Belt stretch

The technology necessary to measure the effects of stylus drag and belt stretch exists today, but the people that have access to such equipment don't give a damn about it. They're probably too busy smashing atoms together and sending things to space.

The technology that was around when most records were cut was primitive at best and probably exhibited major speed fluctuations. Achieving super accurate speed precision today probably just enables one to better hear the inaccuracies of yesterdays equipment, but what do I know. I own a stupid belt driven turntable :)

Stylus drag and belt stretch is an idea (something, such as a thought or conception, that potentially or actually exists in the mind as a product of mental activity).

I have an idea. Perfect speed precision will guarantee slow transients.

I think we might be better off if we tried to figure out the inaccuracies of yesterday's equipment (such as how it reacted to cutter drag) and compensated for it. If a lathe slows down while the cutting head cuts a big transient on a lacquer, our TTs need to speed up the disc for the same transient. If you disagree that a lathe slows down when cutting a big transient on a lacquer, you might be indirectly saying that a cutting lathe has perfect speed precision while cutting a lacquer. Buy one and mount a tonearm to it and you should hear more accurate speed precision than any TT can provide. I don't know, but I bet that a cutting head on lacquer produces more friction than our styli do on vinyl.

Because we track our cartridges at anywhere from 1 gram to 3 grams or so, we tend to think that the braking action of the stylus in the groove is minimal and that a belt-drive is then able to overcome this negative force with ease. This is the first false assumption.

Stylus force drag is very serious indeed. I took the following from the website "www.Micrographia.com", (here's a link to Pressure) on the issue of the pressures involved: "Neglecting factors such as the elastic deformation of vinyl, the distribution of forces in a V-shaped groove and the accelerations at the stylus tip during tracking, simple calculation based on these figures gives a stylus pressure of 240 grams per square mm, or 340 pounds per square inch.

Johnnantais,
In a thread about belt stretch due to stylus drag you added the information above to the discussion, but either I or you are confused. You seem to think that the force seen by the belt and/or motor is something great, like 340lb/sq. inch. That is not the case.

A simple experiment (that you should not do!) is to put a 1"x1" block of wood on your TT, place a 340lb weight on top of it, hold it in place, and turn on the TT. Of course it's not going to turn at all. The pressures you noted above (if the calculations are correct) are only seen by the vinyl and stylus but never by the belt or motor. The forces needed to overcome the friction of stylus drag are minimal.

Here's an experiment that will be hard to implement but easy to think about. Imagine a cartridge attached to your finger with a string, tracking an LP that's turning on a TT. The cartridge would have to stay up somehow, of course. Use your imagination. Because there is no counterweight, also imagine that the 8 gram cartridge is not going to destroy its suspension and cantilever. How much force do you think you are going to have to use to keep your hand in one spot? You probably aren't even going to feel a pull on your finger... and that's with 8 grams of tracking force. Belts and motors don't see as much drag as you think.

FWIW, I don't disbelieve that belt stretch and rebound occur, I just think this is good discussion :) I do think that it's not as serious as some believe, though.