Rotary to Linear Help

[binfordw]

Thought I would ask here for ideas,

I'm looking for a way to convert rotary motion into about 12-13" of reciprocating travel, with a fairly heavy load- 200-250lbs? in one direction only. In the past I used a rather large pulley setup to accomplish this, but Im wanting to redesign things into a small size and do away with large and costly pulleys. I've been thinking about it for awhile now but cant seem to come up with a design that would work.


I know this isnt alot of info to go on, but if anyone has any suggestions I'd love to hear them.

Thanks

Ben W

[neilw20]

Have you ever thought of using a pneumatic cylinder?

[Al_The_Man]

If you do consider pneumatic and want to deliver stroke-to-stroke consistent speed timing and positioning, then I would look at using an air over oil pneumatic system.
This has the advantage of a hydraulic system with lower cost and less noise than all hydraulic.
If this is just simple point to point positioning, then travel limit switches should be quite accurate.
Al.

[binfordw]

Well It needs to be powered by 120v AC so it can be used in a variety of places. I was pretty sure there was a way to pull this off without using large pulleys, but I havent been able to come up with anything yet.

[Al_The_Man]

Then a linear actuator is probably the answer, these are self contained units with a motor and gear box on one end, probably as portable as you are going to get.
Search ebay with Linear Actuator for an idea. They also come with settable limits.
A heavier duty option is Nook Ballscrew Jacks. http://www.nookindustries.com/Jack/JackInch.cfm
Al.