# Thompson Saginaw ball screw



## Paul40 (May 29, 2011)

Not really a tractor question, but I'm sure there are a few small garden tractors around that use these.

I have a Thompson Saginaw ball screw to lift my snow blade. Until recently, it worked great. Now it will not hold the blade in the raised position. The blade slowly lowers, just from the weight of the blade.

I opened and removed the powerhead, but everything seems to be fine in there. There is nothing in there that resembles a brake. I can't seem to find a way to open the lifting mechanism, enclosed in a sealed tube, to see if I can see anything that might be amiss. Judging by the outside appearance and shape of it, I have a hard time believing that there is some sort of brake in there, but I'm willing to be corrected/enlightened.

Has anyone ever had any problem like this? What did you do about it?

I'm planning to switch over to a hydraulic system, but that will have to wait until I don't need the blade on an almost daily basis, plus I don't have heated workshop to get out of the -20° weather to do the work. In the meantime, it's a bit of a p.i.t.a. to have to keep the blade in the "up" position by frequent use of the push button.

Any idea would be appreciated.

Paul


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## sixbales (May 18, 2011)

Howdy Paul

Welcome to the tractor forum.

A worm gear cannot slip down on its own. You must have some power leakage to the motor. I would suspect the switch. Try disconnecting the power to the motor and see if it drifts down.


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## Paul40 (May 29, 2011)

Hi sixbales

Thanks for the reply. It's definitely not a problem of stray power.

A worm should have no problem turning a gear, especially one with an 18:1 ratio and very little friction because of the balls. I could give you a number of examples where I've had a worm driving a gear, and one is when a vehicle with non-power, recirculating ball steering hits an obstacle, such as a curb. It's fun watching the steering wheel spin, less fun if your thumb happens to be in the way.

T/S specify the static load capacity on their units, which leads me to believe that there is some sort of brake, other than the friction of the worm, or the gearing between the motor and worm. I've managed to slow it down some, by relocating the pivot location, and filling the gear head with grease, but it still goes down. I'm working around it by giving it a short "up" power shot every so often, but still a p.i.t.a.

Oh well, only about three more months of snow

Cheers, Paul


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