Tire-making, continued....

I've gotten in some of the materials (kevlar thread, latex, fumed
silica) but not all (still need fabric).

I also stopped by china-mart and bought a $12 26" white-wall "beach
cruiser" tire packaged under the Bell name, but marked Innova. I decided
to cut apart an existing tire to see how it was made, and all I had
around was better-quality tires and it seemed a shame to cut up a usable
$50 Schwalbe or Continental. I did have a pair of no-names I got off a
Worksman bike, but even those are the kevlar-belts and they were used so
little that the center treads still has the nubbies on it.

First off I was surprised at how thin it is made; I'd have guessed that
it was at least twice as thick as it turned out to be. The sidewalls
measure around .09" thick, and the center area (in-between the tread
blocks) measures right around .1" thick. The tread blocks measure
another .09" taller than that. The tire is made in three layers--black
casing, white-wall layer, and then the center tread layer on top. Once
cut, a thin section of the white-wall rubber is visible all the way
across the tire.

The tire came rolled up into a small box, and I had always thought
(since seeing these tire packages in Wal-Mart) that these tires used
kevlar beads, but that's not so--they just use stranded wire cable.
Three turns of cable approximately .04" diameter each, which seems to
indicate a "working" weight capacity of around 60 lbs each (as per this
page)-
http://www.govart.com/hardware_wire.html
The bead wire is not really picture wire, as the bead wire is 3 core
strands surrounded by eight outer strands (not seven strands as the page
says picture wire always is). Still, three or four turns of the kevlar
thread should come fairly close to the same strength. The kevlar thread
I bought is #346, which is .026" diameter and has a "strength" rating of
140 lbs, which--I would guess--is the typical breaking strength.

The fabric used for the tire casing, I don't know if I will be able to
duplicate. It isn't even "fabric" in the usual sense, it's just a grid
of loose moderately-thick threads--they wouldn't even stay together if
they weren't embedded in rubber. It's a square-weave (two sets of
threads 90-degrees apart, and tilted 45-degrees to the plane of the
tire) but one way has only about 10% of the threads of the other.... one
way they are .065" apart, and the other way is .435" apart.
,,,,,,,
I may just have to pick a medium-weight nylon mesh and try that. I tried
looking for window screening but that's all fiberglass or polypropylene.

The fumed silica is a rather odd substance. Still in its double-bagged
package, it feels like the squishy foam stress-reliever desk toys. It's
solid, but can be squished into whatever shape you want, and it stays in
that shape once squeezed... and it has a rubbery "bounce" if you thunk
it. It's also very light-weight, a gallon of it weighs only 10 oz.

The latex I haven't opened yet. The label says it is white, which I was
hoping, because the auction didn't say and I'd seen some brush-on
elsewhere that was light green.

I haven't bought any carbon black yet, don't need it right away....
~