You are right, there is transfer ratio of about 15. But nevertheless I can apply as soft as possible touch on platter, and very hard push on motor, result is same.. Belt is slipping on pulley if allowed to do so.
There was TT designer that said toothed belt or chain would do best, I tend to agree.
Interesting stuff. The motor is synchronous, so it definitely rotates at constant speed, unless it slips an entire pole, leaving smaller slip at the motor pulley as the most likely cause of speed variation. Something I've been wondering about, particularly in relation to the motor you and I have chosen is to fit a pinch roller and use 1/2" tape from a VHS as the belt. Obviously, a rather larger pulley would be required.
Your acid idea is a definite possibility; Revox/Studer tape machines had an etched capstan and I remember local radio engineers talking about dipping their shafts in drain cleaner to restore that slightly rough finish.
Your acid idea is a definite possibility; Revox/Studer tape machines had an etched capstan and I remember local radio engineers talking about dipping their shafts in drain cleaner to restore that slightly rough finish.
I found smaller pulleys with low angle of attack (aka close to the platter) have more slip. Using a larger pulley and farther away from the platter increases the amount of surface area in contact with the pulley, and ensures that there is a greater arc across that contact.
I am also experimenting with driving the platter directly (belt around the platter, like a VPI) or belt around the Sub-Platter (like a Rega). Subplatter will create more flywheel effect from a heavy spinning platter on it but a slower motor speed, whereas direct platter engagement allows a higher motor RPM but direct coupling of any motor speed fluctuations.
And I prefer flat belts.
I am also experimenting with driving the platter directly (belt around the platter, like a VPI) or belt around the Sub-Platter (like a Rega). Subplatter will create more flywheel effect from a heavy spinning platter on it but a slower motor speed, whereas direct platter engagement allows a higher motor RPM but direct coupling of any motor speed fluctuations.
And I prefer flat belts.
The only obvious limitation of the LAB500 Table is the counterweight is somewhat light requiring low mass headshells for your cartridge.
I apologise; I wasn't clear. I meant adding a pinch roller to bear upon the pulley and prevent slip
Funny, just roller is 10x nosier than motor (actualy motor is silent so it is infinity times nosier). Thats fixable, but aesthetic is my main issue....
Yes, it is pure mechanics. Just as downside we have much more reliance on belt quality, and need very long belt that is more difficult to find... Compromises again
Slowing down motor is not an issue today with uPC generated signals, just torque needs to be correctly considered. I drew big motor with 22 Hz, no problem.
However, IMO , don't see why driving sub-platter would make more flywheel effect, or inertia, inertia just platter mass related. IMO also both situations ill transfer motor fluctuations directly, just will lower motor speed they will be less in frequency.
No need to apologize, I got it at first, but also looking at pinch roller as pulley, have one of 16mm OD. Nevertheless it is probably stupid idea as they will never be as concentric as fine machined metal pulley... Still need to experiment with roughening pulley surface, might be in combination with tension device , aka pitch roller attached.
By the way, I tried now iPhone wow measurements with and without tension fly pulley, Seems no change at all. At the end I already have 0.03% speed fluctuation, need to see how far it has to go.