4 Blade Fan

john charlton

john charlton

Well-known member
I have read somewhere that the 4 blade fan is as prone to throw a blade as the original 2 blade fan . I have run the 4 blade on various cars/trucks over the last 45 years approx have I just been lucky ???

John in warm cloudy autumnal Suffolk County England .
 
John
I've also run one on both my Model A's for 45 years and not had a problem. In all those years I haven't seen a four blade fan break either.
 
I bet that you guys don’t turn your engines over by using the fan, I’ve seen old shade tree mechanics do that, too much strain on the fans
 
I have had a four blade fan crack. Fortunately the blade started hitting the hose clamp and making a lot of noise, and so I stopped the engine before the blade broke completely and flew off. The blade was cracked about two-thirds of the way through. I finished breaking it off , and the broke off the opposing blade (surprisingly easy to do) and drove 125 miles home with just two blades. No heating problem at all.

W. Michael
 
My car came to me with a four blade fan separated into 2 parts. I ran it that way for 12 yrs. Was fine and no heating problems
 
Fan blades breaking are caused by the blade exceeding its fatigue life. This means that a blade's life is dependant on its ability to withstand a specific number of bends at a maximum level of operating load known as stress. As engine speed is increased the change in air flow resistance across the blade causes the blade to bend. When this happens the blade's internal level of stress increases. Once engine speed is lowered the level of stress is reduced. This single occurrence is refered to as one operating life cycle of the blade. The geometric design, materials used, and method of manufacture all affect how many operating cycles a blade can withstand before failing/breaking.
 
Any fans can break.I've seen plenty of them break,Carerpillar,Mack,Cummins,Perkins,John Deere,Ford,etc.Fans are a big seller at the junkyard here.Those steel hub/flexible stainless blades on modern cars grenade on a regular basis.My dad lost one on a 4 year old Dodge van.I went to the yard,they had a dozen of those engines,the good fans were gone and the rest were cracked.I lost an aluminum fan in 1998 in my A pickup.What a racket that made.It had voids in the casting.I had bought it in the early 70's,so it was most likely from JC Whitney,although I did buy a lot of stuff from the Amherst flea market back then.It was never in a true plane,one blade was a little forward of the other,and weren't in a straight line either.I like the new 2 blades,and am using two right now.I have a 4 blade on the pickup,but that will get a new 2 blade this winter when I do the engine and radiator.
 
When I bought my Pickup, it had a 4-blade fan. The rivets holding it together failed and took out my radiator. I am now using the 6-blade plastic fan in order to protect my Berg's radiator.
 
I have seen a lot of plastic fans damage radiators , sometimes the fan doesn’t get damaged even— the blades flex , have even see a plastic blade through the hood of a BMW so don’t assume that a plastic blade can’t cause damage.
 
I saw a GMC General with a Cummins in it that slung a fiberglass composite blade off.The hub was steel,and that's what broke.The green fiberglass blade itself was fine.I bought an 82 Chevy S10 pickup with a plastic blade sticking out from the front of the grille.That one was an expensive aftermarket fan,with a heavy duty radiator the owner had bought as an upgrade.
 
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