Truvativ has launched a teaser site for the “Hammerschmidt”. The problem is, being a teaser site, there really is no useful information to help us figure out what exactly Hammerschmidt is, so we’re forced to use our brilliant skills of rampant speculation. Popular opinion, and the prediction that we’re most inclined to agree with, is that Truvativ is planning on rolling out a gearbox of some sort, likely a two- or three-speed unit which would replace the front derailleur.
The advantages of such a gearbox would be twofold. First, the elimination of the front derailleur, with its lazy shifts under power and dropped chains in the rough stuff, would be a great step forwards. Second, and probably the more significant benefit, is that by fixing the position of the chain up front on a single chainring, one of the chief drawbacks of single pivot suspension designs would be eliminated.
Single pivot bikes have been given a new lease on life recently, largely thanks to improvements in platform suspension technology which allow the bikes to pedal acceptably without the aid (and therefore extra weight and complexity) of extra pivots and linkages. However, one of the significant drawbacks of single pivot bikes is that they are still sensitive to changes in the position of the chain on the front rings in relation to the main pivot. When the main pivot is placed directly in line with the chainring which is holding the chain, then the tension from pedaling is neither pulling the suspension up nor down, and therefore the suspension is left free from pedaling forces, and pedaling bob is nearly eliminated. If the position of the chain changes up front, (as it does when you change from the small to the big ring) then pedaling forces are no longer kept out of the suspension, and the bike will either firm up under power, and lose its ability to soak up bumps, or soften, and start to bob more under power.
Bike designers have found a decent compromise in single pivot bikes by placing the main pivot in line with the middle chainring, which is where most riders spend most of their time. However, the suspension still firms up when you are in the granny gear, and softens noticeably when jamming in the big ring. If the Hammerschmidt is able to replace the front three rings with a single ring and a gearbox, then regardless of what gear you are riding in, the chain could be designed to always pass directly in line with the main pivot.
Scans floating around from the German magazine Bike illustrate this point well. Check out the location of the main pivot in relation to the single chainring. Sadly, however, our German is not nearly up to par, so if anybody can translate the article, we’ve posted it after the jump.