Onza HO (High Output) 6Al/4V titanium cranks first appeared in 1993 and they looked as if they had arrived from another planet. The design was so out-there that most people’s first reaction to them was… WOW!
Unlike other titanium cranks at the time which were CNC machined and/or utilize titanium tubing, these were produced using investment casting. This process used a negative cavity crank mould which had hot wax injected into it in order to produce an exact replica of the cranks. The cranks were then bonded together into a ‘tree’ using hydrogen so a small batch of right and left hand cranks could be produced. They were then dipped in liquid ceramic and coated up to half a dozen times. Once the ceramic coating had hardened, the was was melted out by heating to ~350 degrees F. The ceramic shells were then heated up to ~2000 degrees F before being moved into an atmosphere-free vacuum and a titanium electrode was melted at between 3100-3300 degrees F and poured into the ceramic shells. Once cool, the ceramic was vibrated off using a pneumatic hammer. Then each crank arm was individually cut away from the mould at a temperature of ~2400 degrees F.
While the cranks were advertised as being for sale, they actually weren’t. Two different prototype versions were made but Onza never got past the prototype stage due to the expense of the manufacturing process and the fact that many of the prototypes didn’t survive testing.
Easily identified by the round holes in the arms. These were seen on Greg Herbold’s Koga Miyata and also featured in early 1993 reviews and the official 1993 Onza advertisement – as below:
It is clear that these look less ‘prototype’ and more ‘production’. Instead of round holes in between the spars, additional material has been removed so the holes follow the profile of the spars.
In total, there were only 15 prototype sets produced, which makes them exceptionally rare and sought after.
A few intact mk2 examples have turned up for sale over the years and we saved out ebay listings from 2003 and 2004 – the latter sold for $841.00 (£456.64) which seemed incredibly expensive at the time.
Length: 172.5, 175mm
Axle: Square taper
Colour: Natural titanium
Weight: 400g (175mm/110 BCD) for crank arms only