I've mention this before and finally have a picture to post of it. Here is the vacuum generator that 177 designed for our 2004 robot. We used it to actuate our shifting mechanism. The advantage to this setup was that because it operates at a negative pressure almost no pnuematic related rules apply.
The globe motor turns the crank opperating the cylinder which acts as the vacuum pump. The check valves on the cylinder allow us to push air out of the system. This weighed approximately 6 lbs. The other weight savings gained by using this over pnuematics were so creative I'm tempted to wait until build season is over to mention.
Pete