Fan Clutch Eliminators

[toobroketoretire]

Back in the early 60s when fan clutches first appeared people immediately hated them because they didn't understand how they worked (the fear of the unknown). So along came the solid aluminum "fan clutch eliminators" that replaced the fan clutch. In theory it sounded like a good idea BUT the 5 and 7 blade G.M. fans were out-of-balance ON PURPOSE to prevent excessive fan speeds. So when a fan clutch eliminator was used the vibration caused by the out-of-balance fan was so horrific the water pumps came loose. If you doubt the fans were out-of-balance take a good look at a 5 blade G.M. fan and notice how 3 blades are on one side and two on the other side. The 7 blade fans are the same way but the out-of-balance isn't nearly as obvious because of the 2 additional blades. The out-of-balance fan combined with the fluid coupling of the fan clutch prevents the fan from unnecessary high speeds.

Fan clutch eliminators are still sold but they are only intended for balanced fans and not the 5 and 7 blade G.M. fans used from the 60's into the early 80's.

 

[Vettehead Mikey]

Oh dear, another dose of misinformed mind-numbing fractured fairy tales. :eyerole

Don't feed the troll, kids. ad

If you were to put any of the 5 or 7 blades fans on a dynamic balancing machine, you'd find that they're perfectly in balance. The blades are offset to minimize aerodynamic 'drone' or flutter. The idea of this design feature limiting rotational speed by inducing imbalance makes no sense at all.

 

[toobroketoretire]

The idea of this design feature limiting rotational speed by inducing imbalance makes no sense at all.

Maybe to you it doesn't but to the mechanical engineers who designed them it makes perfectly good sense. I started this thread with the very dim hope of teaching you something but it's obvious my effort failed.

 

[stevolwevol]

The clutch is supposed to free up engine power when the fan is not needed, so if a fan clutch is working properly, then why eliminate it?

 

[Vettehead Mikey]

You could also try to tell us that the earth is flat - that makes about as much sense.

Here's some basic reading for you, if you're still in the mood to learn

Re: Why are radiator fan blades non-symmetrical?

 

[Vettehead Mikey]

The clutch is supposed to free up engine power when the fan is not needed, so if a fan clutch is working properly, then why eliminate it?

The same as some people having wild fantasies about the reasons why engineers do things, others believe they can sit under a tree and out-design them. There's a billion dollar aftermarket part business that depends on their ignorance.

 

[Antz81]

You could also try to tell us that the earth is flat

Are you trying to tell us it isn't?

 

[Vettehead Mikey]

Are you trying to tell us it isn't?

They walk among us literally in this case. Happened about an hour from me

Flat or round Earth: Man faces charges after explosive debate in Brockville, Ont. | CTV News

 

[dougelam]

You could also try to tell us that the earth is flat - that makes about as much sense.

Here's some basic reading for you, if you're still in the mood to learn

Re: Why are radiator fan blades non-symmetrical?

Why would a company or companies spend hundreds of thousands of dollars to purposely offset their fan blades?

oh I know, toobroke wasn't available for a consult at the time

Since air flow thru the radiator is what keeps the engine Temps under control why would someone what to reduce it?
That's just plain stupid

Sent from my SM-T530NU using Tapatalk

 

[toobroketoretire]

Too Proud To Learn

You could also try to tell us that the earth is flat - that makes about as much sense.

Here's some basic reading for you, if you're still in the mood to learn

Re: Why are radiator fan blades non-symmetrical?

Yes, offset blades reduce the so-called "siren" effect that causes a whistling noise like an air raid siren. If you look closely at the fan on your alternator you will see the blades are not spaced evenly to make it run quieter. But offset blades also are used to reduce the maximum speed by inducing a vibration into the fan which slows it. It is that vibration combined with the fluid coupling of the fan clutch that limits how fast it'll spin.

