The (long) History of my DIY Steward Platform (Part 3)

 See here for part 1 and part 2 of this story.

Once the base and actuators had been refurbished, it was time to move on to the upper platform, or rather, to planning the upper platform.

Up to this point, the upper platform was just a hexagonal frame with a few cross braces (still unassembled here after being brought back up from the basement):

This frame previously held the temporary office chair that served as the pilot’s seat.

This time, however, the goal was to build a much more complete cockpit with three monitors and two seats. Whether two people will actually be able to ride on the motion platform at the same time is still an open question, to be honest. But I wanted to keep that option available, which led to the first major design decision: the entire cockpit has to be movable to the left or right so the load can be balanced as evenly as possible when flying with either one or two occupants. In other words, a second base is mounted on top of the existing frame:

This upper frame can be mounted in two different positions: centered for two-person operation, or shifted to the right so that the pilot’s seat sits more or less in the middle of the base for single-pilot flying. The upper frame is secured to the platform frame with a total of five M10 x 120 mm machine bolts. Each bolt passes all the way through both the upper and lower 52 x 52 mm beams, creating a very solid connection.

The challenge from this point on was to attach everything exclusively to the upper frame, while using the additional structural elements to make the whole assembly as rigid as possible without adding too much weight. Here’s an animation showing the basic concept:

This is only a rough layout concept. Many important details were still undecided or only sketched out at this stage. In particular, the bracing and support structure required for the three monitors isn’t included in this drawing yet.

For the seats, I went with two folding boat seats. I got the idea of using boat seats from a YouTube video by [N4279], who also used them in his DIY Cessna 172 simulator.

Boat seats are typically very lightweight (around 3 kg per seat) while still being surprisingly sturdy. They also happen to be a good fit for the relatively compact cockpit in terms of size. And last but not least, I really liked the 1950s-style design of the upholstery.

The seats are bolted directly to the upper frame and aren’t adjustable. For now, that was the simplest solution, and we’ll see whether this weight-saving shortcut comes back to haunt me later.

The instrument panel, which I originally started building about two years ago as a modular “desktop” dashboard, has finally found its permanent home. I’ve also completed the previously missing right-hand third of the panel with a blank insert for now. This area will most likely house two additional round gauges, along with the simulator’s own controls, such as the motion platform enable and emergency stop switches, as well as various status indicators for the dashboard and motion platform CAN bus controllers.

The control yoke is still my old CH Products Flight Sim Yoke. For the time being, I don’t really see a reason to replace it or build a custom one. Like my entire instrument panel originally, it’s designed to be clamped to a desk, which is what ultimately shaped the design of the dashboard support structure (more on that in my first blog post).

Unlike the yoke itself, I’m not particularly happy with the matching rudder pedals. Since they were also designed as a portable desktop unit, mounting them in my “floating” frame isn’t exactly straightforward. On top of that, I’ve never been very impressed with their rather imprecise pedal mechanism. So one of my next projects will most likely be designing and building a custom set of rudder pedals.

Also visible in the photo is the central support beam, which is attached to the lower frame using the fifth M10 bolt. From this support, a diagonal brace runs forward to the front crossmember, providing much of the rigidity for the entire front section.

What’s still missing are a few additional diagonal braces to stiffen the structure against twisting from side to side. Finding suitable locations for these without making the already limited footwell even more cramped is proving to be quite a challenge.

That’s where the mechanical side of the cockpit stands at the moment. The next major project will most likely be designing a suitable set of rudder pedals. I’d like to build them as suspended pendulum-style pedals, staying as close as reasonably possible to the original design used in the Piper Arrow III.

Fortunately, the Piper Arrow model I’m using in X-Plane is surprisingly detailed, so it provides an excellent reference. We’ll see how much of that design I can realistically reproduce.