Hi Laszlo, sure, there are better devices. This CNY70 was first I started to play with as it is simple, this sensor also works great for average speed.
At bottom line this device is just to confirm speed stability of platter (or wow and flutter). I'm not sure this is the best way to measure it, many paths are opened, I will see where this road goes and how much effort is to be invested,..... Industrial shaft encoder would probably solve the problem.
I can always play test LP and make classical W&F test, but this brings LP, cart and arm into equation, with TT rotation that's 4 variables. I prefer to analyze problems one at time as to many variables confuses conclusions...
At bottom line this device is just to confirm speed stability of platter (or wow and flutter). I'm not sure this is the best way to measure it, many paths are opened, I will see where this road goes and how much effort is to be invested,..... Industrial shaft encoder would probably solve the problem.
I can always play test LP and make classical W&F test, but this brings LP, cart and arm into equation, with TT rotation that's 4 variables. I prefer to analyze problems one at time as to many variables confuses conclusions...
A question to historians among us. Not that I need motor as I solved the issue, but couldn't stop myself not to pick this up from flea market this morning.
This is kind of optical instrument with half of mirror on the shaft. Have no clue yet what it was for.
Motor is definitely 2 phase synchronous, but I'm wondering which type of rotor is this, it has no magnets, hysteresis ?
This is kind of optical instrument with half of mirror on the shaft. Have no clue yet what it was for.
Motor is definitely 2 phase synchronous, but I'm wondering which type of rotor is this, it has no magnets, hysteresis ?
It is a permanent split capacitor motor.
https://us.aspina-group.com/en/learning-zone/columns/what-is/008/
I run this motor, quite noisy probably due to old ball bearings, also connected it to TT with longer belt; 10 times worst wow than with actual set up... Put whole thing back together and into the hell of my garage 🤣. Looks very nice but not best to use.
Read article, this says about stator and how to drive it, that's clear. I'm wondering about type of rotor that is...
If it is split-phase induction motor consists of a squirrel cage rotor
I think it would not be synchronous This motor has good start torque and definetly locks at 1500 rpm, must be synchronious. Doesn't behave like cage rotor asynchronous....
I think it would not be synchronous This motor has good start torque and definetly locks at 1500 rpm, must be synchronious. Doesn't behave like cage rotor asynchronous....
In the meantime I found my wife's old iPhone 8, took while to clean storage and install new iOs so I can install RPM and WOW app.
Now I have one phone that can stay with me, and not borrowing all the time 🙂
Also cleaned re-oiled main bearing and let TT run for some minutes.
New results are even bit better, really to my satisfaction.
I can say 2 things from experience:
Latest takes:
Now I have one phone that can stay with me, and not borrowing all the time 🙂
Also cleaned re-oiled main bearing and let TT run for some minutes.
New results are even bit better, really to my satisfaction.
I can say 2 things from experience:
- App shows very small deviations: it is big difference if bearing is re oiled or not, if TT is running for few min or cold start, belt tension as discussed before
- App shows approx 0.24 RPM higher speed than supaspin
Latest takes:
Do you plan to try a non-elastic belt, like a dental floss or a VCR mylar tape? Just out of curiosity... It would need a different pulley, though.
That would be interesting Laszlo. I cannot change pulley but I think existing one will work with both. However I cannot change motor position, how to tighten non elastic belt is an issue.
Another question is how to make endless belt , particularly with floss, there will always be a knot?
Another question is how to make endless belt , particularly with floss, there will always be a knot?
Still playing with RPM app, whats left of free trial measurements. I think I will buy app at end.
This time I left TT spinning for half an hour. @33.33 RPM W&F 0.08%, at 45 rpm 0.06-0.07% . When looking in their database of 250 TT's that they showed me, these results were achieved by one Ariston (only belt drive here), one Lenco, one Dual, one JVC and 4 Micro Seiki's. all together 8 TT's out of 250 achieved 0.0xxx W&F. If this is to trust, me very very happy Muppet 😎
PS, speed is some 0.24 rpm higher as shown by phone than in reality .
This time I left TT spinning for half an hour. @33.33 RPM W&F 0.08%, at 45 rpm 0.06-0.07% . When looking in their database of 250 TT's that they showed me, these results were achieved by one Ariston (only belt drive here), one Lenco, one Dual, one JVC and 4 Micro Seiki's. all together 8 TT's out of 250 achieved 0.0xxx W&F. If this is to trust, me very very happy Muppet 😎
PS, speed is some 0.24 rpm higher as shown by phone than in reality .
Another thing regarding phones used, friend asked me to check differences between phones since I have 2 with same app. So here is iPhone 8 and 11 spin at same time at platter, only one was started slightly later than another. Doesn't seem to be big difference at all, might be in average speed calibration but that doesn't matter . Interesting that both oscillation curves are rather same, except one is delayed due to button press difference in time.
