The Enlightenment wrote:

While I was researching pneumatic positioning systems I came across
this web site which may be of interest to rec.aviation.military. It
looks like a German Kid who's putting together a full motion flight
simulator as a cooperative 'open source project' that is affordable
for a home user.

http://www.cadsoft.de/people/kls/fltsim/index.htm

This is some background on the technology :

6.5 bar (100psi) air has a great tradition for use in Industry because
of its cheapness, clean nature and power. Several years ago the FESTO
company brought out pneumatic positioning systems using a 5/3 way
analog servo valve. With modern control electronics pneumatic servo
systems can now position with full force against a disturbance to
within an amazing 0.02mm. The analog servo valves cost about US$500
however by using normal 5/3 way solenoid valves and pulsing them (PWM
pulse width modulation) almost the same accuracy (0.2mm) can be
achieved for US$50.00

I predict incidentally that compressed air servo systems will replace
hydraulics in many aircraft. Safety, economy and ease of service will
promote that.

100psi pneumatics do not compare favourably with 1500psi (some sims I've
dealt with) or 3000psi (aircraft) hydraulics in performance terms. He's
just not going to get the dynamics he needs because of the low supply
pressure and the compressibility of his chosen working fluid. However
he's still got to invest in pumps, precision-valves and plumbing and the
maintenance thereof. He'd be better off looking at electric drives, of
the kind that are already busy replacing hydraulics in affordable sims.
Oh and he's going to have "hours of fun" trying to integrate a cheap
head-tracked display system also. Top marks for enthusiasm and effort
though.