Based on the OX-5 parts list, under the right hand exhaust manifold there was a heat box. I would assume it was for Carburetor Heat to stop ice forming in the carburetor. But, according to Ted Barber, in his book The Barnstorming Mustanger, the WACO NINE he flew herding Mustangs in Oregon did not have Carburetor Heat. It was only when he got a newer plane that he learned about Carburetor Heat. I'm not sure what the heat box on the Curtiss exhaust was used for.
The picture of my WACO NINE from 1927 clearly shows the heat box on the right exhaust with a piece of tubing going into the cowling. Nothing in the WACO drawings shows a Carburetor Heat arrangement of control to operate it. I'm adding the box to both manifolds and we will have Carburetor Heat. I wonder how someone with straight pipes gets Carburetor Heat?
The lack of Carburetor Heat appears to be one of the reasons this engine developed a bad reputation. The other reasons, according to Parks Air College, were the need for Miller valves, better fits assembling the engine, and better oil. They flew 1,000 hours between overhauls doing flight training in 1929. I believe the coil in the magneto was also a problem, shorts and opens.
They are very nice looking but I believe they are a little small to get enough temperature rise. The inlet is on the engine side so the air has to flow around the exhaust to enter, giving a little more heating. They also placed the outlet near the edge opposite the inlet to give as much time for the air to heat as they could in such a small box.
The outlet pipe is spot welded to the box and the box is spot welded to the lower shell.
I started by deciding what size to make the box and the made cross section strips from poster board to work out the size of the blank. Clearly I could have done this on the CAD system but sometimes its more fun to just make patterns.
I'll gas weld the corners and the outlet tube, then spot weld the baffle to the inside of the box. The bend in the baffle is to direct the flow around the ends to add more time for heating.
Now I need to make the blank pieces.
Wednesday, April 16, 2014
Sunday, April 13, 2014
The next part to make is the heat box which gets spot welded to the bottom shells before assembly.
Then I have some patterns to make to trim the excess steel along the edges, and some fixtures to hold the inlets in proper alignment while welding.
I leave a gap at the ends. If the blank moves a little it won't hang up on the block.
I also made a large block from the ash to form the inlet end. It has the shape like the block I made for the outlet of the manifold. I also put a radius on one edge so it wouldn't crease the steel. The other edge is square to fit snug at the ends.
Once the shape is correct the outside edge is lightly shaped to form a tight radius .
Occasionally wrinkles form in the inside corner which can not be easily worked out. The trailer hitch ball works well to shrink them back.
The inlet end will get rounded better when the 2 halves are welded.
They come out very well.