Linear actuator repair ??

[Mr_fixit]

Anyone ever repair a linear actuator?. I have one that I broke. I have an idea to fix it, but I'm looking for advice. Especially if anyone ever repaired one .
The motor works fine . It appears that the nut thingie on the ball rod thingie is stripped or broken. I think I might be able to fix it?

I took the larger tube off that covers the hydraulic cylinder looking thing that has the screw inside. Inside I found a smaller tube and a screw that looks like a jack screw of most small car jacks, but the diameter was larger than a car or van screw . AT one end of the tube had 2 crimps. Between these crimps I'm guessing that there must be some nut type thing that rides along the screw. The hydraulic cylinder looking shaft slides up and down the screw, and it not supposed to. Is there a shear pin maybe? a nut that's broke? The cylinder won't slide apart from the screw.

If I could get one of these nuts, which I think must be between the crimps, I'd cut between the crimps, replace the nut thing and weld the thing back together.

Does anyone know what I'm trying to say and how these things work at this level? Thanks.

 

[larry_g]

Did you break it by overloading it? If so that would have pushed the nut above the crimp.

That surely looks like an acme screw so yes it would have a nut that follows it. When you say that the shaft slides along the screw does it feel like the threads are gone in the nut or the nut is disengaged from the shaft? If you pull the shaft to full extention does the nut jamb in the shaft and then seem to screw down the acme screw if you rotate the shaft? I believe that you are correct that the nut is held by a crimp and if the crimp has let go then its just a matter of reafixing the nut to the shaft. If the threads are gone from the nut then You've got a bigger fix on your hands. Me I think if the threads in the nut were good I'd extend things to full extention and then give the rod a few love taps on the crimped end and see if the rod would come off the nut.

good luck. I know that Mcmaster Carr used to sell acme screws and nuts so maybe parts there but would probably be machine to fit. One t hing I don't see t here is how the rod is prevented from rotating? Do they rely on the rod ends to do that ?

lg
no neat sig line

 

[Mr_fixit]

It feels like the threads are gone completely, it's very loose. But I can't feel any loose parts rattling around. Nothing fell out either. And it won't pull apart.

I was hoping maybe that there was a shear pin holding 2 1/2 nuts together and one stayed and one sheared and maybe would be stuck in the grease at the far end of the shaft.

When it stopped working I was using at as a power angle on a quad plow, and I hit an immovable object pretty hard. Something moved. And then everything did.

Yes, the pins at the ends hold the shaft from rotating.

 

[Mr_fixit]

I found the nut. It's in the picture, bottomed out, near the motor end. It's plastic, so I didn't know it was the nut.. To find the nut I had to I cut the bottom crimp off, pulled out a washer. Couldn't find anything else in the tube except a washer thing. That's when I realized it wasn't in there. The washer fit on top of the nut, The nut is supposed to fit the tube only one way becasue the nut & washer have like a keyway cut into them. It fits in the tube and is locked in when it slides in the crimped tube keyway.

I put the nut & washer where they belong, cut a large washer in half, and welded it back to the tube where the crimp used to be. Fixed.

Your advise means a whole lot more now, after it's fixed. thanks.

That's what happened. The nut jumped out of the tube.

 

[larry_g]

Glad to hear you figured it out. Did you fix it so that it will blow apart again when it hits a hard object? Fix it to good and the next problem may be more serious. Is there a shear pin or bolt in the system that is supposed to prevent these shock loads from busting the cylinder? May should consider it.

lg
no neat sig line

 

[Mr_fixit]

No , this fix IS probably too good. This linear actuator did work a couple years before my screw up. I got this part from a wheel chair van ramp, so I'll also keep my eye out for another one to use as a spare. It probably only cost about $20 bucks.


That and a couple hours of wiring/welding got me a real handy power angle.


Or maybe the next time it breaks I'll probably hook up some small hydraulic cylinder & pump like on a regular power angle plow.
The linear actuator works well, but it's a little slow for what I'd like.. There's no shear pin. I don't think it was designed to pop out , I think that's just what happened.

If it's overtaxed, there is a system that clicks , if you try to stress it beyond its 250 lb rating.