Acme pulley?

[PaulEsch]

I'm driving an axis with an Acme 10TPI rod. I'd also like to have the Acme rod drive a secondary axis (in parallel with the first) at a slightly different speed. So I'm thinking about a belt system with two differently sized belt pulleys to try and achieve the ratio.

What sort of thing can I attach to the Acme rod that can also accept a belt to drive the other axis?

And is there such thing as a variable pulley contraption that will let me adjust the ratio without changing out the pulleys?

Thanks,
Paul

ps. I'll post pics when all is done. Right now I've been fiddling with two motors and trying to sync their speed ratio, but that is just not working well enough. It became obvious to me that 4 turns of the Acme rod should equal 1 turn of the other axis, and timing two motors does not take enough into account (like start up, slow downs, etc.).

[PaulEsch]

Guess I'll reply to my own post...

I had some extra Acme nuts for the 10TPI rod. So I took a 3/4 particle board and cut a circle, then 2 plexiglass circles a little larger than the wood. Sandwiched between the two nuts it makes a great pulley. I'm actually using standard office rubber bands (size 64) to drive the pulleys and it is working very well.

My desired ratio was 4 to 1, so one pulley was about 4" and the other an inch.

My application is not critical to the millimeter, but rather the centimeter, so this worked out very well.

I now have 2 sets of pulleys working with 2 rubber bands to drive a fairly complex circuit.

Cheers,
Paul

[pippin88]

Paul, I'm interested in what application you needed this for?

Can you explain / post pictures?

[PaulEsch]

Paul, I'm interested in what application you needed this for?

Can you explain / post pictures?

I'll post pics/video once it is done.

Basically I am making a winder, but unlike normal winders I can not rely on the material to auto-place the next wind. In other words, the material will roll over the previous wind or leave spaces if not tight enough.. Unlinke a thick wire, which will lead the next wind due to its height.

So precision is important for each wind.

The material is 3/8" polyester ribbon. Think pom-poms. So I am winding the ribbon around a 1/4" aluminum rod and the edges must just touch, not overlap.

I have a 120v motor running at about 50v turning a pulley, which runs the 10TPI ACME rod. This provides the feed. Think printer head.

Then the rod also turns another pulley that runs at 1/4 speed which actually turns the aluminum rod. Think printer platen.

So there is a feed and a turning rod. As the feed moves along the ACME rod, the ACME rod turns the roller rod which rolls the ribbon on the aluminum rod.

From there I put the rod in a heat-setting oven to keep the curl.

Then the 18" rolled ribbon is cut into 3" sections for sale.

This is the crux of my wife's business. Selling the 3" sections on ebay.

I'm working to automate most of her manual labor.

Cheers,
Paul