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CWR's Pitts Build

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Nov 10, 2009
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SW Florida (94FL)
I decided to start a thread which will become a build thread for my project. Some of the project dates back a long ways and there's little in the way of photos from the start of this project. I'll document what I can from the work already done and add things I'm doing now as the work progresses.

First, just to get this started, I'll cover the work I did on my engine mount fixtures and parts from earlier this year. As usual I did the design work in Solidworks, made drawings of the parts and then got my hands dirty making stuff.

I have most of an engine, an IO-360, that was disassembled for modification. The project it was destined for never happened and I acquired the engine. Some parts are missing, some parts are obsolete for aerobatic use and some parts didn't do well in storage but the crankcase is perfect and the engine was assembled temporarily to get all the parts in one place. I wanted to take the mount geometry directly from the engine to create a fixture instead of trying to use the entire engine as a fixture;

Flanged Bushing.JPG
This is a flanged bushing and four of them mount on the engine case. The ears on this part attach to braces joining one corner to the next. I did not want to weld this assembly together so I'm bolting it together. No warping will happen at this stage.

Geo Fixture on Eng.JPG
This is how the assembly will look when bolted to the engine. That blue lump is a rough model of the engine.

Geometry Fixture.JPG
Once it's all connected together and tightly attached it can be removed. The assembly is a 'negative' of the engine mount geometry. The X-braces keep the assembly square and are made of two pieces each edge welded in-place with the fixture bolted to the engine. All the parts are numbered so they can be re-assembled correctly but the only loose parts are the X-braces, the rest stays assembled as I move this fixture to the frame for assembling the weld fixture.

Geom Fix on Legs.JPG
I designed some angled legs out of 2" square tube that set the angle of the mounts (30°) and get welded to the base frame which is made of 1-½" square tube. The nuts you see under the legs are tack welded to the leg so you don't need as many tools or hands.

Eng Mount Fixture Frame.jpg
This is the frame. The four holes will be used to attach the weld fixture to the firewall when the time comes to complete the mount itself.

Fixture with Bolts.JPG
The legs sit on the base frame like this.

Geom Fix on Legs & Frame.JPG
The geometry fixture determines the exact locations of the legs relative to each other and the whole assemblage of parts is shifted around on the base frame until everything is centered and parallel. The legs will get only glorified tack welds to hold them to the base frame.

Sockets & Ring on Fixture.JPG
The first thing this weld fixture will do is hold the parts in place for the dynofocal ring to be built.

I'll show some the parts made from the CAD model in my next post.
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