Chinese hoist motor problem

[alan frostParticipant @alanfrost17805]

[alan frostParticipant @alanfrost17805]

I repair everything I can (probably like most on here) but am puzzled by the construction of a (presumably) Chinese motor which drives my cheapo hoist . These are available (250Kgm) from £50 to about £100 and unless you are willing to pay 2X or 3X this , they are all that seem to be available.

Symptoms are a buzzing as if trying to start but no movement. Dismantled it and I'm puzzled by the construction. From the gearbox end we have end cap ,endcap bearing, armature, then a quite strong compression spring fitting over a splined section of the shaft, the splined section fitting into an aluminium (?) disc retained in the casing by the winding and other end cap. The disc about 1/2 inch thick floats freely in the casing and is internally splined to rotate with the armature. Then of course comes the other bearing which screws !!! into the endcap, after which a large Nylock nut screws onto a threaded portion of the armature. This is followed by the fan and fan housing.

Both bearings rotate freely and perfectly when unassembled but when assembled, possibly due to the friction caused by the compression spring which presses between the armature and the aluminium disc the armature is very stiff to turn, so stiff in fact that not enough starting torque is generated hence stalled "buzzing". No amount of adjustment to the locknut or screwing the bearing tighter or looser ( remember this bearing screws into the end cap) has enabled me to find a low friction position)

Overall the construction appears to be quite well made.

Any of the other recyclers from this site had one of these unusually constructed motors (in my view) to bits and found the secret of freeing up the armature. It all worked very well for several weeks before the fault developed.

[I.M. OUTAHEREParticipant @i-m-outahere]

Hi Alan.

Without a photo it is difficult to make a suggestion but i would think this disk and spring are part of a magnetically released brake system .

When an EMF is present in the windings a magnetic field is created and could be used to pull or force the disk along the shaft alowing the armature to turn freely .

IAN

[alan frostParticipant @alanfrost17805]

Ian,think you may be right in that although difficult to see the face between the end cap and the disc there may be a ring of friction material around the circumference of the disc to give friction between the disc and end cap.

I had assumed the gearbox which gives a large speed reduction would in effect give enough braking due to the high gear reduction. I can't really investigate the disc further without extracting the windings whch I am loathe to do. Maybe some grease on the splines (avoiding the friction ring) would assist magnetic force in attracting the disc away from the end cap.

 

Will have another play tomorrow and if necessary will extract the winding to get a good look at the disc ,even if this is destructive (if I can't fix it I will be less loathe to risk destruction ) as knowledge gained this way might be useful if I ever have to repair another. Will report back.

Generally speaking I have been pleasantly surprised with how well made the motor appears altho its also true it has stopped working.

Chinese products seem to go pretty well for me with the exception of the highly stressed items such as angle grinders. compressors, SDS drills and now, hoists. Unfortunately practically all the reasonably priced of these items , indeed practically all available, appear to be Chinese made. These items for me are very occasional use items and I usually shy away from digging up one of my small bags of gold to pay two or thee hundred pounds for an occasional use item.

With machine tools where stresses are highest I tend to stick to older European or British machines but with the general handyman's workshop items there is n't much choice. A possible exception is Costco who tend to import a lot of more reasonably priced U.S products but one does n't get the choice of several product ranges there.

Rgds.

 

 

Edited By alan frost on 28/04/2012 23:36:09

[SpringbokParticipant @springbok]

Hi Allan

Do not have one of these but a mill that I have gave off the same symptoms and turned out to be a dirty/stiicking solanoid. maybe of minor help.

Bob

[alan frostParticipant @alanfrost17805]

All repaired and working, and back on duty hauling trailers full of infill back up a very steep garden slope. Well I did promise to report back. Fitted a new cheap Maplin DPDT switch (which was one problem ) and a weaker compression spring to cut down the amount of braking from the aluminium disc (still more than adequate) due to the high reduction gearing..

 

Quite tricky to repair as the "wiring harness" was a bit of a mystery until I realised the power cut switch when the hoist is fully wound in only has to work when lifting and is not wired to operate when winding out-fairly obvious when considering it as a complete hoist but baffled me for a bit when the motor was isolated on the bench. Have now received a bigger model but glad this one repaired as it saves me modifying the mechanical mounting.

 

If anyone is repairing acheapo  hoist , I feel i'm now fairly familiar with the innards of one. Reminds me of Italian engineering in that everything is done very cleverly in the cheapest way possible but it works well. (Give or take a low quality switch.)

Edited By alan frost on 01/05/2012 18:58:17

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