DonsDeals Blog: Home Built DIY 3 DOF Flight Simulator Movement Cockpit

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Monday, October 10, 2011

Home Built DIY 3 DOF Flight Simulator Movement Cockpit - Motion Platform 2.

DIY Motion Platform 2 - Page 1

3-DOF Platform 2 - Cockpit fittings and hood to be added

MOVIE CLIPS of Platform 2 in motion are on Page 2 along with some photos. Page 3 has dimensioned drawings.

JAN '08 After the experience of building the 1st motion cockpit I thought it would be interesting to see whether a more conventional 3-point support type platform might be designed which would be a bit less complex mechanically and so a bit easier to build. Keeping the cost down was still an objective off course as was maintaining a reasonable range of motion, including some decent heave capability - many lower-cost 3-DOF platforms I've seen seem to have very limited vertical stroke.

My intention was to use the DIY linear actuators I had worked on already to drive the movements (more detail about these here). Given their thrust capacity (about 50 kgf ea. maximum) this would require that the bulk of the weight of the platform and payload be carried by a separate load support mechanism. The role of the linear actuators is then primarily to accelerate and decelerate the moving mass. The load support mechanism is also used to constrain unwanted horizontal linear movements and yaw rotations. After considering the options I went for two actuators at the front and one at the rear - the center of mass of the payload is likely to be closer to the front given the likely weight of screens, instruments, controls etc. I've recessed the pilot's legs into the platform in order to reduce the overall height, to reduce the extent (and weight) of any superstructure required and to move the payload center of mass down closer to the physical roll and pitch pivot points.

These pivot points, with the load support mechanism, are positioned directly below the pilot and are probably a touch further to the rear than I would like - however the pilot's legs are where they are and clearance needs to be left for the pitch movement. All designs require some compromises. Any resulting pitch moment should not unduly challenge the actuator capacities however - the main thing is to balance the vertical force.

The load support mechanism is a spring loaded half-scissors mechanism. It has two legs in an inverted "V" arrangement pinned at the top and running in horizontal linear guides at their base. The base of each leg is drawn into the mid-line of the platform by bungee or shock cords which provide the spring effect. Downward load on the legs from the platform through the gimbal forces the base of the legs to separate and stretch the bungee cord which resists the force.

Read More...
http://buggies.builtforfun.co.uk/Sim/platform2.html

MOVIE CLIPS of Platform 2 in motion are on Page 2 along with some photos. Page 3 has dimensioned drawings.

Below are three short movie clips showing the platform in motion. The first two show principally heave motion generated during a flight in stormy weather, the last clip shows the platform motion during a quick takeoff - I've still to adjust the motion controller settings to get the magnitudes of each DOF movement correct.

Clip1 Clip2 Clip3

And just added - Clip 4 this one with the platform "loaded" with roughly 110kg and with some modest flight movement generated by FSX, I'll do something more adventurous shortly! NB the annoying squeak is rubbing between two bits of wood somewhere - I haven't found it yet.)