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View Full Version : Ideal Muni (Was RE: Hardened Hubs?)


Kittle, Peter
2000-04-10, 07:38 PM
As someone waiting (and waiting, and waiting) for a Telford, I've had plenty of
time to think about the ideal Muni. A couple of Chris's comments about the DMATU
make sense to me, but a couple others don't--especially about the new Vortex.
First, the steel issue--I haven't held a Vortex frame, but I have held a Telford
frame, made of the same 4130 chromo tubing--and it was so light it made me do a
double take to make sure I was really holding the thing up. In terms of overall
weight, I think that the frame is the least of any high-end uni's worries--it's
the rotating mass of the rim and tire that are likely to be the real weight hogs
(my 24x2.6 tire alone weighs around 4lbs). As the owner of two aluminum-framed
bikes (and former owner of two steel bikes--damned thieves), I'd prefer steel
any day--more compliant ride, less likelihood of catastrophic failure. Now a
titanium Telford would be interesting ... As to the design being weak: is that
necessarily true? All cycle frames have to be held together by welds (or brazing
or lugging or ...), and it seems that the multi-stay design used on the Vortex
(which is somewhat similar to the designs of the Telford and Hunter) shouldn't
be discounted just because of the multiple welds at critical contact points.
I've not heard any reports of people breaking Hunter or Telford frames, despite
some amazing abuse thrown at them--it's usually the hub that breaks. As hub
technology gets better and better, I suppose that frame breakage may become an
issue, but it doesn't seem to be one now. Anyway, just a few thoughts.

Personally, my ideal muni would be a Titanium Telford with one of the prototype
Hunter hubs, Moxey seatpost, nonextistent flyweight 3" tire, XTR cranks, Easton
Cully pedals ... of course, I'd probably just want to hang it in my office and
stare at it all day long.

Peter

> The ATU lacks a few things I expect in an "ideal" mountain machine. It has a
> not-so-common number of spokes, not-so-common-on-mountain-bikes seat tube
> diameter, skinny rim, narrow tire clearance,no seat handle, steel frame, etc.
> The new Vortex has addressed most of these issues, but I still don't like the
> frame design. It's still made of steel (heavy) and the two skinny fork pieces
> on each side are not even connected to each other except at the bearings and
> at the seat tube (weak).
>
> But hey, it does have the right axle.
>
> Chris
>
>
>
> On Mon, 10 Apr 2000, John Foss wrote:
>
> > > I've tried DM and I've tried unicycle source, and there's no way to buy
> > > the DM hub without buying the whole enchilada.
> >
> > But it's a great enchilada! If you can afford it, why go through the
> hassle
> > of trying to make something else fit around it? Your existing unicycle
> > probably won't fit with that hub anyway, so it might be worth it.
> >
> > John Foss, the Uni-Cyclone http://www.unicycling.com (http://www.unicycling.com/)
> >
> > "Lay down -- I think I love you" - Bumper sticker seen in Sacramento
> >

Chris Reeder
2000-04-10, 09:48 PM
"Kittle, Peter" wrote:
> -it's the rotating mass of the rim and tire that are likely to be the real
> weight hogs

I don't think rotating mass on a unicycle is a big issue. The speeds are much
slower than on a bike, you have tons of torque anyway,and if anything a tire
with more rotational inertia is going to plow over obstacles all the better.

> As to the design being weak: is that necessarily true? All cycle frames have
> to be held together by welds (or brazing or lugging or ...), and it seems that
> the multi-stay design used on the Vortex (which is somewhat similar to the
> designs of the Telford and Hunter) shouldn't be discounted just because of the
> multiple welds at critical contact points.

Similar, yes. I like the Telford frame because of its large triangle built into
the frame. (Although one leg does have quite a curve to it, which is still
questionable to me. Is that to prevent the "ramrod" effect?) See any large
triangles in the Vortex or the Hunter? I'll let you answer that. But you are
right, hub breakage is far more common.

