[simpits-tech] Pneumatic thoughts again...

[Gordan Sikic]

Hi Akin,

\begin(digression)
I am mainly refering GA type of aircrafts, like C172, where one directly 
feels erodynamic forces. With boosted commands things are bit different, 
but in general the principle remains.
\end(digression)

Don't include trimming  this way. What you need is to feed the 
simulation program with the position of the trimmer along with position 
of other control surfaces, and use output of the simulation  to 
calculate force on the stick.  

(I know you already know this, but for clarity :)
Trimming is _not_ directly linked to the force on the stick, but just 
one of the inputs needed to calculate the force.  With trimming, you are 
simply shanging the "floating angle" of the elevator. On the other hand, 
every different speed requires different elevator angle in order to fly 
horisontally. If one doesn't trim the airplane, he well feel force of 
the stick, if the speed is different from the trimed one.

It means that you won't need position of the stick only, but other data, 
like speed in order to calculate "zero force position of the stick". If 
oyu want to reproduce forces completly, you'll need some other data like 
accelerations, control surfaces balancing, kinematic of the lincage, 
altitude,  sitick speed (besides position)....

Of course, making this approach will result in _dramatic_ increase of 
fidelity. I've tried "flying" PC-9 trainer (without visualisation, just 
cockpit instruments and "force feedback"), and it was incredible 
experience. After that, using some "force feedback" joystick simply 
didn't feel right anymore.....


btw,
Why don't you use electrically driven motors directly, to avoid  losses 
connected to energy transforms;  in this case, you'll need compressor to 
provide preassure: It means electrical energy(or chemical energy of 
combustion engine fuel) -> mechanical energy  of moving parts of the 
compressor(kinetic) -> preassure of the gas (with heating) ->back to 
mechanical

(few more questions, I would like ot hear other experiences :)
What is your estimation of power of the compressor needed (given that 
the force on the stick that is experienced goes up to "30kg" (300N)? 
What about compressor noice?

Another question I would lilke ot ask you is "how fast" could you build 
up the force using pneumatics?

What is your suggestion about water vapour in the air? Is it going to 
make any problems?




I know I'll be banned from the list after this, but I beg you to  
forgive me:)



ciao,

Gordan
 
mailto:gordan.sikic@inet.hr