rotary to linear converter 13

[nelsonk11]

I need a way to convert rotary motion to linear motion just like a rack and pinion, but it can't be a rack and pinion or a ballscrew. Anybody have any ideas.

 

[GregLocock]

A drum and a piece of string?

I think you need to ask a slightly better question.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[ivymike]

crank-slider?
hydraulic pump and pistons?
pulley and string?

 

[John2004]

I think some type of bar linkage or a disk cam with a translating follower would be the simplest, but much would depend on the loads, speeds, and what it is that you are moving and/or doing. Perhaps and electronic cam or servo system ?

A lead screw system is another fairly simple option for rotary to linear translation.

 

[BrianPetersen]

Need some more information on the application.

How big, how much force, how accurate, is there contamination, is there lubrication, does it need to back-drive or does it need to resist back-driving, does it need to transmit linear force in both directions, etc.

 

[hydtools]

Scotch yoke

http://en.wikipedia.org/wiki/Scotch_Yoke

Ted

 

[dvd]

An automobile?

 

[eromlignod]

Sprocket/pulley & belt/chain.
Cam & pushrod.
Slider crank.
Four-bar linkage.
Drum & cable.
Hydraulic pump & cylinder.
Ratchet & pawl.
...

Don
Kansas City

 

[unclesyd]

Here are two some what different approaches, the rolling ring from Amacoil and the belt drive slide from Techno Inc.

http://www.amacoil.com/index.htm

http://www.techno-isel.com/tic/Catdas/Voyager01.htm

 

[bigBboris]

Push-pull chain

http://www.schubkette.com/e/Introduction.html

 

[nelsonk11]

A few more details seem in order. The need is based upon a valve actuator which has an approximate mass of 4 grams, needs to move .400 inch in approximately 20 msec. Positioning accuracy should be to .001". The killer requirement is that it must be able to return to a default position in the absence of power. The rack and pinion is perfect except for the backlash of the gear set. To eliminate this would require more force and consequently watts than are available for this battery driven device as well as reducing overall speed. Power cannot exceed 10 watts. Duty cycle may be as high as 75%. By the way, reliability is paramount since this is a life support product. Thanks everyone for your assistance. I'm new to the post and appologize for any breach of protocol.

 

[unclesyd]

Adding to the post by BigBboris here is the Serapid push pull chain we used on our conveyer lines for 2000 lb synthetic fiber cans.

http://serapid.com/gb/accueil1.html

 

[gt6racer2]

Why not use a solenoid w/ spring for return on no power ? Even better, if the load trying to push the valve back is low you could use a latching valve so you're not constantly energising the coil.

 

[eromlignod]

Could you use a rack & pinion with a spring-loaded anti-backlash pinion?

Don
Kansas City

 

[MikeHalloran]

The real killer requirement is the 20ms.

Takes a lot of voltage to get a solenoid up to full current in that kind of time.



Mike Halloran
Pembroke Pines, FL, USA

 

[IRstuff]

I don't get your 75% duty cycle number. Move in 20 ms and retract 6.7 ms?

TTFN

FAQ731-376

 

[nelsonk11]

75% duty cycle is 20msec to position and immediately 20 msec to return then pause 12msec. The chain idea is good, but way too big, this package must be in a profile of < 2"x2" x 5". It also can't be just a solenoid since it needs to be proportional.

 

[nelsonk11]

The rack and pinion is probably the best, however, our challenge is to not use this design if possible.

 

[IRstuff]

Is this a school project?

TTFN

FAQ731-376

 

[alansimpson]

Voice coil actuator with servo amp. Could be expensive and steep learning curve.