Shimano patent radically reimagines the crankset

Direct mount design abandons crank arms as we know them

We’ve spotted a Shimano patent that suggests the company is working on its own version of direct mount chainring cranksets. The patent describes both a road and off-road flavour.

The patent particularly focuses on the use of multi-material chainrings and cranksets. That means there’s an emphasis on bonding durable metal teeth to a carbon carrier to save weight and using specific materials in different locations to optimise crank construction.

The patent drawings for the mountain bike crank look rather similar to existing options on the market, but Shimano has its own distinct take on the road side of things.

Composite chainrings use a carbon carrier bonded to metal teeth
Composite chainrings use a carbon carrier bonded to metal teeth

The splines for a direct mount chainring are usually relatively close to the crank spindle. For the road crank Shimano has outlined, the diameter of the direct mount system increases significantly to form an integral part of the cranks themselves.

A direct mount chainring, but with a much larger diameter spline than we're used to!
A direct mount chainring, but with a much larger diameter spline than we're used to!

What the particular advantages are remain to be seen. We imagine it can result in some saved weight with a streamlined and optimised crankset construction with a ‘slot-on’ chainring. Call it a fully integrated crankset if you will.

Whilst the patent states that “it will be apparent [that] the invention can have more sprockets” no drawings showing this are present. We imagine a single-piece, two ring chainring would have to be designed to work with the direct mount system.

It’s also unclear how exactly the chainring is secured on the large diameter carrier, although the patent mentions “rivets [or] screws”.

This diagram demonstrates how the construction uses tailored parts and materials
This diagram demonstrates how the construction uses tailored parts and materials

The construction for the cranks is described in a number of ways, though the focus throughout is on using lightweight “carbon-reinforced” materials.

Shimano details structural members (17,19) which take the pedalling forces as well as a reinforcing piece (75) and finally a cover (15), which can all be made from the materials most suited to the job they are intended for.

Both the road and off-road cranks are envisioned as multiple piece designs with each part designed for a specific purpose.

Weight savings are made with a hollow crank construction
Weight savings are made with a hollow crank construction

This construction also allows the production of a significantly hollow crank, saving additional weight. Shimano also discusses a number of ways of constructing the primary structural member, though we imagine a one piece carbon fibre construction is the most likely.

It’s only natural that Shimano is exploring direct mount chainrings and cranksets and it will be interesting to see how the contents of the patent will manifest themselves in the future.

Do you think Shimano is on to something here? Or are the aesthetics too challenging? Let us know what you think.

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