Showroom 2 DOF Diy Helicopter motion platform for UH1 Xplane

The Sim of AGGLOMERATION
Pre –Amble: The condition of Sim being only one letter removed from a word that describes activity that could send you blind seemed too serendipitous not to play with, hence the Title.

The short version of the inspiration for this arrogant idea that we might be able to build a serious motion sim, begins with a you tube Video showing a person hooking two motors to a uni-joint mounted car seat via some flexible control rods and having most of what was required to call it a 2 degree of freedom motion simulator!

Yep! That’s how simple it seemed.

Most of the detail of our project will be of little use to anybody, because it is purely an agglomeration of scraps we had laying around. If you were to try to copy almost any part of it, you would find it could be done, simpler, probably better, and, unless you got the part for nothing, cheaper.

I guess the work so far should be divided into two parts;

v Main body of the machine.

v Controls.



Later we will have to address the computer and all the software of the simulator and UH1 aircraft as perhaps the third part, but to date we have done little but purchase the video card we think is the best we can afford.

We began, for example with a gate made from heavy box section steel. Outside dimensions>1600mmx1000mm. Two trolley jack wheels welded on cam shaped hinges at the front mean that if the thing has to be moved it can be wheelbarrowed with these front wheels folded under. The gate happened to have a cross bar about 500 from one end to which we bolted two extremely heavy chunks of angle iron, (salvaged long ago from a television camera mount). This projects 300mm straight up to accommodate a heavy boat trailer roller. (maybe it is from a boat trailer?) This is the main pitch baring on which the entirety of the moving parts sits. To this was welded two chunks of heavy thickness steel that support again, bearings i had in a box (possibly boat trailer wheel bearings) that are now the roll axis freedom granters.

Bolted to these roll axis bearings is a solid piece of U-section steel that was once a post for highway guard rails. The heavy gage U channel is 170mmwide, 85mm deep, and about 800mm long. It just so happened that we had taken out about half of the 170mm floor of the channel for some long forgotten project so this left two projecting 400mm arms projecting rearwards that we bent to 45 degrees to be the arms the main motors would attach to. We experimented with two 240 volt AC garage door motors, but long story short, we ended up with two wheel chair motors and mounts.

About the next major find/acquisition were two Toyota coaster bus seats being given away. We were envisioning a two place machine, but as it would be flown singly most times our thinking ran to a sliding arrangement that could be adjusted left or right to suit. Two old car roof racks attached to rails that would fit inside the u channel allow this at present. [may permanently fix it as 2 place as things are becoming more difficult to keep this flexibility.] Using 12 roller blade bearings to lock the rail in the channel to one degree of freedom, sliding forward and back, allows for perhaps the most important part of a UH1 HEUY experience, the rotor vibration! Acquiring a tread mill machine for nothing, we stripped it and salvaged many parts. From the main 180 volt dc motor to the arching oval tubes that support the console/hand holds, including many fine brackets, screws, and bolts, we used a lot of it. The 180 volt DC motor is mounted to a plate attached to the seat and rails that sit locked by bearings to the u channel. The shaft of this motor has a small cast iron pulley wheel through which is drilled a threaded hole. Bolted to this is a control rod end bearing. The other end of this is attached to a spring welded to the U channel. At anything above about 40 volts the motor spins transmitting a force that essentially tries to slide the seats assembly back and forward. Rotor Vibration.

Primitive, but possibly immersive if it were just a dumb on off with the simulator power switch/relay, but we hope to pulse modulate it to the rotor vibration of the X-Plane UH1. A big bottle neck occurred trying to find a satisfactory way to connect the wheel chair motors to the 45 degree arms protruding from the rear of the seats. After more than 12 months, we finally found that many motor vehicles have a small rod that connects the sway bar to the sub-frame via two swivelling booted joints! It was almost as if we had ordered the part to be made to the specs we required! This is perhaps one of the few useful/useable and transferrable parts of our story. If you are lookin for a way to connect your motors, go to a metal wreckers/recyclers` and look for a front end of a small truck or 4WD.

From pieces of the tread mill frame we have fabricated a triangular box section that is bolted and welded inside the space between the two 45 degree flat sections that protrude from the main roll and pitch assembly (U Channel) the seats sit on. At the midpoint of this is frame is welded the ratchet mechanism of a Nylon strap tie down. Where the webbing would normally slot is a steel cable. The other end of this spools onto a shaft that is attached to a roller door spring. This spring assembly is aligned at ground level along the fore/aft axis of the machine. This addition allows a balancing of the pilot/pax weight in pitch, and maybe because of the 45 degree distribution of the inputs, a little in roll also. The adjustment possible with the ratchet allows for one or two persons.

The only other part of the machine completed so far is the deck for the foot rests and pedal yaw control. Using the arched uprights of the treadmill to slope from the seats downwards and forwards, we have mounted a flat plywood deck between them. This extends the C of G forwards considerably, but it is necessary to have the whole body in sync with the seats. As a P.S. we have joined to steel rods in a hinged configuration as a mobile support for the foot rest deck. Don`t know if this will be necessary, but have seen it on other machines of this type so have it on hand if required.

CONTROLS

The controls have so far been developed almost totally independently of the main sim structure though some reference has been made to dimensions and anchor points in the hope to transfer them when it is complete.

Beginning with a salvaged Office Chair, we attached a plate beneath it to support a Microsoft joy stick we purchased from a charity shop for 3 dollars. It was the product just before USB plugs and as luck would have it, it was simply a matter of wire for wire soldering it to an actual usb cable to convert it. Extending the length of the shaft of the stick was a delicate but doable task, as was isolating the button contacts on the board inside the base. The collective is a shaft inside a shaft mounted to a telescope mount tilted sideways. The outside shaft allows a twisting throttle. To this we have attached a bicycle hand brake cable that terminates inside the Microsoft joy stick to operate the throttle mechanism there. This has so far only proved partly successful, and another throttle dedicated pot might be the end point answer. The friction on the telescope mount provides a luxurious smoothness to the pitch control action.

Attached to the chair frame is a 10 ohm pot resistor with a plastic gear salvaged from a photocopier machine. Acquired from the same photocopier, a spring tensioned toothed belt is secured to 2 points on the collective lever. This is so that the movement of the collective pitch varies the resistor pot to be read by an attached arduino. A small black plastic project box is attached to the end of the collective in which 5 momentary ON and 1 rocker switches were mounted. Not in any resemblance, a recreation of a Huey collective, but the momentary ON`s are connected via wires running down the collective tube to the button contacts inside the Micro soft joy stick base. The belt pot arrangement used for collective pitch is the same mechanism we used on exercise foot pedals we found at a garage sale that now simulate rudder.