·:[ Darryl's Coot Building Journal ]:·
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[3 hrs] Today I drilled and cut material off of the engine pylon front support piece (814-3).

Damage to the original piece can be seen on the bottom right of this photo. I made the top hole (on the right) slightly smaller to keep a bit more structure in the area.

Notice that the outer perimeter of the second hole from the right looks different? I had to clean up some scratches that resulted when one blade on the double-bladed fly cutter came lose and moved out on the shaft. Doh!

Here is a view of the underside…

[1.5 hrs] After months and months of Coot building inactivity, I finally actually drilled, sawed, and filed today.

The part is the 814-8 pylon doubler. This piece attaches to station 96, and doubles the forward vertical pylon support. The piece that I have from the partial project I purchased is not airworthy—it has a fracture owning to (1) the plane rolling in a road accident (while being trailered) and (2) lack of a stress relief hole at a critical point. You can see the fracture in the large image (click on the photo).

Here is a view from the back-side.

Oh…my new part really is relatively symmetrical. The photo is deceiving because the camera is centered between the old and new parts.

Bending the 1/8″ 2024-T3 aluminum pieces for the engine pylon can be a challenge. Your average Harbor Freight sheet metal brake just isn’t up to the task. I needed a new 814-3 piece and the 814-8 smaller piece as well.

Last July, Russ Milham mentioned to me that Andy Anderson could get them bent at a reasonable price. Indeed, at the Arlington air show last July, Andy seemed happy to do so. I purchased the sheet at Wicks at Arlington (and, as of a month ago, no longer at Arlington), and sent Andy on his way home, thinking I would see him again in July 2008.

Andy was passing through town this week, so he brought the pylon piece and spent the night at our house. Andy also snapped a photo of the bending process for the -8 piece:

Bob Leonard did this work is at his company, Trilet Industries, in Oregon City, OR.

Here are the results:

Note that the longer -3 piece must be bent at greater than 90 degrees to account for the taper of the pylon (front to rear). The -8 piece must fit on the inside of the -3 piece.

The bends were perfect. The -3 piece fits snuggly in the rest of the pylon.

Two of the most difficult parts for a Coot builder to construct at home are the vertical “spars” for the engine pylon. Each is formed from a sheet of 0.125 2024-T3, and bent to a slightly greater than 90 degree angle. Your average sheet metal brake will not make these bends. A big hydraulic press with a radius die can.

My engine pylon is complete except for the front spar and the engine bed, that were both damaged in a trailer roll-over accident that a previous builder had. I’ve built the pieces for a new bed, and need to weld it together when I feel my welding is “aircraft grade.” This composite picture shows the damage to the pylon spar:

A big crack can be seen at the top (left side of photo). A new piece is need, manufactured by bending an 1/8 inch thick piece of 2024T3 to the correct dimensions.

Andy Adams found a shop that can handle this for about $100 (and the sheet of 2024 is about $100). So I bought a sheet at Wicks in Arlington at the air show today. Andy kindly agreed to take it to the machine shop and get it bent. (I suspect I’ll get it back from him when I see him next year at Arlington.)