View Full Version : cheap source of linear activator here.

Your Old Dog
01-14-2009, 07:52 AM
Just wanted to make you guys aware that there is a cheap source of rather powerful linear actuator available to us at $69.00 an recently $59.00

I successfully used one to raise a heavy ham radio mobile antenna from stowed horizontal position to vertical. It moves the nut about 7" in 65 seconds. At the one extreme the actuator must overcome some serious mechanical disadvantage and does so with ease. I am using it on my bench with a metered 12V powersupply and it draws less then two amps in my application.

I'll post pictures when my project is complete and in the buff :D


01-14-2009, 08:00 AM
You can also drive around looking for people that have C band satellite dishes pointed north...

Doc Nickel
01-14-2009, 08:05 AM
Other option:

Most treadmills have a short-throw linear actuator as well. I now have a crateful of six or seven of them, ranging from a little, cheapy rack-and-pinion type with an open-frame induction motor, to a monstrous beast with a motor the size of a can of Foster's, a chrome-plated ram, and a foot of travel.

Most are simply an ACME screw with a shaft/tube/nut arrangement, and could easily be extended by replacing a (for example) 6" screw with a 3' (or whatever) chunk of ACME rod.

Since my big Rockwell Vari-Drive drill press has no rack for the table, I've been considering doing the old "electric camper jack" mod that was in HSM several years ago.

I figure if it's got enough beans to lift a 200-pound jogger and the treadmill itself, it ought to be able to lift a drill press table. :D


01-14-2009, 08:07 AM
Our OZ State Motoring Clubs and others have had them for quite while. Our local club (RACV) has them in a case with a 12v DC impact wrench - for changing car tyres.

I'd thought of buying a set for when my wife is driving on her own - but she prefers to call the RACV - which is sensible.

01-14-2009, 09:23 AM
I use the camper jacks on my snow plow for the angle drive and the scoop actuator. They are rated to lift a ton and to hold 2.5 tons.

01-14-2009, 09:35 AM
Ray...could you tell me how to measure the amp pull on a 12V motor?
I have the quill drive I built for my mill drill a few years ago. I used to use a car battery and a charger but never liked the idea. It worked fine but was cumbersome at best and the charger overheated a couple times when being run all day.
A good heavy duty charger is huge also.
I see some good looking 12V power supplies on Ebay that put out 12V @26 amps.
I'm betting this is enought to drive a 12V windshield wiper motor but I'm not sure how many amps it pulls during hard usage like drilling.

01-14-2009, 10:31 AM
Just wanted to make you guys aware that there is a cheap source of rather powerful linear actuator available to us at $69.00 an recently $59.00

The only problem is that the general rule of thumb on the various Internet forums is that anything from Harbor Freight with moving parts has a lifespan of less than 1 year.

I've been through 2 vibratory tumblers, 3 ultrasonic cleaners, and 3 purple paint guns and 2 rotary buffers, and I'm finding that the HF rule of thumb holds true :)

01-14-2009, 10:44 AM

Cut exactly three feet and six inches of regular 14 gauge house wire. Use that piece of wire to supply power to the motor along with whatever wire you normally use. Connect your multimeter to each end of the 3.5 foot piece of wire. Set the meter on the 2 VOLT range DC. It will read the amps directly as the numbers after the decimal. 26 amps will show as 0.26X with the X being tenths of amps. It won't matter which lead goes to which end of the wire, the only difference would be a minus sign that you may ignore. Using this method you can measure up to 200 amps at 12 volts.

Technical detail: 3.5 ft of 14 gauge is a 0.01 ohm resistor acting as a shunt aross the meter input. By measuring the voltage drop it gives the amount of current flowing.

PS: Did you get the copper?

01-14-2009, 11:16 AM
Thanks for the explanation Evan...now I know why I couldn't get it figured out before :(
Nope...didn't get the copper yet...I'll check the mail again today!
Thanks again!

01-14-2009, 11:38 AM
BTW, you can wrap up the shunt wire in a coil and put some clips on the ends (well soldered) and use it as a regular tool whenever you need to measure high currents. If you make the wire twice as long and double it with two pieces in parallel you can measure up to 400 amps. Good for checking starters and batteries.

Your Old Dog
01-14-2009, 10:09 PM
Lazlo, on the ultrasonic cleaner, leave it plugged in and make sure and use one of those computer spike cubes. My first one crapped out in days, the second one has been used over a year.

On the purple sprayer, you'd need a crowbar from Sears to get mine away from me :D My rotary tumbler is still working fine. Remind me not to loan you any of my tools !!

Torker, I won't buy a meter that does not have a 10 amp setting on it. Normally, you would just interrupt one of the leads of the device you want to measure and put the meter in series with that. I've never tried Evan's suggestion. I instead went out and bought a clip on amp meter and it gets some pretty good use, just got to remember it will only work on one wire so I made up 8" extension cord with all wires loose so I can get at them!

01-14-2009, 10:17 PM
Lazlo, on the ultrasonic cleaner, leave it plugged in and make sure and use one of those computer spike cubes. My first one crapped out in days, the second one has been used over a year.

That's about how long mine have lasted -- a year :) I took my last one apart, and the problem was that the piezoelectric crystal was vibrating itself loose from the underside of the stainless steel pot.

My rotary tumbler is still working fine. Remind me not to loan you any of my tools !!

I'm talking about the 5 lb vibrating tumbler. Do a Google search on "Harbor Freight Vibrating Tumbler Fire." We were joking about this at the last Austin metalworking club -- nearly everyone of us had the 5 lb vibratory tumbler catch on fire. The motors have sleeve bearings. After awhile the bearing seizes, and the motor catches on fire:

"Bought one from Harbor Freight when they first came out with them. The motor bearings burned out on the first one, replacement burned out, replacement burned out, replacement burned out. Got my money back and went to Cabela's and bought their brand for $5.00 more. Have used it 2 or 3 years so far with no problems, plus you can't beat their customer satisfaction, replacement for life."


"Although I like a lot of things at Harbor Freight, the tumbler just didn't work out. I went through three of them last year, before deciding to just return it. They would run for ~ 1 hour, then shut off. I assume the motor was over heating. When I contacted their tech support people, they told me they thought their supplier had worked that problem out, but I guess not. I even bought one of them at a different Harbor Freight store, thinking it must have just been a bad lot, but they all had the same defect. That's my experience with their vibratory tumbler."

MickeyD just suckered me into getting the new 18 lb tumbler, and it's made much nicer than the 5 lb model:


01-15-2009, 12:43 AM
Speaking of vibratory tumblers, why do machine shop suppliers ask an arm and a leg for these machines?
I've been using a large one from Dillon Precision (http://www.dillonprecision.com/#/content/p/9/pid/23660/catid/8/Dillon__039_s_CV_2001_Vibratory_Case_Cleaner__220_ v_Euro_)(reloading supplies) for years and I didn't have to sell the farm to acquire a quality unit with an absolutely astounding warranty. I'm not trying to drum up business for Dillon Precision but anything they sell has always been covered for life, and it doesn't matter if it is on it's fifth owner, it's still covered.
I've been dealing with these guys since the mid 80's and have always been looked after very well.
It always amazes me to see some of the big tool suppliers ask close to a thousand bucks U.S., for a machine that doesn't have the same quality.
Am I missing something here?