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  • Schlumpf double-fixed

    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.

  • HammerSchmidt double-singlespeed gearing

    HammerSchmidt double-singlespeed gearing

    Does the HammerSchmidt crankset work with a fixed wheel?

    Nope. The cranks themselves freewheel, so the bike would no longer be fixed. If you put Hammerschmidt cranks on a fixed-gear, it will turn it into a freewheeling-enabled double-singlespeed bike.

    But, yep. Nothing would be damaged, it just wouldn’t be a fixed wheel. And… you could run a superlight singlespeed rear wheel. A Shimano or White freewheel weighs a lot more than a 15t (or 12t Phil!) fixed cog.

    Can I use this thing on a road bike?

    Sure. With a little help from a framebuilder. You’d need the proper “ISCG 03 or ISCG 05 tabs” (whatever those are) retrofit to the bottom bracket.

    The HammerSchmidt only has two chainring sizes available: 22t and 24t, which forces you to choose a very small cog if you want to use it on the road.

    Road Gearing

    I had thought the spread was too big, until I did the number-crunching. I like a wide range, because of where I like to ride. A normal gear for most times, and a low low for climbing.

    • 24/15 = 44″ and 70″ gears – I’d run this setup any day.
    • 24/14 = 47″ and 75″ gears – If it was a fixed drivetrain, it would be ideal.
    • 24/12 = 54″ and 87″ gears (for time trialing over mountain passes?)

    Offroad XC (non-Downhill riding)

    • 22/15 = 40″ and 64″
    • 24/16 = 41″ and 65″

    I calculated the low gears with Sheldon’s gear calculator, then multiplied by 1.65 to get the high gears.

    I could have (should have) just chosen Schlumpf Speed Drive Bottom Bracket from the “internal gear hub” dropdown, since the multiplier is also 1.65. The numbers aren’t the same, but they’re close.

    These gears and opinions are theoretical in nature – follow your own folly.
    I would really like to hear about (and see) any road bikes set up with HammerSchmidt crankset. And if Truvativ wants me to test one, I think I can add the tabs…

  • Protected: Optimal Tire Pressure

    Protected: Optimal Tire Pressure

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  • ibikenz’s beautiful bike graphics

    ibikenz’s beautiful bike graphics

    My type of Aucklander…, originally uploaded by ibikenz.

    ibikenz’s bike graphics are really cool. I’d wear the T-shirt. Check out the ‘Bicycle Friendly North Shore’ blog – it’s Spring down in New Zealand!

    a few of ibikenz's bicycle-types graphics

    I was in Auckland, NZ for three hours once, in 1988, on a layover from Australia. Two weird things happened in Auckland – I was paged on the PA, but it turned out to be a DIFFERENT “Philip Williamson” (50ish, British) who was wanted.
    And my bike stayed there. It was supposed to go to OAKland, but they took it off in AUKland.

  • New blogs for old subjects

    I set up two new blogs, one for my portfolio and resume, and one for my bike tinkering stuff. I may just leave my unpalatable political philosophizing over here.

    www.PhilipWilliamson.com: my portfolio and resume. Stuff I’ve made over the last 20 years, professional and personal work from the last 20 years. PlayStation game console interfaces, toy store website design, assemblage sculptures, weird comics and more.

    www.BikeTinker.com: Me breaking stuff on my bike and having to fix it. I’d like to showcase people’s bike makeovers there, too. Maybe sell some bike-related kits or artwork.

    I also made a blog about my dog, but I haven’t put much time into it… I kind of went on a WordPress bender, there.

  • Optimal Tire Pressure for bicycles

    Optimal Tire Pressure for bicycles

    EDIT 2022:

    Just use Jan’s calculator:

    Run it for your bikes and write the pressure on the tires or the rims.

    Ignore all this old stuff:
    Here’s a short overview of tire pressure on the Problem Solver’s blog. It’s a little more concise than this page, and has more pictures.

    The Calculator

    The pressure calculator was created by Dave Adams, who sent it to me because of a tire pressure post I’d put up with an extended chart. You can open the spreadsheet in Open Office, Excel, or Google Docs and use it for free. Just remember “Dave Adams” when you use it.

    How to Use It

    Fill in the yellow fields in the spreadsheet (tire width; bike and rider weight; percent of weight on each tire). Go pump your tires. You can make (copy) a tab for each of your bikes, and make the tires and rider fatter or thinner over time (or adjust for touring loads).

