Vinyl temperature
On Friday, October 28, 2016 at 1:34:44 PM UTC-4, wrote:
The elasticity of vinyl (and many other materials) varies with temperatur=
e.
It seems to me that at lower temps would allow the phonograph stylus to m=
ore faithfully follow groove displacement.
Would there be any advantage to a turntable which chilled the record duri=
ng playback?
And what would be the optimum temp? Too low and the vinyl would enter the=
glass transition and become brittle.
i thought of this reading a discussion about using summer car tires in co=
ld weather.
It is an interesting question, but you first need to do some math, and then=
to understand the forces involved.=20
First (and I will first calculate in old and new currency here):
How fast is the stylus going?
A 12" Disc uses from about 11-7/8" to about 5" for actual signal. To make l=
ife easier, we will use 12 and 4. Meaning that the average diameter is abou=
t 8". Pi x 8 x 33.33 =3D distance per minute. Use 838 inches per minute. Us=
e 70 feet per minute. Which is about 1.16 fps, or 4,200 feet per hour. On a=
verage.=20
How much does the stylus "weigh"?=20
Use 2 grams. Use 0.2 x 0.7mm as the stylus bearing area. Giving a total bea=
ring surface of a bit more than 0.14 sq.mm. That comes to 51 grams per sq.m=
m. One sq.mm. =3D 0.00155 sq.in. Or, 645 sq.mm. =3D 1 sq.in. 51 x 645 =3D 3=
9,345 grams per square inch (39.345 kilos). =3D 1,405 ounces per square inc=
h, or ~87 pounds per square inch. Drag something that has a bearing surface=
of one square inch and weighs 87 points at 70 feet per minute over a rough=
vinyl surface while bouncing it 10,000 times per second and, I suspect, th=
ere will be some evidence of that passage. (70 fpm =3D 21.3 mpm)=20
Now, consider that said sylus is jumping up, down and side-to-side at anywh=
ere from about 20 to about 20,000 times per second and all parts between. T=
hat it is as hard as (at least) an industrial sapphire or diamond is a good=
start. Steel needles back in the day moved much faster, but had a much gre=
ater bearing area - but were designed to play one (1) time per use. ONE TIM=
E. Edison learned early, and developed the vertical diamond stylus.=20
Cutting to the chase:=20
Too cold, and the diamond (read small, dull chisel) will shear off the shar=
pest points on the groove. Too hot, and the vinyl will be in a plastic stag=
e and those points will be rounded, or even folded over. Vinyl has no memor=
y, so would not 'recover' as some plastics.=20
Ideally, any given vinyl disc should be played no more than once (1 time) p=
er 24 hours to give the surface a chance to equalize in temperature and to =
give the peaks and valleys a chance to re-polymerize with the rest of the s=
ubstrate. I would go so far as to suggest that no vinyl disc should be play=
ed about about 80F or below about 85F (15.5C to 29.5C).=20
As to "summer" tires vs. "Winter" tires: once the vehicle has gone a few mi=
les/km on smooth pavement, the friction has warmed the system to the point =
that it should make no functional difference. This is not to suggest that t=
here are no differences in rubber formulations - there are, and they are si=
gnificant. And, those differences are most significant when the tires are a=
ctually being used per their design: A winter tire on an icy or ice-and-sno=
w mix will have definite advantages over a summer tire, even were it to hav=
e an aggressive tread design. And a winter tire driven on a hot asphalt roa=
d in the middle of the summer will wear out very quickly. But on dry paveme=
nt in the winter after those first few miles, the tires are about equal - b=
ased on actual tread design.=20
Peter Wieck
Melrose Park, PA
|