Chain Tension

This month’s tech column is going to be about chain tension. But before I get on to that I should probably ramble on about something pretty much unrelated for a while. In this case I want to get you to take a minute to think just how awesome bicycles are. I was awestruck the other day watching the aftermath of the London tube and bus bombs. People were talking about their fear of getting back on the underground but saying they had no option… No option!?!? It’s the middle of summer the tube network only extends about 8 miles from the centre of London anyway and London is virtually flat. Why not get on a damn bike?! Do you know what the statistics for terrorists bombings of bicycles are? I had dreams of seeing the roads of London suddenly full of cyclists cruising down the empty bus lanes, saving their tube-fare and getting some much needed exercise… Sadly it never happened. But remember that that bike of yours can do more than just tricks.

Anyway back to chain tension. We have all experienced the dilemma pretty much every time you take off your back wheel and come to put it back on. Sure you can run a Halfords/Fly Cobra inner-tube, but sooner or later you will need to take your rear wheel off, and when you do you will have to set the position of your back wheel just right to get the chain tension you want. You will also need to be thinking about getting your tyre central in the stays of course. After some wrestling you get it set and then you have to check it by cranking the pedals round a few times, because the chain tension varies! Why is that? Why do we have to adjust and re-adjust the wheel position so that the “tight-spot” isn’t too tight and the “loose-spot” isn’t too loose? Why is there even a tight and loose spot in the first place?

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When the very first bicycles were being developed, simplicity was king. We are talking about Scotsmen scooting about on wooden frames with wooden wheels and wooden forks. This soon developed into the first real bicycles, where rather than pushing along with your feet on the ground cranks were fitted directly to the wheel of the “ordinary” (or penny farthing).

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