carbonfiber unicycle frames?

maestro8 said:

Sounds like someone's confused about CF...

'Carbon fiber ' (http://en.wikipedia.org/wiki/Carbon_fiber)is just what
its name implies... it's a fiber, thinner than a human hair. Like
fiberglass, carbon fiber is woven into a lattice-like fabric which is
then formed and set into plastic. This material is then called 'carbon
fiber reinforced plastic' (http://tinyurl.com/2zfuxx).

Note: this material isn't "solid CF" it's merely plastic with embedded
CF fibers.

As I've pointed out many times before on these fora, CF's strength
exists only along the length of the fibers. In a fork or a uni frame,
the fibers run the length of the legs, to support the weight of the
rider. Any impacts on that frame would apply force along the sides of
the fibers, where they are the weakest... and this is why a CF uni
frame must be handled with care.

I've never bought 'a witch'
(http://www.megomuseum.com/woz/images/WitchHeader.jpg) before but I've
seen witch costumes for sale for about the price of a pair of pedals.

I dont want to start an argument with you, because you would win...

I meant it would have to everywhere, like not hollow.

--
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email: mornish AT gmail DOT com

'truth' (http://www.scq.ubc.ca/?p=677)
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Det-riot said:

i know, i was using that to show how strong CF was in some aspects.

oh yeah, ofcorse its strong. I just want to compair it to Cromolly.

--
thejdw

kington99 said:

A hobnob is an oaty biscuit, the fact that they don't exist in america
just goes to show that you have no culinary heritage 🙂

Quoted message said:

Quoted message said:

don't follow Jesus, follow me!<<

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Quoted message said:

i do not belive that Carbon Fibre will make a good uni frame. uni frames
have more twisty(very official word, right) forces applied to them
that, say a bike fork.

look at the back triangle of a carbon bike. they see way way more force

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mornish said:

I meant it would have to everywhere, like not hollow.

It seems you completely missed my point. Was I unclear?

CF is only strong in certain directions. Whether solid or hollow, it
makes no difference with a piece of this material. The construction of
the frame does not change the fundamental properties of CF.

In other words, a frame built to support a rider would not be able to
withstand impacts as from a UPD on a Muni ride.

Conversely, a frame built to withstand such impacts would most likely
not support the weight of a rider.

Understand?

--
maestro8

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contemplate the extent of human stupidity. -- François-Marie Arouet de
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Quoted message said:

It seems you completely missed my point. Was I unclear?

CF is only strong in certain directions. Whether solid or hollow, it
makes no difference with a piece of this material. The construction of
the frame does not change the fundamental properties of CF.

In other words, a frame built to support a rider would not be able to
withstand impacts as from a UPD on a Muni ride.

Conversely, a frame built to withstand such impacts would most likely
not support the weight of a rider.

Understand?

so did you just make that up, or pull it out your ass

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Quoted message said:

It seems you completely missed my point. Was I unclear?

CF is only strong in certain directions. Whether solid or hollow, it
makes no difference with a piece of this material. The construction of
the frame does not change the fundamental properties of CF.

In other words, a frame built to support a rider would not be able to
withstand impacts as from a UPD on a Muni ride.

Conversely, a frame built to withstand such impacts would most likely
not support the weight of a rider.

Understand?

so did you just make that up, or pull it out your ass

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I've seen an all carbon Jamis DH bike go off a 40 foot ravine and come
out unscathed, as long as you have a flexible resin it comes out very
nice.

--
kerosian

Farmdale Freeride September 29-30th

DustinSchaap said:

why would you kill the 5 yr olds? there's so much more fun things you
can do with them 🙄

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I've seen an all carbon Jamis DH bike go off a 40 foot ravine and come
out unscathed, as long as you have a flexible resin it comes out very
nice.

--
kerosian

Farmdale Freeride September 29-30th

DustinSchaap said:

why would you kill the 5 yr olds? there's so much more fun things you
can do with them 🙄

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unicyclepa said:

so did you just make that up, or pull it out your ass

He knows what he's talking about. A carbon frame would have to have
kevlar integrated for the frame to withstand confrontations with rocks
and such, but even then it would only last so long before you'd have to
repair it. touring frames on the other hand could be pure carbon and
not have issues because they don't have to deal with impact.

Carbon is strong torsionally while kevlar is extremely abrasion
resistant, hybrid fabrics that use a weave of carbon and kevlar which
takes on the strengths of both while only minimally retaining their
weaknesses. Rally cars use underbody panels made of the carbon/Kevlar
with a sandwich core material, and are much stronger and lighter than
aluminum. the panels need to be reinforced once or twice a season
depending on how rough the roads are.

The major advantage to a well engineered carbon bike frame, is that it
will be flexy (even more so than steel) vertically, so road vibrations
and bumps get absorbed in the frame, and the frame will be super stiff
laterally so all pedaling forces go to the wheel instead of some being
lost in frame flex. What would be the advantage of carbon fiber as a
unicycle frame material? Obviously it would be lighter, but is it worth
the durability loss? It seems like frames are already really light,
andthere are better places to focus on to cut the extra fat.

--
onetrack

"People over here have a dangerous habit of adding quotes to signature
lines."
-Klaas Bil

I pulled a sick trey varial hickflip over an 8 set yesterday, but
unfortunately it was supposed to be seat in to seat out. I've named it
the dioflip
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Hassen't a CF fame already been made? Sombody might have a ride report
for that frame.

--
thejdw

kington99 said:

A hobnob is an oaty biscuit, the fact that they don't exist in america
just goes to show that you have no culinary heritage 🙂

Quoted message said:

Quoted message said:

don't follow Jesus, follow me!<<

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how it withstands forces relays heavily on how its layed up. With
current techneacs and resin a frame could be made very impact
resistant.

