Re: Titanium Muni built by Vulture Cycles

Discussion in 'rec.sport.unicycling' started by chissakid, Apr 25, 2006.

  1. chissakid

    chissakid Guest

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  2. Chissakid, aluminum is much weaker than titanium, so while it may be
    less dense, you need more of it. Brittls depends on alloy and hardness.
    Titanium is much less prone to fatigue and cracking than aluminum when
    welded correctly. Aluminum bike frames are notoriously stiff because if
    they weren't, they'd break super fast.

    A disc-brake muni seems like a mixed blessing. I wouldn't want to walk
    out of a trail because I smashed my rotor on a rock during a missed
    pedalgrab.


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  3. unicyclepa

    unicyclepa Guest

  4. GhettoSmurf

    GhettoSmurf Guest

  5. unicyclepa

    unicyclepa Guest

  6. chissakid

    chissakid Guest

    Gerblefranklin, thanks for your reply. When Scott Bridgman was looking
    for material to build a frame, he chose aluminum. I asked him about
    that, since Ti seems more in vogue. He wanted a lighter-weight frame,
    he said, which he welded together himself, and then heat-treated it in
    his shop. He's a custom fabricator in New Jersey, so he could have
    chosen any type of metal. The result is the hollow Wilder aluminum
    frame.

    Our experience, and the few folks we've talked to who have a Ti frame
    have had problems with cracking, requiring re-welding. These riders
    are really hard on their cycles, so it could be that no material would
    have held up. Carbon fiber has also been problematic. We'll keep on
    experimenting with all of it anyway. :)


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  7. tholub

    tholub Guest

    chissakid wrote:
    > Gerblefranklin, thanks for your reply. When Scott Bridgman was looking
    > for material to build a frame, he chose aluminum. I asked him about
    > that, since Ti seems more in vogue. He wanted a lighter-weight frame,
    > he said, which he welded together himself, and then heat-treated it in
    > his shop. He's a custom fabricator in New Jersey, so he could have
    > chosen any type of metal. The result is the hollow Wilder aluminum
    > frame.
    >
    > Our experience, and the few folks we've talked to who have a Ti frame
    > have had problems with cracking, requiring re-welding. These riders
    > are really hard on their cycles, so it could be that no material would
    > have held up. Carbon fiber has also been problematic. We'll keep on
    > experimenting with all of it anyway. :)




    Let's not put forth the Wilder frame as the paragon of unicycle
    strength. I think it is pretty well understood that, for material of a
    given strength, titanium is lighter than aluminum, all else being
    equal. Titanium is quite a bit harder to work with, so it may be that
    the average TI weld is not as good as the average AL weld, just because
    more people are comfortable with AL.

    In any case, the frame material does not make a whole lot of difference
    in unicycle performance.

    [image:
    http://www.unicyclist.com/forums/attachment.php?attachmentid=12454&d=1141711177]


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  8. GhettoSmurf

    GhettoSmurf Guest

  9. GhettoSmurf

    GhettoSmurf Guest

    unicyclepa wrote:
    >
    > so




    so your wheel would be off to one side. harder to balence.

    I recentlly dished my wheel on a muni ride. (not on purpouse) and it
    was harder to stay up right


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  10. tholub

    tholub Guest

    GhettoSmurf wrote:
    > so your wheel would be off to one side. harder to balence.
    >
    > I recentlly dished my wheel on a muni ride. (not on purpouse) and it
    > was harder to stay up right




    If your rim is not centered *relative to the bearing attachments*, it
    will be harder to ride, but even with your wheel dished to accomodate a
    hub brake, it will still be centered relative to the bearings. The
    affect on how it rides would be negligible.


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  11. chissakid

    chissakid Guest

    Tholub,

    I agree with you on the performance issue. I could ride the lightest
    gear on the trails and still not keep up with my boys. But the overall
    weight has a lot to do with rider endurance.

    I used to ride the steel-framed DM Vortex with a 28-inch Gazzaloddi and
    brakes. It weighed about 18 pounds. The rolling power was great, but
    jumping over obstacles, especially after I'd gotten tired, was
    difficult. My oldest son, Casey, didn't seem to tire--ever. So I got
    on his Wilder with a 24-inch Gazz, total weight about 12.5 pounds.
    Huge difference. I rode a Wilder until last year, when I switched to a
    Kris Holm and installed a Gazz. I agree with Vivalargo--the KH line
    competes with the best. It's aluminum, lightweight and affordable.

