Fobco Star Single Phase Buzzing, struggling to turn. Intermittent fault.

[SenditSi]

Hi

Let me start by saying I'm very new to 1960's power tools and only have a basic understanding of what's going on here.

I've recently acquired a Fobco Star single phase and its worked perfectly untill last night. Switching the motor on, it's now buzzing/ humming, turning the pulley ever so slightly (a few mm of rotation at most) but not starting. It looks like it wants to, but just can't get the torque or power down to get up to speed. Do this for a few seconds and white smoke appears from the motor housing.

This is intermittent. I took the belt off and it ran freely. Switched power off and on a few times and then starts buzzing again (no belt this time).

Everything seems to spin very freely with no resistance. The pulley wheels are nice and smooth by hand. Belt seems to fit just right. Mechanically I can't see there being anything wrong. Anything that would hinder the movement of the spindle or the motors rotation.

Ok so it looks like a motor issue? I can't see any capacitors here. We go from the plug socket, to the switch, to the motor.

The switch is delivering power every time (creating the buzzing and slight movement) so I don't see that being a likely fault.

The motor I've opened up and all looks good to me. All connections are solid, no blackening of signs of arching at the terminals. To my novice eyes it all looks fine? Single Phase motor made by General Electric Co. LTD. of England.

I'm tempted to just source a replacement motor and go from there. But I'm wondering if anyone has any experience with such issues and if this may be an easy fix?

Thank you in advance

 

[Seadog]

If it has a start capacitor then almost certainly that's what has failed.

 

[SenditSi]

Bypassed the switch and same issue so have ruled that out. Very fond of this original motor don't necessarily want to replace it

 

[SenditSi]

If it has a start capacitor then almost certainly that's what has failed.

Hi seadog I've been googling this but can't find any answers. Can't see a capacitor anywhere unless it could be within the motor housing?? Will keep reading.

 

[Bornfree]

If its intermittent it will probably be the centrifugal switch sticking.

 

[Redsailor]

It's a split phase start motor. As mentioned above possibly the centrifugal switch in the rear of the motor is stuck in the run position, see if it moves freely.

From your photo the windings do look as they have overheated somewhat.

 

[Agroshield]

If it has a start capacitor then almost certainly that's what has failed.

The picture of the motor data plate might rule out that possibility.

---

In the other photos, the earth wire appears to pass through the switch. This is not at all good.

 

[voipio]

As the ratings plate indicates, it is a split phase start induction motor, which relies on a centrifugal switch to open once the motor approaches rated rotational speed. Look at the the rear motor housing, to see if there is a problem with the centrifugal switch mechanism. The contacts should be closed when the rotor is still.

 

[Martin-Sy]

Centrifugal switch or its contacts would be my guess. My Meddings went the same way some years ago.
Do not let it sit non-rotating for more than a few seconds or you'll burn out the start winding which is only short time rated.
Good luck.

 

[500e]

As @voipio & @Redsailor say check the centrifugal switch clean contacts and moving freely.
But also important the earth wire should be connected to motor frame and body of drill at all times even if switch is off as @Agroshield mentioned

 

[Martin-Sy]

Do not let it sit non-rotating for more than a few seconds or you'll burn out the start winding which is only short time rated.

I must remember to engage brain before posting. The motor isn't starting so the start winding isn't being energised!
But you can burn out the main winding as its effectively stalled.

 

[voipio]

The white smoke is slightly concerning, as it suggests the possibility of more permanent damage to the windings.

 

[Martin-Sy]

The other scenario is that it starts but runs very rough. This can happen if the centrifugal switch is stuck in the closed position.

 

[brightspark]

If its intermittent it will probably be the centrifugal switch sticking.

happened to my churchill drill motor give it a bat and it runs perfectly so sprayed some wd 40 0n the centrifugal switch through the fins and works perfectly

 

[DAPPH]

I binned the original GEC motor on my 80 yr old sphere lathe , it too was being difficult found loads of fine metalic crud had been sucked in the air path inside the windings the centrifugal switch had arched points as well , It gave off serious over heating smells and the motor was hot to touch .

I checked out the cost of the motor being rewound .( pre covid ) . in excess of £450 IIRC ) & it would still have the same problem of sucking in crud .

Solved it by buying a reconditioned slightly bigger motor off one of our members , where there are cooling fins on the outside of the sealed motor , it's the way to go I can tell you .

 

[Jack_K]

It seems like every Fobco I see has a different motor.

 

[6ply]

happened to my churchill drill motor give it a bat and it runs perfectly so sprayed some wd 40 0n the centrifugal switch through the fins and works perfectly

My father sprayed some wd40 on a wall light switch or switched socket. When he flicked the switch on, the wd40 detonated. Lesson learned!

 

[RichardM]

My father sprayed some wd40 on a wall light switch or switched socket. When he flicked the switch on, the wd40 detonated. Lesson learned!

I sprayed some one the shredder cutters and the turned it on to even it out, the flames disappeared quickly, but it stank for ages!

 

[Rrobson]

To determine whether or not it is the centrifugal switch (before you strip it down and physically inspect) you can energise the motor and spin it by hand. The run windings will drag the rotor around and it’ll run no problem.

The motor internals don’t look great though, an insulation test of the windings would tell if there’s any issues but a 9v multimeter may not give you meaningful results…

 

[brightspark]

My father sprayed some wd40 on a wall light switch or switched socket. When he flicked the switch on, the wd40 detonated. Lesson learned!

well you dont lather them with it . a tiny squirt and wipe clean 1st