Induction motor problem

[Robin GrahamParticipant @robingraham42208]

[Robin GrahamParticipant @robingraham42208]

Hi. I've recently bought (new) a Jet floor-standing pillar drill. The machine seems fine (no quill slop, acceptable spindle runout), except that it's noisy and there's quite a bit of vibration. It looks it is the motor at fault – running it on the bench it walks about and makes a racket the like of which I've never heard before from an induction motor. Sounds like it's going to shake itself to death. I know next to nothing of a practical nature about electric motors, so I'm hoping someone here might be able to advise on the likely cause of the problem, and the feasibility of fixing it. It is a single phase 1kW 4-pole motor.

TIA, Robin

[V8EngParticipant @v8eng]

How recently did you buy it and have you contacted the suppliers?

[David JuppParticipant @davidjupp51506]

Maybe check for simple stuff like a bent output shaft – but agree if it is new, take it back and complain.

[Robin GrahamParticipant @robingraham42208]

V8Eng – Bought a couple of months ago from Axminster on a clearance sale, but only just got round to unpacking it. If I contact them they'll probably offer an exchange (they're good like that) but then I've got to crate the thing up (original packaging now destroyed) and the replacement might not be as good in the accuracy department – these machines are variable from looking at reviews. I'd rather just fix it if it can be done. But you're right, I should contact them and see if they'll just replace the motor – I doubt they will though.

Regards, Robin

[John Stevenson 1Participant @johnstevenson1]

Offer them the choice, either supply new motor and you will fit it or come and collect and deliver new one.

Chances are they will take the first option as being the cheapest.

[Phil WhitleyParticipant @philwhitley94135]

I was Gifted (?) a small chinese bench pillar drill, on which the motor was awesomly noisy, especially for it's tiny size, they are in fact very poorly made, usually out of balance to some extent, and also poorly wound, which is where a lot of the noise actually comes from, and there is a good chance that the replacement will be just as bad. If it is a single phase AC induction motor, see if you can source one locally that is British made and will fit the available space.

Phil

[MuzzerParticipant @muzzer]

Some of the Xmas cracker Chinese motors are spectacularly crap on the noise front. A good quality well balanced TEFC motor should be almost silent in unloaded operation. I bought a single phase motor off Craigslist from some new lathe / mill thing that had been converted to 3-phase and fitted it to my pillar drill to liberate a VFD for my mill. I might as well have fitted an engine to it. What with the racket, the lack of variable speed and the availability of the mill, I pretty much stopped using the drill.

It's difficult to comprehend how they could make something that simple be so noisy. The bearings must have been part of the equation, along with (im)balance.

[Jesse Hancock 1Participant @jessehancock1]

I would do as David Jupp suggests, making sure you check the belt because it may have a bad join in it, (lumpy) causing it to throb. Then the pulley castings. If so ask the supplier to replace the belt and or pulley(s). Also you ought to clamp it down as there's a lot of forces acting high up there?

Edited By Jesse Hancock 1 on 24/02/2015 06:12:04

[Ian S CParticipant @iansc]

I haven't come across a "crap" Chinese motor of that size, they do run a bit hotter than a lot of older motors, but seem to be quite well balanced, maybe the duds go north. If the bearings are a bit slack it will vibrate.

Ian S C

[CirclipParticipant @circlip]

Have mainland Chinese manufacturers started to epoxy impregnate motor windings yet? Used to be a problem with Taiwanese suppliers initially.

Regards Ian.

[John Stevenson 1Participant @johnstevenson1]

Depends who you buy off Ian.

One of the biggest motor manufacturers in China is TEC who make good motors and are very highly regarded.

Brooks is also wholly owned by the Chinese now and again they turn out decent motors.

The motors that do suffer are the ones usually fitted to machine that have to fit into a price bracket as the motor is one of the most expensive pieces and it's the easiest one to cut corners on.

[Robin GrahamParticipant @robingraham42208]

Thanks for all your comments. It sounds like there are OK Chinese motors and crap ones, and particularly in view of JohnS's remark:,

' The motors that do suffer are the ones usually fitted to machine that have to fit into a price bracket as the motor is one of the most expensive pieces and it's the easiest one to cut corners on.'

it seems likely that this is a crap one. The machine is certainly built down to a price.

I had hoped that it might be an easy fix, eg bearings, but sounds like it is probably deeper rooted.

I'll try Axminster for a replacement motor, but not got high hopes of getting anything better second time round.

I think I want to keep the machine, so I'll probably be looking for a replacement motor. If I can't find anything British to fit there are plenty of TEC ones on the bay and elswhere which which would fit, and it sounds like they are OK quality (thanks John). With a decent motor I think it'll be a nice enough machine. And OK for for the money even with the cost of a new motor – would have been less happy if I'd paid full price!

Jesse, thanks for your comment – I'm sorry if my original post wasn't clear, I've taken the motor off the machine, and it was the motor alone walking around the bench. The whole machine walking would indeed be scary! My first though was belt / pulleys as well, but there is obviously a problem with the motor.

Thanks again to all for helpful info, Robin

[CirclipParticipant @circlip]

Used to be first fix (Second really after emptying sand from castings) on all initial Taiwanese imports, change motor and put a good one on. Down to people like Sir John educating suppliers that paying a bit more for good gear pays them dividends. Just need to convince the great unwashed likewise.

Regards Ian.

[Robin GrahamParticipant @robingraham42208]

To wind this thead up (probably), took the motor round to John S's Lodge where he stripped it down to look for any obvious faults. Didn't find anything glaring, and, sharp salesman that he is , offered me a replacement at a price I couldn't refuse. The new motor is now on, and although it doesn't exactly purr, things are much improved, and the machine is now quite useable. The quill / spindle assembly is actually pretty good. Of course the problem shouldn't have arisen in the first place, and I'm sure Axminster would have happily replaced the machine, but from what I've read here and elsewhere I'd have likely got one just as bad or worse back.

Should have bided me time and waited for a used Fobco or whatever to come up locally!

Old motor is undergoing further investigation, just out of interest – not bearings, not rotor balance so must be windings. Hmm.

Regards, Robin

[Mike PooleParticipant @mikepoole82104]

I rewound a motor and managed to connect a coil up the wrong way, it sounded rough as the proverbial, we used to test them before sealing the windings as once sealed to dig out the connections would be a wretched business that would most likely wreck the new windings, a quick check soon found my error and the motor ran sweetly. I would be surprised if a motor could be finally shipped with a fault of this nature but maybe it could be.

Mike

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