I loved this. Couldn't have being better explained.

Another point in favor of engine driven fan: Their speed, and the cfm, changes with the engine's speed, even on thermal fans.

As an engineer, I can say that reducing the mass of the fan is the number one goal here. A clutch, thermal or not, wil encrease weight. For a stock engine, running at stock angular speeds, it's ok, but when pushing 6500 RPM, you must have a light fan, to reduce the load on the bearing, and shaft. The high inertia of a heavy fan, will cause stress at the shaft/hub union at every change in engine speed. The lower the mass, the lower the inertia, and the stress.

Túlio Lazzaroni "FORD", Florianópolis SC Brasil.

'74 Ford Galaxie 500 292 V8

'82 Ford Galaxie Landau 302 V8

'98 Chevrolet S10 4.3 V6

'01 Ford Focus 1.8 Zetec

Steve

I agree with everything you say regarding manufactures putting thermal fan clutches on almost all their cars from the late 60`s until they switched to electric fans (and ATF in manual transmissions) to get the last mile per gallon out of   gasoline. And they do work well on systems that were designed to have them as OEM.

Philo was trying to avoid another fan lunching his radiator at high engine RPM. I think that until someone sells an improved Yblock water pump with bigger bearing or more efficient impeller design and larger pulley then his better choice to avoid a repeat is to reduce the rotating mass from the water pump by using no clutch fan and an aluminum fan ( fixed or flex) I don`t think fan noise is an issue and no mention was made of cooling issues, only wasted radiators.

If he buys that BIG TRUCK he mentioned then that's a different matter. Pete

Seems to me that the OEM's went through a considrable number of years where they were firmly convinced of the value of the thermal clutches. High performance engine packages had them - and the towing packages had them. Big Caddies with dual air conditioners had them too.

The OEM's are also "cost driven" - and they eventually went to higher allowable engine operating temps - and cost reductions they got from using electric fans. We don't have the luxury of rigging up high temp engines in our driveways - and we aren't a business buying thousands of electric fans assembled in Mexico. So.....the old technology direct drive fans and clutch driven versions will work well enough for our purposes. 

 
 Steve Metzger       Tucson, Arizona

So....back to your original "problem"......[whew!]

I think a thermal, non-thermal, or even an electric would work just fine for what you're doing (unless you're dragging your 36ft house trailer up to Mt Pilot for the weekend!).....you might take a look at the RPM limits for whatever clutch you're going to use though. I think mine [Hayden] came with an upper RPM limit.....but I'm not going to run higher than "normal" RPM for a 292.

You've probably already seen this..... http://www.haydenauto.com/Featured%20Products-Fan%20Clutches%20and%20Fan%20Blades/Content.aspx

Cheers,


Rick


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1955 F-600/272/E4OD// Disclaimer: No animals were injured while test driving my F-600 except the ones I ran over intentionally!

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This post was created using OpenSuSE Linux x64 and Firefox

If I want to tow or haul something, I'll just hire you..............OK, Big Boy?

FIGHT CONFORMITY! 

You're following just fine. That there should be enough airflow at speed is exactly what I was implying. Maybe the fan actually offers enough restriction to the airflow when it is disengaged that it prevents adequate airflow under heavy load and the solution is to engage the fan to allow the air to pass through. This could be a potential problem when a shroud is in use, and one usually is.


Lawrenceville, GA

I guess I wouldn't say they're "worse" for towing...



The ones I priced for high GCVW[Gross Combined Vehicle Weight] (18,000lbs limit) towing in an F250/350 or larger were over $500 ($588 + shipping) (I think I'm going to have less than $100 in my high mount system including the fan, clutch, pulleys, etc)



I'll stand corrected on the current draw of the big ones for towing. ... they're rated at 36A at full power. (2 fans, 18A ea) AND 6000CFM.









I'm not sure I'm following you here.....



Using the above example, I should be able to pull a hill fully loaded at more than 20 MPH and not need to have the fan running at all.....the airflow through the radiator just from moving through the air would be sufficient........



