Aero V2 150mm : replacement tubeless wheels?

"Delesh" schreef in bericht
ps.com...
I would love to see a really nice carbon frame. It just seems like the
time and money spent on designing/constructing it to be strong/light
enough over an aluminum frame may not be worth the weight savings
unless it is for racing, whereas a lighter wheel/tire design will make
significant savings in weight and usability.
If it takes twice as many (or more) wheels to get agreeable rolling, using
current parts (wheelchair casters) and technology (home made) could well
mean the end result is just a bit too clumsy to make it to mainstream
acceptance. With carbon and specially constructed tires (the 2 most
expensive things in cycling for start-up costs, by chance) weight might come
down to close what aluminum 2-wheels setups such as the Aero 150's weigh
today.

I am sure you know all of this but, I think the reason prices are
relatively high and we will not see any major development in rollerski
design is simply because the market is tiny.
Tiny, and shared by many, keeping production numbers really low. If myself
and my friend are going to manage have our own designs made, everyone can.
Heck, I'm pretty sure I can get that semi-revolutionary 4-wheeler made. Make
drawings ourselves, and just order 2 lengths of alu beam, 4 CNC pieces, 8
laser cut rocker plates, 8 kick scooter/wheelchair wheels and a handful of
hardware, in parts taking from old rollerblades. Jenex would charge $500-600
for something like that, while my proto at retail cost will come to less.
Less also than a good set of ski's that are "just" a curved layered plank.

I am pretty much labeled a
freak by all who see me ski by on my local roads and trails. Bike
riders with all of their expensive gear are everywhere.
If you're going fast over rougher trails, "freak" will turn to "cool", don't
you think?

Its like a thousand lance armstrongs live here. Large companies are not
going to
use their resources for such a small market. It obviously makes any
company that does develop products (jenex, etc.) have to sell them at a
higher cost. So, I guess it means we need to promote and grow our
sport.
I think there's 2 thing limiting rollerskiing from becoming larger :
#1- safety
#2- safety
#3- safety
#1 : With the current scene's favorite products, you're forced to use road
shoulders where in my country cyclists aren't even allowed, as for safety
they get dedicated cycle paths.
#2- You can't use road with decends or sudden turns, as you lack dependable
brakes.
#3- Same for skinny ski's, you can really carve corners like a slalom skier.
This should be the one thing that remains after more useful products arrive.

For #1 and #2, off-road capable rolleski's will be a solution. Current
offerings don't roll off-road, and you're not try them offroad anyway due to
lack of brakes. And attempts carried out for similar products all were
really heavy and clumsy.

If an off-road product, even a single lightweight prototype with working
brakes is made, all it takes is a couple professional skiërs to be seen with
them, overtaking mountainbikers on relatively rough fire roads, and
customers will be lining up. wouldn't you get real itchy if you saw someone
truly XC Rollerskiing and looking pretty fluent and "snow-natural" doing so?

There is a rather large problem with the off road rollerski idea. If
you want to go further off road than packed dirt trails (which some
people already ski on V2 150s) you would probably have to go with
larger wheels as you have been discussing. However, I think it will be
difficult to go with much larger wheels/tires than are currently
available.
"Currently available" means : borrowed from non-sports applications.
I've found that the 6x1-1/4" tires used on nearly ALL off-road rollerski's,
around a dozen brands, are all just tires in a line of various models and
sizes, for industrial and wheelchair use. 8x1-1/4" can be had with pretty
much the same technology, so only slightly heavier. Extra cost : nil. Extra
rollerski frame design effort : minimal. Increase in roll/off-roading :
significant for each step that wheels are larger. I've found such 8" wheels
from the same factory as "our" 6" Jenex wheels, for a fraction of the cost.
If made only a slight bit less overbuilt, they'd be lighter than current 6"
wheels.

I'm also looking at just using 2 wheels, kids bike wheels. I think it will
have to be 12" or 14". A friend that works for a company that has cheap
bikes produced in Asia says they use 12" plastic wheels and 14" spoked
wheels. Quality obviously is quite low, but at least machines already exist
to use lighter/stronger rims and faster tires. The long front end to fit a
14" tire will automatically do it's part to make it less weighted and roll
over trail debris easier. How bad the swinging weight will be...someone will
have to try to know. Anyway, over current kids bike wheels, MTB technology
could truly HALF that weight for the wheel itself. MTB tires are $30, rims
$40 both in full-size, so it wouldn't have to be outragous. Low-end
innertube are thick. Look how our Cheng Shin 6" tubes weigh 42g where a
typical 28" road bike tube of the same girth weighs 70g. Also, thiner tubes
roll faster and with 8 wheels, that might add up a bit.

