Electric motor appears to be jammed

[gremlin_59]

Hi. This is the first time for me!! Hope someone can assist me. I need some advice about my Electra Beckam PK200 table saw. It suddenly stopped while i was using it. There was no warning, I've cleaned it off and stripped off the front arbour/bearing assembly. The motor spindle still, will not turn. I'm thinking it means a new motor assembly. Any one recognisee my described fault? Thanks Graham.

 

[Pete Robinson]

Hi, In order to be of any assistance it would be helpful if you could be a little more specific, ie: when did it jam, what were you doing at the time (cutting 2" stock), when was the last time you used it (has it been standing for a while) as they say, every little helps!!!

 

[gremlin_59]

As requested a little more detail.... When the motor stopped i was ripping 1"clear pine. The saw had been used regularly prior to it coming to a sudden stop. there was no "warning symptoms". I've tried to turn the motor spindle without the arbour/bearing on, it will not turn in either direction.
Hope this helps with your diagnosis

Regards Graham

 

[ivan]

Possible ways to jam a single phase motor:

1/ jammed cooling fan (easy to check for small offcut, not very likely tho' from original post
2/ cracked ball in ball bearing (some fitting skills needed but cheap to replace
3/ loose (and now terminally damaged) centrifugal switch inside motor - but your sawbench motor may not have this feature.
4/ Local motor overhaul (rewind) specialist from yellow pages will replace bearings if you don't want to (but if it's Chinese with poor quality control, the windings could be totally knackered)

All ways round, careful dismantling for inspection is needed before shedding too many tears!

 

[Pete Robinson]

Does it hum when you turn it on like it is trying?

 

[Rich]

Hi Gremlin, are you saying that the motor is siezed? or are you saying that it wont turn when power is applied, if the latter it may just be a case that a thermal overload switch needs resetting, if the former, quite often at work, a standby pump siezes and I have to get a pair of grips on the shaft and give it a good sharp twist and away it goes, is it single or three phase? I would be most surprised if a sealed for life bearing siezed up just like that. I will be interested to know the outcome of this dilemma, Regards Rich.

 

[gremlin_59]

Yes..It does hummm when i press the start button. (Sort of a straining noise) It hums very briefly then cuts it self off. I'm confident there is a physical obstruction stopping it from rotating.

Graham

PS. Why do things break just when you need them most. On the positive side.. i've never used my radial arm saw for anything other than cross cutting until this happened :shock:

 

[Rich]

Gremlin , it sounds as if there is an "offcut" wedged between the blade and the blade shroud, or if it,s three phase then it,s phasing which could mean a rewind for the motor.
Regards Rich.

 

[gremlin_59]

Thanks for all the suggestions. I will be removing the motor for a closer inspection tomorrow evening. I'll post my findings.
In the mean time thanks.
Graham.

 

[Pete Robinson]

Without seeing it first hand it sounds like bearings. Try removing the motor, remove the cowling or fan guard, if there is nothing obvious then I would say this indicates a problem with the bearings. Don't despair though, this is a fairly inexpensive and a relatively simple job to replace them.

If it is bearing failure and you want to have a go, there are usually four long bolts which hold motors together, remove these and you should be able to remove both housings, one at each end, these housings should retain the bearings, remove these and take a close look as there will be a number on the bearing, take them to you nearest bearing supplier and they should be able to sell you some new ones (bearings are usually really cheep!!). Replace the bearings with your nice shinney new ones, bolt it all back together, replace the motor, job done!! Saw good as new!!

Well this may sound like more work than you want to take on and will probably ask yourself if will all be worth it but at the end of the day what have you got to loose!!

Let me know how you get on!!

Pete

 

[Digit]

Without seeing it first hand it sounds like bearings.

It does indeed. Saw dust and resin from Pine could bring a Challenger tank to a standstill! Worn bearings normally signal their approaching demise by becoming noisy, but a broken bearing will beat any known brake for stopping a motor.
Is this a brush motor or an induction motor?
If a brush motor it might be, (hopefully not) a damaged commutator, (means a new motor).
If you haven't got a compressor I would recommend that you get one, they are about the only way to remove dust from motors and switch gear. (But use a mask!)
What ever the cause the motor has got to be stripped. If you get problems I'll try to help.

 

[Taffy Turner]

PS. Why do things break just when you need them most.

First law of Engineering I'm afraid - see my signature for details!!

Taffy

 

[Digit]

The 3 golden rules of engineering:-
1) It always breaks when you need it most.
2) It works better if you plug it in.
3) If all else fails, read the instructions.

Thus speaks an experienced engineer! :lol: Too true!
But I sometimes question No 3. The way the Chinese and Japanese can mangle English is incredible.
Recently my son acquired a new battery for his motor bike, courtesy of Taiwan, the acid was insufficient to fill the battery to the full line so was obviously concentrated, so we topped up with distilled water, emptied the whole mix into a plastic container then redistributed the now diluted acid back into the cells.
And we still can't make head nor tail of the instructions and neither can anyone else!

 

[Taffy Turner]

Yes - 10 years working shifts in the steel industry can engender a certain cynicism I'm afraid! (That was when we still had a steel - or indeed any kind of manufacturing - industry obviously!!).

Ah - the joys of reading an instruction manual written in Chinese and translated word for word by an Italian-speaking Hungarian with a dictionary.

I have a Fox bench morticer, which I was only able to assemble by ignoring the instructions completely. Having put it together, I still could not make sense of the instructions even when I had the fully assembled and working item in front of me to refer to! :shock:

The safety instructions were priceless - "Do not place finger under end when in useful"

Glad they pointed that out then!

Taffy

 

[Digit]

The fun really begins when you find you got two thingamies and a wotsit left over. :lol:

 

[gremlin_59]

Thanks for the humours replies.
I will not be able to dismantle the motor until i aquire a set of security screwdriver bits. The manufacturer has assembled the motor with cap head style pins. The head of which has eight points. (similar to T25 size, but with extra points) So i'll not be playing any further until i've been down the local tool store. Never mind. I can still investigate the full potential of my Radial arm saw. (Positive mental attitude) I will not mention the cursing in the workshop!!

Graham