t/24t gears. I guess this was to keep the worm gear
stable while the gears just held it in place without moving?
http://www.ozbricks.com/bobfay/Pict0127.jpg - this pic here, on the
"newmill" page is what I'm talking about.
Cheers ...
Geoffrey Hyde
"Bob Fay" <rgfay@earthlink.net> wrote in message
news:IvL0y3.24MI@lugnet.com...
>
> "Geoffrey Hyde" <g.hyde@bigpond.net.au> wrote in message
> news:IvKtn1.16vD@lugnet.com...
> > Some photos of what you've tried so far would help a great deal.
>
> http://www.ozbricks.com/bobfay/orthogli.htm
>
> http://www.ozbricks.com/bobfay/yaxis.htm
>
> http://www.ozbricks.com/bobfay/newmill.htm
>
> These may give some ideas. I made a nut out of two 8 tooth gears and used
> a string of worm gears as a lead screw, but I cannot find the picture.
> The best configuration would be that of a scissors jack for a car. Hard to
> do with Lego.
>
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"Geoffrey Hyde" <g.hyde@bigpond.net.au> wrote in message
news:IvLB88.1D9t@lugnet.com...
> Those are some interesting milling machines there Bob. How do you think
> they'd look if built in the newer studless beams? Do you think there'd be
> any insurmountable rigidity problems building with studless beams?
>
> I noticed you had one long worm gear going through a paired set of
> oppositely rotating 16t/24t gears. I guess this was to keep the worm gear
> stable while the gears just held it in place without moving?
>
> http://www.ozbricks.com/bobfay/Pict0127.jpg - this pic here, on the
> "newmill" page is what I'm talking about.
>
>
> Cheers ...
>
> Geoffrey Hyde
Actually the gears cannot rotate as they are meshed with each other. This
causes them not only to support the screw, but act as a nut creating linear
motion for the slide.
I am not sure how well the studless beams will work for my interests. When a
cutter hits the material it is cutting, Lego reminds me that it is a toy.
The studs do make rigid structures possible. I hope to gain some new
experience when the NXT comes out in the Fall. I will surely have to change
my thinking.
Bob
--
http://www.ozbricks.com/bobfay/
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In lugnet.technic, Geoffrey Hyde wrote:
> Some photos of what you've tried so far would help a great deal.
I'm sure they would. Sorry I just haven't taken any yet. But this thread has
given me some great ideas to try...
> I was wondering if it would be possible to see how cloesly you're matching
> up the worm gears to the rack gears, theoretically, it should be possible,
> but if you're using more than one worm gear against a rack gear, the
> construction has to hold it in place and the worm thread on the worm gear
> needs to be precisely aligned with the line of the rotational thread of the
> worm gear next to it or your worm gears will be out of rotational sync with
> each other - unless you're only using one worm gear on each rack part.
The worm gears are aligned carefully, and they seem to mesh fairly well, but I
think ultimately rack gears and worm gears in LEGO just aren't a good match. I
think part of my problem is that there is enough space along the axle for it to
deflect away from the rack, giving room for the teeth to skip.
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"Bill Ward" <bill@wards.net> wrote in message news:Ivo9xE.1oBF@lugnet.com...
> In lugnet.technic, Geoffrey Hyde wrote:
> The worm gears are aligned carefully, and they seem to mesh fairly well,
> but I
> think ultimately rack gears and worm gears in LEGO just aren't a good
> match. I
> think part of my problem is that there is enough space along the axle for
> it to
> deflect away from the rack, giving room for the teeth to skip.
They do not mesh. We need a rack like this ///////////
not ||||||||||| .
Bob
--
http://www.ozbricks.com/bobfay/
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