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This article is in the Features category, and was posted on 14/02/2003.

Hydraulic shifting device (Author: Anders)

The Machinist

The Machinist

Hydraulic shifting device



One of the big maintenance issues on a mountain bike is the wear and tear on the cables. This leads to increased friction, which again leads to bad shifting behaviour.

To solve this problem, you would have to replace the wire cable, with something else, which would not be contaminated with mud and water. Incorporating a completely closed system based on hydraulic fluid, would be the obvious solution.

The development began is 2000, and was inspired by an American company, that produced a similar product. One problem with their product was, that it was very expensive and in our opinion too large.

Schematic drawing Our system consists of two similar hydraulic actuators, connected by a Magura hydraulic tube. The pistons in the actuators are connected to a small length of wire cable that goes into the shifter and rear derailleur in the normal fashion. So when you push the shifter, the oil pushes the piston at the rear derailleur, which then shifts the gears.

The main problem with the system at the present stage is that it is very difficult to fill it with oil. Because of the small diameters of the tube and cylinders, it’s very easy for bubbles to get trapped in the system. So the first filling of the system requires patience and is a two person operation. We don’t consider the system completely finished before this issue has been solved. Slow but thorough!


Internal parts of the shifter

Here you can see the channel for the hydraulic oil

The small tube connecting the two parts is made of glass which selas the system without causing friction; and it doesn't break. The black line symbolises the cable wire, which is fastened with a small bolt on the piston.

Here is the complete system with the outer cylinder. The purple cyclinder is for protection.

Installed on a bike
On the above pictures you can see the actuators on the shifter and rear derailleur. Notice that the cable stops are drilled out; so there’s no way back. And finally the 5WT shock oil used in the system. Maybe you think that the actuator on the rear derailleur looks fragile and exposed, it’s not. The screw on the derailleur will be the first thing breaking.



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