Bandsaw motor not starting

[Terryjb]

I am having difficulty sorting problem on my Elektra Beckum BAS315 bandsaw.
On start up I get a humming noise, but motor does not spin up.
I can get it going by pushing the blade with a stick- it then functions perfectly.

I found and read an earlier topic suggesting replacement of capacitator and decided to do the same.
I emailed support at Metabo (they now I think have bought Elektra Beckum) and they promptly responded and agreed that it was probably the correct diagnosis and gave me the part number and source for a replacement. I got this yesterday and fitted it today , but to no avail.
The motor still hums, but does not spin up, and now cannot be encouraged into to life with a push.

Went back to Metabo who now suggest that it may be the motor. I will tomorrow put the old capacitator back on and hope that the push start works again while I try to find a permanent solution.

In the meantime I would be pleased to accept advice from anyone with a better understanding of how electric motors work and any suggestions on how to proceed.

Many thanks

 

[Dibs-h]

Bob is your man - PM Bob9Fingers if it's urgent. I suspect he'll be along shortly.

Dibs

 

[Argus]

.


As it runs after a push and assuming that you don't have two dud capacitors one after the other, the motor may have (some bigger motors do, some smaller ones don't) a centrifugal switch to switch out the start windings when the motor reaches run speed.
Sometimes these things either jam up up or require the contacts being cleaned.
Basically it's just a set of insulated electrical contacts strapped to a set of weights, attached to the rotor shaft.
If it's jamming, a quick squirt of WD40 up the rear end may do the trick

Otherwise, to sort this out, (if it does have a switch), it is a strip-down job.

.

 

[Blister]

Sounds like a capacitor fault

Not expensive to replace :wink:

 

[Digit]

If the motor used a mechanical switch you could often hear a click when the motor ran down after being switched off. Was this so? If so can you still hear the sound? If not the switch is stuck in the 'run' position and a strip down will be needed as Argus stated.
BTW, don't buy capacitors from machine suppliers, nor bearings either, the price rockets.

Roy.

 

[Terryjb]

Thanks all for advice.
Metabo gave 3rd party supplier details for replacement capacitator which pleased and surprised me- price was OK at £6. But it hasn't fixed problem.
There is no obvious 2nd capacitator that I can see.
The centrifugal switch sounds an interesting possibility.
I will look again in the morning and see if putting the original capacitator back in gets it running with a push.
Thanks again
Terrjjb

 

[9fingers]

Please DONT put WD40 or any other fluid on the centrifugal switch mechanism.
Whilst this might free up a stuck switch for a while, it will later turn into a sticky mess and jam up once more.

What is the power rating of the motor and what is value of the capacitor - look for a number followed by mfd or uF

Post back with an update when you can.

Bob

 

[Terryjb]

Thanks Bob
Power is 0.55 KW
Plate on motor says Cb 20 mF

terry

 

[9fingers]

Hi Terry,

This motor power is right in the middle of the range where there may or may not be a centrifugal switch.
generally for economy reasons they try and design out the switch but starting torque is reduced.

Take the blade off and see if the motor will spin start. try it in both directions. As the motor is slowing down, listen for any click or start of a rubbing noise and report back please.

Bob

 

[Terryjb]

Thanks Bob
I hope to follow your instructions shortly.
As it does not currently spin up at all with the replacement capacitator I have checked by part number that the correct one was supplied - it was. However I have a new concern as I note that it is rated at 12 mF. I think I will therefore, before proceeding, refit original capacitator and see if I can get back to where I was.
Will get back to you later today.
terry

 

[Terryjb]

Hi Bob
Refitted original capacitator.
Removed blade
Push started in both directions
No click heard in either direction on slow down
Slight rubbing noise heard - I think- in each direction
terry

 

[9fingers]

OK, a rubbing noise as it slows down suggests a centrifugal switch.
The fact that you can spin start in either direction means that the starting circuit is not having any influence.
This is causes by
1) open circuit capacitor ( not likely in this case as you have tried a new one)
2) defective contacts on centrifugal switch (if fitted and in this case possibly so)
3) open circuit starter winding - bad news very likely not to be repairable but usually rare.

A few motors have the switch behind the fan but outside the main case but most are inside.
If you can see how the motor goes together, then carefully take the back end off very carefully
Take photos and mark all the wires with where they go especially if you have more than one of each colour - there are no standards of colour coding.

If you can't see how it comes apart, take a few photos and post here or email them to me
[email protected]
Do you have a multimeter capable of measuring resistance and AC volts up to 250 minimum?

Bob

 

[Terryjb]

Thanks again Bob
I have to go to a tutorial soon which will take up most of the afternoon, so may not be back with photos until tomorrow.
Nothing to indicate that there is an external switch. I think the back should be easy to remove and I think also that I have a suitable multimeter.

Terry

 

[9fingers]

OK Terry,

When I say external, that type have the switch behind the fan cover and behind the fan so unless you are part way through dismantling, it would be regarded as internal. The easy thing is that you don't have to open the main motor casing.

Bob

 

[Terryjb]

Bob
Sorry I misunderstood
I have just removed the cover to expose fan
Behind fan is cast iron plate secured by 3 bolts
Rotating fan by hand definitely produces rubbing sounds

Running out of time now, but very grateful for your help. Will try to get photos when I have removed the back plate perhaps this evening
Terry

 

[9fingers]

Ok Terry,

I'll be online this evening and on and off during the day.
I'm waiting for my timber supplier to confirm my order is ready for collection so kicking my heels a bit.
Might even have to tidy up the workshop this afternoon :shock:

Out of interest, what are you studying?

Bob

 

[Digit]

Might even have to tidy up the workshop this afternoon

Now, now, now! Careful Bob, those sort of actions can lead to all sorts of mental problems! :twisted:

Roy.

 

[Terryjb]

Archaeology. Distance learning with Leicester Uni. Just one of my retirement projects

 

[9fingers]

Hi Roy,
I'm currently doing the sympathy bit sitting with SWMBO who is feeling c r ap at the moment with a heavy cold but daytime TV is starting to affect my mental state anyway.

Give that I will have to plane up some sawn timber (when I get it Grrr!) I'll need the space so a mild tidy up is probably needed as well as empty the cyclone ready for the flood of shavings.

Bob

 

[Digit]

Archaeology. Distance learning with Leicester Uni. Just one of my retirement projects

http://www.google.co.uk/url?sa=t&rct=j& ... _A&cad=rja

This group might interest you, if you can put up with me there as well as here.

Roy.