Direct drive vs belt vs rim vs idler arm

Dover,
Can you comment on how the Transrotor system might differ to those of Linn, Rega, VPI et al?

Dover, Sorry for being such a "creep". I do recall your citing Kelly's formula. It just seemed to me that he later modified his ideas. As I said, I may be wrong. If all I can do is to try to remember what someone else wrote, I am no authority. Anyway, from now on I will wear suspenders.

Halcro - Breaking newsflash -
This Fatbob could have the magnetic drive, where the belt drives a subplatter and it relies on magnets on the platter to "lock" to the attracting magnets on the subplatter. They say it reduces wow and flutter by a factor of 10.
Personally I would call this floppy drive - maybe thats the issue, certainly not as direct as a DD, idler, or thread drive..
http://www.positive-feedback.com/Issue50/transrotor.htm

The main difference is the heavy platter in comparison to the Linn/Rega/VPI. The VPI's are driven around the perimeter of the platter, so they run higher speed motors.
As far as motor for the Transrotor goes, I couldn't find any specs on the Transrotor whether its ac or dc. I assume no error correction but you could measure the back emf in the motor and use that to control speed, but there is nothing measuring the platter. As Richardkrebs says you have to engineer the motor/drive system/platter as a group. From what I hear in the video, my old Roksan, Sota & Townsend Rock TT's, which use rubber belts, would be more speed stable than the Fatbob.

I just did some review of Kelly's posts. The missing link, I think, is the fact that he would say there is no such thing as a perfectly inelastic belt. (Such a belt would not bend around a pulley.) So there is no case where E = infinity in the real world. He does say that string drive and mylar tape significantly reduce the problem of belt creep, probably to insignificance but not zero. (I pursued this only to reassure myself vis my memory, not to critique belt drive turntables.)

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