Performance and Weight of steel - vs. – aluminum 29”

Hi all,
As several of you might have read, I was waiting for a KH 29 for some
time. It finally came and I am in love again.

The KH frame is really beautiful – and of course the “MUC blue” helps.

I was shocked at the weight savings of this set-up. I had a steel
frame with a GB4 seat post. I replaced it with the standard KH 29 frame
and Kris Holm seat post (without the brake lever. Amazingly, the weight
saving was about 40% (3.2 lbs. down to 1.9 lbs.)!!!! My entire ride
weighs in at just over 10 lbs. (10.2). Of course this is not the KH
set-up but my attempt to build a light, effective cross-country ride for
my weight (150 lbs.)

KH 29
KH seat post w/o brake bracket
CF seat
Mavic 17mm tandem rim w/ alloy niples, 3X
Nanoraptor tire
Suzue hub with 155 Euro cranks
Oydessy Twisted pedals


This morning I took it out on it’s virgin ride. The frame is
wonderfully stiff (yes, I have an air saddle). On the steel frame I
often could feel the fork blades give as I torqued laterally. None of
that with the KH.

I’m one happy camper. Be for warned, I have my eyes set on a new uni
course record for the Tour de Wolf course!

Tommy


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Tommy Thompson
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Sounds nice. I must say I really like the look of the new blue KH
frames.

Regarding the steel vs aluminium, I hadn't really thought about it that
much in the unicycle context. Coming from a bicycling background
(sorry!) it's certainly cheaper (because of less building skill
involved) to build a light aluminium frame than a light steel frame, but
aluminium framed bikes feel dead to ride because of the lack of spring
in the material (and they tend to crack for the same reason). A good
(but relatively expensive) steel frame gives a much livelier and more
comfortable ride, but it must be built by a good builder if it is to be
both light and stiff enough. Titanium almost gives the best of both
worlds, but at a serious cost premium for the materials.

For a unicycle though, the lack of spring of aluminium may well actually
be an advantage, as unis don't rely on the spring in the frame for
liveliness like bikes do. Just as long as the frame doesn't get cracked
in a crash (you can bend a bent steel fork back, within reasonable
limits).

How much of the overall weight of a unicycle is the frame though?
Certainly on my muni (26x3 nimbus 2) I reckon the tyre and saddle
probably account for a good proportion of it.

Rob


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rob.northcott - Speed Freak (apparently)

You do not need a parachute to skydive. You only need a parachute to
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Tmornstar wrote:
*Be for warned, I have my eyes set on a new uni course record for the
Tour de Wolf course!*

As if the standing record (held by Tommy) was not already sufficiently
out of reach.


--
Memphis Mud - Student of GrandMaster 2T

NAUCC 2006 in Memphis, TN.
Beale Street. Graceland. Blues Music. BBQ. Deep woods MUni. Rolling
Crosscountry. Jump over the Mississippi River (really!).
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Rob,

I totally agree with your regarding your observations/ preferences of
steel over aluminum for a bike. On my cross country uni, with its 29"
wheel, I can build in enough suspension with the construction of the
wheel and the tire pressure. However, as I'm trying to torque the
frame around a turn or over a root I don't want to feel the wheel
twisting laterally beneath me. Granted, I've just started playing with
this new ride so I'm still in the honeymoon of my new love affair. Too,
we'll see how it holds up.

Tommy


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Tommy Thompson
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Tommy - what did you do about the bearings? I assume that the KH frame
requires 42mm OD bearings (as per the specs on the KH website).

Chris


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KnowFear

Chris... who DOES have a WMD (Wheel of Mass Dismounts).
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Hi Chris,

You are so right. The bearings on a KH need to be 42mm. I had to buy
the bearing shims that UDC sells to bring my bearing size up from 40mm.
So far, after only two rides now, all is well. Still smiling!

Tommy


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Tommy Thompson
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Hi Tommy,

One more thing - what about the spacing between the bearings? How
different is the Suzue from the new KH hub in this regard?

thanks again
Chris


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Chris... who DOES have a WMD (Wheel of Mass Dismounts).
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When I tossed in the Suzue hub the bearings were just a touch narrower
than the bearing holders - perhaps just a couple of mm. I did nothing.
Perhaps, over time, the bearing will pull a few mm out from the hub but
I really doubt it. Thus, to answer your question, it is close enough to
call it a fit.

Tommy


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Interesting. It's lovely to read of someone who's getting so much
pleasure from the riding experience.

I'm no engineer, but I do remember from my scuba diving days that
aluminium air cylinders were heavier, size for size, than their steel
equivalents. Simplistically: aluminium is lighter (well, less dense)
than steel, but you need more of it.

Of course this depends on the steel. There are many sorts. Also, there
are different types of strength: resistance to stretching, bending,
twisting, or compression. In the same way, there are different sorts of
stiffness.

My Pashley MUni is made of "Reynolds tubing" but it doesn't say whether
it's 453, 501, 531, etc. All I know is it feels like it's made of
scaffolding poles. It's made of lighteweight material: lots of it. So
if I eat 500 low fat doughnuts, will I lose weight?

For a unicycle, the weight of the wheel and tyre combination makes most
difference because it affects acceleration and deceleration. The weight
of the frame and seat combination should in theory be somewhat less
important - especially if you realise that a pound or two in weight
saved here can easily be wiped out by the contents of your camelbak, or
a big breakfast.

But if you count your legs as the "springs" because they support the
biggest part of the mass of the rider/uni combination, then any savings
on the weight of the uni are savings to "unsprung weight" which will
make the uni easier to ride over roots and bumps.

But at bottom, it's just much nicer to ride a nice piece of kit, and
I've noticed that even a couple of hundred grammes saved on a tyre have
made my own 700c more fun to ride.


--
Mikefule - Roland Hope School of Unicycling

Not happy he who thinks himself not so.
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Hi Mike,

I echo what you said about the meaningful weight of the
wheel/tire/cranks/pedals as opposed to the weight of the frame. I would
LOVE to figure out how to save 1 pound of weight off my wheel - rather
than the frame as I did by going to the KH 29. I'm shaving weight off
where ever I can these days. In fact, last night I had a dream that
rode the Tour de Wolf trail (our local cross-country racing course) on
a 700X38 tire. That would be a REAL and meaningful weight savings that,
I'm sure, would produce some amazing performance enhancements. However,
should I bend the wheel or bust my butt I won't have nearly as much fun.
But in my dream I was FLYING! Ahhhh, the dances we do.

Tommy


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Tommy Thompson
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