Landing Gear & More

12/27/2009

Firewall

I decided to make the firewall in one piece. The material is stainless steel 0.018. A buddy will be guiding me when it comes to shrinking and stretching the material as I form the flange around the perimeter. I started to use the original firewall that I acquired with my salvaged Skybolt, but it soon became apparent that it was not symmetrical :0|. So I decided to use one half of the old firewall as a pattern, then flipped it over for the other half. The initial pattern was from 1/4 ply. This pattern was used as a router guide, from which I routered out a final template out of 3/4" MDF. I then added a 1/8 round-over to the template with the router. For spring-back when bending the flange, I slightly beveled the edge of the 3/4" template. That part was actually pretty tricky: I made a jig for the bed of the router to angle it somewhat, but I couldn't get it to not interfere with the 1/8 radius previously cut. I couldn't add the 1/8 radius afterwards, since the bearing guide would make contact with the lower region of the 3/4 MDF (which would be angled in slightly), resulting in the cutter going deeper into the template (the end result would have been a round over with a 'small step'). So, I did it the artisan way...I scored a pencil line around the template right at where the round-over starts, then I colored in the area below that line (bevel area) with pencil. I setup the bench mounted disc sander at the required angle and gradually worked my way around the template, sanding, until I removed the shaded pencil area. All seemed to come out OK.

The steel sheet was then cut out with some overlap, for now. I then made another cloned template from 3/4" MDF. This had no bevel/round-over etc. This piece sits on top of the primary template, with the steel sheet sandwiched in the middle. This was all then clamped together using 6,000,013 C-clamps (in the UK we call them G-clamps...they do look more like a G...). the top template is there to keep the steel sheet down while the hammering goes on. For final locking reference point, I drilled the top two engine mount locating bolt holes through the whole sandwich. Now I need my buddy to continue with the hammering/shrinking/stretching...

Heel Rails

I decided to keep the flooring to a bare minimum, so heel rails it was to be. These were made from 6061-T6 x 0.063. The most tedious part was fabricating and welding in the attachment tabs. I used 3-sided tabs for where there was no inherent support from the fuselage structure, and simple flat tabs where the tubes would take the weight. An annoying mistake I made on the first two tabs, was to align the tabs flush at the top of the tubes, which is fine - as long as all the tubes are the same diameter :0|. These tubes are like, 7/8, 3/4, 1 1/8 etc. Luckily I only did two before I caught on. I am considering powder coating these heel rails...

Spring Steel Landing Gear

The engine mount is now back from finish welding. I decided to add a torsion strap (see pic). I added a bushing on the outside (see pic bottom right). A slot will be cut through this, slotting through the socket, too. A pinch bolt would then be utilized through the bushing. I am not going to utilize this, for now. It might come in handy, later down the road...

Prior to modification, the engine mount weighed 8 pounds. It now weighs just over 17 pounds. This gives me a total weight for landing gear modification of almost 48 pounds. About the same weight, and a lot cheaper than the Groves gear. If I missed anything from the following comparison, please let me know.

Comparison:

Groves Gear

00.30 - 0.90 4130 various small fillers (ballpark)

39.00 - alum gear (for 1800GW)

00.92 - tube 4130 3/4x0.49x30"

00.60 - tube 4130 3/4x0.35x27"

00.21 - tube 4130 7/8x0.49x6"

00.85 - tube 4130 3/4x1.88x9"

01.30 - support channel 4130 2.5x10x0.90 2 of

00.86 - clamp plate 4130 1.75x7x0.375 2 of

00.65 - bolt nut washer AN6-42A 4 of

02.56 - grove axle 2 of

00.48 - alum bearing block 1x1x1.25 4 of

00.24 - alum radius plates 1.5x7x.250 4 of

n/a - brake linings (gun drilled)

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47.97

Spring round tapered steel (RV/Wittman style)

35.80 - legs 2 of (custom made for Skybolt S 1800GW)

00.25 - bolt nut washer 4 of (ballpark)

00.30 - 0.90 4130 gussetts

02.00 - fairings & wood (competition balsa) dampers

00.30 - brake linings (best guess)

9.30 - engine mount weight difference (sockets, brace trubes)

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43.85 47.95