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Use a motor to rotate a nut on a fixed threaded rod?

I am creating a time-lapse dolly, and at the moment I am working on the drive system. One thought was to use a threaded rod+nut to propel the cart, and I want to look in to this method because it seems fairly versatile. So I would have a taught, fixed threaded rod running through the middle of my 8"x6'x1" track. The cart sits on top of that. I have the motor and the cart pictured below.

How can I get this motor to spin a group of nuts (attached to the cart) so that it propels the cart along the threaded rod?

Picture of Use a motor to rotate a nut on a fixed threaded rod?
IMG_6832.JPG
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orksecurity5 years ago
Simpler to spin the rod, of course, with the motor off the dolly rather than on it. Simpler to wire too; you don't need a wiring harness that flexes as the platform moves.

But if you want to spin the nut (there should probably be only one per threaded rod, to avoid the risk of them getting out of synch and jamming against each other -- and might want to be only one drive rod for the same reason) -- you need to embed it as the hub of a gear or belt pulley or something else that the motor can apply driving force to, and you'll need thrust bearings of some sort to transfer its sideways pressure to the cart without undue amounts of friction. (Said thrust bearing might be as simple as an UHMW plastic washer...)
rickharris5 years ago
This is a small linear actuator - the thing your looking at making - The motor is connected to the threaded rod - in this case by drilling a hol in the rod but a simple tube connector would do - The the yellow plastic part has a nut trapped between the parts running on the rod. When the rod turns the nut and the yellow plastic travel

I can draw details if you like.
DSCN0692.jpg
A set up like this would do. i think.
Dolly.jpg
Perfect, saved me drawing it :)
:-0 made a few!
particularly important is the rubber hose bit.
frollard5 years ago
Its a wonderful plan - but its a lot harder to rotate the nut and still extract that torque as linear motion than it is to affix the motor at one end and just rotate the threaded rod, having the nut fixed on the trolley.

There are varying grades of thread -- involving their diameter, courseness (threads per inch), and machining accuracy. If you just want to move something slowly any old threaded 'redi-rod' will do. If you need precise, repeatable stuff then you need to step up to specially machined rods.

Basically, use a few inches of nylon or other plastic tube and use a pipe clamp to attach the tube to both the threaded rod and your gear-motor. Pass the rod and lock-nut it to some bearings to give you some strength, and just have a fixed nut on the cart.
sblaptopman (author)  frollard5 years ago
Okay so I already have the threaded rod, and there is a lot of dip. How could I have it rotating without that dip (Taught but still able to rotate) Is there some sort of washer that would allow me to do that?
Supported at both ends with the support of the cart it should be fine - it doesn't need to be super tight.

You can have it rest on a plastic support in the middle so that when the cart is at the end it isn't rubbing on the ground, but when the cart is in the middle the threaded rod is lifted off the plastic - so the two don't hit each other.
sblaptopman (author)  frollard5 years ago
Also, if it's not too much to ask, could you make a quick drawing of what you mean with the rotation of the rod?
iceng5 years ago
Here is a rotating nut inside out stepper motor..... A
steppeRod.JPG