    The Science

    According to Frank Berto and Jan Heine (of Bicycle Quarterly magazine), two top bicycle science guys, the most efficient bicycle tire pressure is one that gives you a 15% drop in tire height when you get on the bike. “This tire has too little air!” It’s squishy and hard to turn. “This tire has too MUCH air!” It loses energy bouncing off small surface irregularities. “This tire is JUST RIGHT!” Fifteen percent is the Mama Bear of tire drop.

    Given that you want each tire to ‘drop’ 15%, and bikes don’t weight the front as much as the rear, you don’ t want the same amount of air in each tire. It seems obvious when you think about it, but it was  revelation to me.

    Most bikes put 60% of the weight on the rear, for a 40-60 fore-aft weight distribution. The “Quickbeam” tab in the spreadsheet is set up this way, and I actually weighed the bike with me on it to get the split. I could have saved some work and trusted to Bicycle Quarterly, but I like to check things for myself.

    Low-trail French Randonneuring bikes are different, with only 55% on the rear. The “Ross” tab in the spreadsheet is for my low-trail Ross Super Grand Tour fixed gear tourer. Also weighed out accurately to confirm the BQ numbers.

    Dave says his equation looks like this:
    PSI = 153.6 * Weight / (TireSize^1.5785) – 7.1685

    History

    A few years ago, in the Spring of 2007, Bicycle Quarterly had a “Tire Drop” article based on Frank Berto’s research about proper inflation for best efficiency, in which they published a very useful graph, and instructions on how to set up your tires.

    It didn’t have a line for 35mm tires, which I used at the time, so I added another line, and extended it to allow for heavy loads. Jan Heine gave me permission to republish the Bicycle Quarterly graph with my additions, and it turned out to be pretty useful for some people. I actually had an internet friend send it to me, not knowing I’d posted it in the first place.

    graph showing optimal inflation for bike tiresDave Adams saw the post in his research on the same subject, and sent me a copy of his spreadsheet, which I’ve been using ever since. With his permission, I posted it to the  RBW (Rivendell Bicycle Works) Google Group, where it’s also archived.

  • Mountain bikes with drop bars

    Mountain bikes with drop bars

    I’m a big fan of flared drop bars on mountain bikes. Any bike, really. These days, there are several to choose from, and more on the way.

    The trick with the off-road drops, is getting a stem that will get the bars high enough. Proper high-rise stems are less common than the bars that need them. My Bontrager has On-One Midge bars, but uses a kludged stem-and-extender setup to get the bars high enough.

    Winter Bicycles makes stems that fit the bill. The super-high-rise stem Eric made for a Fat Chance “Monster themed” bicycle looks like a perfect match for the Bontrager. Four-bolt face plate, extra tall, and with bike mojo.

    Read all about it.

     

  • Skate deck pedals on Eggbeaters

    Skate deck pedals on Eggbeaters

  • Torpedo internals

    Torpedo internals

    The newly rebuilt and reinstalled wheel seems to be in high gear all the time, so I’ll have to pull it all apart again.

  • Hubstripping site is for sale

    The Hubstripping site is a great resource for learning about internal gear hubs, and connecting with people who can actually help you get one back on the road.

    It was a great resource for rebuilding the Sachs Automatic I bought on eBay. Through the comments section, I met very helpful people. One fellow had scanned the original maintenance poster and put it on Flickr, and Jens at Scheunenfun.de sold me a replacement driving ring after I broke the original. Where else can you get something like that?

    Apparently Marco has moved on to other things, and has put the site up for sale. I hope the new owners maintain and expand it. I wonder how much a site with 15,000 visitors a month goes for?

  • What is a Torpedo Automatic hub anyway?

    What is a Torpedo Automatic hub anyway?

    Ha.

    We’re glad you asked.

    Fichtel & Sachs Torpedo Automatic "blue" hub

    A Sachs (Fichtel & Sachs, or F&S) Torpedo Automatic is a two-speed internally geared hub. It’s like a Bendix kick-back, but German, and you don’t have to kick back. It changes gears automatically at a preset speed.

    At a certain speed, governed by a tiny spring, centrifugal force kicks out two brass “wings” inside the hub, and they engage the overdrive. About halfway across an intersection (7 to 10 mph), the high gear will kick in by itself, and you’ll suddenly be pedaling harder and going faster. It’s pretty perfect.

