HP-24 Project

Update 30 November 05: More push and pull

I spent last weekend at the shop working on mockups of some of the cockpit interior items. The first thing was a mockup of the knee hump, which pretty much sets the location for everything else in the cockpit. I've got a friend who is 6'1" and about 210 lbs coming up to the shop in the next weekend or so, and I'll put my parachute on him and see how he fits. Once the knee hump is located, then I can locate the glareshield and instrument panel, and then I can locate the canopy jettison latch on the glareshield, and then I can do the mold for the little composite piece that extends the canopy frame in to where the jettison latch graps hold of it.

Another thing I did last weekend was to mix a little pot of grease (that's what we've taken to calling cabocil and resin mix because it handles so much like axle grease) and potted in the bushings on the #2 bulkhead for the canopy nose pivot. Hopefully, the waxed aluminum shaft that I used to make sure the right and left bushings are colinear will release. Once I get the shaft out I can grease that #2 bulkhead into the fuselage plug and start worrying through the canopy pivot development.

What I've got in mind is a typically European system in which the instrument panel pivots up with the canopy on normal opening, but in which the instruments stay with the ship on canopy jettison. However, I am trying to design the instrument panel support system so as to avoid the longitudinal metal tubes that I see there in some ships. I don't like the idea of having all that metal in front of the pilot and pointed right at them.

Another thing I've got going is a pre-production run of parts for the push-pull tube guides that I'll use in locations where there are non-trivial radial loads. You might recall from prior Updates that I tooled up and made a bunch of short-throw linear roller bearings for the elevator and aileron push-pull tubes. Those work great where the radial loads are very small, but I can't use them where the radial loads are more than trivial, such as where two non-colinear push-pull sections meet. The design I'm going to try instead is something I've seen in Libelles. It's based on two pulley-shaped Nylon or Delrin rollers that the push-pull tube passes between. So far I've chopped out sixteen of the pulley rollers on the lathe, and I'm waiting on delivery of the 686-2RS ball bearings that each roller will get two of. I'm beginning to think that the ball bearings might be going a bit overboard for this, but they are only about $1.25 each in quantity, and it's nice to do details like this properly. I figure that there will be two of these pulley-roller guides in the elevator circuit and one for the ailerons, and everywhere else I'll use the ball rollers.

Anyhow, here's my working drawing for the pulley roller. I did up a relatively nice drawing for it because I'm pretty sure I'll be shopping these things out on mfgquote.com in the long run. Later there will also be drawings for the bearing spacers and also for the aluminum support angles that join the rollers to each other and to a bulkhead.

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page updated 30 November 2005 all text and graphics copyright (c) 2005 HP Aircraft, LLC