TheBoy wrote:
I think the primary benefit of the spinner is to protect the propeller. The counterweighted Hamilton Standard props have exposed bearings and the "piston" of the prop is a slightly delicate surface. Operating in dirty/dusty environments the spinner protects the prop. My experience is that a standard Montgomery spinner on a HS prop does nothing for speed or cooling. The backing plates are known to crack, so the spinner itself can be a bit of a maintenance issue.
I have "heard" that they were installed by the military for use in Korea to prevent snow & ice from fouling the counterweight mechanism.
Seems to have little to no speed advantage. Reno racers had done without them recently and went faster than ever. The Montgomery 42J15621 spinner adds about 12 pounds to the nose of the aircraft.