Matt Mc_Carthy wrote in a message to Roy J. Tellason:

 TW>> With the modern Plastic fans and tight shroud to maximise air 
 TW>> flow through the radiator the hazzard is decreased some.

 CA>> I think the 'maximize the air flow' is a cover up to avoid 
 CA>> admitting any responsibility for those injured because there was 
 CA>> none before. 'Air entrainment' would increase air flow if the 
 CA>> shroud was not there.

 RJT> I've had any number of people tell me that they thought I oughta 
 RJT> get one in my truck,  even though they had no particular reason 
 RJT> to gain from my doing so...

 MMC> Well, you did say earlier that it runs hot without the shroud!

Yeah.  Temp gauge runs up to between 1/3 and halfway when it's been sitting
there idling long enough.  Take it on the highway and it gets way over
there...

 MMC> The "shrouding" began in the late 1950s to early 1960s as A/C was 
 MMC> becoming more common in cars, and cars began spending more time in
 MMC> heavy traffic at slow speeds.  A round fan "near" the center of a
 MMC> square radiator simply wasn't moving enough air THROUGH the 
 MMC> radiator at low vehicle speeds, and too many new cars were 
 MMC> overheating.  This happened to coincide with the beginning of EPA
 MMC> requirements, and manufacturers "detuned" engines as a first step,
 MMC> which also resulted in higher engine temperatures.

Which aspects of things had they changed there?  This motor came out of a
car which was a 1975 model year.  The truck is a 1978.

 MMC> Along with the higher temperatures, they began putting sealing 
 MMC> strips at the rear of the hood, so the heat could no longer 
 MMC> escape over the winshield as it did in older cars.

I don't quite understand that,  there's a set of what looks like vents
across the bottom of the windshield,  but they sure don't open into the
engine compartment.  Dunno why they'd build things that way.

 MMC> Now the fan HAD to build up enough pressure to force the 
 MMC> naturally rising hot air back down UNDER the car to escape.

Yeah.  I've _felt_ that breeze,  standing next to an idling vehicle.

 MMC> This led to the further disastrous developments already discussed
 MMC> here.  Instead of the one-piece stamped four-blade steel fans that
 MMC> had been used for decades merely for 'circulation', the industry
 MMC> went to heavy five and seven-bladed fabricated fans, ie: steel
 MMC> hubs with different material flexible blades riveted or welded on.

This one's two parts,  if I remember right,  rivets in the center.

 MMC> At the same time, they changed to a smaller sized fan/water pump
 MMC> pulley (or a larger size crankshaft pulley), to speed up the fan.

Now there's something I could probably fiddle with.  The whole setup in
this vehicle is a bit off,  there being this unused a/c compressor sitting
in there,  the dual belts,  and I'd have to change all of that,  and the PS
pump to get it to a non-A/C setup.  So I just left it in there.

 MMC> This was good for city drivers, but at highway speeds, the fan was
 MMC> using as much power as the rest of the vehicle, and was extremely
 MMC> noisy.

I'm not sure,  but I *think* that on this one the blades tend to flatten
out at higher speeds,  using less power.

 MMC> Then came the fan clutch, some thermal controlled, and some RPM
 MMC> controlled.  A good idea, BUT!  It ended up with too much spinning
 MMC> weight on the two puny bearings built-into the water pump, and a
 MMC> LOT of premature water pump failures, which if not recognized by
 MMC> the owner (seldom) often resulted in the entire water pump shaft
 MMC> failure.

Those setups were built into the water pump?  I've never had one of those, 
and was of the impression that it was in the fan hub...

 MMC> Instead of redesigning the water pump with larger shaft and 
 MMC> bearings, some manufacturers added a separate mount for the fan, 
 MMC> and divorced it from the water pump altogether.  This was "nearly 
 MMC> ideal" as they could now slow the water pump to reduce cavitation 
 MMC> wear on the impeller, reduce the load on the water pump bearings, 
 MMC> and at the same time increase the speed the fan even more to get 
 MMC> the needed airflow.

Dunno if it was "cavitation wear" or not,  but when I changed out
the pump last time around there wasn't much of the impeller left!  There
were nontrivial portions of that sucker that were just *gone*.

 MMC> Of course, ALL of this could have been solved by installing a 
 MMC> larger or thicker radiator.  The last "big" car I owned had the 
 MMC> hugh shroud, a seven-bladed fan with stainless steel 'blades' 
 MMC> riveted on, and a thermal controlled fan clutch.

Every time I've mentioned the idea of switching to that sort of a fan
people have talked me out of it,  saying that I'd end up with more trouble
than it was worth.

 MMC> I noted that the radiator had three rows of water tubes, but the 
 MMC> tanks had positions for five rows of tubes, two of which were 
 MMC> never used.

I've noticed that about some of them too,  what a waste!

 MMC> If the radiator would have been built to use all five rows of
 MMC> tubes, I probably could have gotten rid of the shroud, clutch, and
 MMC> reverted to the simpler four or five-bladed fan at a slower speed.

Didn't you have an option for a different radiator in there?

 TW>> But for Some opening the hood is a Mistake. BUT that is what keps 
 TW>> mechanics feeding the family and placing a roof over theri 
 TW>> Heads!! :-)

 CA>> Auto mechanics lean towards the dishonest side of business to 
 CA>> manage to earn a living. The tempation to cheat seems too great 
 CA>> for many of them to resist. 

 RJT> I get *so* tired of that sort of stereotype,  which I think is in 
 RJT> large part perpetuated by those who don't understand something 
 RJT> and figure that because they don't understand it that those who 
 RJT> do are out to rip them off.  Goes back to the same sort of 
 RJT> stereotype about "tv repairmen" and no doubt those who are 
 RJT> technically savvy in terms of computers,  when it comes to those 
 RJT> who don't.  Not that there aren't some crooks out there,  but...

 MMC> That stereotype now fits everywhere!  Look at Investment Banking,
 MMC> CPAs, corporate ledgers, Accounting firms, Enron, Tyco, MCI, AOL,
 MMC> etc.  Crooks are no longer limited to the 'technical trades'.

True.    I think this is also tied in with how much more
complicated things have tended to get,  and with people
"assuming" that there are aspects of a lot of situations that
they're just not equipped to understand,  or deal with unless they have the
help of an "expert"...

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