JW411 wonders if the Wright Cyclones (R-1820-76) as fitted to the USAF's SA-16 Albatross amphibians were direct drive - they were not. According to tables of American aero engine specifications, the -76A and -76B (standard for the SA-16) had 3:2 reduction gearing. However there were ungeared versions of the R-1820 available (which I was previously unaware of) and listed in these tables, including the R1820-50 and the -103 series. Not certain of their particular applications.
David D