If you don't believe me buy a "fan clutch eliminator" and see how fast your water pump will be shaken loose. Two years ago in another forum a guy was complaining about his water pump constantly loosening. He tried new bolts with new lock washers, he tried new bolts with lock washers and Loctite, and he even tried using studs and nuts. No matter what he did he couldn't keep his water pump tight UNTIL I told him his fan clutch was locked up. He checked it and sure enough it was locked up solid and when he replaced it his problem vanished. Every good mechanic back in the 60's and 70's knew about how locked up fan clutches would shake water pumps loose but I guess you weren't aware of that happening back in those days.

I am always eager to learn new things but you aren't and that's what separates us.

 

[Vettehead Mikey]

But offset blades also are used to reduce the maximum speed by inducing a vibration into the fan which slows it. It is that vibration combined with the fluid coupling of the fan clutch that limits how fast it'll spin.

I am always eager to learn new things but you aren't and that's what separates us.

Sure, I'm always ready to learn and regularly do so from those who present credible information. You're not in that category.

Can you provide some sort of evidence that the fans are actually out of balance? Either some third party data, or preferably your own testing? If you have access to even the simplest bubble balancer, you'll see that the fans are indeed balanced. I did this exact test to settle a bet in about 1970 on a fan from an Olds 455 engine.

Once you've done that, please explain 1) how this imbalance limits a fan's rotational speed 2) and does so without transmitting vibration to the engine and without destroying the fan clutch itself.

Please explain two more things:

1) why would GM and all other manufacturers make life difficult by going the 'imbalance' route to solve a problem? There's much simpler solutions.

2) How come there's tens of thousands of owners running around with clutch eliminators and have no issues?


It's no secret that early GM SBC pumps suffered from bearing failure/sheared shafts, which resulted in a product improvement in the early 70's, but this has no connection to the fan or fan clutch.

I'm sure you'll make another leap of logic to contradict that.

 

[Vettehead Mikey]

BTW- offset fan blades did not first appear with the advent of fan clutches. They existed for decades before that. How come these direct coupled fans did not destroy or loosen the pumps they are attached to?

 

[kpic]

Maybe to you it doesn't but to the mechanical engineers who designed them it makes perfectly good sense. I started this thread with the very dim hope of teaching you something but it's obvious my effort failed.

As usual, it doesn't make good sense to anyone except you.

The problem is you aren't teaching anyone because you are wrong. The only reason others here bother to answer is to avoid people who visit the site believe we are a bunch of idiots.

Anything that rotates must be balanced or it vibrates. That being said, the primary reason for the different length is noise reduction.
A radiator fan could easily be balanced by removing material.
http://i32.tinypic.com/72yvb4.jpg
See the little notch inside the red circle? That is one of the ways a compressor wheel is balanced. If all that was required was balance at a relatively low RPM; they'd make a symmetric fan and balance it by removing weight.

Yes, unlike car tires and ceiling fans which add weight to balance the rotating mass; other rotating assemblies remove weight.

I hope your next teaching lesson won't be how you balanced car tires by machining material off the rims. Yes, it would work; however only until you bought another set of tires.
I figured I ought to warn you or give you new ideas whichever the case may be... :L


BTW, the fan clutch disengages because at a certain point the air flow through the radiator is sufficient to keep the engine cool.

 

[toobroketoretire]

The fan clutches used on C3's never "disengage" as there is always some drive force present. The drive force changes according to the temperature of the air exiting the radiator core. If the air is real hot a severe duty fan clutch will spin the fan about 90% of the crankshaft speed up to the point where the fan's INTENTIONAL unbalance limits it's speed. I suggest you Google "Fan Clutch" and learn something about them before telling me how you "think" they operate. If you turn a 5 blade fan so the two blades are at the 9 o'clock position and the three blades are at the 3 o'clock position and let it sit overnight you'll find the three blades at the bottom the next morning. I have done this many years ago right after I put a 5 blade clutch fan on my '59 Chevy Impala. Every time I checked the position of the fan prior to starting the engine the three blades were ALWAYS on the bottom. That is absolute proof the fan is out-of-balance. To test your 7 blade fan check it's position in the morning before you start it. Mark the top blade with chalk or water color paint and the next morning you'll find that blade in the same (top) position because the heavier part of the fan will ALWAYS end up on the bottom. Why? Because it's heavier!

