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Replacement motor - low vibration?

JimmyB

JimmyB

pfm Member
The current motor on my old kit turntable has started audibly 'cogging' so thinking I'd like to change it for something a bit quieter! It's mounted directly to the suspension so need to keep vibration etc. to a minimum.

Could probably fit a Premotec which will run from the current DIY Armageddon but are the new Rega 24V motors or any of the Pro-ject motors quieter with less vibration?

Would also try DC but kits seem overpriced for what you get (e.g. basic control circuitry).

Any experience out there of what the current best option may be?
 
Have you oiled it, and adjusted any thrust pad?

Cogging is going to be in the 400-600hz region depending on motor type. Much more likely you are hearing a dry motor or dropped thrust pad.
 
No thrust pad and oiling didn't help unfortunately. It's been pretty much spinning continuously for 10yrs now so maybe it's wanting a rest.
 
That's a good thought, thanks, didn't re-think that enough. As it is the motor won't sit happily if rotated through 180 deg (know this from when I built it)..BUT, if I re-position the wiring (made easier by now being driven by the Armageddon) and possibly lengthen a bit then that might be a solution.

Part of me fancied trying a new motor with speed control probably best I don't start a new project.
 
In recent years I've played with Linn LP12 (premotec) and Project motors. I have a "Meldano' AC controller so I can adjust frequency (speed), phase, and voltage. The Porject motor has much less vibration than the higher voltage Linn motor, and rotates at 300rpm at 50Hz, so you need a different pulley size, or an adjustable PSU - adjusting phase helps, but less so than with the Linn motor - but I had to use that with step up transformers so there was another variable. My current TT is a Transcriptors Skeleton, but I use the Papst AC motor as used on early Gyrodek, but I use the much larger Transcriptors pulley, as this gives more 'grip' on the belt and better speed stability than the tiny Gyrodek pulley, and so I run the motor at a much lower frequency too. The vibration is completely undetectable and so I don't have to mess about with the phase as it seems to be fine at 90 degrees.
 
Heard of the "Meldano" somewhere, sounds like a nice project to have built if it was still available. Did look into using a Raspberry Pi and motor drive board to create a speed controller pretty much off the shelf but that was more for DC.

Got a Linn motor sitting somewhere that was meant to be the original for this deck but unfortunately it just created too much vibration for where it was to be implemented.

Just moved the motor through 180 deg and it 'sort' of worked, can still hear it but it doesn't appear to be audible during playing music. Added a bit heavier weight of oil when I was at it (better access) which may have helped slightly. I call that a result for now.

Cheers for the help all, will be looking at the 16V & 24V Pro-ject and Rega motors for when it does finally go.
 
The Linn motor would always feel like it was vibrating without a load on it. If a small drag force was applied to it then it should have been silky smooth. This was one of the Armageddon tests. The premotec data sheet also describes how to balance the motor winding currents for minimal vibration.
 
You should try running one with silicon oil in the bearing, the drag kills the cogging stone dead.
 
Used a good quality winter bike oil when I turned it through 180 degrees, probably not ideal but did the trick!
 
sq225917 said:
You should try running one with silicon oil in the bearing, the drag kills the cogging stone dead.
Click to expand...

Hi Simon, I've just put together a Geddon clone and will be interested to try the higher viscosity oil idea. I think I remember you had some impressive results from this method with the TT speed tests a while back?. Can I ask what voltage you were running the motor at for this, please? At the moment I get 116v/ 90v with the transformer straight in (with a 0.2uF cap on one phase) and 65v/72v with a 4k7 resistor (defintely less motor noise with the lower voltage but not sure if the music is loosing some "oomph" maybe)

I'm also going to try mounting the motor via a cork / nitrile pad to isolate the motor noise a bit (I know I'll lose the speed adjustment but I'm happy to trade off absolute speed precision for a reduction in transmitted motor noise so long as the speed is reasonably close)

I have to say I'm very chuffed with the Geddon - I know it's a very amateur project by the standards of some of you guys stuff but incredibly rewarding to build one's own PS and even with some small motor issues it already sounds pretty damn good :)
 
sq225917 said:
With a Geddon your limited to thin oil as there's no adjustment.
Click to expand...

I did a check after adding the thicker oil (I run it with a geddon) and turning the motor through 180deg. Speed showed no change including with a strobe disc after adding the thicker oil so can try it. If you need to clean it our again then run some electrical cleaner through it and add some lighter weight afterwards.
 
sq225917 said:
You should try running one with silicon oil in the bearing, the drag kills the cogging stone dead.
Click to expand...

I think Si means in the TT bearing not the motor bearing.

Once the platter is up to speed the motor has little to do, with some thicker oil in the TT bearing the motor has to constantly work thus less chance to cog.
 
Now there's a thing, on Si's suggestion, after turning the motor through 180 deg it was slightly improved but still there. Then changed the bearing oil which didn't help at all so then re-read and thought he'd meant the motor and I'd screwed up.......

..long story short, lubing the motor has made it pretty much silent.....happy mistakes.....

since cleaned it out and sourced some oil from work specifically for small motors so now it's bedded in a bit seems to be a lot happier.
 
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