Fwd: [Chrysler300] Fan, Fan Clutch, Fan Shroud

[Steve Albu <saforwardlook@xxxxxxxxx>]

I had an assignment at the Chrysler Proving Grounds in Chelsea, Michigan in
the early 1970s, where we made the various choices of components that
affected cooling and perhaps one of the most important ones in choosing
among the various fans and fan drives was the rear axle ratio.  On the
letter cars, the ratio is usually 3.2, but the New Yorker might likely be
less numerically, so that may be why a 4 blade fan w/o a viscous drive was
used.  Of course the radiator chosen for the application factored in as
well as other variables such as tire size/wheel diameter, likely use of the
vehicle, and of course the presence of a/c, etc.  I always felt the
decisions that were made were too skewed in the interest of saving money
rather than protecting for the worst case environment/application when
running a/c for example and protecting for any radiator sludge accumulation
over time.  Today's cars are designed very differently and protect well in
the most extreme circumstances.  My 1997 Chrysler Concorde never is a
concern relative to cooling on the hottest day with the a/c at full blast -
the way a car should be designed.

Steve Albu

On Wed, Jul 25, 2012 at 7:15 AM, Keith Boonstra <kboonstra@xxxxxxxxxxxx>wrote:

> **
>
>
> A fan clutch allows the fan to run at a lower RPM than the water pump
> shaft that powers it, reducing both power consumption and noise under
> the hood. With the right pitch to the fan blades, a 70% reduction to
> the RPM still allows enough air to be pulled through the radiator to
> handle cooling in almost all circumstances.
>
> There are two styles of fan clutches used - thermally activated and
> non-thermal. Both function by using a viscous fluid to allow slippage
> of the hub in the outer body. A "non-thermal clutch", when fresh,
> should slip by approximately 70%. As the clutch ages the slippage may
> increase to far more than that, and lead to a lack of sufficient air
> being pulled through the radiator and overheating - especially at idle
> speeds.
>
> The "thermally activated clutch" has a bi-metal coil on the front of it
> to sense the air temperature as it comes from the radiator. When the
> heat rises it sets off a valving change within the clutch. Normal
> rotational speed of a thermal clutch should be, as in the non-thermal
> one, something like a 70% reduction. But when the radiator rises to a
> certain level, the fan will speed up to somewhere around a 30% reduction
> instead. You can hear the fan speed up and slow down as you drive under
> demanding conditions - and that's, frankly, a reassuring sound to hear
> it doing its job.
>
> I can't say how the engineering decisions were made regarding all the
> variables of clutches, blades and shrouds on the various years, models,
> and engines, but we can be sure the bean counters had a role in choosing
> the least costly way to keep a given engine just cool enough.
>
> Keith Boonstra
>
> -
>
> On 7/25/2012 12:17 AM, 2HsandaHeritage@xxxxxxxxxxx wrote:
> >
> >
> >
> > Hi Group,
> >
> >
> >
> > I am somewhat confused about the operation of fan clutches and the
> > reasons for their use.
> >
> > My questions apply to 1962 vehicles with 413 engines because I am
> > familiar with them and have the parts book.
> >
> > A 300H w/o air has a fan clutch and 7 blade fan.
> >
> > A 300H w/air has a fan clutch, 7 blade fan and a shroud.
> >
> > A New Yorker w/o air only has a 4 blade fan.
> >
> > A New Yorker w/air has a fan clutch, 7 blade fan and a shroud.
> >
> >
> >
> > I have always thought that the purpose of a fan clutch was to lessen
> > the energy required to rotate it when it was not needed for cooling.
> >
> > I also thought that the viscosity of the fluid in the fan clutch
> > changed with temperature so that it would increase in rpm to match
> > that of the water pump when needed for increased cooling.
> >
> > The shroud on air conditioned cars is there to help the 7 blade fan
> > pull more air through the radiator that is blocked by the ac condenser
> > in front of the radiator.
> >
> >
> >
> > The above makes sense to me except for the difference between the 300H
> > w/o air and the New Yorker w/o air.
> >
> > Why would the New Yorker only have a 4 blade fan and no fan clutch?
> > Perhaps robbing HP was not considered important for tha New Yorker.
> >
> >
> >
> > Doug Warrener
> >
> > Fair Oaks, CA
> >
> > 300H
> >
> > 62 300 Sport Conv.
> >
> >
> > [Non-text portions of this message have been removed]
> >
> >
>
>  
>


[Non-text portions of this message have been removed]



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