: Not that I will ever have the money to buy a set of the new Onza cast
: titanium cranks anytime in the near future, but I wonder if the Physics
: masters would mind comparing the strengths/weaknesses of this girder
: design with tubular cranks and comenting on the future of cast titan.
I almost resisted the urge to comment but here it goes. I first saw a prototype out of aluminum in Summer of '91. I looked strange but they worked well. They were machined by hand and I was wondering how Onza was going to make them. I never thought they would have cast them out of Titanium!
Since I moved back to the Bay Area I had not followed the cranks evolution since '91. So I gave my friend who machined the prototypes a call. He told me that the cranks were getting hairline cracks near the peadal. He did not tell me what the problem was but I could make some asumptions. The biggest problems I see with the cranks are 1) They are cast. 2)They are tapered from bottom bracket to pedal.
The pedals are lost wax cast using 6Al/4V Titanium. The alloy is good but lost wax casting as any artist knows is easly flawed. The cracks could have been from flawed casting.
The other problem is that the cranks are tapered from the bottom bracket (the width, not the thickness) to the pedal. What this does is put the most stress near the pedal and the result was cracking. A tubular type of crank will distubute this force evenly over the lenth of the crank.
I would not put these cranks on my bike. Cold forged cranks are much better. There are many other reasons notch factor of titanium, heat treatment from casting ect.
Save you money untill you see all the racers using them.
