2 blade fan or 4 blade fan? That is the question!

[MrTube]

Perhaps because they were mass producing four blade fans for newer cars and it didn't make sense to make two different sets of blades?

[Chris Haynes]

Originally Posted by MrTube

Perhaps because they were mass producing four blade fans for newer cars and it didn't make sense to make two different sets of blades?

Which brings the question if two blades pulled air better why did they switch to mass producing four?

[A29Adriver]

If your "A" stays cool with the fan that is on it, it doesn't matter whether it is 2, 4, or 6 blades. Comparing airplane variable pitch propellers to automotive engine fans is similar to comparing apples to oranges. If you have an original metal fan, the possibility of it "blowing up" is much higher, than if you have an aluminum or plastic fan, 95% of those hoods that you have seen with a hole from a fan blade occurred due to the original metal fan rusting from the inside out and then having a catastrophic failure that hopefully only caused damage to the hood/radiator and not a person.

Take a magnet and check to see if your 2 bladed fan is metal or aluminum. If metal, think seriously about replacing your fan. If you have a four blade fan, look carefully to see if all the rivets are still solid and holding well.

Just because Henry used it doesn't mean that it is the only thing that works, as many of the previous comments have noted, 2 or 4 or 6 blades or even no fan can keep many model A's cool enough to drive in normal weather (70-95 degrees).

[MrTube]

Originally Posted by Chris Haynes

Which brings the question if two blades pulled air better why did they switch to mass producing four?

If four blades pull more air the "A" doesn't need it and I don't want to waste the little 40HP it has doing so for no reason.

[John S]

Originally Posted by MrTube

Now we're comparing props on air planes which consume 1000-3000HP to the model A's fan. Whats next boat props?

All you had to do was ask...http://www.mercurymarine.com/propellers/
How's this for off topic? Sorry, I couldn't resist.

[Milton]

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Originally Posted by Chris Haynes

When I got my first A in 1961 it had the Ford replacement four blade fan on it. What was Ford's reason to switch to a four blade fan?

Because the A fan was already cracking and breaking. Ford tried a fix on the 32 fan, better but still somewhat complicated to manufacture. In 33 the four blade fan was created and used as a service replacement on both A & B engines because it was more robust. Practically immune to rust failure since the blades were one piece pairs rivited together and to the hub.

[Tom Wesenberg]

"Now we're comparing props on air planes which consume 1000-3000HP to the model A's fan. Whats next boat props? "

I'm waiting for someone to come out with a squirrel cage fan for the Model A! Afterall, you've never heard of a Franklin throwing a blade, have you? LOL

BTW, what do you call the fan used on a Corvair? Would that be a squirrel cage, or turbine, or ??

[josh1331]

Who is tom ? To purchase a fan balancer? Please/josh

[Tom Wesenberg]

Originally Posted by josh1331

Who is tom ? To purchase a fan balancer? Please/josh

I don't really make and sell the fan balancer, but Brent caught me in a weak moment.

If you can't find 4 small low friction ball bearings, I might be able to find some at the local surplus store.

[Randy(PA)]

What was Ford's reason to switch to a four blade fan?

Cost reduction/ manufacturability.

[Marvin/TN]

Yes, some of the Cousair's did have P&W R 4360 on them. The R 4360's had 28 cylinders, 56 spark plugs, 56 coils, 4 mag's

[CarlG]

Originally Posted by Chris Haynes

When I got my first A in 1961 it had the Ford replacement four blade fan on it...

All 3 of the Model A's that I have owned had the Ford replacement four blade fan on them. They have always worked good for me.

[TinCup]

Ok so someone gave me a 1967 copy of "How to Restore Your Model A". I was just going over it to see and compare it. Lo and behold on page 99 was this gem which is relavant to this conversation. Now I don't know the guy that wrote it but it was an interesting take on the whole 2 blade vs 4 blade discussion.

Click here for article.

[old skool]

Thanks everyone. I went out and inspected my fans a little closer. After a closer, look I dont think I will use them. I could see some splits in the metal. That last posting was great. Good article (that one is going in my notebook).

Marty

[Terry, NJ]

So many As are having their HP (Pferdstarke) increased that the longer blades might be going super sonic at the higher RPMs. When I was flying this was an occasional problem. The answer was to use a shorter bladed propellor. Another way to cut the resistance of the air would be to make the blades a little narrower and change the angle of attack. It wouldn't move quite so much air, but what air it did move would have less resistance and therefore less bending pressure.
Terry

Originally Posted by Christoph

And why do "they" use fans with 6 to 9 blades in modern cars ?

And if you use a 2 blade, why dont you use a shrout to make
a better air-flow and reduce aerodynamic losses?
Have a look into your modern car.

Best regards from Frankfurt
Christoph

As i installed a new HD-radiator, i (being in fear) as well switched to a
6 blade plastic (ja - its ugly) from the well known vendors. I cant understand why its so much smaller in diameter For sure this will reduce airflow (knowing this, i wouldnt have bought it).

Summary:
Using the new radiator it feels as if i wouldnt need any fan at all.

[Terry, NJ]

Yaaaay! My four blades win! LOL Good article! However, The shortened blades perform pretty badly, (Scratch that idea!) Thanks for posting!
Terry

Originally Posted by TinCup

Ok so someone gave me a 1967 copy of "How to Restore Your Model A". I was just going over it to see and compare it. Lo and behold on page 99 was this gem which is relavant to this conversation. Now I don't know the guy that wrote it but it was an interesting take on the whole 2 blade vs 4 blade discussion.

Click here for article.

[steve s]

Originally Posted by John S

All you had to do was ask...http://www.mercurymarine.com/propellers/
How's this for off topic? Sorry, I couldn't resist.

That's an interesting link. It turns out that altitude matters for boat prop selection too! Who'd a thunk it?

[Purdy Swoft]

I think that the pitch of the fan blades are more important than the number of blades. The 2 blade original and repro aluminum 2 blade fans have more pitch and move more air. The fan is only needed when idling or at low speed.The old model 46 riveted four blade fans are more prone to slinging a blade than the original 2 blade model A fan ,that most know by now is dangerous. I've had two of the four blade fans sling a blade. It is very difficult or near impossible to remove the water pump without removing the radiator, when the 4 blade fan is used. If you've got to take the headlamp bar off, you just as well remove the radiator. The aluminum two blade fan looks right, moves more air and is more safe.

[Duffy1]

Do a search . There has been a study made comparing 2 blade ,4 blade and 6 blade fans . 2 blade fan moved more air .

[Chris Haynes]

I am installing an electric fan on my AA.