View Single Post
  #168  
Old 05-15-2012, 01:56 PM
NZtyphoon NZtyphoon is offline
Approved Member
 
Join Date: Feb 2012
Location: NZ
Posts: 543
Default

Quote:
Originally Posted by 41Sqn_Banks View Post
It's interesting to note that publications from 1938 and 1939 give maximum take-off engine speed of 2850 rpm for both Merlin II and III. Publications from 1940 give 2850 for Merlin II and 3000 rpm for Merlin III. The increase is not associated with the use of 100 octane fuel.
This most likely has a great deal more to do with the adoption of two speed and CS propellers; in 1938 the majority of the Hurricanes and Spitfires were still using the fixed (coarse) pitch two bladed wooden props, so the maximum allowable rpm was fixed at 2,850.

The Merlin III had the universal prop shaft allowing de Havilland or Rotol propellers to be fitted, and the availability of two-pitch and especially CS props would have allowed for higher rev limits with less strain on the engine than a fixed-pitch unit. It also makes sense that in wartime some restrictions are lifted to allow for maximum power. One of the reasons 100 Octane fuel was originally adopted was to allow greater take-off power.
Attached Images
File Type: jpg HSSDmk1lineup.jpg (298.5 KB, 3 views)
File Type: jpg Spitfire I Cozens 19a.jpg (126.7 KB, 4 views)

Last edited by NZtyphoon; 05-15-2012 at 02:13 PM.