Motor polarity

Technical MGB discussion
Vic Butler
Posts: 414
Joined: Wed Dec 21, 2016 6:07 pm
Forename: Vic
Surname: Butler
Location: North West Hampshire

Re: Motor polarity

Post by Vic Butler » Tue Jan 14, 2020 10:25 pm

Good news Dave and it's satisfied my curiosity. By rotating the cylinder where the magnets are the polarity has been changed.
In your first posting on this subject you stated that the aerial had been isolated. That's the reason. I wonder if it had been assembled incorrectly at one time. It's a permanent magnet motor more than likely and I think they have to be reassembled in the same original orientation.
The round wiper motor on later B's is a permanent magnet one and the yoke (cylinder) has alignment marks with the gearbox and has to be refitted with the marks aligned. It's nothing to do with the gearing but getting the correct polarity.
1977 Stage 2 MGB GT
1975 SWB Series 3 Land Rover with a later 2.5 petrol engine
Ian Fozzard
Posts: 268
Joined: Fri Mar 27, 2015 8:18 am
Forename: Ian
Surname: Fozzard

Re: Motor polarity

Post by Ian Fozzard » Wed Jan 15, 2020 9:10 am

Thanks Vic and Dave, good that we got that one sorted out!!!!

For all of us casual bystanders could we have a simple explanation of how this works please? A simple circuit diagram would be very illuminating😁
I still can't see how it reverses itself........

Ian F
Vic Butler
Posts: 414
Joined: Wed Dec 21, 2016 6:07 pm
Forename: Vic
Surname: Butler
Location: North West Hampshire

Re: Motor polarity

Post by Vic Butler » Wed Jan 15, 2020 10:37 am

Ian, I've forgotten basic physics so I don't know why but I'll find out if I can. It's obviously something to do with the orientation of the permanent magnets. That's my theory. Doubtless physics lessons in the late 1950's early 1960's would have covered it but I can't remember. All I know is permanent magnet electric motors have to reassembled correctly hence the alignment marks on the wiper motor.
1977 Stage 2 MGB GT
1975 SWB Series 3 Land Rover with a later 2.5 petrol engine
Ian Fozzard
Posts: 268
Joined: Fri Mar 27, 2015 8:18 am
Forename: Ian
Surname: Fozzard

Re: Motor polarity

Post by Ian Fozzard » Wed Jan 15, 2020 10:47 am

Thanks Vic. No need to spend any more time on it (enough spent already!!) but if anyone has a simple explanation already prepared I would appreciate the enlightenment. Car electrics are certainly still a bit of a mystery to me......
Ian
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