Good question:
- good one, tight, is from generic electronic store, guaranteed made in PRC
- loose, funny ones are from HIFI audio store, don't remember the brand
Dont know, yet.
On the good belt graph you see just random "hair" of noise which is quite normal on all TT's and at this one very small.
Then I just change belt, and get very precise 0.5 sec intervals.
Pulley ratio is about 13.8, so suspected times are 1.8 sec (platter 1 turn) 0.13 s (one motor turn) and 0.016 s (8 pole pairs in motor)..... 0.5s +- doesn't fit anywhere, even close.
I think if it is to bearing it would show it with any belt.
Nothing to be sorry about. I invested so much time in making TT that few hours more dont mean much, at least we made small progress in understanding performance results of surface treated pulley...
Is it simply an undamped oscillation set up by compliance of the belt and mass of the platter? Agreed, something has been learned about pulley surface finish. Just not sure what.
By the way, my plan for (VHS) capstan motor having slimmer shaft and only a sleeve bearing below is to replace the shaft with a 4mm shaft taken from a floppy drive, fit pulley on shaft and machine it in place (this assumes I can get the shaft concentric in the lathe). I also intend to fit lignum vitae sleeve bearings (salvaged from old lawn bowls) at each end of the shaft. This will make for a slightly awkward support structure above and below the motor, a little like the idler support for a Garrard 301, but I don't mind.
By the way, my plan for (VHS) capstan motor having slimmer shaft and only a sleeve bearing below is to replace the shaft with a 4mm shaft taken from a floppy drive, fit pulley on shaft and machine it in place (this assumes I can get the shaft concentric in the lathe). I also intend to fit lignum vitae sleeve bearings (salvaged from old lawn bowls) at each end of the shaft. This will make for a slightly awkward support structure above and below the motor, a little like the idler support for a Garrard 301, but I don't mind.