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DeonC 18th March 2004 01:52 AM

DIY turntable idea
 
Hi guys

I have been really inspired by the sight of Posthorn's DIY Turntable (see the following thread: Posthorn\'s DIY Turntable thread). Not that I really need another TT- I already have three good TTs, and with another one on it's way (I have a Technics SP10 MkII, Technics SP15, Linn LP12, and there is a Harman Kardon Rabco ST-8 on it's way to me) :spin:, but I found an old motor that I have lying around, and the DIY bug bit me again :smash: :nod: :cheerful:

The motor that I have is a huge old AC hysteresis motor. When I say large I mean that the motor is between 3" and 4" in diameter! It came from an old Akai reel-to-reel deck. How suitable do you guys think would this motor be for a DIY TT design? :scratch: IOW, won't it be too noisy? I know that brushless DC motors are regarded as the best, but how does the AC hysteresis motor compare ITO suitability for a project like this?

The last question I have (for now) is slightly more philosophical- if you had this motor would you build a belt-drive or a direct-drive TT? :D Just curious. If I go ahead I'll probably build a belt-drive with a large flywheel (due to the high revolutions that the motor turns at- 1500RPM - 3000RPM). A flywheel will also help isolate the platter from motor-noise. :idea:

I would love to hear the comments and ideas :)

Deon

analog_sa 18th March 2004 06:25 AM

Quote:

The last question I have (for now) is slightly more philosophical- if you had this motor would you build a belt-drive or a direct-drive TT? Just curious. If I go ahead I'll probably build a belt-drive with a large flywheel (due to the high revolutions that the motor turns at- 1500RPM - 3000RPM). A flywheel will also help isolate the platter from motor-noise
Hi Deon

How can you possibly use this motor to build a DD table? 3000rpm?!

I think starting a TT design from the motor is simply wrong, even if you got it for free and have no other use for it. If are diying a TT you probably expect to end with something better than what you already have. The significant in both design and cost TT parts are the main bearing and the platter - a nice DC motor is dirt cheap in comparison. The flywheel add-on is probably great and with sufficient inertia may overcome some of the problems of the motor but this is more of a design afterthought.
So, what will you do about the main bearing?

regards

Raka 18th March 2004 06:55 AM

You can always build a low Hz power supply to reduce the speed of the motor, and build a large diameter pulley.

DeonC 18th March 2004 06:29 PM

Quote:

How can you possibly use this motor to build a DD table? 3000rpm?!
Well, it'd have to work through a 'gearbox', or basically the motor will drive a step-down gear, which will drive the platter. It can be made to work :smash: :D

Quote:

The significant in both design and cost TT parts are the main bearing and the platter
That part will remain whether I use the hysteresis motor or a DC motor. What I like about this motor is the sheer size. It is a BRUTE of a motor.

Quote:

The flywheel add-on is probably great and with sufficient inertia may overcome some of the problems of the motor
That's the point- I want to know if the hysteresis motor is worth working with. I want to know if it is worth it continuing. I can easily get a few second-hand TTs that will be used for the main platter and flywheel. You can still pick up old Lenco L70 and L75 TTs for a song (I had three at one stage), and they would be a great basis to start with. Stepping down from 3000RPM to 33 1/3RPM is a step-down of exactly 90 times.That is not so hard to achieve. The point is that the power of the motor coupled with the inertia of the two heavy platters will provide great speed stability.

Once again, this is not meant to be a reference TT (my Technics SP10 has that position), but simply a fun project. :devilr:

Thanks,
Deon

analog_sa 18th March 2004 07:54 PM

Quote:

Once again, this is not meant to be a reference TT (my Technics SP10 has that position), but simply a fun project.
Please ignore my opinions above. I have no interest in killing time.

Posthorn 18th March 2004 09:32 PM

Thanks!

Don't forget the chain to drive your concrete platter on ship's propeler bearing ;-)

Hope you have some fun


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