Fan blade numbers

[pflaming]

I' ve seen fans with 4, 5, 6 blades. So why, more blades, more air movement, but blade pitch would do the same.  Which is the quietest and still move enough air? 

[DJ194950]

A friend put a 6 blade on his 37 Ply. and told me he never even drove the car with that fan because just reveing the motor in the garage he could not stand the noise it made.

DJ

[pflaming]

Mine is a six (6) blade. Will find a fan with fewer blades.  TKS Doug.  I need to drive up and visit you. Your responses on the forum are always positive, I appreciate that. Best.

I  have six fans, all are six blade fans. 

paul

Edited April 28, 2017 by pflaming

[DJ194950]

Anytime there Paul!

DJ

[Merle Coggins]

Fan noise is all about blade design and air movement. The more air you move the noisier it will be. However, there are some blade designs that can reduce the noise. I'm no expert on that, but I've seen fans that are less noisy and move just as much air when needed. 

[Don Coatney]

In a healthy cooling system no fan is required above 30 MPH. And if you run an electric fan above 30 MPH it actually increases the heat load on the engine as the charging system works harder to generate the power to run it. I know this as my thermostatically controlled electric fan always shuts off above 30 MPH and the engine temperature stays at the temperature of the thermostat even when the ambient temperature is over 100 degrees F.  

[JBNeal]

Merle is correct on fan blade design as I had this demonstrated to me awhile back at an antique fan restoration operation in Ft. Worth.  I had a 1950s Emerson 12" oscillating fan that needed a new cord and I wanted them to get the blades off because I could not.  They gave me the nickel tour of what they had worked on awaiting customer pickup/shipment, and I was amazed at how quiet these antique fans of all sizes were...the most impressive was the 2-blade pedestal fan whose mfg also designed airplane propellers during the 30s and 40s...when that thing was wound up, it was like standing in an Arctic blast with very little noise...I did not have a decibel meter, but we could have a normal conversation with that thing on.  The owner lamented that this attention to detail began to disappear in the late 60s with the advent of cheaper made asian copies that would replace these relics...he said that almost all fans now are noisemakers that move a fraction of the air that the quiet American made fans could.  This point was accentuated a few weeks later when I stopped at a roadside burger shack and noticed the 6" noisemaker by the cash register not moving hardly any air on that hot day...when nobody was looking, I turned it off to see that the fan blades were almost flat 

[Don Coatney]

This guy is a 3 speed made in the 1940's. Moves a lot of air with very little noise. Just don't stick your finger in it.

[Plymouthy Adams]

an asymmetrical 7 blade fan is proven not only to move more air, move it quieter but will take less HP in doing so...you will not find an era correct for the center hole I am thinking for your application but one from the future can be modified...just be aware that the normal pitch may be greater than the blade of the era and that you would have sufficient room between the rad and the forward edge of the fan and that the back side will also clear the engine/accessories when mounted..  At speed the air must be able to pass and if a flat blade fan is in there and close to the rad..it will inhibit the forced flow at road speed and hot spot your rad. 

[pflaming]

Don, I have the thermostat unit, bought the same one you have. I will install it and note the difference. TKS

is a pusher less efficient than a puller fan?

Edited April 28, 2017 by pflaming

[JBNeal]

Pusher fans are usually used to address packaging constraints in automotive applications as road debris can really do a number on the blades...puller fans do much better when coupled with a properly formed shroud