The technique and feel used when rollerskiing must be as
similar as possible to snow skiing. If you introduce very large wheels
or suspension systems I think it will introduce dramatic changes in
feel and technique.
True, and it sucks. Snow ski's are so light and simple, hard to get in that
ballpark.
That's why for now I believe in using four small wheels, at one point
replaced with high-end versions that are lighter, roll smoother, and faster.
Low-end 150mm 2-wheelers are considered "best" for simulating ski motion, so
I have good hopes a high-end 4-wheeler will get close. The rocker
"suspension" systems means that the virtual wheelbase (length between rocker
pivots) is unsuspensed. However with each wheel rolling over a 1" obstacle,
the corresponding end of the wheelbase is only lifted 1/2". More hits, but
small ones, each lifting the skier for just a fraction.
2-wheel setup as Aero, 80kg skier : 1" obstable requires to lift 40kg over
1", 2 times
4-wheel rocker setup, 80 skier : 1" obstable requires to lift 20kg over
1/2", 4 times
I think I rather have two 1/2" twigs to roll over than one 1". And then,
weight on each hit it halved.

Those small high-frequency bumps might also be where a high-tech carbon
frame could truly add something other than saving weight. Absorbing
high-frequency input at the rocker pivots, and offering a nice low-frequency
push-off "spring". If all the carbon and tire knowledge in the world were
put into a protype, I bet it would be very convincing for anyone that tried
it. Unfortunately only sale numbers will bring tmanufacturing cost and
retail price down.

...I think it will introduce dramatic changes in feel and technique.
In essence it would be a different sport
with different but similar technique.
That was tried with things such as Crosskates, and failed. XC Rollerski's
will have to be reasonably light and ski-like, so when the skier closes his
eyes, he must hardly be able to tell a difference. If that is accomplished,
sales migh well be very good.

I think the idea requires a radically new design to be successful.
Radically simple, perhaps. IMO the 2x2 rocker system that Siriro just
introduced is just that. I've not read any reviews on it yet, and it's just
for rough pavement and racing, but it just LOOKS right.

I can't live with the idea that centuries of wheel technology can't match
rolling off-road the speed of a 2-meter long ski that slides with friction
over stuff that fell from the sky. Yes, mountainbike wheels are huge where
rollerski's get tiny wheels, but consider how :
-low-end 150mm wheels, 2 on a ski, are considered "faster than snow" on
pavement already.
-mountainbikes should lap similar times on groomed snow as skinny ski's,
faster on summer-dirt.
-doubling the amount of wheels halves the rolling resistance of the tires
themselves.
-wheels rolling shortly behind each other (4 within a meter) might follow in
each other's track before the compressed soil has had time to rebound,
making RR lower for each next wheel to come buy. If a 5-wheel rollerblade is
rolled over a golf course, I'm convinced the 5th wheels will experience much
less resistance than the first. And 5 wheels roll night and day easier than
2, one on each end, carrying the same total weight.

I would be extremely disappointed if a 4-wheel rocker design, even with
current stupidly quatruple overbuilt wheels, could make a huge leap forward
over the V2 150's of this world.
Front wheels might even be upgraded to 7" or 8" with minimal weight penaly.
Rear replaced by a single 12" or 14" bike wheel.

I would love to have a product that I could use on mountain trails
but I think it is a very difficult problem.
Please tell me it can't be done :-)
I'll be glad if it can be used on the same trails that are used in the
winter when snowed over. No need to be able to rollerski where even a snow
ski can't go.
I'm not familiar with the exact trails that make up race venues, but if they
aren't totally rock-infested, it would be nice if similar speeds could be
rached. Climbing might suffer a bit, and on fast surface or pavement the
wheels will be faster, but if the trails can be attacked with decent safety
(brakes) and without annoyance from a constant stumbling....oh momma!

Anyway, I think a great brake setup would be a lever (like the v2 brake
design) that actuates a small hydraulic or mechanical disc brake on the
rear wheel. This simple design could probably made light and would have
tremendous braking power with the ability to modulate. It would also
eliminate the rear tire wear and the possible overheating of the tire
on longer descents and have better performance in the extreme braking
or wetness of mountain trails or with knobby tires (for off road
applications you are talking about).
Realize that a disc brake can only absorb as much heat as it's got material
in the rotor. A mountainbike has 2 rotors of 100g+ each.
A speed reducer/brake, as I hope to someday have, that wedges a roller in
between 2 wheels, will have the tires heat up by half for the same brake
power. The brake roller might need attention though. When using a 14" rear
wheel, a simply rim brake might suffice. Then, a disc break would barely add
weight, and work in the wet also. Disc front hubs would work fine as a
rollerski rear. I'd want brake levers on the poles.
A less efficient lever/caliper setup might be required to not get an on-off
switch, as rotor/wheel size relationship makes for the grabbyness of a
brake. Good thing, calipers exist for short cable pull, and levers for long,
that would work. In case of hydraulic brakes, mixing brands could have the
same effect, but be expensive. Then, people buy bikes too, and those are
even more expensive with their many parts.

I also think a solid tire around a shock absorbing wheel (like the
Michelin tweel) could be developed for rollerskis.
YES! I had not thought of that. I did a bit of reading (okay, Discovery
Channel watching) on that, and it might be an interesting match for this
purpose.
Perhaps Michelin would be interested to work with me on it, for their
research towards world domination of the Tweel...
How cool would it be if we could just buy Tweels to replace our 150mm tires?
Tweels do have a hard time matching tire performance though. Flat tires
"only" happen to those that won't use sealent anyway.