4 blade fan is it at risk to

ford31 - Many use the repro 2-blade aluminum fan the major vendors sell with very good success. One thing is you need to make sure it is balanced and the blades run in the same plane.

I have no first hand experience with this, but I have been told by those who have that a 4-blade fan sometimes does not balance well, and won't necessarily move more air than a 2-blade (because of each blade interrupting the flow of the blade behind it - more blades, more interuption). Also, to answer your question a 4-blade fan is at risk as much as a 2-blade.

I just read recently that a 2-blade fan turning at 1-1/2 times engine speed doing 50-mph exerts a force of 2800+ pounds at the tips.
 
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Here's what happened to a friend's four-blade on the way to this year's Michigan Model A Roundup. The problem was not with the fan per se, but the pulley.

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He was able to drive the last 10 miles just by removing the belt--yay for thermo-siphon!

Steve
 
We have a reproduction 4 blade fan on our A. It seems pretty solid, I just hope its not a big risk.
 
Any fan is at risk.That 4 blade one is not a Ford fan though,it looks like an old JC Whitney fan with steel blades bolted onto a pot metal hub.I have seen those go exactly like that from people in the past tapping on the back to remove them and cracking the pulley.A GOOD 4 blade Ford one seems as good as any.I have 2 bad aluminum 2 blade ones here.One grenaded at about 60 MPH,only had a few hundred miles on it.The other has one blade drooping so much it is unuseable.I see dozens of fans gone on equipment and cars now.The plastic ones on the modern cars are coming apart with age,when you go to the junkyard to find one you have to look at the roots of the blades for any signs of the plastic turning white.Just like looking for a crack on an A fan.If you see white it is flexing too much and getting ready to take off.The stainless steel paddles on some of the cars and trucks are parting company with their centers too.As it stands right now I would much rather use a good Ford 4 blade than an aluminum one.Good is the key,old and greasy,not pitted and rust swelled between the two blades where they cross and rivet to the hub.I do have one I am looking at,it has no rust,lots of grease,original paint,nice taper and keyway,but the rivets are loose in it.Both blades are still tightly piloted on the center,so I may re-rivet it.I feel 99% of all fan explosions can be prevented by regular inspections.Those cracks start out small,then get larger.I hear,well I look at it all the time.If it is looked at closely every day it is used you will find the crack when it starts.I rarely look at my 4 blades,and I look at my one piece 31 when I remember it.If it takes off I will have nobody to blame except myself if I fail to look at it daily.It takes one minute with a flashlight.Just do it when you check the oil and water.
 
is there any warning signs? or just replace with repo,I wonder if the alternator had anything to do with pulley problem,we also have alternator
 
Last week at the National in Vancouver, a Model A came to the meet with a four blade fan where the rivets to the pulley had broke loose. Made an awfull mess to the radiator.
 
The rules:

1. Never trust any fan. New, old, 2 blade, 4 blade etc. There are reports of every type of fan failing.

2. Any fan that has pretty paint needs to be stripped down and inspected before use. There are many guys that will make a crappy fan look pretty, including professional restorers. Remember rule 1.

3. Use a minimal amount of paint and no fillers. If the fan is that pitted then do not use it. The idea is to see any crack as it is starting.

4. When in doubt see rule 1.

All the fans will give you a hint they are failing. You just need to look for it.

One side comment. The fan with the failed pulley above. I see there was and alternator. I wonder if the failure could be related to the extra tension on the belt needed to get an alternator to give full output.
 
I did see one of those pot metal hubs split like that for another reason.It rubbed on the water pump housing and it cut through it like a lathe.I have no idea how the guy could have missed it putting it together,but he did.Somebody suggested he missed the keyway when he put it together,and after the key ate into the soft metal bore it started to wallow around.Everything was so destroyed we could only guess at what happened.
 
I've had the aluminum 2 blade fan on my car for 8 or 9 years. No problems at all and no overheating. The fan works well. It replaced the original fan, which had developed cracks in it. Good thing I discovered the cracks before a broken blade would let go.
Rog
 
My only issue with the 4-blade fan is that it is much heavier than the two blade type. This might increase the rate of front bearing wear or wobble and possibly expose the nose of the casting to damage at some point. I have noticed that the 1932 Model-B water pumps I come across are often damaged or repaired at this area, sometimes so far back that the grease fitting is broken off. However, the Model-A casting seems to have a slightly longer or thinner front nose, because the 4-blade fans don't seem to cause this problem on an "A" pump.
 
I have on my car a two blade that was once a four blade.Someone separated it and only used half of it. It works great and cools real good.Boy do i ever keep an eye on it.RAY
 
ford31 said:
our a has a 4 blade fan are they at risk also? what is best repo fan
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The old four blade fans that were used on the 1933 and later four cylinder Ford trucks are just as dangerious as the original 2 blade model A fans. I have had two of them to sling a blade. one of them took out a radiator and damaged a new repro hood. I only use the repro two blade aluminum fans. Ihave been useing them for over 30 years with NO problems.
 
Has anyone ever considered putting together a smaller crankshaft pulley to slow the fan down? It would also slow down the generator and pump, of course. The generator reaches full output at a fairly low speed anyway, so that wouldn't matter. I don't know about the pump.
 
Bob S said:
Has anyone ever considered putting together a smaller crankshaft pulley to slow the fan down? It would also slow down the generator and pump, of course. The generator reaches full output at a fairly low speed anyway, so that wouldn't matter. I don't know about the pump.
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One of those used to be available from a place in California. I believe it was used by racers or other folks who spent their time at high rpm's. Since we work so hard to get our generator or alternators to spin fast enough, it always seemed like an impractical idea to me.

However, here's another way to go--an oversize fan pulley. Slow the water pump and fan but not the alternator.

Steve
 

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Bob S said:
Has anyone ever considered putting together a smaller crankshaft pulley to slow the fan down? It would also slow down the generator and pump, of course. The generator reaches full output at a fairly low speed anyway, so that wouldn't matter. I don't know about the pump.
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I see that Snyders and others offer a small 2 3/4 inch diameter crankshaft pulley.
 
steve s said:
One of those used to be available from a place in California. I believe it was used by racers or other folks who spent their time at high rpm's. Since we work so hard to get our generator or alternators to spin fast enough, it always seemed like an impractical idea to me.

However, here's another way to go--an oversize fan pulley. Slow the water pump and fan but not the alternator.

Steve
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That is the 6 blade fan I run on my car, it always runs cool and what is the worst that can happen with plastic? Of course it looks nothing like the oridginal but with my paint job that is the least of my worries.

still painting wheels in WV

dusty
 
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