Direct drive vs belt vs rim vs idler arm

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.)

The Hymn of modern Turntable owners

The Bright Side Of Life

Hello Mr dovir I see you seem to not read my postings...again for the record that movement was because this particular TT has a hung suspension and when you put lateral side force thats what happens the platter moves...LOL

no other turntable has ever been able to accomplish this task..Does it really matter?! maybe ..maybe not..but it clearly shows that constant change of load(big load) does not affect its speed stability...IMO this is a big deal if you like to play lots of different music(frequency extremes) like including organ music etc...

Lawrence
Fidelity Forward

01-04-13: Richardkrebs
Dover
Yes we are measuring an error and correcting it before it gets worse.
This is the old argument about feedback correcting an error that has already passed. The nature of this feedback and the torque/ platter moment are critical here. The motor must totally dominate the platters rotation.

Mosin
Okay, let's go further. Do you think a special merry-go-round could be built for the little girl, so she could spin as many kids around as you can?
This goes to torque, and how one might approach building a turntable with a low torque motor, yet having mass applied so that performance would equal a turntable with a high torque motor.
I suppose the point here is that there are quite a few ways to skin the proverbial cat.

Hi Richardkrebs/Mosin

Interesting thoughts. Based on the tables I own.

Richardkrebs – I agree with your thoughts as they would apply for DD and Idler but not for string drive. I would also revise the wording to read motor/controller instead of just motor - to be explicit.

Mosin – I support and agree totally with the concept you have described. In fact based on my direct experience I believe the Verdier Platine original design when properly set up, satisfies your conditions. Are you familiar with it?