People often ask us have you seen anything really new.  Sure we say, there is this new carbon frame, that new fork etc.etc. but it’s not often that we actually see something truly revolutionary that stops us in our tracks.  However, one of those moments happened at Eurobike as SRAM presented their new planetary crank set the Hammerschmidt.

The Hammerschmidt set.

Its called a planetary hub because the central cog (or sun) has 4 small cogs spinning around it (or planets).  The gear operates much like a freehub with pawls which engage when you turn the cranks.  These pawls can be disengaged using a shifter to allow for two different gear ratios -1:1 and 1:1.6 (nicknamed Overdrive this means that 1 revolution of the crank equals 1.6 revolutions for the chain).  Effectively you get all the benefits of a single chain ring set up but with the versatility of a double ring setup.  The system actually offers you a 22/36 or 24/38 depending on the model (All mountain or Freeride).

An exploded view of the Hammerschmidt.

The system does not suffer from problems when shifting under load so you can change gears while pedaling at full pace, an obvious advantage to freeriders and all mountain riders and a major advantage to downhillers for whom fractions of a second could be the difference between winning and losing.

This is a demo model using a transparent cover.

Hammerschmidt has been developed by SRAM with this in mind but it is not the only advantage.  Not only can you shift under load but you can shift whilst coasting as the system does not require a revolution to drop or raise the chain, its instantaneous.  It is even possible to shift while backpedalling!  There are no problems with maintenance and the chain is held in check as it does not flap around as much due to a big chainring.  In fact ground clearance is vastly improved due to the smaller ring.

The basics of the planetary system.

Fit wise there are a few requirements.  The crank will only fit onto a bike with ISCG 03 or 05 chain guide mounting tabs.  The crank has an inbuilt chain guide.  Similarly the bottom bracket features a proprietary BB/Crankset interface.  There are two models available the All mountain edition featuring 15mm crankbolts an X-0 shifter and a lighter weight than the Free ride version which is slightly stronger but heavier with 12mm crankbolts and an X-9 shifter.  Shifters are completly opposite to how a normal shifter works with a reverse action to normal and as a result you must buy the Hammerschmidt specific shifter.

In practise the shifting is unbelievable, a complete redesign of how cranks and front mechs work.  From the demo models we saw at the show it really does work.  It also looks really strong and the increased clearance and lack of chain flap is a really big advantage too.  Also the chain isn’t going to cross as much as the chain line now runs over the rear mech only.  We did wonder about chain tension slightly though and would not be surprised to see SRAM produce a gravity rear mech similar to Shimano’s Saint which features a stronger and tighter spring.  That is not to say that it is a problem, the demo model we used on a turbo trainer was faultless.  Overall this seems like a winner, we can only see one problem - the price.  At €595 it’s not cheap but that does include crank, bottom bracket, base plate and shifter.  This set will also be available on bikes from 16 companies for ‘09 including the Scott Ransom and bikes from the likes of Orange, Marin and Nicolai.

The Scott Ranson featuring the Hammerschmidt.

For more info see the dedicated website at www.magicmechanics.com.  In particular the video here.