Step 7: Cylinder Barrel Baffles
The cylinder barrel baffles consist of eight curled baffles and two inter-cylinder baffles. The curled baffles wrap around the cylinder barrels and force the air to flow through the fins around the cylinder barrels. The inter-cylinder baffles block the air from going between the cylinders.
The drawing shows how my baffles are assembled. The barrel baffles are sized to leave a 120-degree opening on the bottom of the cylinder and a 2-inch exit gap at the top of the cylinder. I did this based on advice from some cooling gurus whom I trust. The outer baffles are bolted to the forward and aft baffles. The inner baffles are held in place by the inter-cylinder baffles and by the tie-rod straps across the exit openings.
The first picture shows six of eight cylinder barrel baffles that wrap around the barrel fins. As you'll see later, the other two barrel baffles are already riveted to the aft baffles. The second picture shows the details of the brackets used to attach the Cylinder 3 and 4 outer baffles to the forward baffles that seal off the engine along the accessory case. The third picture shows the tabs and threaded tie-rod strap I'm using across the exit gaps to secure the tops of the barrel baffles. This design does away with the safety wire. Note the black liner material on the inside of one of the baffles. I will line all barrel and cylinder head baffles with 0.025-inch high temperature silicon rubber sheets. The liners will allow the baffles to seal tightly against the cylinder fins to eliminate air leaks and to eliminate chafing. This black liner is just a surrogate until the silicon rubber sheets arrive.
The next two pictures show the top and bottom inter-cylinder baffles. They span between the cylinder barrels and completely block the air from going between the barrels. The top baffles were made as two pieces. It was the only way I could get the baffles to slip into place on the engine. The flat plate is made of 0.060 aluminum. (Overkill, probably.) The strap plate is 0.025 and is bent up in such a way as to block off the space between the last fin and the barrel base. The little fingers on the strap fills the gap between the cylinder bases and the crankcase. The plates are held together with a screw and nutplate. The bottom baffles were made as one piece from 0.025. For now, the top and bottom baffles are being held together by threaded rods running between the cylinder barrels. I will replace the rods later with long fasteners once I determine the length needed. The plans mention using safety wire. I'm ditching the safety wire and going with the long fasteners. The bottom baffles are also attached with two screws and nutplates to the overlaps on the bottom of the inner barrel baffles.