DIY Linear Actuators For A Flight Sim

[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 on homebuilt linear actuators of his own design.

The actuator is powered by a large DC motor moving timing belts along the length of the enclosure. These timing belts are connected to a shaft that’s coupled to the frame with a few bungee cords. The bungee cords are important; without them, the timing belts would be carrying all the load of the sim – not a good thing if these actuators are moving an entire cockpit around a living room.

Also on [Roland]’s list of awesome stuff he’s building for his flight sims is a vibration system based on the BFF Shaker. This board takes data in from sim software and turns it into vibrations produced by either unbalanced DC motors or one of those ‘bass kicker’ transducers.

It’s all very cool stuff, and with all the crazy upgrades [Roland] is doing to his sim rig, he’s doing much better than paying $300/hour to rent a Beechcraft Baron.


17 thoughts on “DIY Linear Actuators For A Flight Sim

    1. id imagine becuase its hard to use pneumatics as a servo as position is load dependant and can vary depending on load, unlike an electric motor/hydraulics. question is , why didnt he use hydraulics?! :) imho.

      1. Because all electric servos are superior to hydraulic for this application. This implementation isn’t quite as robust but look at all electric injection molding machines vs hydraulic.

    2. This was pretty much my though. Not for the actual actuator, but as a replacement of the bungees. Set and maintain a static and constant pressure on the actuator equal to the average load on the unit and you have excellent gravity compensation, with long friction and a constant force. (With a bit of smart programming you could even use them to assist in fast accelerations/stops) Bungees have an uneven force over the stroke, tend to dry out and snap over time.

      I’d also advice to replace the teflon bushings with recirculating ball-bearing bushings. They’re pretty cheap, have zero slop, nearly zero resistance (even under load) and are pretty much maintenance free.

      1. Also, I am not a big fan of the housing being made out of wood. Wood absorbs moisture, rots, swells and isn’t dimensionally stable over time or under load. Plus, it has unexpected failure modes.

        1. On the other hand, it’s cheap to buy, cheap to “machine” and is fairly light… even glass fiber composites would be very expensive, steel would be heavy, aluminium is difficult (expensive :P) to work with and pure plastics apart from the price suffer from creep, which would be very bad :P

  1. @waterjet
    People use PVC for other reasons than just being cheap. Last time I checked PVC pipes are the most popular building material in the US that has largely replaced copper pipes or iron. Plus for applications such as spudguns air pressure is a serious limitation. People generally use less than 100 psi. Iron/copper really becomes more obvious when you exceed 300 or 500 psi

    1. The problem with PVC isn’t its strength, it’s its failure mode which in air applications is to shatter into a zillion very sharp ballistic fragments. This isn’t a problem with water pressure because there is little stored energy in the fluid pressure, and the fragments of a rupture aren’t shredded and accelerated. With air in the pipe it becomes a cloud of dangerous missiles if it fails.

      There are other plastics which don’t do this; the polycarbonate used for water filter bodies is reasonably safe. But PVC is easier to find in more form factors, easier to work with, and cheaper, so people use it even in “gun” designs where they’re holding the pressure chamber up against their face, which is just dreadfully suicidal.

      1. Lol I know I know… I am a member at spudfiles. The real problem is that people don’t use pressure rated PVC but DWV (drain waste vent) PVC pipes and fittings, which aren’t pressure rated at all. For example all cannons with cleanout caps are DWV. So if you see one it will likely fail. Real pressure rated PVC fails very very rarely. If it does it’s mostly due to mechanical stress or low temperature.

        PVC is popular also because it is lighter than metal. If you have a compressor or pump that only outputs 90-150 psi max then in order to get decent power out of it it has to be large bore. The larger the bore the greater the mass so 3″ PVC cannons are common but not 3″ iron cannons (not to mention price). Anyway there is a way to overcome this problem – just use higher pressure. That’s how I started converting fridge compressors into high pressure air compressors ->
        (capable of reaching 500 psi and more)

  2. Well done! His setup is better than a lot of approved flight simulators I’ve seen in ground schools – and the careful descriptions are light-years ahead of the usual shaky phone-cam video.

    The bungee v. hydraulic/pneumatic argument neglects one thing: Bungees have their weak points, but they don’t leak. They’re light, easy to replace and inexpensive which is why they’re still used on ultralight/LSA airplanes as well as early Piper/Taylorcraft designs (some of which are still being built as bush planes).

    I’ve seen pneumatic race car simulators – I think Festo had one where the pressure expanded a helically wound hose and created linear motion but you’d better like to play with O rings and teflon tape, and enjoy the sound of compressors for that kind of setup.

    For all of that, I wonder if the feedback motor has that “special” setting where you land the airplane about a foot too high and it touches down with an unmistakable pit-of-the-stomach feeling and a resounding thump. For that matter, a wobbling nosewheel in the pedal feedback would be the ultimate reality touch.

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