July 29, 2010

Simplicity itself

I've been tinkering in the garage lately, trying to get a winter/gravel bike rolling - and it's sometimes frustrating what my initial vision is, and what I have to work with - be it parts, or financial ability.  I've had the frame, and it's been taken down from the wall and readied.  I came up with some older road wheels that are stout, and have good hubs.  Finally, I scored most of the parts i needed from a friend that is moving, whose bike I'm re-purposing for the task.  While a complete bike isn't ever a bad thing, I don't have any need for an aluminum, tiny-clearance, road bike:  been there.  The winter-bike (what's this, part 6 now?) is steel, once again, with plenty of tire clearance... though, not nearly as much as my FINAL, someday winterbike/gravelbike, the Surly Long-Haul Trucker, 26" wheel model.

Until that time, however, I have gone through a throng of annual winter-bike build ups.... Purple Hippo, "it", The Crudwell, Monokog(swell), the singlespeed version of my long-gone Trek 720, Schwinn World Sport, and others.  Each time, I must admit, they get a little sweeter, a little more involved.  This year's is no exception.

So, a heavily frame-savered Trek 450, fenders, room for Nokian's new(ish) Hakkepeliitta A10 700x32c studded road tires.  I've waited a long time for a road tire with studs that could potentially fit under the fenders of the Kogswell - but I'm keeping that bike in reserve this winter.  My first season on studded tires was last year on the Monokogs, and I'm hooked... SO confidence-inspiring, I can only imagine that getting a little speed back on a more "traditional-for-me" road bike will be stellar.  Swap on my trusty Panaracer Pasela TourGuard tires for drier days, and I should be in good shape.  In fact, spurred by a post from KC-Bike.net, here, the pictured Specialized Infinity 700x32 tires that barely fit into a more modern alloy-framed bike with fenders removed *should* fit into an older steel bike frame WITH fenders... so those might be the tires of choice for otherwise dry days, and definitely for gravel road adventures or rail-trail riding - which is the other motivation for this build.

In the "these parts just won't work" arena, I'd been drumming my fingers for a few weeks - wonder if I'd ever get the bar-end shifters I needed, whether or not to use the STI levers that came with the bike... and then looking at my giant lobster-claw winter beef gloves, and wondering how I'd shift.  And then remember why I went single-speed in the first place, way back many winters ago.  Trying to keep things cheap, but being kind of impatient, I rolled around more ideas in my head.  I don't want to go single-speed, because after last year - well, I want gears.  The gear ratio that was simply brilliant in deep snow and on rutted ice was murder on smooth, flat pavement.  Sometimes reaching 300 RPM (ok, not really) on 175mm mountain cranks was nuts... and I always felt like I was NEVER going to get home.  In fact, even on a dry day it would take up to 20 minutes longer to make the trip, just because of gearing.  Anything steeper, however, and I begin to lose the wicked-awesome traction and plowing ability of a super-low gear.  So, okay... gears.  I want 'em.  I also want "cheap", "simple", "reliable".  

Something called the Surly "Dingle" popped to mind.  A cool solution to a fixxie's wish for more than one gear on a single-sided hub... or four gears on a flip-flop.  Rivendell Quickbeam riders?  Rejoice.
You see... it's kinda weird, I get that:  you're adding gears to an otherwise "simple" single-speed... so why not just put the dérailleur back on, and shift?!  I know, I know... It's like, I want the single-speed experience... but I want options.  It's part of the reason I like my bar-end shifters on my otherwise modern-drivetrain bike:  I like having gears, and it's convenient to be able to shift...but the bar-end make it so it's not TOO convenient.  So, this next thought that fell into my head gave me pause enough to give it a try.  

For complicated q-factor, crank-length and bottom bracket width reasons, the triple crankset I was going to use wasn't going to work.  I opted or a double front chainring, super-compact:  a 42x28 Sugino set-up I had laying around which would have been perfect... but the bottom bracket was too narrow, and the granny ring met the frame.  Ugh.  Again, think about the notion that I want this project to go down with as LITTLE out-of-pocket expense as possible.  Yes, there are tons of ways to solve the issues I was having by throwing cash at it, or waiting patiently and visiting lots of swap meets ... but stay with me, here.  

Instead, I resorted to a 1-x-"X" set-up... the "X" usually being an 8 or 9, cassettes of which I had both, so the rear drivetrain was still open or discussion.  Lots of 'cross racers run this kind of set-up, on the notion that the "weak" or "lazy-shifting" part of the drivetrain is usually the front.  So, I'll just eliminate that variable.  It's be interesting trying to buy ONE shifter, but whatever.  Worry about that later.  I remove the granny ring from the Sugino crankset, and swap the 42t ring over to yet another Sugino "double" crankset - thereby also eliminating the granny-ring mounting points, which were also dangerously close to contacting the frame.  There... all better.  Hmmm.... perhaps I can make things even simpler?

