[TR] Push or pull

Jim Muller jimmuller at rcn.com
Wed Oct 24 06:57:08 MDT 2007


On 23 Oct 2007 at 20:53, Randall wrote:

> oddly enough, some fan makers do say to turn the blades around
> when configuring as a pusher instead of a puller...
> Apparently their fans are more efficient
> when turning in a particular direction.

There are reasons why this could be true.  IIRC (and I'm not going to 
go look right now) my Spitfire's fan, an electric Lucas, I think, 
yellow plastic, has blades which are curved.  Reversing the fan 
wouldn't change the air direction but it would change whether the 
concave or convex side of the blade faced the oncoming air.  There is 
also the matter of whether the motor is in front or behind, for 
example in a region of less or more turbulence.  There are enough 
degrees of freedom in a physical setup like this that no single 
"rule" is going to predict how it behaves.  So we can't say a priori 
that either way is the best.  But if the manufacturer says so, then 
they probably know something about it as a system.

-- 
Jim Muller
jimmuller at rcn.com
'80 Spitfire, '70 GT6+



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