DeTomaso Mailing List: April 1997, Message #94
     



From: MikeLDrew@aol.com

Subject: Fwd: Re: Meriha fans

Date: Mon, 14 Apr 1997 02:19:53 -0400 (EDT)



All,



Chris Bupp sent this to me instead of The List, for some reason.  BTW, I flew

C-12's (Beech Super King Air B-200, a twin-turboprop executive plane) in

Korea for a year, which is the only reason I have anything more than a

passing familiarity with the principles of propellers (and thus radiator

fans.)



Mike

---------------------

Forwarded message:

Subj:    Re: Meriha fans

Date:    97-04-13 12:06:14 EDT

From:    Whatcop

To:      MikeLDrew



Mike;



Your answer on fan blades is quite insightful and fits what little I remember

about aerodynamics.   I could say that I would have thought you too young to

remember all that stuff about PROPELLERS, as most of your career has been

flying planes with the dog whistle type of thrust producers......but I won't.



You did mention about a four blade fan that has blades NOT at 90 degrees

apart.  I believe that is to prevent noise from harmonics that can occur with

symetrical blade set ups.  Many factory engine/water pump fans, especially on

domestic cars, have blades unequally spaced around the circle.  I suspect

this noise problem would have been more likely to occur with the big, large

pitch fan blades on many older front engine rear drive vehicles.



I would also assume such assymetrical blades are NOT used on prop aircraft

because of their size and weight and resultant much lower rpm to prevent tip

speed from going supersonic.   I would also have to believe that assymetrical

blade systems would be much harder to balance, and that would be very bad for

a plane, since the prop is also the flywheel for piston engines............



chris