I still like the single-speed idea, but that "dingle" cog lingered in my head.  Then I remembered something I'd read about Ultra-racing legend Lon Haldeman.  While I can't find the exact article, Lon Haldeman, among other amazing things, started and ran the Pac-Tour organization (another item on my long "to-do" list)... and I remember hearing or reading that on many occasions Lon would ride cross-country on a three-speed bicycle.  However, this was not the "gentleman's three-speed" or Sturmey-Archer internally geared 3-speed set-up, but more of a hybrid of a traditional road bike set-up.  I examined my stack of used cassettes, the fact that I had a good, long-cage rear dérailleur in place, and the fact that I had a single-chainring up front.  Hmmm.  But, I'd still need a shifter, right?  Wrong.

It's quite simple, really:  
I took apart three cassettes to get the cogs I wanted from each, and a multitude of spacers.  I then arrange the three cogs that I want in the most centered location on the freehub body, for optimum chain-line in relation to the chainring up front, using spacers behind, and in front of the triple-cog "cassette" I've created.  Of course, using spacers between the cogs themselves is paramount here., or the chain won't fit.  In essence, I am choosing two ratios that would be ideal for the conditions I'm expecting:  for snow and ice riding this winter, or really steep routes, I chose a 26 tooth cog.  For smooth, fast pavement riding on dry days I picked my old favorite, the 17 tooth cog.  And, finally, a step between them is a 21 tooth cog.  17,21,26 x 42.

Chain tension is handled by the rear dérailleur, and shifting is manual.  Most rear derailluers have limit screws that allow you to set the outer and inner limits of travel, to accommodate variances in wheels and cassette combinations and frame spacings, dropout hanger thicknesses, etc.  In this case since the cogs are positioned near the center of the freehub body, you almost have to completely tighten down the limit screws on both ends.  Your outer, zero-cable-tension position should be centered directly below the outermost cog, and the inner below the biggest cog -- just like normal, but just more extreme.  The total throw of the dérailleur is just really short now.  Okay, shifting.... well, one could use a bar-end or a down-tube shifter... the shift lever will only move as far as the limit screws on the dérailleur allow it to, so as long as you are in friction-mode, you're good... but I'm sparing even THAT expense.  

In the guise of single-speed simplicity, and keeping my hand on the bars and not worrying about how thick my gloves are vs. how dexterous I need to be to operate my shifters, I'm keeping this a manual system.  With a twist... literally.  Most modern dérailleurs that are set up for index shifting have a barrel adjuster on them, for trimming in the final indexing.  If you tighten this barrel adjuster all the way down, and then loosen it all the way up again, you may notice there is quite a bit of difference between fully tight, and fully loose.  Turning this adjusted puts tension on a cable, just like a shift lever at the front of the bike would - so I'll employ it as my "twist shifter".  I took a small, 4" long length of shifter cable, and I inserted it into the barrel-adjuster end of the dérailleur so the soldered, molded cable end that is normally nestled inside the shifter is now down inside the barrel adjuster itself.  The cable end that comes out is attached to, with the adjusted tightened all the way down, to the pinch bolt, just like you were running shifter cable on a normal set-up.  With the rear wheel elevated off the ground, pedal the cranks forward and start turning the barrel adjuster, which adds tension to the cable.  Voila!  The dérailleur moves, slowly, towards the next cog in line - and you've just shifted to your middle cog.  Keep turning, and it shifts to the largest cog.  The limit setting stops it from there.  Yes, you would have to plan ahead, stop, shift manually, remount the bike and continue.... but just like on ANY single speed set-up, chances are you won't do that unless you REALLY have to.  You simply pedal harder.

Finally, depending on the particular dérailleur and it's available barrel-adjustment length, you might even be able to squeeze in a fourth cog... but I'm not sure why you'd need to if you choose your ratios carefully.  Beyond that, I'd consider actually adding a shifter up front, and putting six or more gears back into play.  For the purposes of this build and the intended use, three is plenty... and the idea is to choose gears that would in of themselves make adequate single-speed ratios, so you aren't forced to stop and switch gears too much.  In my case, I'd save the 21t cog for the nasty days, knowing that it'd take a long time to get home anyways.  Using Sheldon Brown's gear-inch calculator, it's very close to what the Monokogs had on it as a single ratio.  The 17t will be perfect for dry days that are just cold, and the 26t cog figures out much taller than what the Monokogs had, for REALLY nasty conditions... or really steep hills on minimum-maintenance roads.  Fun, fun, fun!!!  I won't have to shift much.. but I *CAN*.  I love that.

So, the simplicity and "purity" of the single-speed set-up remains intact... but, you have options along for the ride.  Even better, those options are available without having to remove a wheel, adjust chain tension in the dropouts, or manually move a chain between ring and cogs.  Shifting is convenient... but not TOO convenient.   Plus, my "need" list for the rest of the project just got a whole lot shorter, and I've brought a little uniqueness to this latest winter-bike.  How it plays out in the field remains to be seen, but I'm pretty satisfied at this point!

Pics to come.... perhaps even a video of the set-up.
Thanks for reading!

1 comment:

Chris said...

I would gladly trade you my QB sugino crank for something with a 42 or 44 single speed crank...

You know my number...