Chris

John Foss
2000-04-10, 10:15 PM
> I don't think rotating mass on a unicycle is a big issue. The speeds are much
> slower than on a bike, you have tons of torque anyway,and if anything a tire
> with more rotational inertia is going to plow over obstacles all the better.

Rotating mass if anything is more of an issue on a unicycle. This is the mass
that resists your effort every time you speed up or slow down, using your
precious energy each time. Unfortunately we unicyclists have to speed up and
slow down a lot!

> Similar, yes. I like the Telford frame because of its large triangle built
> into the frame. (Although one leg does have quite a curve to it, which is
> still questionable to me. Is that to prevent the "ramrod" effect?)

I think the purpose is to make the Telford the nicest looking unicycle frame
around. I think I've also heard Geoff mention the curve provides a little bit of
shock absorbtion. But I prefer to think it's for looks. By "ramrod" effect, do
you mean the effect of a straight vertical fork on transmitting trail bumps
directly up the seatpost? That's what we get on almost all other unicycles...

Sore from this weekend's rides, jf

Chris Reeder
2000-04-11, 01:14 AM
John Foss wrote:

> Rotating mass if anything is more of an issue on a unicycle. This is the mass
> that resists your effort every time you speed up or slow down, using your
> precious energy each time. Unfortunately we unicyclists have to speed up and
> slow down a lot!

Just for kicks, I ran out the calculation for accelerating an object in a
straight line vs. rolling an object. Bottom line: it takes twice as much energy
to accelerate any mass that's on the outer rim of your tire as it takes to
accelerate the same mass if it were glued to your frame. So a 10 lb unicycle of
which 4 pounds is a Gazzoloddi and rim will be just as hard to accelerate
forward as a 14 lb unicycle with an inertia-less tire and rim. But remember,
this only counts for forward and reverse accerelation. Vertically, a pound is
still a pound.

So would someone please send me an inertia-less Gazz for Christmas:)

Chris

Tall Paul
2000-04-18, 02:25 PM
Chris Reeder <reed8990@uidaho.edu> wrote in message
news:38F27C65.827CAA5F@uidaho.edu... <SNIP>
| Just for kicks, I ran out the calculation for accelerating an object in a
| straight line vs. rolling an object. Bottom line: it takes twice as much
| energy to accelerate any mass that's on the outer rim of your tire as it takes
| to accelerate the same mass if it were glued to your frame. So a 10 lb
| unicycle of which 4 pounds is a Gazzoloddi and rim will be just as hard to
| accelerate forward as a 14 lb unicycle with an

Ahhem...

Wrong: You said twice as much. Therefore a 14lb uni with weightless rim is the
same as a 10lb uni with a 2lb rim! Or 10lb + 4lb rim = 18lb + 0lb rim!

The fact is you need the inertia to keep you going. Bumps apply horizontal
forces which must be overcome. The heavier the rim, the more of the horizontal
force is converted into vertical force - which will not push you over. - Why do
you think coker unis cruse over anything! A more striking example of this was
Miark's Jelly filled 20" compared to my alloy 20" - Sure the allow was faster
indoors, esecially at accellerating, but the jelly filled tyre just kept going
and could cruse at a faster speed.

Given that pretence as much as the weight of the uni as possible should be the
rim/tyre and nothing else.

Tall Paul <><

| inertia-less tire and rim. But remember, this only counts for forward and
| reverse accerelation. Vertically, a pound is still a pound.
|
| So would someone please send me an inertia-less Gazz for Christmas
|
| Chris

Chris Reeder
2000-04-18, 03:42 PM
> The fact is you need the inertia to keep you going. Bumps apply horizontal
> forces which must be overcome. The heavier the rim, the more of the horizontal
> force is converted into vertical force - which will not push you over. - Why
> do you think coker unis cruse over anything!

I agree completely.

