Best cooling fan for best cooling?

[Roxo]

I recently bought my first Model A, from the forums I have read about the original fan blades blowing apart, I have decided its best to replace mine. I did the magnet test and the mag stuck to the fan blade so I know the blades are not aluminium.
I would like to stick with the original two blade look, but also want the best for cooling as I plan to use my truck as a daily driver. I see there is the cast two bade aluminium, four blade stamped steel and the six blade plastic. From experience does anyone know if one is better than another?

[AL in NY]

Unless you go with some aftermarket electric or multiblade nylon fan, the aluminum 2 blade replacement fan works best(IMHO). It pulls more air through the radiator than the 4 blade Model A steel fan.

[Purdy Swoft]

I agree with AL in NY . The repro aluminum fan also looks correct .

[Roxo]

Thanks AL
You would naturally think four blades are better than two. But life's experience tells me that's not always the case. The web sites don't give any info on the airflow of any of their fan blades.

[Joe K]

Those who know engines know that above 20 mph, a fan is unnecessary: motion of the car through the air puts through MORE air than even a revving motor fan can pull.

However, for those moments standing at a light waiting for green, and for the acceleration to "air speed" the fan is essential. If you boil over, it typically occurs between zero and 20mph.

Above 20, the additional blades of a 4 or beyond fan serve only as greater impediment for the air passing. More blades equals more impediment.

(In more modern cars the fan is made "thermostatic" - you hear it come on as your stopped and you don't hear it but it turns off as the cooling needs are met by motion alone. A VW diesel of my experience the fan would run rarely if ever, the advantage of diesel thermodynamic efficiency. Additionally the fan not running continuously improves one's gas mileage.)

There may be cases where a four blade fan is to advantage. Industrial motors (mostly stationary or low speed) is where they cometh originally - and for a reason.

But for the Model A in automobile mode, 2 blade fan in the original aerodynamic form is best - and as it turns out for the aluminum fan repops - the safest.

Joe K

[Roxo]

Sponsored Links (Register now to hide all advertisements)

Thanks Joe
That all makes sense to me. I'm sure glad I decided to ask this question before placing my order. Without giving it some real thought, it's easy to just assume the more blades the better the cooling. I hope this thread helps others looking to replace their fan blades.

I also was wondering if a six blade was to push more air would it also draw down on the horsepower of the engine?

[Purdy Swoft]

The pitch of the fan blades has a lot to do with how much air any fan can move . The old four blade fans are flatter and don't move as much air . I have seen flow rates between the two and four blade fans in one of the national model A magazines . I can't remember whether if it was in the model A news or the restorer. I think that the original fan moved over eight hundred cubic feet of air per minute . It would take a while to search this info out of all the mags that I have saved over the years . Old fans are dangerous . I have had more 4 blade fans fail than the original two blade fan . I now only use the repro aluminum model A fans .

[Purdy Swoft]

The more air that the fan moves , the more horsepower that it draws . I want my model A to look as original as possible .

[WHN]

To add to the confusion. Remember the Model A has a thermal syphon cooling system that starts at about 180 degrees and moves about 36 to 38 gallons of coolant per minute in a properly maintained system.

The water pump and the engine fan are a small addition to help cooling.

Go with the two blade aluminum fan. While your at it, think about replacing water pump with a leakless one. Enjoy.

[Dick Steinkamp]

Originally Posted by Joe K

...

Above 20, the additional blades of a 4 or beyond fan serve only as greater impediment for the air passing. More blades equals more impediment. ...

Before most new cars went to electric fans, the engine driven fans had lots of blades...generally an odd number.



I would think they would have gone with 2 blades if 4 and beyond was the wrong thing to do.

[Roxo]

I like keeping the original look as much as I can in my not so original truck LOL!
Thanks for your help guys. I will be ordering the aluminium repro.
I believe my fan is in great condition, but I don't need it going through my hood or my head to find out it's not.

[Roxo]

Dick Steinkamp makes a good point.

[jwilliams81]

Your side engine pans need to be installed too. They are part of the cooling system.

[Purdy Swoft]

The four blade fans that have failed for me always cracked across the flat area where the blades rivet to the pulley . As the crack progresses between the rivets , the fan blade turns loose . You can usually feel some vibration when reving the engine before the blade flies .

[Roxo]

I never thought of the side pans as part of the cooling system. I will check on them. I know I don't currently have them.

[CarlG]

Originally Posted by Purdy Swoft

The four blade fans that have failed for me always cracked across the flat area where the blades rivet to the pulley . As the crack progresses between the rivets the fan blade turns loose You can usually feel some vibration when reving the engine before the blade flies .

When my 4-blade fan failed, it was the rivets that came loose. The blades never cracked or came off, but it was enough to take out a perfectly good radiator.

[Roxo]

I'm glad to hear about the Four blade fans. I was strongly considering them at one point.
Does anyone know what they call the engine lower side pans?

[AL in NY]

Engine pans.

[Werner]

Hello!

The efficiency of a propeller decreases with the number of propeller blades. This is because every single sheet gets into the turbulence and slipstream of the previous sheet.



The original metal propellers are twice bad: poor aerodynamic profile. Thin sheet that tends to flutter.



The reproductions made of thick aluminum are flow-optimized, torsionally rigid and have a high pitch (pitch angle).

[Chuck Sea/Tac]

The air tests were in the model A times.