This is not the case for any towing I have done....



The clutch fan on my tow vehicle (3/4T 4x4 ) when pulling my 5000lb boat doesn't engage fully UNTIL I get on the hill. Pulling at 45-50 MPH & full throttle, I can watch the temp rise until it reaches about 210 when I hear the clutch engage. (then it sounds like a C-130 running up!!)



Clutchfans don't fully DIS-engage either. They're designed to still provide some power to the fan all the time.......














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1955 F-600/272/E4OD// Disclaimer: No animals were injured while test driving my F-600 except the ones I ran over intentionally!

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This post was created using OpenSuSE Linux x64 and Firefox

I'm not understanding why electric fans are worse for towing. First off, many electric fans have more efficient blade designs than engine driven fans. This means that the electric fan can move more air for a given power draw which makes it difficult to compare electric and engine driven fans directly. Electric or mechanical, it simply has to move enough of a volume of air in order to cool the engine sufficiently; the means of moving that volume should not matter.

Now, looking on Summit, I picked a fan, a flex a lite 398. It is a 16" that moves 2500cfm and draws 17 amps.

Since fans are round, we can assume that the volume that will pass through can be represented by a cylinder. The formula to calculate the volume of a cylinder is Pi x r squared x height. Pi x r squared is 1.396 feet. We know this fan moves 2500cfm in one minute so height must be 1790.493ft. This means that the fan moves a column of air 1790.793 feet long in one minute. That is equal to .339 miles in one minute and since there are 60 minutes in an hour, that equals a velocity of 20.347 mph. So in this instance, this fan will be worthless above about 20mph. In reality it will be a slower speed that the fan is no longer required because the area of the radiator core will be much greater. If we use my trucks radiator, which is 26" x18" or 3.25 square feet, it works out to 5819.103 cfm of airflow across the core at just over 20mph.

Another, Flex-a-lite 180 moves 3300cfm with a 15" blade and 18 amp draw. That's equivalent to traveling 30mph or 8580cfm across the core at that vehicle speed. Just how much air flow do you need?

So if airflow is what is required to cool an engine, how is it that an equally sized, more efficiently designed electric fan is no good for towing? I personally have no experience with towing so there could be a variable I'm not considering but it isn't adding up. In fact, one of my friends has a Chevy 1500 with the towing package and it has factory electric fans.


Lawrenceville, GA

Nah. I do think he's trying to illustrate why an electric fan might not be the best choice in every case.....



I had the same questions when I was selecting the fan for my 292......it's going in a truck (a REAL truck) not a 1/2 ton car that will never tow or carry anything...... so when I work the engine I want enough airflow to keep everything cool. Electric fans are great for most of the vehicles out there cruising along on level ground......



Go try to buy an electric fan system to replace the engine driven fans on a motor home though (or any F-250/350/etc truck that will tow something BIG) and the electric fans required to do the job become VERY expensive and they draw upwards of 50-100 AMPS to make enough power to run the motors....to move the air!



Just consider if your engine driven fan needs 1-2hp HP to turn it at 3500 (towing RPM) that's



around 750-1500 WATTS. At 14V that would be around 50 to a little over 100A (possibly exceeding your ALT output!! )



This is why I am staying with the "high-mount" fan on my F-600 and using a clutch.













yeah.....go for it but you'll need a trailer to bring your big 20kw generator along!!.....a 25hp 12v DC motor would need an alternator capable of supplying more than 1500 AMPS !! Otherwise you'd need to power a 240v motor for the fan!!



I suppose 25hp for the fan is a bit of an exaggeration.......






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1955 F-600/272/E4OD// Disclaimer: No animals were injured while test driving my F-600 except the ones I ran over intentionally!

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This post was created using OpenSuSE Linux x64 and Firefox

The water pump is made by Elgin. I bought it off ebay from one of the supplier. Cost about $80.00

Here is one

item 220773721563

marv