Dual-motor Dual?

[coecky]

This one seems to have an electric and a spring motor. It says Dual, but which type, what period, etc.? I cannot read the indications on the left hand selector, but the right hand one seems to be the speed control. Where can I find more information on all this?

[epigramophone]

Dual powered motors were fitted to some European portables in the 1930's. The idea was that the machine could be run on electric power indoors and spring power outdoors. I have a dual-motor powered Paillard portable which also has a dual sound system.

As well as the conventional acoustic system it has an electrical pick-up head which can be fitted to the tonearm in place of the Maestrophonic soundbox. This pick-up is wired to two jack sockets on the back of the case, which when connected to the output sockets of a valve radio enables electrical amplification to be achieved.

[Phono48]

I have five machines that use the Dual motor. Two Electrolas (one with the electric pick-up), a Dual, a Paillard, and a Pathé Olotonal. The plate on the left that you can't read is the voltage selector, and is the earliest of the two selector plates used. These motors can be a bit problematic if they haven't been used for some time, but a total strip-down and thorough cleaning usually brings them back to original working condition. The brushes on the electric motor take a beating, because even when the spring is driving the motor, it still turns the electrical parts, so the brushes are being worn down at all times.

[GrafonolaG50]

Is this the same Dual that is making turntables and audio equipment these days?

[epigramophone]

My good friend the late Philip Knighton overhauled the motor of my Paillard and rewired it to modern safety standards. He described the original wiring as "lethal".

[coecky]

The brushes on the electric motor take a beating, because even when the spring is driving the motor, it still turns the electrical parts, so the brushes are being worn down at all times.

But what happens to the spring when the electric motor is the driving force? Doesn't it unhook, or is there a mechanism to prevent this?

[Phono48]

Yes, there is a mechanism to stop the spring unwinding, and it took me ages to see what exactly it did. The shaft on the intermediate cog, between the governor and the turntable spindle, has a "slipping clutch" arrangement in the form of a spring would tightly round the shaft of the intermediate wheel, which is in two parts. Too complicated to explain fully, but it's all to do with the coils of the spring allowing movement of half the intermediate gear to only go one way, because if it tries to go the other way the coils of the spring grip it's shaft, and prevent it moving.