Titanium vs aluminum.

Well I am starting to think about putting together a freestyle uni and
after now having to upgrade every single stock uni I have bought, I
want to do this right.

I am a huge fan of Miyata unis, they have history, style, and a great
reputation. They also have amazingly light, custom fitted, and strong
frames, but they come at quite a price (about 450 Canadian shipped).

The other option I have been looking at is the New Koxx signature frame
from municycle.com or maybe someone more local has it. This frame is
wayyy cheaper than the Miyata one, (I'm estimating around 280 shipped
based on the shipping of the Miyata). But it is also heavier and weaker
than the Miyata I believe.

My major question is how much difference is there between Titanium and
Aluminum? From what I hear Titanium is both stronger and lighter, but
how much so?

Is it worth the extra 170 dollars for something that is custom fitted,
and however much stronger and lighter?

Please only give factual answers not just the Koxx frame is sexy and
aluminum therefore it is better.


--
ntappin

'how to build a strong comfy saddle from junk.'
(http://tinyurl.com/hxcb3)
------------------------------------------------------------------------
ntappin's Profile: http://www.unicyclist.com/profile/10800
View this thread: http://www.unicyclist.com/thread/52943

Ask around and see if you can find some reviews on the frames, Just
because you know the material, dosn't mean you know its strength. See
if you can find anyone that has broken one of them, and find out how.


--
Evan Byrne
------------------------------------------------------------------------
Evan Byrne's Profile: http://www.unicyclist.com/profile/9367
View this thread: http://www.unicyclist.com/thread/52943

ntappin wrote:

My major question is how much difference is there between Titanium and
Aluminum? From what I hear Titanium is both stronger and lighter, but
how much so?

Please only give factual answers not just the Koxx frame is sexy and
aluminum therefore it is better.



Please ask only answerable questions, not just how much difference is
there between titanium and aluminum. What "difference" do you mean?

Lighter? You mean denser. Titanium is denser with a specific gravity of
4.5 as opposed to aluminum at 2.7. Both materials are considered
lightweight but of course 10 pounds of aluminum is heavier than one
pound of titanium, or lead for that matter. Light doesn't mean anything
is this context.

Cost? Although titanium has dropped dramatically in price do to
improvements in production and refinement, aluminum is still
substantially cheaper. Any alloy of aluminum is cheaper, and there are
some strong ones like 7075-T6.

Tensile stength? Ti has a yield strength of 830 MPa making it much
stronger than aluminum at 200 MPa.

Machinability? Aluminum, any alloy, hands down. Titanium is a pain to
machine.

Weldability? Titanium is a poor heat conductor and, therefore, welds
much more easily than aluminum.

Titanium is a cool, high tech material having few, if any, unicycling
advantages over aluminum.


--
harper

-Greg Harper

B L U E S H I F T

*jc is the only main man. there can be no other.*

This is still my nth post....*AWESOME!!!*

"I'd like to dress up like a baby, lick your toes, and then have a
plate of spaghetti while watching Letterman." - Rafiel Laserbeam
------------------------------------------------------------------------
harper's Profile: http://www.unicyclist.com/profile/426
View this thread: http://www.unicyclist.com/thread/52943

harper wrote:

Titanium is a cool, high tech material having few, if any, unicycling
advantages over aluminum.



I don't think that's true. Everyone likes the aluminum KH frames
because they're lighter than steel frames; a titanium frame could be
stronger than the KH at the same weight, and wouldn't fail in the way
we've seen KH frames fail. With titanium, you could probably have a
crown design similar to the KH, but with the seat tube going all the
way through the cross-bar, greatly increasing the range of possible
seat heights (which on the KH is limited to about 3cm).

But it certainly would be significantly more expensive.


--
tholub
------------------------------------------------------------------------
tholub's Profile: http://www.unicyclist.com/profile/804
View this thread: http://www.unicyclist.com/thread/52943

Part of the reason that titanium is popular on bikes is that it can be
more flexible than Al - no fatigue problems - so you can get a hardtail
that's got a bit of springyness in the frame so doesn't have too harsh
a ride. That might make a uni frame too flexy, unless it just used
thicker tubing, possibly removing any advantages.

Would be damned shiny though.


--
johnhimsworth

Never argue with an idiot; they drag you down to their level and then
beat you with experience.
------------------------------------------------------------------------
johnhimsworth's Profile: http://www.unicyclist.com/profile/1788
View this thread: http://www.unicyclist.com/thread/52943

johnhimsworth wrote:
Part of the reason that titanium is popular on bikes is that it can be
more flexible than Al.


