Titanium Muni built by Vulture Cycles

[chissakid]

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.

[forget_your_life]

@chissakid

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.

[skilewis74]

@johnfoss

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.

Another thing w/ that Ti muni frame or any small produced frame it should be tested really hard by someone like Kris or the SB guys.

In my Metalurgy class the teacher mentioned Finite Analysis. Using that you could design and test a frame out of any material, then it should perform as expected when made.

Sorry to re-resurect an old thread.

[feel_the_light]

It is super cool to hear this news from Roger

I Also liked Sponge’s stuff. These are great times indeed. I’m guessing that KH Taiwan stuff will hold strong bang for buck(it is so light there is not many grams to cut). Yet I clap for everyone, I am sure, for this new high end stuff.Gotta love it. I think ti uni’s will be super cool. Not much lighter then a KH though.