Bowden cable

Hello, I am referring to this: http://en.wikipedia.org/wiki/Bowden_cable This is the cable that is used in brakes and gear shifting mechanisms in bicycles. Any suggestions on controlling this using an actuator which can be controlled by arduino. Thanks

I would also be interested in the answers to this in a general sense but I think most people would ask you a few questions such as

the speed at which you wish the action to happen the distance the action has to happen over the forces involved the frequency of operation the 'criticality' (okay so it's not a word but whatever) of the system

I was actually planning to replace my current manual shifting of bicycle gear with an arduino controlled one. The gear shifts depending on the speed of the bicycle.

Wouldn't it make more sense to replace the bowden cable as well?

Derailleur gears or hub?

There’s quite a bit of effort required I’d guess… not like moving a Sherman tank but more than a simple 9g servo can provide.

Also I guess the gear change will need to be aware of the loading as well as the speed. So you’ll be needing a gear change actuator, a speed sensor, a load sensor…

… me thinks you have an engineering problem more than an Arduino problem…

but having said that you should Google a little…

You may get some ideas

My bicycle has Derailleur gears. I was actually planning to use a servo to control the bowden cable.

I'd suggest using some sort of worm drive, to give you a large torque multiplier and the ability to hold the mechanism in position without consuming power.

PeterH: I'd suggest using some sort of worm drive, to give you a large torque multiplier and the ability to hold the mechanism in position without consuming power.

In the manner of the Shimano 7970. If you retain the bowden cable you are obliged to retain the return springs. This puts a huge increase in load on the actuator and hence demands greater torque, incurring a probable decrease in actuator speed, or an increase in weight, or most likely both.

I have never seen a Shimano 7970. I simply don't move in the same circles as anybody who thinks they need one, and can actually afford it. The Tour de France has just finished. Check their bikes. They might tell you if this is a good idea. Even if it is, the Arduino side of this problem would be quite trivial.