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The Hirth Joint + the Ultra-torque Campagnolo Crankset
Review of their Newest Technology in Campagnolo Bicycle Parts

hirth couplingIn the early 1900's the hirth joint, or more correctly in the industry, the Hirth coupling, was develop by Hellmuth Hirth as a type of fool proof, high strength locking joint used to connect two ends of a shaft together.

It is characterized by a set of teeth on the end faces of each half shaft that mesh together in a self centering and self aligning locking joint. It offers a high strength connection on relatively small diameters for reversing gears in ships and cooling water pumps in almost every industry.

Today the Voith Turbo Corporation, incorporates this design into power transmission components for the automotive, rail, nuclear and marine industries. In fact Voith Turbo adapts this technology to all industries that can utilize its simplicity of design to transmit high torques at both small and large dimensions.

So it is no wonder that Campagnolo was interested in incorporating such a proven technology into their newest line of cranksets. After all it has withstood exhaustive technological testing for performance and reliability in the most extreme environments of nuclear energy and jet engines.

Advantages of Using the Hirth Joint in Crankset-Bottom Bracket Design:

  1. The axle of the new ultra-torque Campagnolo Crankset can be spliced in the middle of the bottom bracket shell without the use of external flanges or bushings. These are not necessary with the geometry and design of the hirth coupling. With no additional flanges, there is less rotational mass and thus greater pedal efficiency and smoother riding.

  2. External bearings can now be mounted on the half spindles tight up to the crank leaving the entire circumference of the bottom bracket shell available to allow for a larger hollow spindle. With greater spindle diameter the bicycle gains rigidity

  3. With the larger spindle diameter, the crankarms can be made thinner and still yet still create a rigid crankarm-spindle connection. Thinner crank arms allow Campagnolo to maintain a consitant Q-factor (lateral distance between pedals), uncommon in typical external bearing designs.

  4. On both the drive and the left side of your bicycle the Campagnolo crank arm can be fused to each half axle, so no added length is needed on the spindle to allow pinch bolts to hold the crank in place. This offers a weight savings and no risk of the pinch bolts coming lose and dropping a crank arm.

  5. 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. The cups are threaded into the bottom bracket shell, then each half "L" shaped axle is positioned, and lastly a 10mm bolt is torqued in place to hold the two halves of the crankset together.

With a quick review of the Hirth advantages, what's not to love about the Hirth Joint/Ultra-torque Campagnolo Crankset combination.

Further Information:
Campagnolo Bike Parts
Index of Campagnolo Bicycle Part Articles

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copyright Jan. 2007