HP-24 Project

Update 5 March 2007: More little parts and stuff

This weekend I didn't have any great plans, so I plugged along on parts of a bunch of other stuff, and made reasonable progress at it. To begin with, I made simple jigs and welded up a bunch of little test articles of a possible design for the pintles that the control surfaces will pivot on. The proposed design is based on a bent steel rod welded to an anchor plate that gets potted into the forward part of the control surface. The bent rod protrudes out the front of the surface and engages a gudgeon potted into the skin of the wing or stabilizer skin. This is just one of three or four hinging systems we're looking at now.

I finished off the airbrake testbed, and got it to the stage of completion where I hold a pretty strong conviction that I understand all of the basic issues of airbrake design. Now I can rotate the input shaft on the box and have both the main and secondary paddle come right out, and also stow back in again without interference. So I think I'm ready to start making one-off tooling for the real first article airbrake boxes. I'll see if I can work on that this week.

I also finished making, and quite importantly straightening, a set of weldments for the landing gear oleo system. Earlier, I had some trouble getting the overcenter knees to close properly. I'd get them jigged up straight, and they'd open and close fine, but when I welded the knee parts onto the struts the uneven heating of the MIG welding would warp the parts so the knee wouldn't close all the way. That's when I had one of those "aha!" moments, and mentally reviewed something that Udo Rumpf had posted to HP-Gliders a while back - the landing gear knees have to close all the way, without springiness, or else your HP will have inexplicable gear collapses. I reassembled the top and bottom portions of one of the knees, used my OA torch to heat up a strategic part of the knee, and forced it all the way closed. The heating was enough to soften the steel just right so that pressing it closing bent it back into the proper shape it had before the MIG welding. Problem solved!

While I was up at the shop I also worked a bit with Raen on her bicycling. She did a bit of riding with training wheels removed; just enough to get an idea of what it was like. After that, I put the training wheels back on, except higher so that is more angular freedom between two-wheeling and three-wheeling.

Next weekend I'll plug away at some of the airbrake and landing gear stuff, and maybe get to the point of molding some of the airbrake box parts. I've also got some work to do fixing and fitting out the ASK-21 trailer. One of the things that wants for doing there is to repair the main clamshell hinge - that'll be an interesting job, and I'll have no good idea of how to approach it until I see the parts. I don't figure there'll be any huge part of it I can't figure some way to zotch together.

Landing gear weldment set. It's not completely finished; I still have to weld the forward pivots in, and close the forward ends of the yoke tubes.

My six test pintles. They're pretty rough, but just fine for testing them for strength, stiffness, and buildability.

The finished airbrake development testbed...


...and closed.

Homebuilt aviation is not for folks who don't try things at home.

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page updated 5 March 2007 all text and graphics copyright (c) 2007 HP Aircraft, LLC