Sunday, October 29, 2006


Lego Axis!

I attached my motor to the threaded rod on my Lego axis, booted up the software, and started it running; only to watch it spasm and without actually turning. Turns out, everything was way too tight for the little stepper motor to handle, and it just couldn't get the job done. (It did seem harder to turn than I remember, but I could still spin it by hand...)

Pulling it apart, I took out the drive nut and threaded the rod back through the Technic holes. Between the imperfections in the rod and snuggness of all the Legos, it actually gripped the legos themselves and drove back and forth pretty well (though I wouldn't trust it to be accurate without any actual threads in the legos). The first half of the video below is the Lego Axis running without the drive nut.

I moved the Technic pieces further apart, and worked the threaded rod back and forth through them until I was able to build up the supports, with the drive nut, and still have it move smoothly. I had to increase the distance from the nut itself, and I got rid of the two outer support guides.

To recap on the design: I've got a 10-24 threaded rod going through
the holes in Technic Legos. I've got 4 Technic pieces, with 2-4-2 spaces inbetween each, and the drive nut centered between the middle two. They're all attached to a flat piece, with the drive nut resting one of its corners in the center of one of the hollow round support pieces, which is attached to the underside of the platform. Attached to the bottom of all of that are the wheels (currently attached with two axis, though I'm not happy with those and I'm hoping to replace them with just the 1x2 round-+ axis pieces if i can find 4 of them!)

There's nothing to keep the axis 'on track', it's implied that the threaded rod will be supported on each end (probably by a technic brick on each end) and that those will be setting the 'axis' 'on track'...

There is a little bit of wobble, but it's tolerable, and it lessens/disappears if you slow it down. The video behind the link first shows the stage originally running without the drive nut, and then shows it with the above modifications and the drive nut.

Super cool! Welcome to the wonderful world of slightly crooked threaded studding rods. :-(

I had to confect a sliding joint that left the collar nut freedom to move normal to the axis of the studding rod before I could get steady movement.
you guys should really check out acme threaded rod:

6 feet = $7 + shipping.
Nice find, Zach. Good prices. I wish the darned things started in diameters smaller than 1/2 inch, though. :-(
Less than half-inch probably leaves it with too small a spring constant to be useful for a metal-cutting machine, and/or too little resistance to bending moments.
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