> | Just for kicks, I ran out the calculation for accelerating an object in a
> | straight line vs. rolling an object. Bottom line: it takes twice as much
> | energy to accelerate any mass that's on the outer rim of your tire as it
> | takes to accelerate the same mass if it were glued to your frame. So a 10 lb
> | unicycle of which 4 pounds is a Gazzoloddi and rim will be just as hard to
> | accelerate forward as a 14 lb unicycle with an
>
> Ahhem...
>
> Wrong: You said twice as much. Therefore a 14lb uni with weightless rim is the
> same as a 10lb uni with a 2lb rim! Or 10lb + 4lb rim = 18lb + 0lb rim!

We're comparing oranges to apples here. When I say "unicycle", I mean total
weight, of which a certain amount is the rim. Therefore:

A 10 lb (total) uni with a 2 lb rim = 8 lbs of frame plus 2*(2 lbs of
rim)= 12 lbs.

A 10 lb (total) uni with a 4 lb rim = 6 lbs of frame plus 2*(4 lbs of
rim) = 14 lbs.

Chris

John Foss
2000-04-18, 05:32 PM
> Given that pretence as much as the weight of the uni as possible should be the
> rim/tyre and nothing else.

This might be true for riding in a straight line on level ground and never
changing your speed, but for more ordinary riding, every time you change the
speed of the wheel you use energy. It's well known among bike racers that
rotational mass is the first place they go to reduce weight, going for the
lightest possible wheel that will hold up to their riding.

Some unicycle racers still prefer a heavier wheel as the momentum makes it go
straighter and makes it maybe easier to control at high speed. But there's no
real scientific evidence of this because the fast rider base is so small it's
almost always the better "engine" that wins, not the equipment.

But for any kind of tricks, MUni, sports, or other activities except long
distance riding, a lighter wheel will be easier in the long run.

Unfortunately we must all sacrifice some lightness in favor of parts that
won't break...

Stay on top, John Foss, the Uni-Cyclone http://www.unicycling.com (http://www.unicycling.com/)

"I'm not into pain. I'm into juggling." - A grandpa with small child at the
Davis Picnic Day, walking away from the free unicycle lessons toward the free
juggling lessons (and already able to juggle!)

Scott Bridgman
2000-04-18, 07:29 PM
The issue of rotational inertia is helpful or hindering depending on the ride
situation. Once generated, rotational inertia and the implied stored energy is
nice to carry you over/through things. Like a flywheel, the rotating mass/tire
tends to resist changes in speed for a smoothing effect. That tendency for a
rotating mass to store energy presents the rider with greater crank forces
during rapid acceleration and/or deceleration which will tax the leg muscles.
I've riden both the Gazzo 26x3.0 (heavy) and the 26x2.1 Hot S (light) and find
the lighter tire better for MUni. For me, hands down lighter is better. After
blowing out 3 Hot S lighter tires from sidewall injuries I needed something
stronger so I'm trying the Panaracer 2.3 now which is strong and lighter than
the 3.0. It seems to have just the right amount of inertia. I'd still give up
any inertia perks for a light tire anyday. Pulling hills and riding over rocks
while ascending is easier on a lighter machine. If you're hopping/jumping
against gravity, a lighter machine is easier on the wrist, elbow and shoulder
when pulling the MUni along. In fact, several pounds lighter makes it lots
easier on those joints. A MUni of around 12 pounds or less would be an ideal
weight for me. I'm presently finishing up work on a 7075 tube frame MUni that I
hope will come in at around 12 pounds. We'll see. Tubeless tires are making the
scene now in standard rim widths. I'm told no downhill tubeless stuff is out. I
think tubeless offers some weight reduction without compromising strength. I'm
experimenting with a Mavic 321 rim to see if it can be made air tight. We'll see
how tough it is to seal the spoke nipples and install a valve stem. For MUni, I
think lighter is better all the way around.

"The Muniac"