Rek-O-Kut M-12 upgrade project.

[uvoscillator]

Dear Trolls !
Just have simple idea how to upgrade my ROK, and make various LPI on it.
What I want to do is simply de-attach cogwheel gear that takes spinning from platter, but leave overhead on platter anyway like on Kingston cutter. And I'll use some kind of servo to drive clutch (? handle) controlled with MIDI by CC.
I think it must works good, and useful for making automated lead-in-outs, spaces etc.
I've some experience with arduino programming and Max/MSP programming, so there is space for experimenting.
BUT I would ask your advice to make right choice of motor to run leadscrew.
I'm sure someone before done something like this, so please share your experience about low noise motors that can be controlled.
Thank you very much for any tip !

Sergey

[tragwag]

I'm rigging up a similar system and considering this motor:
http://www.ebay.com/itm/12v-DC-Worm-Gear-Motor-Variable-Speed-12vdc-Gearmotor/221045903362?rt=nc&_trksid=p2047675.m1851&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D261%26meid%3D4096716020321062830%26pid%3D100005%26prg%3D1088%26rk%3D4%26rkt%3D5%26sd%3D400522843533%26


I don't know much about speed control, so I figure this is an all in one option.

[uvoscillator]

hi ! nice to hear !
thanks for this ! it's impossible to understand how much vibration produces this DC before try )

[dubcutter89]

hi!

these motors are also used in windshield wipers...maybe a cheaper source!

another way would be to rip out a cheapo rim driven turntable and re use the motor and machine a rim-disc onto the feedscrew... if it's a dc motor then you could easily make an adjustable pitch!

Lukas

[uvoscillator]

thanks !
and what is the expensive ways ?

[opcode66]

Search for "super quiet dc motor"

Here is an example

http://www.crouzet.com/english/products/micromotors/dcmind-brush/dcmind-brush-dc-motors-quiet.htm

[uvoscillator]

Hmm, thank you Todd for the input.
I've look around and find that I need motor only around 2RPM for my purposes,
so may be DC is not best choice ? do you think stepper can be good enough for that ?
Kingston lathe uses stepper ? And it is quiet enough ? Even on Lead-in-outs ?
Thanks !

[dubcutter89]

2RPMinute ??? You mean 2 RPSecond (120RPM)? (Turntable 33 1/3 RPM = 1.8 seconds per revolution)

Steppers, as the name says, do steps (audible), you can misuse them as synchronous motor if you feed sine/cosine but I'm not sure if it will turn smooth though...

Why not use a standard (low noise) cheapy gear motor:

http://www.ebay.de/itm/AC-Wechselstr-Getriebemotor-1-9-U-min-230V-Pelletmotor-Drehmoment-ca-18-Nm-/161101621758?pt=Motoren_Getriebe&hash=item258267a9fe

http://www.ebay.de/itm/2rpm-Abtriebsdrehzahl-12v-Nennspannung-DC-Getriebemotor-/181263894894?pt=Motoren_Getriebe&hash=item2a342b896e

http://www.ebay.de/itm/Modellbau-Getriebemotor-12V-120U-min-Gleichstrommotor/260683988509?_trksid=p2047675.c100009.m1982&_trkparms=aid%3D333001%26algo%3DRIC.FIT%26ao%3D1%26asc%3D20895%26meid%3D6081158367209367946%26pid%3D100009%26prg%3D9313%26rk%3D3%26rkt%3D10%26sd%3D181263894894

[uvoscillator]

2RPMinute ??? You mean 2 RPSecond (120RPM)? (Turntable 33 1/3 RPM = 1.8 seconds per revolution)

Thanks for the reply ! Yes, that is true, crank turning 2rpminute on my r-o-k when cut 120LPI on 33,3.
So I want to do it simply drive the crank, and unlink from platter at all.

Why not use a standard (low noise) cheapy gear motor:

Not sure how much torque I need till now...
BTW controlling speed on DC motors it's just changing voltage?

[opcode66]

This person wants to make a pitch system. Not a platter motor.

Yes controlling speed on a DC motor is just changing voltage.

MIDI only gives you 128 values via CC messages. So, you would only get 0 volts (stop) and then 127 steps up to your max voltage (speed). That isn't very fine tuned. They made the MIDI protocol that way in the mid 80's. It has plagued the system ever since. Newer DJ gear uses it's own MIDI protocol that has extended CC values (double byte). That way, the pitch sliders and other knobs could be more precise. They implemented their own MIDI to do this. Unfortunately, with standard MIDI software and MIDI devices, this is not possible.

[dubcutter89]

I know that uvoszillator is making a pitch system...was just wondering about that low rpm.

