# Small Linear Actuator



## Cogsy (Feb 2, 2016)

I need a smallish ~4" travel linear actuator and I'm wondering if anyone knows of a common source they can be repurposed from, for cheap of course. I've seen them on ebay for around $60 from China but with the Chinese New Year and shipping I really don't have the time to wait.

While I'm at it, I think these things have set rates of travel. Is there a way to alter them so I can vary travel speed at will?

Thanks for the help.


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## Brian Rupnow (Feb 2, 2016)

Hi Cogsy--if they are driven off a DC motor, you should be able to put a speed controller (potentiometer) on the wiring to control the speed at which the actuator extends or retracts.---There are many aftermarket sources for these things out of USA, but you are on the wrong side of the world. I don't know of anything that uses them that you might find in a wrecking yard.---What are you going to do with it?----Brian


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## Swifty (Feb 2, 2016)

Old electric reclining chairs may be a source for actuators.

Paul.


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## Brian Rupnow (Feb 2, 2016)

Okay Cogsy--now you're going to owe me---I had shut off my computer and went upstairs to bed, and lay there thinking of where I had seen electric linear actuators. I remembered, so I have plodded back downstairs and rebooted my computer to tell you where I HAVE seen what you need.--There are a host of different mobility devices to move disabled people in and out of bathtubs, on and off the toilet, and as Paul points out, to elevate their chair to help them stand up. I actually designed a machine to assist a disabled friend of mine last year.--Also, check out adjustable hospital beds, dentists chairs, and barbers chairs. .Hope this helps. Now I'm going back to bed.---Brian


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## ninefinger (Feb 2, 2016)

Look at treadmills - the ones with electric adjustable incline.  Should be near the right amount of travel.  I just opened mine and it has one.
Mike


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## Wizard69 (Feb 3, 2016)

Cogsy said:


> I need a smallish ~4" travel linear actuator and I'm wondering if anyone knows of a common source they can be repurposed from, for cheap of course. I've seen them on ebay for around $60 from China but with the Chinese New Year and shipping I really don't have the time to wait.


There is an endless variety of such actuators.   Unless you specify what you want to do, choosing one will be difficult.  


> While I'm at it, I think these things have set rates of travel. Is there a way to alter them so I can vary travel speed at will?
> 
> Thanks for the help.




You can get slides that are pneumatic, air over oil, stepper driven, linear motor drive, hydraulic, even steam driven if you look hard enough.    Probably a lot of variations on all of those.   Speed control depends upon the chosen method of drive.


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## Griffin (Feb 3, 2016)

Electric car seats.?


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## Cogsy (Feb 3, 2016)

Thanks for the tips, I'll start keeping an eye out for treadmills and mobility equipment, and I'll check electric car seats at the wreckers too. (and Brian I will reward your efforts with an ice cold beer next time I'm in Barrie)

I should have specified that I need an electric actuator, so it will be DC. I recently built a manual injector mechanism to force toothpaste (and similar liquids) through an expanding 2mm x 2mm matrix for a university research project. I used cup type seals for sealing and made it manually lever operated. It works perfectly but for the next stage of experiments I need to apply constant force, although I may want to adjust the speed of injection. So I figure an actuator is my best bet. We're hoping to get a grant by the end of the year but for now we're having to use our own funds and as a poor student I need cheap options.


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## Blogwitch (Feb 3, 2016)

You can't get much cheaper than a length of threaded rod and a matching nut brazed into either a belt sprocket or a gear and driven from the side by a small electric motor using either a gear or belt. Or drive the thread with a motor and the nut doing the pushing or pulling, doing it this way, can produce a more compact unit as the nut and thread can be inside of a tube. Threaded rod is available from 2mm upwards so you can make it as small or large as you need.

We used to make a few of them to fit into model boats to move stuff about. My largest one was to pull up a small daughter boat up a ramp onto the mother ship, about 10 inches of travel, all controlled by limit microswitches, very simple and failsafe. 

John


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## BrianS (Feb 3, 2016)

Like other members said I don't know the exact dimensions or type of actuator you are looking for but maybe this would give you some ideas:
[ame]https://www.youtube.com/watch?v=HN1xSIgnwDA[/ame]

Hope this helps...
Brian


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## Woodster (Feb 3, 2016)

An old motorised Satellite dish would be a good source for a DC linear actuator. It must be an old one though, as modern set-ups use a Horizontal polar mount with a DiSeq controlled rotary actuator.


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## GLCarlson (Feb 3, 2016)

ninefinger said:


> Look at treadmills - the ones with electric adjustable incline.  Should be near the right amount of travel.  I just opened mine and it has one.
> Mike


 
SurplusCenter sometimes has these. About 1000 lb push, 6" travel, 110vac, reversible. Take-offs or extras from a treadmill, I think. About 25 bucks. If they have them, buy a few...great for can crushers, other misc uses.

Or, heck, just build one. A hunk of Acme 6tpi 1", a plastic gear or two, and a 24-110 v motor. Chunk of 1" plate for the gear train. Not very hard.


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## Cogsy (Feb 3, 2016)

Thank you all for your great suggestions - I love this forum and how helpful everyone is.

Thinking about it more, with everyone's ideas in mind, I think the best/cheapest/easiest way to go is to drive a piece of all thread rod with a cannibalised battery drill. I can install limit switches at each end of travel and use the variable speed as is. Then I just make a driven piston with a nut inside and some sort of guide pin arrangement so the piston doesn't spin.

Now having read through the thread again, I see I am copying exactly what Blogwitch already posted - so I owe you a beer too John! I thought I had at least come up with the limit switch idea myself...

I'll post a pic or two of the finished mechanism when I get it sorted.


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## S3MIH3MI (Feb 9, 2016)

Not sure how small of footprint your looking for but Princess Auto in Canada has a large selection of them. 

http://www.princessauto.com/en/search?No=15&Nrpp=15&Ntt=aactuator


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## Cogsy (Feb 9, 2016)

That sort of actuator would be perfect. Here in Western Australia though I have to import them from China myself to get pricing like that and I don't have the time for that unfortunately. Once this device is fully sorted though, I'll likely make a mark 2 with more professional components (as long as we get our grant funding).


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## Wizard69 (Feb 10, 2016)

You could always get something like a wine bottle cork press and slap a motor on it.    Even something like those cheap 1/2 ton imported arbor presses could be giggled up that way.    Another possibility is one of those battery powered caulking guns.

You make this sound like a project with a temporary time frame so investment in expensive actuators might be counter productive.   Especially if you just need to squeeze a tube.  My thinking here is to have something that is useful after the project / research is finished.   All three of the ideas above would be very useful after completing this research.


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## rodw (Feb 18, 2016)

What about an air ram? Would be easy to calibrate your constant force. There are a few second hand on ebay....


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## Cogsy (Feb 18, 2016)

I like the look of them but I know nothing about them, like adjusting the stroke length, etc. Plus I've now found it needs to be super portable and at times will be run where I probably wouldn't have access to an air supply.

I just got a crudely made actuator to move under it's own power today, using a chopped up 24V cordless drill. I have to add microswitches to control it and pretty it up some and it should be good enough for now.


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## Nick Hulme (Apr 5, 2016)

If you want to make it as short as possible look at the design of old automotive screw jacks, several nested threaded rods allowed them to give more lifting motion than their initial height, 

 - Nick


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