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Pneumatic controls, somewhat OT, Flight Simulator, Link Trainer

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  • Pneumatic controls, somewhat OT, Flight Simulator, Link Trainer

    We have a WWII era Link Trainer in our museum and it is sacrosanct but of course there are visitors who would like to 'have a go' in it.

    Pleasing the visitors is our business which leads me to this way of thinking......

    Click image for larger version

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    The question is, 'How to move' the fuselage?'. The yaw rotator is not a problem as I have an old ship's radar base for that job. The roll and pitch actuators are what needs to be solved.


    One option is to use double acting pneumatic cylinders at low pressure, 50PSI maybe. I know pneumatics are used in machine shops so I expect some practical expertise on this site.

    Comments if you please.




    Attached Files

  • #2
    Oh dear! What dumb thing did I do to get the 'art work' displayed twice?
    Last edited by The Artful Bodger; 05-15-2022, 04:32 PM.

    Comment


    • #3
      What’s reasoning for wanting to use 50 psi over something higher?

      Comment


      • #4
        Originally posted by The Artful Bodger View Post
        Oh dear! What dumb thing did I do to get the 'art work' displayed twice?
        You uploaded the artwork as an attachment twice, but only placed one of the images in your post.

        I do not recommend using air, air compresses and will not give precise control.

        ​​​​​​If you're unwilling to blow the museums budget, I'd suggest leave the Link simulator alone and make a VR cockpit like I did for my flight simulator hobby.

        Another option is not have the link simulator move, but turn the stick and pedals into computer joysticks, place a monitor in the front or a projector screen, play a flight simulator with it.

        Or, do as above and utilize motion, but use large linear actuators $$$$ to move the roll and pitch. Yaw could be driven by a motor, or go full blown and have enough linear actuators to drive a proper motion platform. Software and hardware is off the shelf but will blow your budget.

        My home VR cockpit does not have motion, but it does have force feedback and tactile transducers in the floor that make me feel every bump and vibration. Thinking about adding force feedback for the rudder pedals so force trim works on the helicopters. Also thinking about adding a belt tension system that gives the feeling of G's. The belt tension system though goes down the rabbit hole of linear actuators...

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        • #5
          One thing to think about with pneumatics is there will be air noise associated with it. It may or may not be an issue depending where you have the control solenoids located at. You can also get mufflers to knock it down some.

          RB211 brings up some good points abouts it’s downside as well. Linear actuators or hydraulics may be the better option.

          Comment


          • #6
            All the new full motion simulators use giant linear actuators. The older simulators use hydraulics. Problem with hydraulics is that they require a very large water chilling system and vast amounts of water to cool the hydraulics. If you ever take a tour of a pilot training facility, the mechanically astute will notice giant water ducts. Hidden away are the hydraulic pumps usually in their own sound proof room. You'll also notice what looks like mainframes actually running the simulators. Bizarre mix of old and new. Hobbyists have much more modern systems in their home cockpits. Hard to believe the 777 is nearing 30 years of age and even in our brand new ones, still utilize 1990's technology. With government regulation, the cost to certify new systems in old airplanes is expensive, and if you change too much, requires entirely new training for the pilots. This is precisely why you see people's privately owned Cessna's with avionics that blow away anything in airliners.
            Topic creep, sorry.

            Comment


            • #7
              Originally posted by oxford View Post
              What’s reasoning for wanting to use 50 psi over something higher?
              If I use 50, or say 100PSI, I can use regular plumbers fittings including washing machine solenoid valves and I can use a small shop compressor.

              Comment


              • #8
                Originally posted by RB211 View Post

                You uploaded the artwork as an attachment twice, but only placed one of the images in your post.

                I do not recommend using air, air compresses and will not give precise control.

                ​​​​​​If you're unwilling to blow the museums budget, I'd suggest leave the Link simulator alone ....
                Well, yes, I did say sacrosanct. The project under consideration is a simulation of a Link Trainer and is not a modification of the one we have that is in working (more or less) order.

                ...and make a VR cockpit like I did for my flight simulator hobby.


                The purpose of the Link Trainer was to teach basic instruments and their use, nothing VR.

                No budget for massive linear actuators. No scenery simulations.


                However... the concept does include flight simulator software!!! More on that later.

                Comment


                • #9
                  Originally posted by oxford View Post
                  One thing to think about with pneumatics is there will be air noise associated with it. It may or may not be an issue depending where you have the control solenoids located at. You can also get mufflers to knock it down some.

                  RB211 brings up some good points about it’s downside as well. Linear actuators or hydraulics may be the better option.
                  Yea, the noise is a consideration. Most of the noise will be the escaping exhaust air and the compressor. The compressor can be at a distance and I guess we could pipe the exhaust to a distance also.

                  Linear actuators would make a simple project but $$$! Hydraulics, yes we could do that and we have an expert in that field plus we have a decent tractor wreckers' in town.

                  Comment


                  • #10
                    Expansion on the concept..

                    The Link Trainer of WWII (before and after) was a blind flying simulator where the student sat in a closed in cockpit. He had basic instruments for instrument flying and basic aircraft controls. The simulator moved in pitch, yaw and roll according to the student's control inputs and the instruments gave a realistic interpretation of his (virtual) flight. I am thinking of replicating such a trainer.


                    The Link used pneumatic actuators (bellows), cams, valves and various clever doohy-hickies and they had an ingenious electro-mechanical system to drive the instruments and to guide a remote table top plotter that traced the student's progress on a map. That was the instructor's position and it also had a duplicate of trainer's instruments.

                    Times have changed and we can do it more easily than that....

                    The student's inputs of stick, rudder, trim, throttle and so on will be passed to a regular flight simulator program. The FS program will update the instrument display (student and maybe instructor position) and we will use a micro (Arduino Mega for example) to actually control movement of the trainer.

