Schlumpf double-fixed

Like the Truvativ HammerSchmidt, and predating it by about 10 years, is a Swiss bottom-bracket two-speed planetary gear changer. It comes in several types (1:1.65; 2.5:1; 1:2.5).

Can I use the Schlumpf with a fixed gear?

Yep. Ever since late 2009, according to their website. The older ones no, the newest ones, yes. The internals are symmetrical, so they engage as well forward as backwards.

You can use a Schlumpf for a two-speed fixed setup, or mate it to a 3-speed fixed gear hub for six fixed gears.

The SpeedDrive has the same 1:1.65 gear ratio as the HammerSchmidt, so the same nice spread can be had on a road-going fixed-gear. There are lots of chainrings available (9, vs 2 for the SRAM HammerSchmidt): 27, 28, 30, 32, 34, 36, 38, 40 or 42. The rings are bigger, so your cogs are going to be bigger to get the same gears. That’s a bonus, since bigger drivetrain parts last longer.

A 34t ring and a 21t cog would give you a 44″ low and a 73″ high gear. I like that.

If you’d like to play with the numbers, Sheldon Brown’s gear calculator has a dropdown for the Schlumpf. Of course it does!

Can I slap this on my bike and go?

Nope. Just like for the HammerSchmidt you’ll have to modify your frame. The Schlumpf needs to have a 45° angle beveled into your bottom bracket to set against. Schlumpf says they can rent you a mitering machine “in most countries.” The bevel doesn’t keep you from reinstalling a normal bottom bracket on your frame, so it’s non-destructive.

What’s with the crazy names?

All the best high-performance, sturdy internal gear and niche-market hubs have intense chunky German names: Rohloff, Schmidt, Fichtel und Sachs, Schlumpf. I’m sure that’s why SRAM made up “HammerSchmidt.” It sounds bad ass.

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philip

UI/UX Designer, bike nerd, artist.

3 thoughts on “Schlumpf double-fixed”

  1. [I was referred to you by Tito Santiago of Castle Hill Bikes (Bronx)]
    Please help! I’m looking for help with adjustments to my Pacific Cycles IF Mode bike (with a Schlumpf drive in the bottom bracket):

    In particular, in LOW gear, the pedal crank randomly “skips” as if there was a broken sprocket tooth or chain link; But I know that this is not the case because then the skip would be consistently every x-number of pedal cranks. It only occurs under pressure (like going uphill), and VERY inconsistently, i.e., it could be every crank revolution of the pedals, and then not for 10-15 cranks! Interestingly, it does not seem to happen if I back-pedal for a little bit very so often…but that makes it hard to keep momentum when going uphill!

    I also had an issue with “slippage” in the HIGH gear (that I think I’ve fixed it, but I’m not sure of an objective measure of how much to tighten the black ring: it FEELS like it is a rubber belt – rather than the internal chain I know that it is – and “slips” under pressure, i.e., more than casual pedaling. It seems to improve if one tightens the black [self-locking?] ring at the bottom bracket (axle), but I don’t know how much to tighten it. I do know that if I tighten it too much, the crank barely moves!
    What is the purpose of the smaller silver [self-locking?] ring at the BB (axle)? “Bearing play”?

    Can you recommend someone I could turn to in NYC area for service/advice? Also, any (online) manuals that might help me understand how to adjust these problems. They are figuratively – and literally – not apparent, unlike regular bicycle mechanisms!

    Any advice, manuals, recommendations, or referrals to others(NYC) who know would be very much appreciated.

    Thank you for your time and consideration. Sincerely,

    David Gellman

    718.432.9292

  2. [I was referred to you by Tito Santiago of Castle Hill Bikes (Bronx)]
    Please help! I’m looking for help with adjustments to my Pacific Cycles IF Mode bike (with a Schlumpf drive in the bottom bracket):

    In particular, in LOW gear, the pedal crank randomly “skips” as if there was a broken sprocket tooth or chain link; But I know that this is not the case because then the skip would be consistently every x-number of pedal cranks. It only occurs under pressure (like going uphill), and VERY inconsistently, i.e., it could be every crank revolution of the pedals, and then not for 10-15 cranks! Interestingly, it does not seem to happen if I back-pedal for a little bit very so often…but that makes it hard to keep momentum when going uphill!

    I also had an issue with “slippage” in the HIGH gear (that I think I’ve fixed it, but I’m not sure of an objective measure of how much to tighten the black ring: it FEELS like it is a rubber belt – rather than the internal chain I know that it is – and “slips” under pressure, i.e., more than casual pedaling. It seems to improve if one tightens the black [self-locking?] ring at the bottom bracket (axle), but I don’t know how much to tighten it. I do know that if I tighten it too much, the crank barely moves!
    What is the purpose of the smaller silver [self-locking?] ring at the BB (axle)? “Bearing play”?

    Can you recommend someone I could turn to in NYC area for service/advice? Also, any (online) manuals that might help me understand how to adjust these problems. They are figuratively – and literally – not apparent, unlike regular bicycle mechanisms!

    Any advice, manuals, recommendations, or referrals to others(NYC) who know would be very much appreciated.

    Thank you for your time and consideration. Sincerely,

    David Gellman

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