I guess you don't really need much torque, and as most(all?) of this ultra slow turning systems use some kind of gear
you will have plenty of torque anyway... Maybe just buy a motor and give it a try..?

If MIDI gives you 128 Steps (7 Bit resolution) you will have more than enough "fine tuning" for an ultimative pitch computer...

An example:

Thinking of a linear transfer function between MDID and Pitch mechanism LPI (you could also use non linear functions to fit your needs...)

(Midi Input) x 2 = LPI

Midi 1 = 2 LPI (super nice runout groove)
...
Midi 60 = 120 LPI (what your rek o kut is doing know on 33rpm)
...
Midi 128 = 256 LPI (about 27minutes on a 12" - no need for more?)

So you could adjust your Pitch from 2LPI to 256LPI with MIDI - WOW!
(BTW, what's the difference between 256 and 254 LPI on a disk anyway..)

The Problem is to make your motor do this...(RPM range factor of 100 is a lot - this is why neumann used 2 motors...)
DC motors can be controlled by Voltage or you could use a PWM (7Bit resolution for example...)


Give it a try!

Cheers
Lukas


LPI Chart by Steve E.:
https://lathetrolls.com/viewtopic.php?f=9&t=824

[uvoscillator]

Give it a try!

Exactly Lucas !
0-127 looks more than enough, especially if it will be just several preprogrammed speeds !
I'm looking to steppers now, just heard that nowadays there lot of improvements like 'microstep' (about 6400 divisions in one turn) etc...
Thank you very much for the reply !

Sergey

[opcode66]

A stepper motor should not be used for a pitch system. You can get away with steppers on the platter since the platter itself is generally heavy and helps to smooth out the bursts from the stepper.

A stepper on a pitch system will create audible noise in unmodulated grooves. Each step will be heard via the playback stylus. In order to not be heard the step would have to be smaller than the tip radius.

If you were going to create a system with several fixed pitches then why go through the bother of making it MIDI to begin with? My impression was that this person wanted to make a variable pitch system where MIDI CC messages would be interpreted as pitch changes. You could write code to come up with a CC envelope for to control pitch given the program material. If that is the case then 127 values plus 0 isn't very fine tuned. If you simply wanted to change between a few fixed pitches or over a scaled range as suggested above then it is fine. If you only want a few fixed pitches then you could use a rotary switch and switch out between different voltage values to feed the pitch motor. Or, just put a big old potentiometer on it and call it a day.

As stated above, you need two motors to do it right. But, the second (fast) motor only goes on for lead in and lead out. The rest of the time the normal pitch (slow) motor is running.

[cohearent]

Actually the Sontec Pitch Computer used a stepper motor. This was designed by Gerry Block. It is still being used by Bernie Grundman, The Mastering Lab, and Stan Ricker. Although I agree that a stepper motor wouldn't be my first choice, it has been done successfully.

[audadvnc]

We're doing something similar on our 1940 era Scully lathe, having disconnected the carriage drive belt pulley from the turntable driveshaft. We move the drive belt onto a DC motor with a step-down gear (about 100:1) and drive the motor with a PWM feed from an Arduino controller running a routine based on the Arduino input and output examples. We get amplitude from a DC rectified audio signal and have the Arduino do its DC -> PWM trick. I manually run the lead-in and lead-out grooves using the Scully mechanics.

There's a bit more to it, but ... It works! I do find the noise of the DC motor somewhat objectionable (similar in volume to the vacuum system), but I don't have any vibration getting onto the lacquers.

[opcode66]

A stepper could be used on a lathe like a Neumann (and I'm guessing Scully as well) because there is a fly wheel on the leadscrew. The flywheel does what I said the platter did in my earlier post. It tends to smooth out the burst from a stepper motor in order for it to operate more like a dc motor. The steps are still happening, but because of the momentum of the heavy platter or flywheel, the leadscrew on the other ends turns more or less evenly. There wouldn't be notches in the concentric grooves, but there would be flutter to the speed and therefore a mild variation in groove spacing over time. That is unavoidable however you dampen a stepper motor from my understanding. Without a flywheel, I would say, go DC.

[uvoscillator]

Thank you guys ! I'll pay attention as always. One more words about servo's ? They more like DC with gear ?

[opcode66]

Servo motors are like steppers in a sense. If you pulse a stepper then you can be somewhat accurate about turning the motor to a particular location within a revolution. I.e. you could pulse it so it turns half way.

Servo motors are what they use in robots. When you need to articulate something accurately and hold it there you use a servo motor. Servo motors turn to specific locations based on the PWM frequency that drives it. You can approximate smooth rotation by turning the servo one step (frequency value) at a time until the max value (just before full rotation), then send it 0 PWM and start working value up to the max value again. That is how you can make a servo motor turn like a normal motor.