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Fixing a small motor

Chris Pearson

I want to fix an ancient 1/8 hp motor (Carter Electrical Co Ltd). As far as I can tell, the centrifugal switch has worn out, so that will be fun making a new one.

My question is what resistance seems reasonable for the coils. IR is good (well into the tens of megaohms) but they are a little dark and I would like to be confident that there has been no internal shorting.

The main coil is about 18 ohms and the starting coil 33 ohms. My maths tells me that the running current should be around 0.4 A. I cannot remember a lot about motors, but I realise that the impedance of the coils will be higher at 50 Hz than the (DC) resistance and that back EMF reduces the current. I hope therefore that the resistance values are about right.

Grateful for any reassurance!

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    Looks as if you could file a touch off the back of the weighted pawl to allow it to swing in a bit further and with a bit of brasso and old sock rubbing perhaps  get another 50 years out of it (!)

    Maybe some wet and dry to take out the grooving.. It may not have been pulling clear at full speed as it should. A lamp on the starter winding will tell you that.

    Some designs have pinhole to allow a wire, or thread  or similar to hold the sprung pawls out of the way until it is assembled, and then this has to be withdrawn and they click into contact position. Cannot see that in the pic here, but if assembly seems impossible that is a clue to to look for.

    Of course for each start it only gets about five seconds of rubbing before pulling clear so the starter contacts and winding are not heavily worked electrically speaking.

    M.

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  • 0

    Looks as if you could file a touch off the back of the weighted pawl to allow it to swing in a bit further and with a bit of brasso and old sock rubbing perhaps  get another 50 years out of it (!)

    Maybe some wet and dry to take out the grooving.. It may not have been pulling clear at full speed as it should. A lamp on the starter winding will tell you that.

    Some designs have pinhole to allow a wire, or thread  or similar to hold the sprung pawls out of the way until it is assembled, and then this has to be withdrawn and they click into contact position. Cannot see that in the pic here, but if assembly seems impossible that is a clue to to look for.

    Of course for each start it only gets about five seconds of rubbing before pulling clear so the starter contacts and winding are not heavily worked electrically speaking.

    M.

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