When we built Fly Baby in 1966 we installed a Continental A-65 engine we rebuilt, and a set of used engine baffles. The baffles were modified to fit the cowl we built. Later the fuselage was round with stringers. The cowl and baffles were modified to fit the wider firewall. Still later a Continental C-85 engine was installed. The result of all this and the years of flying are a worn, raggedy set of baffles.
My goal is to save all the pieces which can reasonably be saved and tighten things up so we get good cooling flow with minimal leaks. I've also rebuilt a set of baffles for the C-85 in my Cessna 140. While doing that I found some things they did which I think will help the baffles wear better and cool the engine better.
Here are the main baffle pieces. There are some small baffles between the cylinders. I repaired them when I overhauled the engine some years ago. I probably won't do anything more to them.
There is a large baffle behind the cylinders, one on each side at the cylinder heads, one in front of each back of cylinders, and a baffle I haven't removed under the crankcase. The 2 front baffles were riveted to the cylinder head baffles and they were screwed to the rear baffle.
I started with the main rear baffle. It's made of soft aluminum so it's easy to work. The bend for the cylinder offset had gotten flattened so I squared it back up. I added 2 holes which will be covered to make it easier to get at the engine mount bolts.
Next the areas formed around the cylinder cooling fins were reshaped to fit tightly to the fins to force air to flow through the fins.
A centerline was marked to help keep the baffle located while working. Well come back to this baffle after the cylinder head baffles.
The cylinder head baffles were held in position with a long rod which ran from the rear baffle across the top of the cylinders to the front baffle. It really let the baffle move a lot and the cylinder head baffles were to badly worn to repair.
A pattern for the vertical wall of the baffle was cut so it fit snugly to the cylinders.
The pattern was used to cut a piece of aluminum to fit.
The horizontal (bottom) portion needed to be reshaped to fit from the nose cowl and a line to the firewall.
The baffle was bent to an "L" shape and the bottom cut to fit the pattern.
One of the things Cessna did was to support the cylinder head baffles with brackets which attach to the rocker cover screws. I made these from galvanized steel with the hope they will not crack as quickly as aluminum.
With the left hand baffle done the same process was used to make a new baffle for the right hand cylinder head baffle.
I repaired the cylinder head baffles first so they would help hold the rear baffle in the correct position while making the extensions needed top fit the new cowl.
I started by attaching a piece of heavy card stock to the baffle with clecos.
The process for getting the shape to fit cowl was to trim the card stock close to where needed. Then used a straight edge between the nose cowl and firewall to make a series of marks for the next trim. I worked the pattern until it was 1/4"below the line.
The baffle is attached to the engine, which is on rubber mounts. The cowl is attached to the fuselage and does not move. The engine basically rattles around inside the cowl so there needs to be a gap to let it move freely. The seals will keep the air from leaking past the baffle.
This process was used until a pattern was made for the complete edge of the baffle.
The pattern was used to make an aluminum extension.
As with the cylinder head baffles a support was made to attach this baffle to one of the crank case bolts.
A piece of 1/2" angle was bent to use as a support for a 1/2" felt seal. The top edge of the seal rides on the inside of the cowl panels.
I'll come back the the seals when all the baffles are done.
I welded up some cracks in the baffle and a lot of the old holes. The old aluminum was painted and all the new pieces were riveted together.
Now I need to work on the front baffles
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