    The hub is incredibly cool, incredibly heavy, and really fun to ride. For me, the only downside is the coaster brake.

    The low gear is the direct drive (1:1), which means that when you’re cranking up a hill, you aren’t running through the gears. Everything’s locked together and you aren’t wasting any power on the transmission.

    The 1:1 low gear is why Bendix Blue-band kickback hubs are the most desirable ones. The Red and Yellow band Bendix hubs have high-gear as the direct drive. The Sachs hubs are regarded as better-built, more durable, and with a better coaster brake than the Bendix hubs.

    Speaking of which, similar hubs are the aforementioned Bendix kickbacks, Sachs Duomatic kick back hubs (like this Automatic, but you backpedal to change gears), and the new Sturmey-Archer (Sunrace) S2C. The SA S2C is the bargain deal, since you can get one for ~$65 brand new, and these Torpedos cost ~$160 shipped from Germany.

    As far as I know, the Sachs Automatic is the only two-speed hub ever invented that will shift for you.

    Sprockets are the widely available three-notch ones used on Shimano and Sturmey-Archer hub gears for the last million years. New ones run $8-$15, and can be ordered from your local bike shop.

    For more information on this, and internal gear hubs in general, visit the Hubstripping site. If you have a Duomatic or Automatic that needs parts, email hansen auf scheunenfun.de. He provided a replacement driving ring for this hub.

  • Gear ratios for Torpedo 2-speed hubs

    Figuring your gears is a little tricky with a two-speed hub that shifts by itself. The low gear is 1:1, the high gear is 1:1.36.

    The low gear is direct-drive. There’s no fussing; the gear you calculate on Sheldon’s gear calculator is the actual low gear. It is the 1:1 gear.

    The high gear is 36% larger. I plugged in larger cog sizes until I got ones about exactly 36% larger. I just noticed that Sheldon’s calculator will let you add fractional cogs!

    I’m a double idiot – I just noticed that Sheldon’s gear calculator lets you choose a “Sachs Duomatic / Automatic” hub in the Internal Gears dropdown. This way is a little easier to read, though.

    I have a 19t sprocket, and a 22t sprocket. I also have 39, 40 and 42 tooth chainrings I think might work for this project.

    The “high gear equivalent” for the 19t is 13.97 (let’s call it a 14). The “high gear equivalent” for the 22t sprocket is 16.18. Again, 16 is plenty close.

    With a 19t cog and a 39t chainring, I get a low gear of 56″ and a high of 76″

    39
    		40
    		42
    19t low
    		 56.1 57.5 60.4
    36.0 %
    high 76.3 78.2 82.1

    With a 22t cog and a 42t ring, I get my ideal setup:  52″ low and 71″ high gear.

    39 2.6 % 40 5.0 % 42
    22t low 48.4 49.7 52.2
    36.0 %
    high 65.9 67.5 70.9

    The Sachs Torpedo 2-speed gives a slightly wider ratio than my double fixed setups that use a 17/21 Surly dingle cog and a four-tooth chainring difference.

  • New F&S Driving Ring!

    A new driving ring for my Sachs Automatic hub!

    Last year I tried to get one of these to replace the one I broke. I contacted Jens Hansen at Scheunenfun.de, and got another ring, but it had 10-knobs, instead of 9. That was the first either of us knew that there were two styles.

    So… last week I emailed him again, to see if he’d encountered any 9-knob rings, and he had one. He was also willing to take Paypal, which is 10x cheaper than Moneygrams.

    Today the part arrived! I was so excited I went ahead and took the hub internals apart and replaced the broken piece. I’ll put up a post about the process in the next couple of days.

    So far it looks good – I’m just checking gear inches.

  • Magical Wheelism’s fantastic machines

    ferdinand (li’l red), originally uploaded by magical wheelism – corey todnem.

    Magical Wheelism, a Flickr contact of mine, draws the most beautiful bicycle machines. I love the way the drawings look, and I love the ideas behind the concepts (so to speak).

    Treadle-powered bikes, bike where you lie prone, bikes with baroque curlicues. Amazing and inspiring. The bikes speak for themselves.

    He says he’ll soon have a prototype built. He’s doing the mitering, brazing and painting himself. I think that’s really cool. Fabricating is when tinkering goes pro.

  • Protected: Seats and posts

    Protected: Seats and posts

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  • New Words

    Bigly
    Smilable
    Motoristic (it means be-engined)