SRAM Hammer Schmidt Crankset

While at Quality Bicycle Product’s Frostbike show, I got a chance to ride the SRAM Hammer Schmidt crank system on a trainer.  Seems pretty clever. When I first saw it in the magazines, I thought it was much more complicated than it actually is, perhaps influenced with my exposure to the Schlumpf crank system.  


Hammer Schmidt 1.jpg


Without getting too technical, the chainring is either driven by the crank directly or, when a geared ring is held stationary relative to the bottom bracket shell, then the chainring is driven by gearing at a rotational speed faster than that of the crank.  The front shift lever pulls a cable mechanism to capture the geared ring at the bottom bracket. A frame must be specifically equipped to use the Hammer Schmidt system, but the requirements are simply to have the tabs on the right face of the bottom bracket shell to mount the engagement mechanism.  A custom builder shouldn’t have any major problem building a frame to use the system, but retro-fitting the system to an existing frame might not be practical, especially for aluminium alloy or carbon frames.

Compared to the Schlumpf system, the Hammer Schmidt seems to have less internal drag.  The SRAM system is not suitable for fixed gear applications because the chainring will freewheel on the crank, thus any fixed gear rear wheel would act like a freewheel when combined with the Hammer Schmidt. 

Most likely the Hammer Schmidt holds the most promise for downhill and freeride applications where the small chainring will improve ground clearance and the system’s constant chainline will work well with a wider range of rear suspensions. 

But wouldn’t it be cool to combine this with a Rohloff?  28 internally geared speeds.  Of course, the Rohloff offers its 14 gears sequentially with no overlap, whereas the Hammer Schmidt mimics a conventional double chainring crank.

Hammer Schmidt 2.jpg





6 Comments

Isn’t that the name of nursery rhyme? No wait that’s, “There goes John Jacob Jingleheimer Schmidt!”

Mark V,

What problems have you had with the Schlumpf system? To my, admittedly novice eye, the Schlumpf is a simpler user interface than the Hammer Schmidt.

I wouldn’t say problems.  The schematic diagram I saw of Schlumpf seemed fairly complex, though I admittedly didn’t spend a lot of time studying it. The SRAM product seemed simpler to me. I also don’t like using my heel to activate the shift (SChlumpf) because my feet are short; thus it’s harder to get a solid contact with the shift button.  I like SRAM’s (Truvativ’s) system since it puts the shifter at my finger tips.  You don’t have to change your pedal rhythm at all with the Hammer Schmidt; in that respect it beats the best road front derailleurs (maybe not DA7970 electronic) because you can shift under full power with no delay in shifting.

ObNerd:

To combine this with a Rohloff, I’d first want to make sure that I could get a perfectly straight chainline out of the deal.

That or I’d want to continue the tradition of Sheldon Brown’s 63-speed overkill, and find some way to hack a regular spider in place of the chainring on the Hammer Schmidt, and another way to attach an 11-speed Campy cassette to the Rohloff for a downright obscene 616 speeds (which I say while trying to imagine how one might attach a triple chainring to the hammer and get 924 speeds instead).

I have a Niner WFO with Hammerschmidt / Rohloff combined.  Other than being a bit on the heavy side, it’s a sweet 28 gear combo.  Always having to ride an xl frame, I’m used to a heavier bike. It’s especially great being able to shift the Hammerschmidt under load or at any point for that matter.  The hardest thing was just forgetting trying to compare the gearing to a standard set up.  You just have to think Rohloff 1-14 and Hammerschmidt high to low.  Rohloff has such low gearing I use the 24t chainring, forget the 22t, no way to pedal in gear one Rohloff with that.  I put red fingernail polish on Rohloff gear selector 1 & 14, white on 5 &7.  Otherwise looking down and trying to figure out where I was turned out to be too difficult as I was getting used to things.  Two months in I now have a feel for the combo.  No more derailleurs - just a rear chain tensioner.  Ryan at Arizona Cyclist in Tucson built it up seamlessly.  So far it’s survived Tucson, Hurricane & Moab and still running smooth.

I also gave up on what gear I’m in with the Nuvinci—other than the inch-worm indicator—there’s a low, medium, high range and certainly not infinite gears.

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