    We lost Scott Bridgman to the motorcycle industry, a great loss in my
    opinion, but he still has his machine shop. Did the Wilder owner
    contact him about repairing the frame?


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  12. vivalargo

    vivalargo Guest

    chissakid wrote:
    > We lost Scott Bridgman to the motorcycle industry, a great loss in my
    > opinion, but he still has his machine shop. Did the Wilder owner
    > contact him about repairing the frame?




    I think that frame is cooked, John, and so does Scott Wallis, who I
    sent it to for inspection. Fun while it lasted.

    BTW, I'm all for a titanium frame--I just don't want to pay for it.

    JL


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  13. johnfoss

    johnfoss Guest

    chissakid wrote:
    > Our experience, and the few folks we've talked to who have a Ti frame
    > have had problems with cracking, requiring re-welding. These riders
    > are really hard on their cycles, so it could be that no material would
    > have held up. Carbon fiber has also been problematic. We'll keep on
    > experimenting with all of it anyway. :)



    I think as the materials get more exotic, your number of prototypes and
    amount of testing needs to increase. Actually the exoticness probably
    has little to do with it, just previous learning using the same
    material. There are very few examples of Ti , CF and Al frame designs
    out there, which means less expereience with the materials. The
    strengths and weaknesses of steel are well known, and there is a much
    larger population of people out there who know how to weld and
    otherwise fabricate it. The numbers get a lot smaller with the other
    materials.

    That horrible picture Tholub posted shows the possible death point of
    any Wilder frame that gets the seat pulled or pushed on a lot. Very
    scary for me as owner of the same frame! That's probably an example of
    fatigue, something aluminum is more prone to. So maybe my Wilder won't
    last forever? :(

    In regards to its stiffness, I think aluminum is probably one of the
    best possible materials for unicycle frames. We need them to be stiff.
    Your unicycle's frame twists a lot, between the pedaling forces and
    wheel wobble below up to the seat above. A non-yielding (stiff) frame
    will lose less energy in this area, which translates directly into
    better performance.

    My CF frame came apart as a result of those twisting forces. The design
    of the frame was sound; it was just an error in the assembly process
    that left a weak spot (which Roger repaired wonderfully). But a carbon
    frame, with normal tubes and lugs, is pretty twisty. A monocoque (sp?)
    carbon frame could eliminate the flex, but would be a quantum leap in
    difficulty and labor to build.

    Actually I've seen a frame like this. A Japanese guy brought it to
    Unicon IX in Germany. One of the most beautiful unicycle frames ever
    made, I'm sure. He said it cost the equivalent of a "small car" in his
    words of very limited English. I should find my pictures of that and
    scan them. I'll add that to my list of things to never get done...

    Anyway, what about titanium? I know it's a popular material for bike
    frames, and is supposed to have a nice flex to it which can make for a
    more comfortable ride compared to a stiff aluminum frame. Ti is a lot
    harder to work with, and I'm sure the examples of Ti frames mentioned
    above were all experimental (only 1 or 2 made) models, so one can
    assume they might need further development.

    In other words, all those materials could probably make great unicycle
    frames, but there hasn't been as much research with them. The KH frames
    represent probably a very long process of prototype and testing, and
    are probably the most efficient design out there, not just the
    cheapest. The Wilder frame was the result of several prototypes as
    well, but probably didn't have nearly the amount of testing the KHs
    have had.


    --
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    John Foss
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  14. zack

    zack Guest

  15. chissakid

    chissakid Guest

    Good points, John. I was initially excited about aluminum bike frames.
    But then the production models had huge tubing compared to steel. If
    you have to double the size and weight, what's the advantage?

    Kris Holm has managed to keep his aluminum frames light (1.5 pounds)
    and strong. And you're right, he tests his products to the extreme.
    He won't announce them until he's satisfied.


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  16. chissakid wrote:
    > Good points, John. I was initially excited about aluminum bike frames.
    > But then the production models had huge tubing compared to steel. If
    > you have to double the size and weight, what's the advantage?.


    if you sawed a high end AL bike frame in half you would see that the
    tube walls are thinner the bigger they get. just because the tubes are
    bigger doesnt meen the frame is heavier.

    the downtube on the Cannondale SUP 2.8 series had almost paper thin
    walls but was really fat...but lighter than steel frames.

    [image: http://chuck.kichline.com/bikes/r9001.jpg]


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