DrivetrainTruvativ has just released details of HammerSchmidt, their planetary gear front transmission mechanism. Using just one chainring, the mechanism produces two gear ratios: a standard 1:1 and a 1:1.6 Overdrive. In the standard gear everything is locked and spinning together—turn the pedal once and the chainring goes around once. In Overdrive, turn the pedal once, and the mechanism’s planetary gearing results in the chainring turning about 1.6 times.

HammerSchmidt is equivalent to running 22/36 or 24/38 front rings, with a single ring. The single chainring results in improved ground clearance compared to a dual-ring, and an integrated chainguide keeps the chain on track. HammerSchmidt is offered in all-mountain (Stylo cranks) and a freeride versions (Holzfeller cranks).

shifterShifting is accomplished by special cable-actuated HammerSchmidt triggers (X.0 and X.9 versions available). The system allow shifting either while pedaling or while coasting. Truvativ says that HammerSchmidt shifts under any amount of load.

HammerSchmidt’s BB features a new proprietary BB/crankset interface—based on the Howitzer BB and compatible with 68, 73, or 83mm bottom bracket shell widths. HammerSchmidt involves a Collar Assembly which locks and unlocks the sun gear (of the planetary gear mechanism), allowing rotation and stop-rotation of the sun relative to the bike. The Collar Assembly is designed to mount to frames with ISCG 03 or ISCG 05 chain-guide mounting tabs. HammerSchmidt’s frame compatibility checker tool is available through dealers (to verify that your frame is compatible).

Truvativ reports that the weight of the HammerSchmidt all-mountain drivetrain has a a slight (172gm) weight penalty compared to a traditional dual-ring drivetrain. The freeride HammerSchmidt model is a mere 11gm heavier than a comparable, traditional drivetrain.innards

SRAM has created a mini-site with videos covering how Truvativ HammerSchmidt was made, how it works, and product details and specifications.

HammerSchmidt Manufacturer Suggested Retail Prices (USD):

  • Shifter HammerSchmidt X.0 2-speed front with clamp $114

  • Shifter HammerSchmidt X.9 2-speed front with clamp $57

  • Crankset HammerSchmidt All Mountain 170 24T ISCG 05 (22T & ICSG 03 included) $595

  • Crankset HammerSchmidt All Mountain 175 24T ISCG 05 (22T & ICSG 03 included) $595

  • Crankset HammerSchmidt Freeride 165 24T ISCG 05 (22T & ICSG 03 included) $650

  • Crankset HammerSchmidt Freeride 170 24T ISCG 05 (22T & ICSG 03 included) $650

  • Crankset HammerSchmidt Freeride 175 24T ISCG 05 (22T & ICSG 03 included) $650

  • Bottom Bracket HammerSchmidt All Mountain 68/73 $55

  • Bottom Bracket HammerSchmidt All Mountain 83 $55

  • Bottom Bracket HammerSchmidt Freeride 68/73 $55

  • Bottom Bracket HammerSchmidt Freeride 83 $55