fnguy

Just what kind of gas are the cores/hubs filled with, and what does that do
for the skater? I gather that it's a spoke-less design, to reduce drag and
turbulence, and the pressurized gas keeps the structure stiff for support?
Not sure how widely this has caught on...

And what happens if they "blowout" while you're doing a hard crossover? ;')

sk88888er

These wheels don't have pressurized cores. Instead, they are a "solid
core". The core is very porous (kinda like a real hard stiff foam).
The cores are stiff & aerodynamic (no spokes & hollow spots to flex &
create wind drag), but the porous nature makes them as light as spoked
hubs.

I personally believe they are of greater benefit indoors than
outdoors. The stiff core is great in the midst of the corner on a
short track at warp speed, as flex is the last thing you want here!
However, on the road, the additional shock absorption a spoked core
will provide, and the additional cooling effect provided with a spoked
hub (albiet with a little wind resistance to go with it), will provide
more benefit than a solid core. Bearings generate heat, hot pavement
transmits heat. Urethane wheels are in the middle of all this. When
urethane gets hot, it get's soft & mushy. A spoked hub will create a
cooling affect that will minimize this heat somewhat.

Gas filled is a misleading statement, as too many skaters think they
are hollow with some type of gas inside a pressurized chamber.
Instead, the term "gas filled" refers to the manufacturing procedure.
Some type of gas is used to create the porous texture.

russotto

Urethane generates heat as well, probably more than the bearings.
--
Matthew T. Russotto mrussotto@speakeasy.net
"Extremism in defense of liberty is no vice, and moderation in pursuit
of justice is no virtue." But extreme restriction of liberty in pursuit of
a modi*** of security is a very expensive vice.

sk88888er

The Urethane does get hot, but only from the friction generated by the
concrete (or similar skating surface). Urethane won't generate heat by
itself.

edward dike, iii

| russotto@grace.speakeasy.net (Matthew Russotto) wrote in message
news:<vnudnVE509PHB67dXTWc-g@speakeasy.net>...
| > In article <8f228453.0402180819.6eb34ad5@posting.google.com>,
| > sk88888er <sk88888er@sbcglobal.net> wrote:
| >
| > >more benefit than a solid core. Bearings generate heat, hot pavement
| > >transmits heat. Urethane wheels are in the middle of all this.
| >
| > Urethane generates heat as well, probably more than the bearings.
|
| The Urethane does get hot, but only from the friction generated by the
| concrete (or similar skating surface). Urethane won't generate heat by
| itself.


"...Urethane won't generate heat by itself...."

So, where then is the energy 'lost', or 'absorbed' to internal squirming/
deformation?

ED3

b fuhrmann

The gas type is meaningless. According to RollerBob (http://www.rollerbob.com),
who does a LOT of business with Labeda (http://www.labeda.com, a truly user
unfriendly and devoid of information site), the claim is that the hub is
lighter and more aerodynamic. He carries one custom made racing wheel with
that hub for micro bearings.

I'm more of a skeptic. The weight difference between them and a wheel with
a standard hub can't be all that much. Ditto for the aerodynamics.

They are a foamed plastic. No pressure inside.

;')

They are a very solid material, impossible to have a blowout.

--
Bill Fuhrmann
Remove DELETE to reply

inlina

Urethane does generate heat in dynamic load-unload (ie. rolling). The
energy lost from viscos damping has to go somewhere, and that is into
heat.

Trivia of the day: Properties of elastomers can be idealised to those
of super-cooled gasses.

Corey 'My wheels burn up on re-entry to the transition' Gibson

fnguy

Hmmm... so when you see "Bont Guy" being towed at insane speeds by a
motorbike, any idea what kind of temps they reach on the urethane?

"He so crazy go long time ten dollah..."

inlina

I'm thinking that once he goes past a certain speed, the wheel isn't
contacting the ground for long enough to fully compress. The damping
isn't happen for as long a time period and over as long a distance,
and he may therefore not be heating them at the same rate as perhaps a
slower speed. Then he's going fast, so the heat transfer to the
environment should be better, maybe. So the wheels don't heat up as
much, I think. OK, now I'll stop thinking cause it's past my bedtime.
Does any of this make sense?

I think the same thing happens in bearing lube. For a given lube (and
the rest of the scenario around it), there speed at which heat
generated/potential heat loss peaks and that's the hottest operating
temp. Perhaps, maybe, I think, dunno (I think I read it in a Shell
catalogue for aviation lube, but their being investigated for
anti-trust stuff now, so perhaps they can't be trusted on this either,
perhaps, maybe).

Corey "If there's one thing working in the automotive industry has
taught me, it's never commit to anything until it happens, maybe"
Gibson

inlina

Now that we've determined they aren't actually gas filled, here's one
for you.

Hyper had a hockey wheel that had a tube of air around them inside the
urethane to 'make them grip better'. You could change the pressure of
it or anything, it was jsut like a big bubble around the core. And
yeah, they gripped, and really deformed, and ****ed in a big way cause
they were DEAD SLOW.

They did pretty well in the 'ISO Gyroscopic-balance Co-efficient of
restitution' test, but you loaded them up with body weight, and the
simply ****ed. One of my team mates said 'These wheels are great, they
grip so well, but I can't keep up with anyone'. Well, duh.

Corey 'I said he should take them down the gas station and put 120PSI
in em' Gibson