Building Robots With Lego Mindstorms

Getting Pumped: Pneumatics • Chapter 10 189

that, using a differential, it’s possible to separate the two turning directions of a

motor on two different axles. Now you only need to connect each axle to a valve

so the valve cycles between its positions using only one turning direction.This is

done using a liftarm as a connecting rod, like in old steam locomotives (see

Figure 10.9).

Figure 10.10 shows a prototype of a complete double electric valve, which

combines two setups like those of Figure 10.9 with a motor, a differential gear

and some additional gearing.We had to use a worm gear to drive the body of the

differential because this mechanism requires ...