Throttle Quadrants & Harnesses

5/20/2009

Throttle Quadrants

I decided I didn't want to fabricate these :0) So I sourced them from Steen Aero Lab. These are very nice quality. The pax quad' has throttle only (no mixture). I understand some builders like mixture access up front incase the second driver has to take over if the pilot becomes incapacitated at say, 9000K feet...but to me, it seemed the scenario of being on final approach with a sudden loss of power due to an inexperienced pax playing with a red lever seemed more of a likely scenario (even though both scenarios are highly unlikely, I think the latter is the worse of the two).

I fabricated back plates from sheet 4130 and welded those in the quadrant locations identified from sitting in the cockpits while making vroom vroom noises. The throttle connector rod between the two quads' was made from 3/8x.035 tubing. A slight dog leg of about 7-8 degrees was applied to the tube to allow for the quads not being mounted exactly in-plane. For one end of the tube, I made my own narrow style fork from a piece of 0.90 plate 3" x 9/16, cold bent it over a .125 piece of sheet steel (radiused at the end), then welded this to the tube. I was going to do the same to the other end, but I felt I would regret not having fine adjustment when final fitting later, so I made me a steel plug on the lathe, drilled it for a 10-32 thread, welded it in with a fishmouth cut, then tapped it. Then for good measure, (although not really needed but I couldn't help myself) I squeezed a rivet through it all.

Restraint system

I almost purchased dedicated acro harnesses, but I decided after some research, that cheaper alternatives which are just as good existed in the car racing industry. I figured the money I saved would help go towards those must-have but expensive seat parachutes (I am planning on Softies from Allan Silver). The harness sets were from Simpson Racing (SFI 16.5 Latch F/X model). The downside of purchasing these, is that i) there is excess webbing due to them not being custom made ii) no ratchet system. The excess: I can trim off some, since I know a local Master parachute rigger who has an industrial sewing machine to terminate the ends properly. The ratchet...I may not ever need one, but if I do, I could get one retro fitted, again, by a qualified rigger.

My newly acquired lathe really has come into its own lately. It's been great for the harness system hardware attach points - making flanged bushings..and more bushings..and more..

I wanted to fit a secondary lap belt, and I wanted the primary and secondary attach points isolated from each other. Inset pic shows the secondary attach point at the seat corner, the primary being attached to the fuselage. For the pilot shoulder harness, the attach points are at ST.110 per a McKensie Skybolt newsletter on BiplaneForum.com.

The PAX shoulder harness attach point is an issue with the Skybolt, due to there not being an ideal point for the harness to pull against. Many are fitted with the harness simply wrapping over the rear seat tube at longeron height. This point, being much lower than the PAX shoulders can cause spinal compression upon impact. Attached pic shows my PAX shoulder harness support. Built similar to the landing gear truss, the main tube is 7/8 x .049, the others are 3/4 x .035. I may still add a wrap-over strap starting under the longeron -->wrapping over the 7/8 tube...the jury's still out on that one....

I made up my own cables for the shoulder harnesses using 1/8 7x 19 SS cable and the nico-press system. A Bearhawk builder buddy had the right gear, so I took my bits over to his place and we made up 2 pairs.

I am now currently working on seat pans. These are the 3" deep pan type supplied by Steen.

Once the pans are done, I plan on making a rotisserie for the fuselage so I can start working on the landing gear...and I STILL haven't decided whether to go Groves or bungee yet :0|