Another Original 2-Blade Fan Takes Its Toll

[AlfinCT]

I'd be glad to buy one. Up to $150-200.

[BILL WILLIAMSON]

TIDBIT: Shortly after buying my 351 Cleveland powered '72 Mercury Montego, got a recall notice saying something like, YO! your car may have a man eating, dangerous fan! Don't even get near it, bring it in for a new "IMPROVED" FAN BLADE!
FUN THING: I meet new people by pulling off the road & raising the hood & wrinkling my brow. One samaritan asked, "Trouble?"----"No, I was just admiring my new 6 blade plastic fan whirring." He was impressed when I put my elbow to the fan and it just went "brrrrp!" Then he went on wih a loooong story about when he blew a fan!!!!-----(Most of our guys run 6 blade plastic fans & I've never heard of one breaking) Bill W.

[ericr]

Originally Posted by Earle

I would be very interested - up to the $150 - $175 range.

BUT...I'm also aware of some of the technical issues behind the failure history of the original fan design. In simple terms, it's due to high centrifugal forces causing a stress concentration at the juncture of the blade with the hub. From there on fatigue takes its toll as the blades are flexed (however minutely) during operation.

Of course, Henry went for the hollow design (probably to try to keep blade weight down and avoid the fabrication costs of machining, forging or casting the complex "airplane propeller" airfoil shape). But then he had to resort to welding (bad for a dynamic, highly-stressed part) as well as the risk of corrosion developing inside the blade where it could not be seen - and that has happened in nearly every failed fan I've inspected. In many cases the corrosion has eaten through to the outside surface of the blade.

Designing for fatigue loading wasn't a well-understood branch of engineering back then so the best choices were not made as to materials, geometry, load prediction, stress analysis, and thorough testing.

What concerns me about the proposed new fan design is whether all of these factors will be fully taken into account. If the new design is to be a dimensionally-accurate replica of the original, and if it is to have solid steel blades instead of Henry's hollow design, then the centrifugal loading at the hub juncture be increased significantly!

Of course a more fatigue-tolerant steel can be selected but that might not be enough. Altering the geometry to increase the fillet radii at the hub juncture (a common way of reducing stress concentration) would ruin geometric accuracy.

If I and many others are going to spend considerable bucks for the new fan we have a reason to be cautious about exactly how the designers have addressed the real cause of the original failures. It is a real safety and car-damage issue. I've had two original fans fail (after having been magnafluxed as "crack-free".). Thankfully, because I inspected before every drive, I caught them before the crack worked its way completely across the blade.

I appreciate the effort that the new designers are making to FINALLY bring us an accurate and RELIABLE fan reproduction that will pass visual high-point judging. I just hope that they will understand the legitimate concern that many of us have and will provide us the necessary technical details and assurance that the design, fabrication and TESTING are being approached properly.

This is truly a SAFETY issue! Can anyone think of any other part on a Model A whereby you can be killed just by standing alongside the stationary car while the motor's running and everything's operating normally?!

The Fahnestock book claims that the design emanates from a desire to structure more thickness to the blades to pull more air than a "thin" blade. Whether that was baloney or not, I don't know. Most other cars of the era, I think, employed a four-bladed fan.

[steve s]

Somehow, this whole thread got by me without me inserting my motivational photos.

Steve







Also, FWIW, the repro four-blade jobs are not without their issues.

[juke joint johnny]

That repop 4 blade fan with the cast hub held together by 4 bolts is another one that flies apart!!! Looks good one minute & flys apart the next .!!!! Lost my rad waterpump and dented the stainless shell on my pickup.
John Cochran

[BILL WILLIAMSON]

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God!! After lookin' at previous fan pics, my Jugular Vein is quivering, uncontrolably!! Seriously, knew a man who DIED when a broken fan blade severed his Jugular vein! Bill W.

[Phil Z]

I too would be interested on a repro fan at about $200 that would pass judging w/o deduction.

[Fred]

Very interesting picture of the torn up fan at the hub...NOTICE none of the big build up of rust that most say is the big problen..

[Purdy Swoft]

I'm happy with my aluminum two blade fans. My cars are all drivers and the aluminum fans look close enough to correct for me.

Just to add to the discussion, the old four blade fans that were used on the 33-34 four cylinder Ford trucks are just as dangerious as the original model A fans. I had one fail on my sept 29 , back in 62. I was driving with the hood off and I was lucky not to be hit by the flying fan blade. It also broke the water pump but that was the only damage. I had another truck four blade fan explode on uncle Albert (AA truck that I had) in 1991, That one damaged the hood and radiator. I had an original two blade fan lose a blade on the coupe in the early seventies. I was running with the hood off and nothing else was damaged. I've been lucky twice not to be hit by a flying fan blade. They say that three is a charm. No more steel fans for my model A's , 2 or 4 blade.

[steve s]

Originally Posted by Fred

Very interesting picture of the torn up fan at the hub...NOTICE none of the big build up of rust that most say is the big problen..

Here's the hub at maximum resolution. There does appear to be some rust in there. I've no idea whether that's enough to be the problem.

Interestingly, the fellow who this happened to replaced it with another original!

Steve

[Marco Tahtaras]

Originally Posted by Earle

Designing for fatigue loading wasn't a well-understood branch of engineering back then so the best choices were not made as to materials, geometry, load prediction, stress analysis, and thorough testing.

Yep, they could have done much better. After all they could have made them to last 160 years instead! Additionally like all the notes permanently affixed to the visor in your modern car, Ford could have imprinted the fan with "DO NOT use the fan to turn over the engine by hand!" That in itself would have improved the life span dramatically!!!

[TinCup]

Touche!

