Introduced in 2008, the Truvativ HammerSchmidt was a technical wonder. While the HammerSchmidt never enjoyed widespread rider acceptance in America, many European bike brands adopted the system. While mostly intentioned for gravity use, we saw the product used for various applications including singlespeeds (hey, it doubled their gearing options). Not a common sight on the trail, the HammerSchmidt is still available and may find acceptance from unexpected sources (Fat Bikes?).
This was our first impression of the product in 2008.
HammerSchmidt two-speed crankset on the Scott Ransom.
The not-quite concealed secret planetary gearbox from Truvativ was officially released today (August 2008) with the launch of Truvativ's HammerSchmidt website. We got the chance to ride the two-speed crankset during a media introduction in SLO, California. The HammerSchmidt shifting is immediate and can be done while pedaling forward or reversed, stopped, or mid-air, should you please. The basic package is an inch-wide disc about five inches in diameter that houses a (been around for a million years) sun-and-planet gearbox. Shifting is done with a revised SRAM left side trigger, however, the lever operated in reversed sequence—big lever downshifts, tiny lever upshifts. This is not to hard to get right, as there are only two choices and you are already in one of them.
HammerSchmidt All-Mountain version is very compact.
Two gearing options (22-tooth Freeride and 24 tooth All-Mountain) are now ready for OEM orders. The single-ring is easily switched with a simple locking ring, without tools. The inside is simple, low gear is direct drive, with the crank’s spider concentric with the four planet gears turning the entire crank mechanism. Switch to second gear, and a clutch stops the sun gear, which forces the planets to overdrive the outer ring gear, At this point, a slight clicking will be heard from the freewheel pawls inside the HammerSchmidt gearbox as the outer ring overrides the inner one. It’s simple as pie, so don’t sweat the mechanics of HammerSchmidt and pay attention to its possible benefits.
The shifter is about the same item as the SRAM X.9, The "anvil" signifies it is a two-speed.
Anyone who has approached a technical climb in too-tall of a gear on a heavy all-mountain bike can attest to the fact that walking is the next option. Not with Hammerschmidt—just click and you will instantly be in a gear that is at least ten teeth lower up front. No fuss, no grinding. The same goes for topping a steep grade. You will, however, find moments when you will like a half step between them, but this whiner-esque subtlety is not the stuff of Hammerschmidt riders. When that moment arrives, you’ll be forced to shift two or three cogs up or down in the rear to moderate the massive differential between the front two selections.
The Sun and ring gears with the freewheeling ratchets exposed.
Weight is a question when you are replacing aluminum sprockets with gears and bearings. In the hand, the HammerSchmidt feels about a pound heavier than a bare two-chainring crank--but it eliminates a lot of complicated (and weighty) junk from the bike. Truvativ calculated the weights of equivalent two-chainring cranksets and surprisingly, after subtracting seven chain links, the front derailleur, a roller guide, two chainrings and the resplendent hardware, you will be adding almost nothing for the heavier Freeride model and 6 ounces for the lighter weight All-Mountain HammerSchmidt crankset (read about this on the Truvativ site).
HammerSchmidt mounts to an international-standard chainguide boss.
HammerSchmidt requires an international standard chain guide (ISCG) boss on the frame (it fits the latest two sizes) to counteract the reverse torque when shifting to high gear. The installation is simple and anyone should be able to take it apart and clean the gears should curiosity get the best of you. I did it in about a minute. A single derailleur cable under the bottom bracket area actuates the shift pawls and it is insensitive to adjustments or cable stretching.
The shifting plate, bolted in place on the bike.
Bad news always follows good news, it seems, so here’s both. HammerSchmidt is so compact that, even if it did not have its own chainguide and bash guard, it would rarely contact logs or boulders—it’s that small. The downside is that most rear suspension systems are designed around the diameter of the middle chainring (30 to 34 teeth), so the small, 22/24 chainring of the HammerSchmidt gearbox will cause many rear suspensions to respond to chain torque—in good and bad ways. Certainly, the very touchy dw-Link designs will not tolerate such an arbitrary shift in the diameter of the chainring. Ahh, growing pains are part of meaningful change. What the HammerSchmidt is, however, is meaningful change. We expect others will adapt similar solutions for two-speed cranks.
A close look at the built-in chain guide and bash plates.