Thursday, 3 February 2011

KISS My Cog. Fixie Bicycle Conversion.

Atlantis Rising

Keep It Simple Stupid, about the only useful principle I learned at university. It applies to software, life -and bicycles. Fixed gear bicycles are the new black (or rust red) although not themselves new, a pennyfarthing would have been fixed, and I remember getting smacked on the back of my legs by my pedals at a young age. Out of nostalgia, or trend following, I've been thinking about building a fixie, then a friend donated an old Dawes Atlantis with a Reynolds 501 frame and off we go.

The main selling point for fixed gear bikes is simplicity. Only one gear, so no deraillieur, shifters and associated nastiness, arguably you don't even need brakes (although this would not be legal in the U.K.) -so you get a simpler and lighter bike. Secondary points are that  it makes you a better cyclist, you don't have to think about gear changes, your pedalling style is  improved; and your legs get stronger. Since I have the family sparrow legs this can only be good.

KISS in action

Firstly some research, I can recommend the late, lamented Sheldon Brown and also Charlie the Bike Monger he's more single-speed but some good advice and a good source of parts.

The original rear wheel on the Dawes had a floppy axle and an obsolete SunTour cassette, so I decided to take the line of least resistance and buy a new wheel with a flip-flop hub from Charlie. A flip -flop hub takes a track cog on one side, which is screwed directly to the hub with a counter threaded lock ring (both supplied with the wheel), the other side takes a BMX style cog with an integral freewheel. The idea, from Sheldon, is to have an easier cog on the freewheel side and use this to get you home when the going gets a bit too tough. Since the wheel came with a 16 tooth cog I got a cheapo 18 tooth freewheel. Aside from being tight, I might need to find the right cog and chainring (that's the big cog attached to the pedals)combination  by experimentation, so chaep cogs first. You also need rim tape for the wheel, I forgot this and live nowhere near a bike shop, last pair of wheels I bought came with the tape installed -so put a note on your page Charlie, some of us are thick!

Whilst waiting for the bits to arrive I sorted out the brake cables -using a funnel of insulation tape to get oil down them, start off wrapping the tape tightly around the cable outer then looser as you get to the end.

When the wheel arrived cog installation was simple- just screw on, lock ring similar but the wrong way. Next the chain, it is important that this is taut but not tight, there's no deraillieur to take up the slack, and that the run between chainring and cog is straight. Luckily it seems to be straight on the inner ring of the Dawes, so all good. Measure up the chain for both cogs, by offering it up, and remove any surplus links, I bought a half link to get the length just right. Then get the chain taught and nip up the chain side nut first, straighten the wheel, then the other side. Make sure that the wheel nuts are bastard tight, unfortunate things can happen to ones manhood  if the chain comes off the cog.

Then it was on with new Aztec brake blocks (twice the braking area of the '50s clone on there), adjust the saddle -which was at a rather alarming angle, and off we go for a spin around the block. And spin you do, no freewheel, no coasting, your legs turn all the time, you can even slow yourself down by back pedalling. Strange but fun, as the actress said to the lady-boy bishop.

I'll let you know how I get on.

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