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 Post subject: Simpsons Electric Turntable
PostPosted: Sat Dec 29, 2018 10:15 pm 
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Victor II
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Joined: Tue Jun 30, 2009 8:17 am
Posts: 378
Location: Victoria. Australia
The Simpsons Electric Turntable is a synchronous A/C electric motor which was sometimes used on E.M.G gramophones.
I've put together a page on the motor at my website.
http://www.gramophonemuseum.com/simpsons-motor.html

The original design had to be started by spinning the turntable by hand where it then steadied at a constant 79rpm.
I recently came across a later patent where the motor is fitted with a spring loaded starting mechanism which also became a power switch. Does anyone have a Simpsons motor with this starting mechanism?.


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 Post subject: Re: Simpsons Electric Turntable
PostPosted: Sun Dec 30, 2018 4:54 am 
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Victor III
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Joined: Mon Jul 02, 2012 9:57 am
Posts: 579
Location: Hampshire, England.
Many thanks Chunny for this helpful and most interesting post. I did not know about the later self-starting mechanism. Two of us recently bought the Simpsons motors which appeared on eBay but neither has the kick-start to my knowledge. Will report further when they arrive !

The potential fire warning about not leaving such a motor switched on is important and, in my opinion, any such installation should include an in-circuit electric lamp revealing the state of play at all times.

Whilst the near 79 rpm speed allows for some "needle drag" to play correctly at 78 rpm, I am told that people who are blessed (cursed ?!) with perfect pitch can sometimes have a problem. I think the inability to achieve any exact speed required is actually an overriding disadvantage and probably why they are uncommon. I suppose these days it is possible to produce some sophisticated electronics to vary the frequency but why bother when other motors (Garrard induction) solve the problems so well in a mechanical way ?


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 Post subject: Re: Simpsons Electric Turntable
PostPosted: Sun Dec 30, 2018 8:28 pm 
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Victor II
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Location: Victoria. Australia
Graham, I am sure you will have fun with this motor. I use the Simpsons motors when DJing. No need to worry about adjusting the speed and they are very reliable.
I like the idea of a lamp in circuit.
The motor was reviewed by The Gramophone in it's August 1932 issue.

"The mechanical noise, the temperature rise and the consumption (about 6 watts) are the lowest of any motor that has passed through our hands. Stringent mechanical tests as well as playing tests with steel and fibre needles, using the heaviest recordings we could find (including the .usual tell-tales of pitch variance—organ, piano and heavy orchestral recordings with sustained string notes), proved conclusively that a uniform speed is maintained under fluctuating loads. A weight of 3lbs. on the needle point with the needle on the outside grooves of a 10-inch record did not succeed in reducing the speed."

Quote:
I suppose these days it is possible to produce some sophisticated electronics to vary the frequency but why bother when other motors (Garrard induction) solve the problems so well in a mechanical way ?


The whole point of this motor is that it has no moving mechanical parts. No governor to add noise. It runs at a constant speed only or it does not run at all.

I picked up a cheap frequency adjuster for motors and it works with this motor, I get 78rpm on the strobe with the frequency set to 49.4Hz. But with all the variables involved, I don't really use it and being bless with not having perfect pitch, I don't really notice it.
I have an audiophile friend who gets physically ill if everything is not set up perfectly and he refuses to listen to 78's because they never really ever were at 78rpm.


78's run at 77.92 rpm at 50 Hz stroboscope illuminating 77-bar calibration markings
and at 78.26 rpm at 60 Hz stroboscope illuminating 92-bar calibration markings.
I believe that was due to the gearing of a standard 3600-rpm motor and 46-tooth gear (78.26 = 3600/46).

Of course, even after standardization, recording speeds for 78's may well have varied depending on how each engineer set up the equipment. By the time LP’s were being made all cutting lathes had A/C synchronous motors to make sure they were running to a true standard and the curse was somewhat lifted for those with perfect pitch.


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 Post subject: Re: Simpsons Electric Turntable
PostPosted: Sat Jan 26, 2019 1:01 pm 
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Victor III
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Joined: Mon Jul 02, 2012 9:57 am
Posts: 579
Location: Hampshire, England.
Two of us bought the motors recently sold on eBay. I asked about the history but the vendor, in turn, bought from auction in York a while back so the trail goes cold.

Both motors are running well in terms of torque in as much as there is no reduction of speed even on the heaviest passages of any record. There are, however, two aspects that concern us :

1. There is a build-up of heat during normal operation which is slightly concerning because the level is not quantified---what is "normal" temperature etc ?

2. There is a "buzzing" or "fizzing" noise heard from the periphery of the stator on both motors---similar to what might be heard when standing underneath high-voltage cables transporting power across the countryside---especially in damp conditions. Generally speaking, such a noise in my (limited) electrical experience would be slightly alarming with thoughts of incipient short-circuiting and mechanical unsustainability in mind. However, the noise is unchanged whether the turntable is physically mounted on the stator or not and also does not vary when the turntable is circulating.

The stator unit is completely sealed so it is impossible to examine the field coils and their insulation. It is eminently possible that they are "leaking" being approximately 86 years old but it is difficult to imagine how such could translate into mechanical noise although the induction process could, I suppose, cause vibration of some sort---but in what ? There are no in-series capacitors as far as can be seen.

Here is a short video showing the "problem"......

https://www.youtube.com/watch?v=rmYOL36FD8w

Continuity from the outer edges of the stator is good and I have taken the precaution of earthing (grounding) the central bearing. I have also incorporated a red light on the deck-board so that the danger of leaving the power on when the turntable is not circulating can be avoided---hopefully ! An RCD has also been incorporated to protect the whole. The motor is fused at 5 amps.

So, at present, we have a mystery and would be grateful if anyone is able to shed further light.

I have attached a report from 1936 (click to expand image) talking about the later model and the comments on temperature and torque are somewhat (but not completely) reassuring.

Does anyone have experience of the later more powerful motors ?


Attachments:
Simpson later motor 1936.jpg
Simpson later motor 1936.jpg [ 1.12 MiB | Viewed 214 times ]
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