The Craftmans Shop > New from Old
Bridgeport J Head Pancake Motor
awemawson:
My Bridgeport mill doubles as a drill press, and the other day I was drilling a 10 mm hole in a bit of softwood when there was an almighty bang and flash from the control box :bugeye:
Oddly the motor will run and not make big bangs in high speed, but gives the same dramatic results in low speed :scratch:
It looks like the control box and contactor have survived but the motor it self is giving me some very odd winding resistances:
Slow A to B = 55.6 ohms
Slow B to C = 27.8 ohms
Slow C to A = 27.8 ohms
Fast A to B = 13.8 ohms
Fast B to C = 14.3 ohms
Fast C to A - 14.2 ohms
Now as you can gather this is a dual speed motor 2800 / 1450 rpm or there abouts with winding switched by a rotary switch on the side of the motor.
So far I've managed to get it off the machine and onto the bench and opened up the switch cover hoping for loose wires but none to see :(
When time permits I'll dig deeper into the motor
So if anyone knows where there is a Bridgeport 'Pancake' motor I'm in the market for one !
Pete.:
--- Quote from: awemawson on September 06, 2020, 07:29:55 AM ---My Bridgeport mill doubles as a drill press, and the other day I was drilling a 10 mm hole in a bit of softwood when there was an almighty bang and flash from the control box :bugeye:
Oddly the motor will run and not make big bangs in high speed, but gives the same dramatic results in low speed :scratch:
It looks like the control box and contactor have survived but the motor it self is giving me some very odd winding resistances:
Slow A to B = 55.6 ohms
Slow B to C = 27.8 ohms
Slow C to A = 27.8 ohms
Fast A to B = 13.8 ohms
Fast B to C = 14.3 ohms
Fast C to A - 14.2 ohms
Now as you can gather this is a dual speed motor 2800 / 1450 rpm or there abouts with winding switched by a rotary switch on the side of the motor.
So far I've managed to get it off the machine and onto the bench and opened up the switch cover hoping for loose wires but none to see :(
When time permits I'll dig deeper into the motor
So if anyone knows where there is a Bridgeport 'Pancake' motor I'm in the market for one !
--- End quote ---
I make that a switching issue. Going by this thread:
--- Quote ---There are six windings in the motor. For low speeds the windings are connected in a series loop with power applied to every other connection. So 440 volts is applied across each pair and the individual windings see 220 volts each. For high speed the windings are connected in parallel pairs. One end of each pair goes to a common point the other end receives power. So each winding sees 220 volts.
--- End quote ---
You should have four times the resistance in the low speed arrangement as in the high speed. Since only one phase combination has that resistance and the other two are showing half what they should, and given that the high speed readings seem to be appropriate, I'd say that the windings are fine but one winding is shorted when the switch is set to low speed. Can only be within the switch IMO.
Might be completely off-track but that's how it seems to me.
awemawson:
I hope that you are correct Pete, and it was that suspicion that had me take the cover off the switch but I’ve still not got any further into it. String of visitors today as allegedly it my birthday, but I find it hard to believe it’s a year since the last one :bugeye:
Muzzerboy:
I've got one you can have. It was working fine when I removed it so that I could replace it with a modern 3000rpm 3kW machine and adaptor plate I got from the late JS. I gave it a good clean when I bought the machine, so it's in a decent state all in all. I even have some spare bearings for it, although it ran pretty quietly.
Where are you? I live near Blackpool and work near Leamington Spa. But IIRC, I can send up to 25kg for £7 via Parcel Farce. Let me know if you are interested.
awemawson:
Yes please thank you very much.
I rebuilt mine 20 years ago from bits of one from John Stevenson so hows that for a coincidence. Someone had sawn the shaft off intending to use the front plate to mount a more modern motor so that was missing and I had to make one. My shaft is two bits grafted together.
I’ll PM you and we can sort something out
Cheers
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