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The strength problem may also be that a cabon filament has no real
compression strength. The carbon filaments are arranged in an almost
fabric like .............arrangment and the shape wanted is made of the
material. I believe an epoxy of some sort is used to stiffen the fabric
much like the epoxy in fiber glass is used. So in compression loading
strength is gained by the fabric elements being glued together. The
carbon filaments and the epoxy becoming stronger together in
compression than they would be seprately. However like fiber glass some
of the strength of the material depends on the epoxy and so some
strength is lost. Drive shafts can be made of cabon filament epoxy
tubes as the torque can be taken up by running the fibers in spirals
and interweiving them or just laying on on top of the other but
alternating directions. Still a inner tube of some other "solid"
material to take the compression of the spirals trying to reduce the
"tube" diameter when they wind up taking the torque might be an idea I
would suspect this inner tube would not need to be too substantial when
compared to an all steel torque tube.

Oops I seem to have digressed. All I wanted to say is I think the real
strength of carbon filament material is in tension not compression so
making the compression memebers of a unicycle out of carbon fiber
material might not be the best use of the material.

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Qweld

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jw, how would a cf rim hold up? im tired of bending rims (i just got a
new koxx one reinforced 2 try it out, which is quite heavy) and i want
a light wheelset that it would still b easy 2 flip on, but can actually
hold up on bad landings down large sets. idk if cf would b good for
this but ik aluminum sure isnt (based on my experience).

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peleschramm said:

jw, how would a cf rim hold up? im tired of bending rims (i just got a
new koxx one reinforced 2 try it out, which is quite heavy) and i want
a light wheelset that it would still b easy 2 flip on, but can actually
hold up on bad landings down large sets. idk if cf would b good for
this but ik aluminum sure isnt (based on my experience).

CF would probeblt crack if it was a trials rim, not absolutly cerain
though.

--
thejdw

kington99 said:

A hobnob is an oaty biscuit, the fact that they don't exist in america
just goes to show that you have no culinary heritage 🙂

Quoted message said:

Quoted message said:

don't follow Jesus, follow me!<<

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thejdw said:

CF would probeblt crack if it was a trials rim, not absolutly cerain
though.

Or, rather, not at all certain? As in, stating opinions based entirely
on hearsay?

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Catching the coker fever.
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peleschramm said:

idk if cf would b good for this but ik aluminum sure isnt (based on my
experience).

Oh yeah, aluminum sucks for rims. Hey, lets make them out of steel!
That's stronger, isn't it?

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Catching the coker fever.
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yea im not sure if cf would b so gr8 for a rim either (from what i hear
from frame info). how come no one sells titanium rims? that sounds
good.

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maestro8 said:

It seems you completely missed my point. Was I unclear?

CF is only strong in certain directions. Whether solid or hollow, it
makes no difference with a piece of this material. The construction of
the frame does not change the fundamental properties of CF.

In other words, a frame built to support a rider would not be able to
withstand impacts as from a UPD on a Muni ride.

Conversely, a frame built to withstand such impacts would most likely
not support the weight of a rider.

Understand?

Carbon fibres are only strong in a single direction, thats true, which
is why CF is usually woven into cloth before being layed up. That way
the fibres are facing in several directions, giving strength
unidirectionally.

However, in CF tubes the underlying fibres are wound onto the epoxy
core in set patterns (rather like winding string onto a pole), so you
can have the strong direction wherever the hell you like. They can be
straight woven, crossed over, mixtures of the two, whatever you like.

What you fail to realise is CF is made up of lots of layers of fibres,
all of which can be layed up in different directions, so the strength
can be made to work in all directions, a single direction or wherever
(to make a bike frame flex up and down, but not side to side, for
example). CF is great because you're not wasting your material in
having strength in a useless direction, you can customise it. With
enough talent, a frame builder, working in CF, could make a frame much
more suited to unicycling than current metal frames, since it could be
layed up to provide strength in all the ways a unicyclist needs, and a
bike fork doesn't.

The only problem with CF is the matrix into which the fibres are set is
rubbish. Epoxy Resin, or whichever plastic you use, is great in
compression (which is where all the compressive strength comes from
Qweld) but is brittle and can crack easily when it is damaged, and
since both the reinforcement and the matrix are brittle, therefore so
is the overall combination.

A better solution would be a 'metal matrix composite'
(http://en.wikipedia.org/wiki/Metal_matrix_composite), so a ceramic
fibre set into a metallic matrix (e.g Tungsten Carbide drills, Silicon
Carbide brake discs), but they are prohibitively expensive and
incredibly difficult to manufacture. A CF/Alu or SiC/Ti MMC would
probably be the best material for cycling frames, as long as you had
infinite money.

Loose.

--
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come on you stranger, you legend, you martyr, and shine..." - Pink
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I have a Roger Davis CF 26". It is a collectors item and I ride it
regularly. It was never designed for big jumps and was state of the art
when it was produced.

With newer technology and backing from a bike manufacturer that is
experienced in CF production, there is no limit.

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Loosemoose said:

CF is made up of lots of layers of fibres, all of which can be layed up
in different directions, so the strength can be made to work in all
directions, a single direction or wherever... a frame builder, working
in CF, could make a frame much more suited to unicycling than current
metal frames

A frame needs strength in the vertical axis, to support the rider. It
also needs torsional strength to withstand the flexing that occurs
during intense uphill or downhill cranking. Finally, it'll need
strength along the horizontal axis to handle the impacts associated
with sidehops and trials moves.

I probably missed a force or two in there.

Nonetheless, it's looking like we'll need fibers oriented in every
direction. Such material isn't produced, as far as I've seen. There
are plenty of weaves and fabrics on the market, but this only gives
strength along one plane.

How, then, would you recommend the fibers be laid?

--
maestro8

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