I was going to say the same thing. Titanium is the holy grail for bike
frames because it has the springiness of steel but can be lighter (OK
Harper, less massive) for the same strength and doesn't corrode. The
downside is it's expensive. Aluminium bike frames are far too stiff,
feel dead and crack.
But for a unicycle frame, the stiffness of aluminium is probably an
advantage because of the pedalling forces trying to move the tyre into
the frame. And lightness isn't really much of an issue anyway because
unicycle frames weigh bugger all anyway compared to the wheel, tyre and
saddle.

Rob


--
rob.northcott

'Dartmoor Muni Weekend'
(http://www.unicyclist.com/forums/showthread.php?t=46116) - Last
weekend in May 2006
Same again next year anyone? It'll be dry, I promise.
------------------------------------------------------------------------
rob.northcott's Profile: http://www.unicyclist.com/profile/7436
View this thread: http://www.unicyclist.com/thread/52943

just here to pile on...Ti is to springy for uni frames...Tholub, have
you seen any Ti bike forks latly?


--
forget_your_life

dream one dream many....
*'R.I.P' (http://tinyurl.com/vr86)*
------------------------------------------------------------------------
forget_your_life's Profile: http://www.unicyclist.com/profile/4558
View this thread: http://www.unicyclist.com/thread/52943

The most important component in a good frame, be it bike or unicycle, is
good design. The secondmost important component is good build; in other
words it was assembled properly with good welds, brazes or joints. It
doesn't matter what it's made out of if those two requirements aren't
met.

Aluminum is stiff and basically brittle. This means frams generally
have to be fatter to retain stiffness. And they have to be stiff,
because if they flex, they will fail that much faster. That's what
worries me about aluminum unicycle frames, because all the twisting
force that goes into them has to be completely absorbed or the frame is
in danger of stress fractures over time. On the other hand, that
stiffness is just what you want for most types of unicycling, so it's
fine as long as the legs or crown don't have to be too fat.

Titanium flexes, which is generally a plus on a bike frame, but is not
desirable on a unicycle frame. So you have to design to minimize the
flex, which kind of eliminates one of the nice advantages of using Ti.
However, if a Ti frame flexes a little bit, it can do that forever
without leading to cracks or eventual failure. If the flex is minimal
enough it will not be noticeable by the rider while even that amount of
flex is probably not acceptable for an aluminum frame.

I love the look of anodized aluminum, but unfinished titanium looks
pretty cool too. Nobody wants to paint it, because then you have to
*tell* people what it's made out of, taking away from that aspect of
the coolness factor.

All of that said, the Koxx frames look great. I borrowed one for the
coasting and gliding competitions at Unicon and enjoyed riding them.
They have very tight clearance on the tire though, so it could limit
your tire choices. Also they're new, so they don't have an established
track record for reliability. I think they'll hold up fine though,
unless you really abuse them. The construction looks very stiff and
beefy.

The Miyata frames have been available in Ti for several years, but I
don't know much about them. Most owners of those frames live in Japan,
and use them for either track or Freestyle, which generally is a lot
less abusive to frames than stuff like Trials or Street. I've never
heard of a failure (with either frame), and I expect the Miyata ones to
hold up as well as, or better than, anything aluminum that's currently
out there.

To me the Koxx frame looks like a better design for stand-up skills,
though Japanese riders make it obvious that Miyata frames can work just
fine. The Koxx frame may be more of a knee-banger for other skills
though, but at least nothing sticks out--it just has the corners at the
top.


--
johnfoss

John Foss
"jfoss" at "unicycling.com" -- www.unicycling.com
-----------------------------------------------

"The worst thing you can do on a unicycle when you land is stop dead."
-- Kris Holm, world's expert on high-consequence unicycling
------------------------------------------------------------------------
johnfoss's Profile: http://www.unicyclist.com/profile/832
View this thread: http://www.unicyclist.com/thread/52943

harper wrote:
Please ask only answerable questions, not just how much difference is
there between titanium and aluminum. What "difference" do you mean?




Looks like you didn't have a problem answering his unanswerable
question...hmm...you must be super man or something.


--
AscenXion

*S*ingle*T*rak'*n*
*O*rder*O*f*O*ne


You've shown your true face, AscenXion, and revealed that only an
exclusive order of people can exist in your world where you are an
intolerant god.
------------------------------------------------------------------------
AscenXion's Profile: http://www.unicyclist.com/profile/12303
View this thread: http://www.unicyclist.com/thread/52943

I know very little about diffrent metal types, strengths and such. But
is it true you usualy weld Ti in a bag?


--
Evan Byrne
------------------------------------------------------------------------
Evan Byrne's Profile: http://www.unicyclist.com/profile/9367
View this thread: http://www.unicyclist.com/thread/52943