                    The micro will receive pitch, roll, heading via SimConnect and move the trainer as required.

                    The micro needs to 'know' where the trainer 'is at'. This would be easy with digital devices such as steppers and linear actuators (however there would still be a need to determine the position at start up).

                    Using hydraulics or pneumatics would require either sensors on each axis or something like the MPU9250 chip https://learn.sparkfun.com/tutorials...okup-guide/all the task of the micro will be to move the trainer until the output of the MPU9240 matches the output of SimConnect.

                    That is the idea anyway!

                    Comment


                    • #11
                      Originally posted by The Artful Bodger View Post
                      Expansion on the concept..

                      The Link Trainer of WWII (before and after) was a blind flying simulator where the student sat in a closed in cockpit. He had basic instruments for instrument flying and basic aircraft controls. The simulator moved in pitch, yaw and roll according to the student's control inputs and the instruments gave a realistic interpretation of his (virtual) flight. I am thinking of replicating such a trainer.


                      The Link used pneumatic actuators (bellows), cams, valves and various clever doohy-hickies and they had an ingenious electro-mechanical system to drive the instruments and to guide a remote table top plotter that traced the student's progress on a map. That was the instructor's position and it also had a duplicate of trainer's instruments.

                      Times have changed and we can do it more easily than that....

                      The student's inputs of stick, rudder, trim, throttle and so on will be passed to a regular flight simulator program. The FS program will update the instrument display (student and maybe instructor position) and we will use a micro (Arduino Mega for example) to actually control movement of the trainer.

                      The micro will receive pitch, roll, heading via SimConnect and move the trainer as required.

                      The micro needs to 'know' where the trainer 'is at'. This would be easy with digital devices such as steppers and linear actuators (however there would still be a need to determine the position at start up).

                      Using hydraulics or pneumatics would require either sensors on each axis or something like the MPU9250 chip https://learn.sparkfun.com/tutorials...okup-guide/all the task of the micro will be to move the trainer until the output of the MPU9240 matches the output of SimConnect.

                      That is the idea anyway!
                      Ah, far more complicated than I realized. The old analog way of doing things can be incredibly interesting, but yet made so much simpler with todays stuff as you mentioned

                      Comment


                      • #12
                        Originally posted by RB211 View Post
                        All the new full motion simulators use giant linear actuators. The older simulators use hydraulics. Problem with hydraulics is that they require a very large water chilling system and vast amounts of water to cool the hydraulics. If you ever take a tour of a pilot training facility, the mechanically astute will notice giant water ducts. Hidden away are the hydraulic pumps usually in their own sound proof room. You'll also notice what looks like mainframes actually running the simulators. Bizarre mix of old and new. Hobbyists have much more modern systems in their home cockpits. Hard to believe the 777 is nearing 30 years of age and even in our brand new ones, still utilize 1990's technology. With government regulation, the cost to certify new systems in old airplanes is expensive, and if you change too much, requires entirely new training for the pilots. This is precisely why you see people's privately owned Cessna's with avionics that blow away anything in airliners.
                        Topic creep, sorry.
                        No need to apologize, your insights are always appreciated. As to running things via hydraulics, it reminds me of what we used to say about the old Moog Hydra-Point machines; All hydraulic systems share one thing in common....they all leak!

                        Comment


                        • #13
                          I remember seeing this a some time ago.
                          [Roland] has already built a few very cool and extremely realistic flight sims, but his latest project will put his current rig to shame. He’s building a six degree of freedom simulator based…
                          Helder Ferreira
                          Setubal, Portugal

                          Comment


                          • #14
                            Originally posted by Noitoen View Post
                            I remember seeing this a some time ago.
                            He has done some clever stuff!

                            Comment


                            • #15
                              Originally posted by RB211 View Post
                              All the new full motion simulators use giant linear actuators. The older simulators use hydraulics. Problem with hydraulics is that they require a very large water chilling system and vast amounts of water to cool the hydraulics. If you ever take a tour of a pilot training facility, the mechanically astute will notice giant water ducts. Hidden away are the hydraulic pumps usually in their own sound proof room. You'll also notice what looks like mainframes actually running the simulators. Bizarre mix of old and new. Hobbyists have much more modern systems in their home cockpits. Hard to believe the 777 is nearing 30 years of age and even in our brand new ones, still utilize 1990's technology. With government regulation, the cost to certify new systems in old airplanes is expensive, and if you change too much, requires entirely new training for the pilots. This is precisely why you see people's privately owned Cessna's with avionics that blow away anything in airliners.
                              Topic creep, sorry.
                              I used to work at Moog plant 15b, which was the motion simulator division.
                              Even though Bill Moog invented the hydraulic servo valve, Moog being the
                              innovators that they are, knew the disadvantages of loud and leaky hydraulics.
                              These were best described as hex-a-pod motion platforms. With model numbers
                              like 6DOF8000, which meant 6 degrees of freedom, 8000 pounds load capacity.
                              These used ball screw linear actuators on each axis. The screws were like 2"
                              in diameter. Moog built their own servo motors and the gears and screws for
                              each actuator. Very impressive. I was a panel electrician at the time, working
                              on installing components and bending wires in panels, much larger than a
                              commercial refrigerator. Anyhow, to test these hex-a-pods, they had one
                              with a 8000 pound cribbing of I-beams. For fun, atop this stack, they had a
                              pilot's chair with one of those huge stuffed animals sitting in it, like the ones
                              you win at the carnival. Another pod had a Cessna on it, without the wings,
                              another had an R-model Mack truck cab. Their real application was for flight
                              simulator cockpits.

                              ---Doozer
                              DZER

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