Thread: Slow starting motor

I have a single phase motor which I disassembled and reassembled.
When I go to start it, it starts very slowly and with a bit of encouragement it will hit top speed.
Inside is a set of points, I think I have incorrectly repositioned the bearings and as a result
I think the points are staying permanently open.
Would this be the cause of the very slow starting even when there is no real load?

Yes, if it's cap start cap run, and the start cap centrifugal switch is open it will do that. Check that the centrifugal switch is working properly.

Regards
Ray

I'd say I misaligned the bearings by about 12mm. So the rotor and stator are misaligned by about the same amount.
I've added to my grief by Loctiting a heavy cast iron pulley to the 1" shaft and it won't budge.
So I'm thinking of putting a spacer behind the bearing to get the points working.
But...will I lose much power with the misalignment within the motor itself?

How many capacitors does it have? one or two?

Originally Posted by RayG

How many capacitors does it have? one or two?

It has the original capacitor inside a metal box fixed to the motor and and recently an additional start cap was added.

The circuit should look like this..

374.jpg


With the centrifugal switch permanently open, the power (when it finally gets going) will be the same, but you won't have much starting torque.

Regards
Ray

Originally Posted by RayG

The circuit should look like this..

With the centrifugal switch permanently open, the power (when it finally gets going) will be the same, but you won't have much starting torque.

The idea is to get the switch working by placing a 12mm spacer behind the bearing, but it would still leave the the rotor and stator
out of alignment...Would this reduce the power of the motor by much at speed?

Originally Posted by GSRocket

The idea is to get the switch working by placing a 12mm spacer behind the bearing, but it would still leave the the rotor and stator
out of alignment...Would this reduce the power of the motor by much at speed?

No, an angular misalignment won't make any difference. ( I assume you are talking about an angular misalignment, ) not a longitudinal misalignment..

Regards
Ray

Originally Posted by RayG

No, an angular misalignment won't make any difference. ( I assume you are talking about an angular misalignment, ) not a longitudinal misalignment..

I think it might be longitudinal? Because the bearings have been misplaced along the shaft to the back of the motor by 12mm.
I probably need to put up a drawing.

Don't really know how much power you will lose, maybe not much?, but I think you should pull it apart and re-assemble it anyway.

Regards
Ray

I am still not quite following how it is misaligned, but if the rotor is not lined up with the stator i guess you will loose as much as a percentage of power that the 12mm equates to as a percentage of the rotor length.

Originally Posted by Ueee

I am still not quite following how it is misaligned, but if the rotor is not lined up with the stator i guess you will loose as much as a percentage of power that the 12mm equates to as a percentage of the rotor length.

It was easy enough to do.
It would have been an easy fix, just slide the bearings along.....if I hadn't glued the cast iron six sheave pulley on so good.

Originally Posted by GSRocket

It was easy enough to do.
It would have been an easy fix, just slide the bearings along.....if I hadn't glued the cast iron six sheave pulley on so good.

why did you loctite it on?...it shouldnt have been necessary?

Originally Posted by GSRocket

It was easy enough to do.
It would have been an easy fix, just slide the bearings along.....if I hadn't glued the cast iron six sheave pulley on so good.

Hi,

Loctite softens with heat. If you warm up the cast iron pulley with a propane torch it should come off easily. It might need to get to around 200 degrees C (depends on the grade of Loctite).

Bill

Originally Posted by eskimo

why did you loctite it on?...it shouldnt have been necessary?

The pulley is probably 100 years old (slight exaggeration) and the centre was slightly flog out and it was impossible to
keep tight on the shaft and imparted a slight vibration to the head. I found by Loctiting, the vibration was almost gone.

Originally Posted by WCD

Hi,
Loctite softens with heat. If you warm up the cast iron pulley with a propane torch it should come off easily. It might need to get to around 200 degrees C (depends on the grade of Loctite).
Bill

The grade was 263. I have applied a good amount of heat to it and got it to move about 2mm.
So the plan is to drill and thread three holes into the pulley and use some flat plate and a bolt to make up a puller and apply the heat...
should work.
Someone said acetone might soften the Loctite so I might check that out as well.