Stylus Drag

Yes, a platter does store energy. Apparently, that alone is not enough to counter stylus drag.

My Final Audio TT has a 19kg platter and very sophisticated motor drive, basically a huge AC motor driven by oscillator preamp and power amplifier which reconstructs sine and cosine waves for the motor and provides precise adjustability for both speed and torque applied to the motor.
As Halcro alluded to above when setting speed, I have to do that with the stylus in the groove.
Once set though it is very stable. In recent tests with the Timeline and KAB there was no speed change from heavily modulated passages both inner groove and outer groove.
Arm and cartridge were Naim Aro/Koetsu Black tracking a 1.8g

Andrew,

I have checked my speed on my BN with a digital readout through my computer using a program that is free called iSpectrum. What I do is play test frequencies and checked the Waterfall plot and it is spot on. My biggest factor is the belt. They need to be replaced when they get old otherwise you get a sling effect. But this has been by ear. I have excellent speed stability which I can watch on a screen. I don't use a strobe but instead the computer to set my speed. Seems to match the strobe though. Once set it stays put. I have checked it often and my speed stays steady.

Stringreen, If you check the other, older thread on speed stability, you will find many reports from many owners of results for many different kinds of turntables. Most were using the Sutherland Timeline as a criterion for speed stability. The sentiment was that the Timeline is superior to what is probably the best of the strobe devices, the KAB, in the sense that the Timeline could show speed errors where the KAB showed none. A disturbing number of tt's were unstable even with no stylus drag factor added, using the Timeline. That's why this thread is completely redundant.

I'm not sure the discussion is staying on topic. The fact that a platter slows when the stylus is in the groove is not the same as what as referred to as stylus drag. As I understand it, I don't think it has ever been measured quantitatively.