ow could i lower the power to this unit to make the motor go slower

[beatles2011]

Hello, i need some help.

I have this record lathe (below) and it operates like a normal record player but just that it cuts them (records). This units motor runs at 78rpm which is a bit to fast for making records now as at 78rpm i can only cut 3 minutes of music. I want to be able to slow the motor down without having to modify anything inside the unit if possible. Is there any type of device / unit that i can attach between the 3 pin mains plug and this unit so i can slow the power to the motor down which would mean the motor would slow down so i can record more music onto a disc.

Let me know if there is anything and if possible link me to a site which would sell such a device, preferably with a digital screen to lower the power (to make the motor run at about 33 or 45rpm or somewhere around that)

Help greatly appreciated. Pictures attached below. Many Thanks

 

[GLENNSPARK]

frequency changer

 

[ian.settle1]

Why would you want to do this you can get a lot more music on a CD with better results?

 

[beatles2011]

I like this old equipment and a unit like this is worth around £1,000. i want to make this 'universal' i.e with different speeds.

 

[beatles2011]

would something like this work?

230VAC LATHE MOTOR SPEED CONTROLLER / POWER CONTROLLER (M028N) | eBay

 

[Lucien Nunes]

No, that will probably just destroy the motor. Those basic phase-angle controls only work for certain types of motor, such as the series brush motors in power tools, not for induction or synchronous motors as in your lathe.

The only way you can vary the speed of an induction or synchronous motor effectively is with an inverter / frequency changer as suggested above. However there are important side effects, because you want to vary the speed over a wide range, not just a few % of pitch trim but at less than half rated speed. The motor capacitor would probably need to be changed in value and additional cooling might be needed. The insulation might not withstand short risetime drive waveforms.

This is a job for an expert, one false move and you will fry your motor. It might not be satisfactory overall, and an alternative drive gearing might be needed (I am not sure what the drivetrain looks like in these BSR lathes). Please do not mangle it, some of us still like to cut our records at 78!

 

[GLENNSPARK]

i think a variable speed pulley drive might be the way here Lucien....

 

[Farmelectrics]

Ask Father Christmas for an I pod

 

[Geordie Spark]

i think a variable speed pulley drive might be the way here Lucien....

Agreed!

What the OP has here is a fairly basic mechanical machine so lets keep it that way !!!

 

[telectrix]

start mucking about with it, at won't be worth diddly squat. it's value lies in the fact that it's original.

 

[Lucien Nunes]

Yes that's the disadvantage with modding the mechanics. These are collectible vintage pieces that some people like to have in original condition. I agree with Glenn that changing the drive ratio is probably the best way to alter the speed, but it might not be easy and must be 100% undo-able if the machine is not to be compromised.

So I also agree with the OP, that if it is possible to run by changing the motor frequency that is worth investigating. I am skeptical, because of the wide speed range. Only a good true-sine VFD would be worth considering. Speed stability, freedom from cogging and vibration, are all critical.

There are also other audio considerations to running the machine slower, it takes experience and understanding of the cutterhead and groove dynamics to get the best quality results from a record lathe especially when running outside the design parameters.

 

[beatles2011]

I though it would be simple to lower the power going to the machine. Why won't just connecting some sort of a speed / power controller work. Since all the mains is powering is the motor i would like to know why it wouldn't work this way?

I don't see why this or the other links wouldn't work?: Plug in Hydroponics Grow Light Fan Speed Controller | eBay

Or this: FAN SPEED CONTROLLER - JUST PLUG IN! | eBay

Or this: DC-51 LED Indicator Gear Motor Speed Controller AC 220V | eBay

Many Thanks

 

[beatles2011]

I used to have a Neuman VMS 70 but it was vary costly to run power wise and also the styli for cutting only lasted about 150 cuts and cost £250 to replace. Could you check out the other links i added to the other reply here.

 

[telectrix]

the speed of the motor depends on the supply frequency. trying to alter this would result in poor performance, erratic speeds, possible motor burn-out. it is a non-starter, a dead parrot, not just resting from a long flight from norway. this motor will be extinct: an ex-motor.

 

[Lucien Nunes]

All those controllers work by the same method: they reduce the effective voltage to weaken the motor's available torque and make it unable to keep up with the original rate of work it was made to do. With a fan, that gets the desired result, because the speed drops until the torque consumed by the impeller matches what the motor can produce. The exact speed doesn't matter, and can't be precisely set, but you can reduce the airflow within coarse limits.

With your record lathe, the motor must run at a very constant speed or the resulting discs will be unlistenable due to wow. Also, its torque requirement is not such a smooth, fixed function of speed - a large change in speed might produce only a small change in torque. These two factors together mean that the type of speed control that works for a fan will cause your lathe to produce records with horrible wow, it will probably speed up as the cutter moves towards the centre of the disc as the drag reduces - you might find you get a record that starts at 12 rpm and finishes at 60 - and probably slow down at loud passages.

There are other effects - the PSC motor in the lathe will not work correctly at much reduced speed and may overheat and be damaged. The speed controller will produce electrical interference that might be recorded as buzz, and the motor itself (which is designed to run smoothly) will vibrate more, again possibly causing hum on the recording. There is much more to an audio recording machine than an extractor fan!

E2A: your links: The 'DC51' has a DC output, the motor won't run on this and will be instantly destroyed. The 'Fan Speed Controller' says in its description "Please note that it will not control the speed of induction motors." which is what you have in the lathe, and the other one is basically the same.

 

[beatles2011]

Well i shall see about getting a professional job done on it. For the time being i shall i have to speed the tracks up in audacity so when the record plays slower than it was cut it will sound normal

 

[the pict]

Yep Beatles on the money here I think
Pict

 

[Lucien Nunes]

Sure, have fun... It's no VMS70 though!

 

[telectrix]

put the antique in a display cabinet and get a cd recorder.

 

[Geordie Spark]

put the antique in a display cabinet and get a cd recorder.

To whom are you referring ???

Beeky chugger. :angry_smile: