On Friday, October 28, 2016 at 7:59:50 PM UTC-4, Peter Wieck wrote:
On Friday, October 28, 2016 at 1:34:44 PM UTC-4, wrot=
e:
The elasticity of vinyl (and many other materials) varies with temperat=
ure.
It seems to me that at lower temps would allow the phonograph stylus to=
more faithfully follow groove displacement.
Would there be any advantage to a turntable which chilled the record du=
ring playback?
And what would be the optimum temp? Too low and the vinyl would enter t=
he glass transition and become brittle.
i thought of this reading a discussion about using summer car tires in =
cold weather.
=20
It is an interesting question, but you first need to do some math, and th=
en to understand the forces involved.=20
=20
First (and I will first calculate in old and new currency here):
=20
How fast is the stylus going?
=20
A 12" Disc uses from about 11-7/8" to about 5" for actual signal. To make=
life easier, we will use 12 and 4. Meaning that the average diameter is ab=
out 8". Pi x 8 x 33.33 =3D distance per minute. Use 838 inches per minute. =
Use 70 feet per minute. Which is about 1.16 fps, or 4,200 feet per hour. On=
average.=20
=20
How much does the stylus "weigh"?=20
=20
Use 2 grams. Use 0.2 x 0.7mm as the stylus bearing area. Giving a total b=
earing surface of a bit more than 0.14 sq.mm. That comes to 51 grams per sq=
..mm. One sq.mm. =3D 0.00155 sq.in. Or, 645 sq.mm. =3D 1 sq.in. 51 x 645 =3D=
39,345 grams per square inch (39.345 kilos). =3D 1,405 ounces per square i=
nch, or ~87 pounds per square inch. Drag something that has a bearing surfa=
ce of one square inch and weighs 87 points at 70 feet per minute over a rou=
gh vinyl surface while bouncing it 10,000 times per second and, I suspect, =
there will be some evidence of that passage. (70 fpm =3D 21.3 mpm)=20
=20
Now, consider that said sylus is jumping up, down and side-to-side at any=
where from about 20 to about 20,000 times per second and all parts between.=
That it is as hard as (at least) an industrial sapphire or diamond is a go=
od start. Steel needles back in the day moved much faster, but had a much g=
reater bearing area - but were designed to play one (1) time per use. ONE T=
IME. Edison learned early, and developed the vertical diamond stylus.=20
=20
Cutting to the chase:=20
=20
Too cold, and the diamond (read small, dull chisel) will shear off the sh=
arpest points on the groove. Too hot, and the vinyl will be in a plastic st=
age and those points will be rounded, or even folded over. Vinyl has no mem=
ory, so would not 'recover' as some plastics.=20
=20
Ideally, any given vinyl disc should be played no more than once (1 time)=
per 24 hours to give the surface a chance to equalize in temperature and t=
o give the peaks and valleys a chance to re-polymerize with the rest of the=
substrate. I would go so far as to suggest that no vinyl disc should be pl=
ayed about about 80F or below about 85F (15.5C to 29.5C).=20
=20
As to "summer" tires vs. "Winter" tires: once the vehicle has gone a few =
miles/km on smooth pavement, the friction has warmed the system to the poin=
t that it should make no functional difference. This is not to suggest that=
there are no differences in rubber formulations - there are, and they are =
significant. And, those differences are most significant when the tires are=
actually being used per their design: A winter tire on an icy or ice-and-s=
now mix will have definite advantages over a summer tire, even were it to h=
ave an aggressive tread design. And a winter tire driven on a hot asphalt r=
oad in the middle of the summer will wear out very quickly. But on dry pave=
ment in the winter after those first few miles, the tires are about equal -=
based on actual tread design.=20
=20
Peter Wieck
Melrose Park, PA
To talk about stylus pressure against the vinyl groove one must also consid=
er effective mass of the stylus + cantilever etc. combined with acceleratio=
n of that moving mass, F =3D MA.=20
Re. tires, the manufacturers of high performance summer tires typically war=
n not to use them below ~40F. The problem is not traction related, the rubb=
er compound becomes brittle and prone to cracking. Also, one cannot count o=
n friction warming the treads if the vehicle is driven at low speeds. This =
link talks about using and storing HPSTs:
http://www.tirerack.com/tires/tirete...p?techid=3D220