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.
Question:
Is the pinch roll side in the picture the correct one or better to place it in the other side of the pulley where the belt is pulled?.
Best regards
Adelmo
Only a second ago, I had the same thought, and now I am reading my thought seconds later. I think that it has merit.
🤣 🤣 🤣
Well, common wisdom is to place it on loose (return ) side. Belt transfers the force by pulling, it cant push.
Pull (or drive) side must be straight and simple , otherwise oscillation can happen there over loose tension-er. On return (or pull) side belt is more loose and right place to put tensioner
What would be explanation to put it on drive side?
Look, sorry guys, Adelmo and lxnay, but I think this makes no sense mechanically. I quickly run 3 scenarios, this is at cold start:
1. No tension idler:
2. Tension idler on "return" side as I would use it:
3. Tension idler on "drive" side:
By the way, putting tension i on drive side produces vibrations, visible and hear able as it is done, Sometimes old wisdom is just ehhh, wisdom.
1. No tension idler:
2. Tension idler on "return" side as I would use it:
3. Tension idler on "drive" side:
By the way, putting tension i on drive side produces vibrations, visible and hear able as it is done, Sometimes old wisdom is just ehhh, wisdom.
Regarding using VCR tape with tensioner, splice on the tape (which is necessary) and however it is well made will produce 0.55Hz multiplied by pulley ratio disturbance, this cant be avoided. Plus it makes tensioner necessary (as tape is not elastic) , adding another source of issues.
For next exercise I will try to chemically etch pulley in order to get more frictional surface, but yes, I'm opened for other ideas... Even this is now getting into the point where it is question does it make sense to improve any further...
For next exercise I will try to chemically etch pulley in order to get more frictional surface, but yes, I'm opened for other ideas... Even this is now getting into the point where it is question does it make sense to improve any further...
Day before yesterday I had swap meet with another geek (like me) from Zagreb, left with Revox B795 turntable on the bench.
Its motor is piece of art, huge Papst driving 2 kg platter directly, with feedback. It is still BLDC, very similar to what is chosen in this thread, but larger.
WOW by phone app is straight away 0.03% at best, average 0.04%, this is same as my home brew belt drive and probably phone app limit (still need to confirm that with better TT, if possible to find).
In any case, Im very happy to have good second TT, which is also DD and comes with Linetrack tonearm. I am fed up of being scared to play any good music from worn and old LP's , just not to damage precious MC cartridge. This will go with MM (as it anyway doesn't comply with MC - only 4g mass in arm) where stylus is replaceable.
Someone messed up with its delicate Linatrack tonearm, no spacers for lowering cart, weight doesn't move, I will need to take it apart. Good news is that critical components seems very good in shape. Job for rainy days 🙂
Its motor is piece of art, huge Papst driving 2 kg platter directly, with feedback. It is still BLDC, very similar to what is chosen in this thread, but larger.
WOW by phone app is straight away 0.03% at best, average 0.04%, this is same as my home brew belt drive and probably phone app limit (still need to confirm that with better TT, if possible to find).
In any case, Im very happy to have good second TT, which is also DD and comes with Linetrack tonearm. I am fed up of being scared to play any good music from worn and old LP's , just not to damage precious MC cartridge. This will go with MM (as it anyway doesn't comply with MC - only 4g mass in arm) where stylus is replaceable.
Someone messed up with its delicate Linatrack tonearm, no spacers for lowering cart, weight doesn't move, I will need to take it apart. Good news is that critical components seems very good in shape. Job for rainy days 🙂
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