What kind of motor is this?

[Lucien Nunes]

Interesting old machine still in use. I've talked about similar motors before but not this type AFAIK. To the trained eye, the shape of this one is a giveaway, from which you can identify its maker and the technology it uses, and probably say something about the available electrical supply. In any case the shape should tell you something. Note that the bare aluminium covers are non standard, these would normally be steel mesh vent grilles.

 

[Lucien Nunes]

some cast iron control gear for vetilation equipment recently,

Any pics? Interested if 1930s or earlier, or unusual design etc.

 

[Lucien Nunes]

Hmm, another duplicate post deleted, not sure why these are happening.

 

[marconi]

In the days before Variable Frequency Drives using Scalar or Vector Control there was:

 

[Deleted member 26818]

That motor is repulsive.
Needs a make over.

 

[stevels4]

It’s obviously steam powered, the wire is actually a pipe and there is a self contained boiler in the enclosure at the rear.
Neither Fleming’s Left or Right hand rules apply here.

 

[Lucien Nunes]

Handy little motor, not sure why they weren't more popular over here. He describes it as a repulsion induction, but I think it's full-time repulsion as it always remains under the control of the brush rocker.

 

[Simon47]

That motor is repulsive.
Needs a make over.

My late father used to tell a tale about a call to a factory where there was a long bench with lots of sewing machines driven off a line shaft - and with a motor at the end to drive it. He opened the lid of the enclosure expecting to find it solid with lint - but instead found it spotlessly clean.
One of the machinists explained that every Friday they had a cleanup session and always included inside the box with the motor - especially the bright brass bit. Yes, they were polishing the commutator on a running motor

 

[Lucien Nunes]

That's not unheard of, Grinding and polishing a comm in the machine's own bearings as it runs, although usually by experienced sparks and 'dynamo attendants.' Normally though, it just needs the dust and carbon blowing out, no actual polishing is necessary, it just leads to excess wear, as the brown oxide coating that builds up is much tougher than the bare metal. Commutation is one of those things that is best experienced in operation, you can tell a lot about the adjustment and condition of the machine and suitability of the brush grade etc by seeing, hearing and feeling. The strapline at the bottom of the in-service maintenance pages of some popular plant used to be 'Use Your Fingers!'

 

[Simon47]

Oh yes, machining etc of the comm in situ - great, and done with the power off ?
Untrained people cleaning and polishing the motor while it's powered and running, that's a different matter

 

[ex 2 Base]

Repulsion type,with brush gear and com, used on early type compressor needing good starting torque.

 

[Richard Williams]

Old

 

[freddo]

Repulsion type,with brush gear and com, used on early type compressor needing good starting torque.

That reminded me that there was a large cast iron oil filled motor starter for a wound rotor motor in a local laundry basement that once fed a compressor, sadly the motor and compressor are long gone, but the air receiver sill remains. Still full of (probably hazardous) oil, had a manufacture date of 1949 IIRC. I wonder if it is still there. Had a little hand wheel to operate the variable resistors for starting, still turned ok. Fed from a large adjacent Memajor switchfuse all wired in poly butyl jute cables in 1 1/2 steel conduit.

How do I remember stupid details like that from years ago but can't remember important things that are happening right now?

 

[Santa]

One of my earliest jobs was working in a small brick factory in the Cotswolds. Every morning my first job was to start the motor that ran all the machinery through an overhead pulley system.

This was a hefty beast, from memory it was a least a couple of feet diameter and was controlled by a big cast steel switch box on the wall This had a lever with four positions, and I had to stand there while the rest of the crew sat around smoking and drinking tea, and move the lever through each position in turn.

There was no gauge or anything, I judged by ear when the revs were high enough to move up.

I wonder if anyone could tell me exactly what I was doing? This would have been in the early 60s.

 

[Simon47]

Could have been some combination of tap changing and star delta.
But in that era, the aforementioned slip ring induction motor with variable rotor resistance would be a good candidate - I'm assuming it was started unloaded but with a massive inertia of drive lines & pulleys to wind up.
With a large resistance across the brushes, the rotor current is limited - so torque is vastly reduced, but so is stator current.
So did the first notch set it slowly tunning up like there's all the time in the world ? Then the next notch add a bit of urgency ? Until it's up to speed and can go to the last notch where the rotor is shorted and it runs as a normal squirrel cage motor.
Presumably, you had to learn by ear how fast it needed to be running before you could go to the next step without blowing fuses ?

 

[Santa]

Could have been some combination of tap changing and star delta.
But in that era, the aforementioned slip ring induction motor with variable rotor resistance would be a good candidate - I'm assuming it was started unloaded but with a massive inertia of drive lines & pulleys to wind up.
With a large resistance across the brushes, the rotor current is limited - so torque is vastly reduced, but so is stator current.
So did the first notch set it slowly tunning up like there's all the time in the world ? Then the next notch add a bit of urgency ? Until it's up to speed and can go to the last notch where the rotor is shorted and it runs as a normal squirrel cage motor.
Presumably, you had to learn by ear how fast it needed to be running before you could go to the next step without blowing fuses ?

You got it exactly, although it didn't blow a fuse, it just cut out at the switch and I had to start again with much mockery from the others

. It was started as you say with the overhead shafts turning, but all the drive belts were disengaged. We just slipped the belt off the side of the pulley to stop a machine - no guards to get in the way.