Comparison of Schlumpf 'Singlespeed' Gears and Traditional MTB Gear Ranges (x-post)-
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  1. #1
    mtbr member
    Join Date
    Jan 2004

    Comparison of Schlumpf 'Singlespeed' Gears and Traditional MTB Gear Ranges (x-post)

    Hey all.

    I've cross-posted this to Drivetrain, Internal Gears and Singlespeed because threads about Schlumpf drives appear in all three. I've never cross-posted before and don't know the etiquette, drop a note if I've done it wrong.

    I've been pretty much exclusively single-speed for a fair while now, but over the last year or two have taken to thinking off and on about going for the double. My initial conclusion was that dingle (here taken to mean two chainrings and two cogs with both chainlines having the same toothsum) was the way forward for me, figuring on riding 41/38 : 16/19.

    However, a graph by Richard Cunningham on Pinkbike inspired me to take another look at the possibilities offered by a Schlumpf, with the key word here being 'look'. I got a great deal out of being able see graphically where the Schlumpf gears lie - as opposed to reading them numerically, I guess. - and I'm posting the chart I made here because I've seen a couple threads about Schlumpf which asked questions which it hopefully may help to answer (and yeah, I understand that in all probability this post will be of interest to approximately one visitor every couple of years... it's all good!).

    Basically, the grey bars are the range of gear ratios given by a certain chainring with the usable cogs on a certain cassette, with chainring and cassette size given along the x axis. The green lines show the two ratios available to you per single cog size using a 44 tooth chainring and a Schlumpf Mountain Drive. The number given in each of the larger green circles is the tooth count of the cog generating the ratios shown by that green circle and the smaller one in a direct line below it. Note that the Mountain Drive is direct drive in the high gear [1:1] and planetary in the low [2.5:1]. The red lines work pretty much as per the green, but are for a Schlumpf Speed Drive with a 32 tooth chainring. This is direct in the low gear [1:1] and planetary in the high [1:1.65] so the cog used is given in the lower of the two circles, with its corresponding overdrive gear ratio given by the smaller red circle sitting in a direct line above.

    As an example, using a 14 tooth cog with a 44 tooth chainring on the Schlumpf Mountain Drive gives me a direct gear ratio of 3.14 (π!) and an underdrive (?) ratio of 1.26. I get approximately the same high gear by using the Speed Drive with a 32 tooth chainring and a 17 tooth cog... an overdrive (high) gear of 3.11 and a direct drive low of 1.88.

    Note that the non-direct drive will less efficient than the direct. This loss of efficiency is given online as being between 2% and 5%, decreasing over time.

    I've had a bit of trouble adjusting from figuring on having one gear that has to cope with everything to having two gears, one for most of the trail and one to either bail me out or get me fast. First impressions are that the MD with a 13 or 14 cog or the SD with a cog in the 16 to 19 range may suit... whatever your take on it, happy riding!

    And a long and happy married life to Will and Kate too, natch!

  2. #2
    The need for singlespeed
    Reputation: zaskaranddriver's Avatar
    Join Date
    Oct 2009
    Is Schlumpf German for Hammer-Schmidt?

  3. #3
    Ovaries on the Outside
    Reputation: umarth's Avatar
    Join Date
    Dec 2007
    It is late, I've been drinking. I saw a graph and now I can barely type.

    I thought ssing was simple.

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