using an akai reel motor as turntable drive?

[federico moreno]

hi everybody

Please, I wish to know if the following motor is good for turntable drive duties.

It´s a reel motor, salvaged from an old Akai GX-255 R´to R´.

Outer rotor, Eddy Current type. Four wires -and no servo input at all-, operated with 4uf cap to provide phasing.

930 rpm@50 Hz, 1120 rpm@60 Hz.

Currently, I´m running it from the mains, with a 40 volts AC transformer and 4uF phase capacitor.

It has adequate torque, and is incredibly smooth and silent, but it has noticeable speed drift. I managed to make a pulley for it, but I cant make it run the platter at 33rpm for a long time (in my diy thread driven TT...)

It´s a strange affair: I don´t know if its 2 or 3 phase; and is evident that is not synchronous...

Is feasible to drive it electronically without a lot of expense or complexity?

the motor looks like this:


and that is the tt that i´m using for test duties: a frankenstein using an hybrid platter (strobo dotted from an old DD, plus steel outer ring to add mass and inertia) -more than a turntable, a tweaker´s platform...-

Cheers!!!

[planet10]

You are going to have to attach the 1st image... from the URL it is in your google mail/ None of us can log into your email to see it.
w
dave

[federico moreno]

this is the motor...

[kevinkr]

This is an induction motor, but I can't really tell how similar it is to a Papst Aussenlaufer motor, but I suspect it might be worthwhile to come up with some sort of eddy current brake like that used on the Garrard 301 or TD-124, the idea being to load the motor down sufficiently that small variations in loading don't cause a very significant speed change.

My TD-124 runs about a 0.5 - 1% slow depending on ambient temperature when stone cold, but it does come up to speed pretty rapidly, and once fully warmed up does not drift at all. (This takes about 10 minutes in a room at 15 - 20C.) I would try some sort of eddy current brake and somewhat higher voltage and see if the speed stability is not better.

[federico moreno]

hi, Kevinkr.
Yes, the motor is some kind of induction motor turned inside out, and now i´m realizing that it shows the behaviour tipical of that kind of motors...

The platter of my TT is partly steel, so a magnetic brake is doable without much trouble: I think that for now I will be using some neodymium magnets from a hard drive, and a threaded mechanism to tune it

I have tested, a lot of motors. One of the best is one very simple synchronous that I made using a microwave oven motor (tray motor): I dissasembled the geared mechanism, putting a spindle in the magnet, a pair of oilite bushings and a metal/wood structure to contain the device. I will post a pic soon.

Another excellent motor is one salvaged from an old changer: is a mixture of induction motor and synchronous motor, nicely machined. The rotor is squirrel cage type, but has attached a permanent magnet... It has excellent torque, and very good speed stability.

But the Akai motor that originated this thread is smoother, devoid of any kind of cogging, and I wish to use it too.

As you have noted, it has some reasemblance with the Papst outer rotor, but with four wires instead of three...

Cheers!

[federico moreno]

salvaged motors: it´s a pity that those marvels end up as landfill...

[federico moreno]

more pics...

[federico moreno]

this one is from an old changer, part induction, part synchronous: as crude as it is, it shows excellent torque and very good speed stability. Also very silent:

[federico moreno]

this dc motor was taken from a HP printer. Nothing fancy, but is powerful and surprisingly silent. I´m using it with a very simple L200 variable voltage PSU: not the last word in stability (there is a little drift, +/- 1% in an hour or so), but no severe wow or flutter.

the part is C2162-6006 HP / (Mabuchi Small DC motor)

[federico moreno]

this beast is from the same reel to reel whose spool motor originated this thread...
it´s a servo AC, for capstan drive.
Eddy Current, outer rotor.

I´m thinking of making a servo for it, looks very promising.