If you doubt my claim about the C3 fans being made out-of-balance on purpose I suggest you buy a fan clutch eliminator and see for yourself how your water pump won't stay tight no matter what you do. Every 1960's and 1970's mechanic will tell you a locked-up fan clutch will destroy water pump bearings very rapidly because of the fan being out-of-balance.

 

[kpic]

The fan clutches used on C3's never "disengage" as there is always some drive force present. The drive force changes according to the temperature of the air exiting the radiator core. If the air is real hot a severe duty fan clutch will spin the fan about 90% of the crankshaft speed up to the point where the fan's unbalance limits it's speed. I suggest you Google "Fan Clutch" and learn something about them before telling me how you "think" they operate.

If you doubt my claim about the C3 fans being made out-of-balance on purpose I suggest you buy a fan clutch eliminator and see for yourself how your water pump won't stay tight no matter what you do.

It isn't a doubt; it is why would anyone do something so foolish.

First no one said it totally disengages or totally engages. There are reasons which you don't know and no one is going to waste their time telling you why.

A standard duty thermal clutch turns the fan at 60-70% of shaft speed when engaged and 30-40% disengaged. Its application is lighter pitch fans.

A heavy duty thermal clutch turns the fan at 70-90% of shaft speed when engaged and 25-35% disengaged. Its application is heavier pitch fans.

Heavier pitch means numerically larger. Yes, there are other duty cycles.

History

The first clutch fan was developed in the late 1960's and was in full production by the early 1970's. This clutch fan was designed to save energy and lower emissions. Before the clutch fan, an engine utilized a fixed style of fan that was directly bolted onto the engine. This direct style of fan is not only inefficient it produced excess noise that was undesirable. A clutch fan has the ability to disengage when not in use, allowing the engine to work more efficiently while decreasing fan noise.

As you see, they used disengages also. A manual transmission clutch slips when engaged which contributes to drive train losses. However, no one states the percentage of slippage, do they?

I don't remember water pumps coming loose when I was a kid. In case you noticed, in addition to noise etc. fan clutches decrease parasitic losses.

I've never met someone so desperate to be right and usually be wrong in my life until I met you.

 

[Vettehead Mikey]

Every 1960's and 1970's mechanic will tell you a locked-up fan clutch will destroy water pump bearings very rapidly because of the fan being out-of-balance.

Well, I'm a '60's and 70s mechanic' and I've never heard of such a thing. Just like the tens of thousands of owners who use a clutch eliminator. As suggested, I googled the topic and found NOTHING to support your points. :eyerole

I gather you have no intention of proving your imbalance theory by actually measuring it? I guess this is like your 400* under hood temp misconception- you won't measure that either. That can only mean one thing.....

 

[kpic]

A clutch fan can fail one of two ways, it can either lock the fan to the clutch causing poor mileage while producing a whirring sound, like an airplane is taking off next to you. Or the silicon grease can start to leak causing the fan clutch not to lock up allowing the fan to "freewheel", failing to pull air through the radiator when needed. To check for this condition the engine must be off, inspect the fan clutch for leakage at the front or rear of the unit (input shaft and temperature controlled expansion spring). If leakage is observed the fan clutch has failed and needs replacing. Next, take the fan blade and turn it, the fan blade should free wheel, if you cannot turn the fan blade the clutch has locked up and needs to be replaced.

Wonder How A Car Radiator Cooling Fan Works? Here Is How

I am always eager to learn new things but you aren't and that's what separates us.

As often as you say that, you sure don't do that.