Fan Blades

[Gold Digger]

I see lots of talk on here about fan blades. I understand after 80 plus years of rust and fatigue they are all subject to disintegration at any given time. I own 3 "A's" and a compressor with original fans and keep a close watch on them all. After building die cast dies and working with the die cast industry for the last 44 years I wonder how strong the die cast one's are. Has anyone had one to brake yet? I wonder after 80 years of use how many will still be intact. I know I need to replace my fans but I just don't have that much confidence in die cast parts and despise plastic.

[Patrick L.]

Original blade failures seem be somewhat common and appear to be getting 'more commoner'. Most seem to like the new blades. I have one but have not yet installed it, still using a 4 blade. I guess if that ever fails, I'll stick on the new 2 blade.

[BN]

Gold Digger, like you imply, cast aluminum has a very low fatigue allowable due to small voids in the casting. Since these voids are random in quantity and location, some of these fans might never fail while others fail relatively soon. Also, they will have a different stress value and location since they are of solid construction instead of hollow like the original fans. It will be interesting to see if these fans start failing as they accumulate fatigue cycles.


So what could be causing the fore & aft cyclic loading of the fan blades on a Model “A”? I think it might be the 2 x engine RPM unbalance force inherent in all 4 cylinder in line engines. It is especially severe for long stroke engines like the Model “A”. Although this force is in the vertical direction, some of it may be translated to fore & aft due to the flexible spring front engine mount. There are only a couple of ways to lessen this vibration. One is by implementation of a rotating eccentric weight turning twice engine speed rigidly mounted to the engine. The other is called a “vibration absorber” which is a small weight attached by a spring to the large vibrating weight (the engine). It is interesting that Henry Ford took out a patent (No. 1,744,218) in 1928 on the “vibration absorber” concept. This patent may be found on this forum by searching on “patent”.


Again, it will be interesting to see if the cast aluminum fans are a real solution to this problem. I think a forged aluminum fan would have a much better chance. I also wonder if there have been any failures (yet) of the cast aluminum fans.

[amodel25]

After breaking two original fans on one outing (my primary fan and my backup) I installed an aluminum two blade fan......25 years ago. It has never caused a problem. I still have the two dents in my hood for reminders.

[Vic in E-TN]

There was an article in the Model A News or Restorer at least 15 years ago by a gentleman in Washington State about carefully welding a large patch on the hub. I cannot find my copy now. It may also be in the multi part tech compilations. I got 2 of these patches done by Dennis Piriano. It was expensive. I put them in a safe place pending a move. After I could not find them I had two more done - also expensive. They are on my cars now. The other cars have new aluminum ones, the new ones that have the correct taper that fit the water pump. I wish that someone with great welding skills would turn this into a cottage industry. The Judging Standards allow the aluminum fans without a deduction. None of my cars will go into fine point judging.
Vic

[Purdy Swoft]

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Ive been running the Snyders aluminum fan since 1977 . Thats 36 years and no problem yet. They were balanced in the first years, then it got to where some were out of balance. I bought one of the black powder coated aluminum fans for my roadster in 05 and its balanced. It had a sticker that stated balanced. I believe they are selling the same balanced fan today.

The old four blade fans are just as dangerous as the original two blade fans. The four blade fans are flatter and don't have nearly as much pitch as the two blade fans. Pitch is important if you want to move more air. The two blade fan cools better.

[Duffy1]

Any history on 6 blade plastic fans failing ?

[BILL WILLIAMSON]

Originally Posted by Duffy1

Any history on 6 blade plastic fans failing ?

Well, Duffy,
In many years working with plastic fanned cars, I NEVER saw one explode/break. For me, I chose the 6 blade fan over the BEER CAN fan. DON'T TRY THIS! but I stick my elbow in it to demonstrate it's "safety"---(JUST GOES, BRRRP!) Bill W.

[Tom Wesenberg]

Originally Posted by Patrick L.

Original blade failures seem be somewhat common and appear to be getting 'more commoner'. Most seem to like the new blades. I have one but have not yet installed it, still using a 4 blade. I guess if that ever fails, I'll stick on the new 2 blade.

Then it will be too late.

That's OK, I'm still using my original steel 2 blade fan. No cracks yet.

[Duffy1]

Thanks Bill . My car has a 6 blade plastic fan which was on it when I purchased the car .( 31 s/w ). I was thinking about changing out to a two blade aluminum fan. I will keep the plastic fan .

[glenn in camino]

I have cast aluminum 2 blade fans on all 5 of my running Model As. All are doing well.