Originally Posted by
A Squared
Pratt and Whitney manufactured a whole bunch of different radial engines with 2800 cubic inches of displacement. Some models are pretty dissimilar with no interchangeable parts The engines installed on the Convair were almost certainly either CA series or CB series engines, both of which had a drive ratio of 9:20 or .45:1 Reference is the Type Certificate Data Shees for the respective engine series.
Thanks,
A Squared. So 2700 engine-RPM would give a prop RPM of 1215. or about 61 blades per second.