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Direct drive/rim drive/idler drive vs. belt drive?

O.K. here is one for all the physics majors and engineers.

Does a high mass platter being belt driven offer the same steady inertia/speed as a direct drive or idler drive?
Is the lack of torque in the belt drive motor compensated for by the high mass platter. Object in motion stays in motion etc. Or are there other factors to take into consideration?
I am considering building up a Garrard 301 or Technics SP10, but is it all nonsense about the advantage of torque.
I am aware that the plinths on these tables can make a huge difference, I've got that covered.
My other options would be SME20 or Basis 2500 of Kuzma Stogi Reference etc.
If I have misstated some technical word, please avert your eyes. I don't want a lecture on semantics, I think everyone knows what I mean.
Thanks in advance.
mrmatt
johnnyb53
3,490 posts
 

08-01-09: Quiddity
Johnny

... The maximal velocity variation for a given length change is the product of the radial displacement produced by the length change and the corner frequency of the filter system expressed in radians per second. The numbers come out in the parts per million range.
How long is the initial transient of a piano note, a string pluck, a drum or cymbal hit? I suspect the initial dynamic jump is well under 1 ms. How large, physically on average, is such a transient "bump" in a record groove that is 1400' long for a 20-minute side? If belt drive flex lengthened that transient by 10-20%, it seems to me we would be talking about parts per million from one standpoint, but possibly a quite audible 15% variation from another.
quiddity
119 posts
 
Johnny B

You don't seem to understand the function of a low pass filter. It is not possible for the belt drive flex per se to affect anything by more than a few parts per million for the reasons given.

A change in belt tension will however create belt creep and this effect will be around 1000 times larger. That was my point.

Mark Kelly
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albertporter
4,927 posts
 
Mark Kelly (Quiddity).

How did you come to choose your moniker? I looked it up:

1. The essence, nature, or distinctive peculiarity, of a
thing; that which answers the question, Quid est? or, What
is it? " The degree of nullity and quiddity." --Bacon.
[1913 Webster]

Anything to do with that?
quiddity
119 posts
 

From the Websters dictionary 1905 edition: "A barbarous term used in school philosopy for essence" - gotta love a dictionary with that degree of vitriol.

My intended career was as an academic in philosophy. My chosen field was logic and the structure of consciousness, especially with reference to linguistics and mathematics.

One of my heroes is Willard van Orman Quine, who was a logician at Harvard.
http://en.wikipedia.org/wiki/Willard_Van_Orman_Quine
One of Quine's books is titled "Quiddities". I rather liked the term so when I established my consulting company I called it Quiddity Technical Services.

I don't like monikers but Audiogon insisted that I register as a business and that I take a moniker which referred to my business name, so there you have it.

Mark Kelly
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albertporter
4,927 posts
 
Excellent story, mine is much simpler.

My Mother and Father picked out Albert Porter for me when I was born and it seemed like a good name for Audiogon as well :^).
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