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Saturday, 24 April 2010

Sturmey Archer X-FDD technical

I have got the hub brake on the custom wheel working now.  I had to wait a couple of days for the special Sturmey Archer brake cable.  Now I have one, I think I should be able to replace it with a standard brake cable without too much heartache when the time comes.  The brake is about as good as the Tektro V-brake which came with the bike, but it will still be just as good in the pouring rain.  Hub brakes behave a little differently from the rim and disc brakes I have used, the best way I can describe it is that instead of a constant braking force being applied at the wheel when you apply a given force at the lever, the braking force seems to grow over a period of a few seconds when a constant force is applied at the lever.  The result is a nice quick stop but to the uninitiated the brakes feel odd.  I do quite like the fact that I won’t have to do any maintenance on the brake for a very long time.


The other feature of the hub I have been playing with is the integral dynamo.  I am quite happy with my existing battery LED lights and I am not currently planning to replace them with dynamo lights.  The hub outputs 6 V of AC which is great for filament lamps but sucks for LEDs and lots of other devices.  I purchased a bridge rectifier from Maplin for 27p to convert the 6V AC into 8 and a bit V DC.  I connected the output from this to both a fixed positive voltage regulator (£1.02) to produce 5V DC, and a battery pack (89p) containing 4 rechargeable Ni-Cad AA batteries.  This allows the Ni-Cad batteries to charge when no other load is attached, and they work in series with the dynohub to power a device when connected.


The whole lot is inside a clip-sealing tupperware box, and the 5V DC and ground wires are connected to a pair of USB ports:


The end result is able to charge devices which are able to charge from USB:


I’m planning to mount the tupperware box on the now unused rim-brake bosses tomorrow.


  1. Very nice on the voltage hackery! I may borrow your design for an allied project.

  2. Shimano do a centerlock version of this hub for disc brakes if that is any use to you. I remember hearing that Sanyo make the internals on both and that they are pretty much identical in electrical characteristics. I think I might add one to the Yuba one day, it could be great on yours.


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