Calculating the pitch and lamination 2

I spent a few days thinking about how I could calculate the pitch, and deciding how to determine the shape of lamination two, which I have cut today. I am primarily working on the first specified profile, which is about 8”, or 8 1/8” from the centre of the boss. I will be able to determine this measurement more precisely as I progress along the entire blade. Mike spent the last ten days at the museum, and took some key measurements for me. With a bit of luck, he was able to trace the edge of the boss and at least two blade trailing edges. I have been having trouble working out the exact location of the trailing edge. The information available from different parts of different propellers contradict each other. The complete T.6296 in Narromine is currently the only complete T.6296 I am aware of and have access to. Consequently, information from it will carry a lot more weight than information I have been able to source from other incomplete propellers.

From analysing the pitch of the T.6296 it is evident that it has been designed in millimeters. The pitch, 3040mm is very close to 10’. I am using 19mm Radiata Pine. Interestingly, other Royal Aircraft Factory drawings I have specify 3/4” timber boards. The difference between 3/4” and 19mm is negligible, but there is a difference. Although 3/4” timber is specified, I am very confident that the Royal Aircraft Factory engineers used 3/4” interchangeably with 19mm. To complete a full revolution, the propeller needs to travel forward exactly the equivalent of 160 laminations, which are 19mm thick. This also gives a very nice figure to work with, 2.25 degrees of rotation per lamination. I cut some pieces of timber which hinge at the centre of the boss and extend to the first profile, 8” from the centre. Because I am not yet sure of the exact measurement, I have cut these pieces of timber a bit longer, at 8 1/4”. Later, I will cut and / or sand them to a much more precise measurement. I am very happy with the pitch at the first profile. I can check it mathematically before I determine the size of the blade profile at that location.

I spent a few days thinking about how I could calculate the pitch, and deciding how to determine the shape of lamination two, which I have cut today. I am primarily working on the first specified profile, which is about 8”, or 8 1/8” from the centre of the boss. I will be able to determine this measurement more precisely as I progress along the entire blade. Mike spent the last ten days at the museum, and took some key measurements for me. With a bit of luck, he was able to trace the edge of the boss and at least two blade trailing edges. I have been having trouble working out the exact location of the trailing edge. The information available from different parts of different propellers contradict each other. The complete T.6296 in Narromine is currently the only complete T.6296 I am aware of and have access to. Consequently, information from it will carry a lot more weight than information I have been able to source from other incomplete propellers.

From analysing the pitch of the T.6296 it is evident that it has been designed in millimeters. The pitch, 3040mm is very close to 10’. I am using 19mm Radiata Pine. Interestingly, other Royal Aircraft Factory drawings I have specify 3/4” timber boards. The difference between 3/4” and 19mm is negligible, but there is a difference. Although 3/4” timber is specified, I am very confident that the Royal Aircraft Factory engineers used 3/4” interchangeably with 19mm. To complete a full revolution, the propeller needs to travel forward exactly the equivalent of 160 laminations, which are 19mm thick. This also gives a very nice figure to work with, 2.25 degrees of rotation per lamination. I cut some pieces of timber which hinge at the centre of the boss and extend to the first profile, 8” from the centre. Because I am not yet sure of the exact measurement, I have cut these pieces of timber a bit longer, at 8 1/4”. Later, I will cut and / or sand them to a much more precise measurement. I am very happy with the pitch at the first profile. I can check it mathematically before I determine the size of the blade profile at that location.

## Comment