[steve s]

Originally Posted by Marco Tahtaras

... Ford could have imprinted the fan with "DO NOT use the fan to turn over the engine by hand!" That in itself would have improved the life span dramatically!!!

Boy, you're right about that, Marco! When I was young, I had 4-blade on my A, and I routinely used it to fine tune the rotor position when setting the timing. Often, I would feel the blade bend, whereafter I would just bend it back until it looked pretty straight. Dumb and lucky!

Steve

[columbiA]

Looking at the fan & WP shaft,it appears the fan was loose on the shaft & the nut was wearing into the end of the fan hub.Also,having to have a tight belt with the alt doesnt help things either.I like a generator where the belt has to be only tight enough that you cant turn the gen pulley with your fingers.

[Earle]

Point well-taken, Marco. These fans, now 80 years later, technically met their "design life", whatever that was in the designer's mind at the time, given the relatively few miles the cars were driven back then compared to modern cars. But if the cars had been driven anywhere near the number of miles we rack up today, the epidemic of fan failures would have begun in the 1930's instead of 70 or 80 years later. Their fatigue life depends on the number of hours of operatin (cycles) not the number of years gone by. Henry lucked out with the decent service the fans provided over the "average" in-service life of a Model A at the time. He likely did not imagine that A's would still be in use 80+ years into the future - and couldn't have designed for it even if he did know. It would have to have been a trial-and-error testing process, if this fan design was even tested pre-production at all.

These fans had an undefined, "limited life" with safety implications at failure. But this concept wasn't something that auto designers concerned themselves with back then.

As an example of a different design philosophy....In aircraft design, flight safety is everything. When a part cannot be designed with "infinite fatigue life", a very conservative analytical prediction must be made of its operational life span. Then, when that time is up, no matter how good the part looks, it must be replaced with a new one. The aviation industry at that time didn't even fully understand designing for fatigue and many people paid with their lives.

To install a safety-critical, limited-life part (like this fan) on your car today with no idea of how many hours (cycles) of operation it has on it, is very unwise. Even if you knew the exact number of operational cycles the fan had on it, it would be impossible to predict how much life it has left in it.

Oh well...Fun discussion but too deep in the weeds. Bottom line - don't use an original fan on your Model A because you're on borrowed time on a dangerous, life-limited part.

[BILL WILLIAMSON]

This has been a very informative thread. I sympathize with the high points car owners on this issue.
I have a stock rebuilt early '29 water pump from my car that has maybe 50 miles on it. It has a beautifully painted 2 blade original fan on it. I would sell it for a fair price or do some trading for a flywheel & housing & starter so I can run my spare engine that I'm buying. Pick up at my place only, too much hassle to ship. P.M.me. Bill Williamson

[Mike V. Florida]

Originally Posted by BILL WILLIAMSON

This has been a very informative thread. I sympathize with the high points car owners on this issue.

One simple answer would be to allow the fan to be displayed much like the tools are.

[Logan]

Originally Posted by Mike V. Florida

One simple answer would be to allow the fan to be displayed much like the tools are.

Thats a really good solution. If someone hasnt brought this up to the national clubs already, some of the master judges should mention this as an alternative.

[Marco Tahtaras]

Originally Posted by Earle

Point well-taken, Marco. These fans, now 80 years later, technically met their "design life", whatever that was in the designer's mind at the time, given the relatively few miles the cars were driven back then compared to modern cars. But if the cars had been driven anywhere near the number of miles we rack up today, the epidemic of fan failures would have begun in the 1930's instead of 70 or 80 years later. Their fatigue life depends on the number of hours of operatin (cycles) not the number of years gone by. Henry lucked out with the decent service the fans provided over the "average" in-service life of a Model A at the time. He likely did not imagine that A's would still be in use 80+ years into the future - and couldn't have designed for it even if he did know. It would have to have been a trial-and-error testing process, if this fan design was even tested pre-production at all.

These fans had an undefined, "limited life" with safety implications at failure. But this concept wasn't something that auto designers concerned themselves with back then.

As an example of a different design philosophy....In aircraft design, flight safety is everything. When a part cannot be designed with "infinite fatigue life", a very conservative analytical prediction must be made of its operational life span. Then, when that time is up, no matter how good the part looks, it must be replaced with a new one. The aviation industry at that time didn't even fully understand designing for fatigue and many people paid with their lives.

To install a safety-critical, limited-life part (like this fan) on your car today with no idea of how many hours (cycles) of operation it has on it, is very unwise. Even if you knew the exact number of operational cycles the fan had on it, it would be impossible to predict how much life it has left in it.

Oh well...Fun discussion but too deep in the weeds. Bottom line - don't use an original fan on your Model A because you're on borrowed time on a dangerous, life-limited part.

First, although I'm not intimately familiar (I don't work on them) I've seen the rebuilding of jet engine components from the very first Messerschmitt Me 262 (Which I believe three still exist) to modern military stuff so I'm not unfamiliar with what you are suggesting. However you are expressing a wide spread misconception. For some silly reason folks seem to assume cars weren't actually driven in "the olden days" as if they were horse and buggies. That misconception is pure BS. When I was a kid it was a real find to come across a Model A with less than 100k miles on it. My first was a '29 Roadster which was fun speculating whether the mileage was 180k or 280k. It was tired. Now granted that was "modern times", but I did a little work on it and drove it 48k miles in the next six years.

Do not down play or underestimate how much these cars were really used.

[BILL WILLIAMSON]

Originally Posted by Mike V. Florida

One simple answer would be to allow the fan to be displayed much like the tools are.

It's hanging on my pegboard just below my MACHETTE Bill W.