Still amazing how your vintage DD preforms! How does it perform otherwise? I can see some are selling for just 145 Eur on Reverb, that's an opportunity
I have another tach on my TT which is very accurate: 33.33 rpm = exactly 1khz from test LP. So I trust this one.
iPhones (driven at that speed) show deviation : one 0.24 RPM and another about 0.1 RPM. This can be adjusted by calibration. Seems that phone apps show precise WOW, but deviate a bit on average RPM
Drive pulley considerations, or subtitle "don't trust machinist and his lathe completely"
I did this exercise month or two ago, but did not have time to post so I do it now.
Of course drive pulley must be perfect in rotation , if it is eccentric we will get oscillations in speed at frequency = motor rpm/60.
Machinist made me nice aluminum crown pulley with central hole that perfectly fits my chosen motor shaft. I fixed it forever to rotor - shaft, with drop of epoxy. So far sounds good, however , eccentricity was still observed, both by looking through glasses and by touching pulley with toothpick supported at solid part of TT, you can call it primitive dial gauge.
My thinking was it is easy, lets take assembled rotor with pulley and shaft back to machinist and let him just touch it. holding by the shaft.
Since I was there several times, he let me in to his machines, and horror to me was that he must center the part in his lathe head by hammer. Soon I figured that this makes no sense as he will never make it a perfect rotating circle like this. Might be it works for average petrol engines, but not for this.
So I took it back home, installed in motor and made rig to fine machine it. While it is rotating in its own environment (bushings and stator) it is best way to make corrections. Long time in the past similar methods I used to save fine petrol engines.
Piece of fine (240) grinding paper was fixed on chopstick. one end of chopstick is fixed by mini wise, other end free flying. When I got grinding paper close to rotating pulley, shh....shh. ...shh noise could be heard, indicating eccentricity. Other end of chopstick was loaded with variable weight (see usb stick and some triviality hanging from it) by slightly moving the weight on the lenght of chopstick I could fix grinding are on vertical surfaces of pulley.
This went on for couple of days of motor spinning, I moved weight up and down to cover whole area of the pulley, and slowly got grinding paper closer to it by knocking on plastic clamp you will see in the picture coming below. After some time shh....shh....shh.. noise become only shhhhhhhhh, or about. To get it perfect one could run this method for years....
Ps It is not that I don't have some experience in machining, however this "simple" TT challenge beats universal mechanical tolerances wisdom...
I did this exercise month or two ago, but did not have time to post so I do it now.
Of course drive pulley must be perfect in rotation , if it is eccentric we will get oscillations in speed at frequency = motor rpm/60.
Machinist made me nice aluminum crown pulley with central hole that perfectly fits my chosen motor shaft. I fixed it forever to rotor - shaft, with drop of epoxy. So far sounds good, however , eccentricity was still observed, both by looking through glasses and by touching pulley with toothpick supported at solid part of TT, you can call it primitive dial gauge.
My thinking was it is easy, lets take assembled rotor with pulley and shaft back to machinist and let him just touch it. holding by the shaft.
Since I was there several times, he let me in to his machines, and horror to me was that he must center the part in his lathe head by hammer. Soon I figured that this makes no sense as he will never make it a perfect rotating circle like this. Might be it works for average petrol engines, but not for this.
So I took it back home, installed in motor and made rig to fine machine it. While it is rotating in its own environment (bushings and stator) it is best way to make corrections. Long time in the past similar methods I used to save fine petrol engines.
Piece of fine (240) grinding paper was fixed on chopstick. one end of chopstick is fixed by mini wise, other end free flying. When I got grinding paper close to rotating pulley, shh....shh. ...shh noise could be heard, indicating eccentricity. Other end of chopstick was loaded with variable weight (see usb stick and some triviality hanging from it) by slightly moving the weight on the lenght of chopstick I could fix grinding are on vertical surfaces of pulley.
This went on for couple of days of motor spinning, I moved weight up and down to cover whole area of the pulley, and slowly got grinding paper closer to it by knocking on plastic clamp you will see in the picture coming below. After some time shh....shh....shh.. noise become only shhhhhhhhh, or about. To get it perfect one could run this method for years....
Ps It is not that I don't have some experience in machining, however this "simple" TT challenge beats universal mechanical tolerances wisdom...
Getting stuff concentric with a new axis of rotation is always tricky. The manufacturer-approved method for getting the head drum on a broadcast videotape machine concentric after replacement was to tap it whilst monitoring runout with a dial gauge. <2um was deemed acceptable. A hammer could be used, but the manufacturer recommended the handle of screwdriver. Tapping stuff with a hammer whilst centring in a lathe is pretty common; I've done it. The important consideration is not the hammer, but the person wielding it.
This story came to my mind. It has several versions.
https://medium.com/indian-thoughts/...s-all-about-knowing-where-to-hit-ec08b5ced0c6
https://medium.com/indian-thoughts/...s-all-about-knowing-where-to-hit-ec08b5ced0c6