In was in the early 1900’s that the hirth joint or hirth coupling was born, from the tinkering of Hellmuth Hirth, the young son of a German engineer. He was fascinated with developing new and emerging technologies for the maiden aircraft industry. Hellmuth developed the hirth coupling as a high strength locking joint used initially to connect two ends of a shaft, in gasoline engine crankshafts.
It looks like a set of teeth milled on the end profile of each half shaft. They mesh together in a self centering and self aligning locking joint. The amazing engineering of the Hirth coupling is that it offers such a high strength connection on such relatively small diameter shafts. It has since been used for reversing gears in marine applications and cooling water pumps in almost every sector including automotive, rail and nuclear.
Thus it is not surprising that Campagnolo was interested in using such a proven piece of technology in their newest cranksets designs. It has a long history of testing for strength and reliability in the most extreme environments from marine to nuclear energy.
Advantages of Using the Hirth Coupling in the Campagnolo Crankset Design:
The axle of the new Campagnolo Crankset can be spliced in the middle of the bottom bracket shell
No need for external flanges or bushings thus less rotational mass, greater pedal efficiency and smoother riding.
External bearings can now be mounted on the half spindles leaving the entire circumference of the bottom bracket shell available for a larger hollow spindle. This larger spindle makes the drivetrain more rigid.
The Campagnolo crank arms can be fused to each half axle, so no pinch bolts are necessary for crank attachment. This reduces the weight making the ultra-torque the lightest crankset in the industry.
The final benefit of using a hirth joint in the ultra torque crankset is that Campagnolo can promote themselves as having THE most easily installed crankset in the industry. With traditional tools the cups can be inserted followed by the half axles and a 10mm bolt to hold it all in place.
Certainly this particular Campagnolo component has taken technological sophistication to the limit offering cycling enthusiast something to talk about. At myWheelsAndMore.com these is further information about Campagnolo’s bicycle parts innovations including the scoop about their newest carbon fiber forming capabilities and new ceramic bearing bottom brackets.