Turnable database with TimeLine

Lew,
If you watch my video of the Raven AC-2 with the Timeline.....you can see exactly what you suggest albeit in reverse.
You can witness the Timeline laser moving incrementally to the left as the record is playing.....whilst when the tonearm is lifted.....the laser is stationary.
This means that the turntable is spinning exactly at 33.33rpm without stylus drag....but runs slightly slower WITH stylus drag.

Actusreus,

If a turntable slows down for a very brief moment due to the stylus drag and the Timeline registers it by shifting the laser spot but then remains constant, how relevant is that drag save for the very brief moment of the stylus settling in the grooves and the turntable adjusting its speed?

I have never witnessed what you describe.
Stylus drag is constant (but variable if you know what I mean)....so that when it slows down the speed of a turntable platter......that speed is changed for the duration.
It doesn't 'spring back' to accurate speed after the initial 'shock'....although with some direct drive turntables using speed-error correction.....this might be a possibility.
I just haven't seen evidence of it using the Timeline?

Tonywinsc,

The problem is you can't know if the drift is due to speed being something other than 33 1/3 exactly or if speed is actually changing during play.

This sounds like such a logical proposition....that no-one seems to argue against it and many have repeated it......
I suggest that it is impossible (without complex computer management).....to design an AC or DC synchronous motor to turn at multiple varying speeds which can line up a laser at an exact point every revolution at both 33.33rpm and 45rpm.
And as none of the motors in any of the turntables we know of.....have such sophisticated (and devious) computer algorithms inbuilt....this argument is simply childish?

I would argue with Tony on different grounds. I think you CAN know if drift is due to "speed being something other than 33.33 exactly or if it is changing during play." At least you can know it to the accuracy of the frequency of the laser flashes on the Timeline. (Since I don't have one in my possession, I cannot describe it exactly.) I think it has more than one laser, at least two and maybe four. (Again, "I think" the early version had fewer lasers.) Let's say that the worst case scenario is it has one laser, which means that there will be a flash of light every ~1.8 seconds. Assuming the astuteness of the observer is not a limitation, that means one could detect whether speed has varied during the 1.8 second interval between flashes. If speed is just inaccurate but is not subject to stylus drag, then the drift of the laser spot will be a constant amount in one direction or the other. (Halcro just gave an example of that with the Raven.) If speed is being now and then momentarily retarded due to stylus drag (or other cause), then the laser spot movement will be irregular or regularly irregular or irregularly regular, within the limits of detection determined by the frequency of the laser flashes, which would be every 1.8 seconds divided by the number of lasers flashing per revolution.

There are two subjects here: 1) How well do the differing turntables hold speed to exactly 33 1/3 rpm? 2) What is the effect on platter speed during heavy groove modulation?
Subject 1 is being answered with the Timeline device testing. And the Timeline device is being used appropriately for these measurements. This is a perfectly valid and interesting exercise.
Subject 2 is also a valid and interesting point. The Timeline device, however is not the appropriate tool in this case. A fine tachometer is required. I find this subject interesting and especially if it were possible to compare the results of speed control with a heavily modulated record on all three basic drive types- belt, direct and idler.