Metrotropolitan Vicker Single phase motor

One thing we do not know is what the external control gear consists of. Possibly some form of variable voltage input via a variable resistance?

Interesting.

Looking forward to the tale as it unfolds!

Dave J

As I mentioned earlier this motor is also being discussed on another forum. Below are some of the pictures from that thread.

Ian P

OK, A picture is worth a thousand words.
It appears to be a switch (centrifugal) start induction motor. The oddity is that it is "inside-out". The induction part is the stator and the powered winding is the rotor.
The most likely reason for this was to get around a patent. It does simplify the centrifugal switch arrangement thoough.
AC power would just be connected to the brushes as shown in the picture.

Robert.

I agree the rotor mounted centrifugal switch is a neat idea but the downside is the brushes/sliprings carry current all the time.

The one picture that I thought might eleicit the most clarification is the one showing the brass plate that clearly shows the model type to be 'BA 147'.

Surely this must be in some old catalogue somewhere?

Ian P

Ah I see now, the switch contacts rotate with the rotor

I suspect that this lady would have known about the design : **LINK**

https://en.wikipedia.org/wiki/Dorothy_Smith_(1898-1975)

MichaelG.

So it turns out that this motor actually has 2 field windings, but on the rotor! There also seems to be a centrifugal switch which I guess disconnects the start winding (which will have a high resistance to get the necessary phase shift) once the motor is going. You can see why this didn't catch on - all that trouble for a 1/4hp motor! Also the windings being embedded would be difficult to cool. I think as Robert suggests this might be to wriggle out of a patent - if this is truly WW1 as initially suggested Tesla's patents would probably still be in force.

Whatever, given the age of the windings and the need to dismantle the motor if the starter switch fails I don't think it would be a good idea to use it "in anger" but rather regard it as a museum piece.

This motor's construction is almost as mysterious as the Antikythera mechanism!

Although the inverted layout works, I can only think of disadvantages, apart maybe from simplifying the centrifugal switch. Everything else feels wrong: high-maintenance and low efficiency brushes? Wouldn't powering the rotor make it bigger and hotter than need be? Isn't it easier to wind stators than rotors?

There must be a reason. If only we could find how it was described in the MetroVic catalogue. Robert's patent avoidance suggestion sounds good to me too.

I think it's early - are those circumferential holes for adding balance weights?  See lead lumps below.

Dave

Edited By SillyOldDuffer on 07/12/2021 15:07:54

There are other examples of "inside out" induction motors. However most of these have the inner part with electrically connected windings stationary and the outer rotating. This means they need no brushes. A well known type is by PAPST (now EBM-PAPST). These are shaded pole types and connonly used for fans
https://www.hermannpapst.de/the-engineer/the-most-successful-developments/the-most-successful-developments/

Robert G8RPI.

...and I think PAPST made inside-out torque motors and hysteresis synchronous motors for high end tape decks?

If anyone wants to seriously research this motor I think the Science museum group have a large archive of Metropolitan Vickers records.

Edited By V8Eng on 07/12/2021 23:33:13

Might be more appropriate to give them the motor, can't be many about

Best place for it, IMHO.

Too much stuff in warehouses already?

Probably true...