Which way the wind blows

[Ed Price]

I would like to get your thoughts about why the Amphi radiator fan pulls air
through the radiator and into the engine compartment. Is there a good reason
for this air movement direction, or did Trippel just follow automotive
convention?

I've made a list of the pros and cons of each direction.

Through radiator and over engine:
1. It's the standard convention, and the Triumph fan pitch dictates that.
2. The coldest air flows through the radiator.

From engine compartment and through radiator:
1. The engine vapors would be expelled from the compartment, rather than
being pushed back toward the bilge and passenger compartment.
2. Hot air would not be pushed toward the rear seat.

I don't think it matters much which way the engine compartment louvers
point, since the current direction has the air intake in the low pressure
area formed by the top or windshield. Besides, the air ram effect is pretty
low at 8 MPH.

Where all this leads is the question of whether it would be a good idea to
replace the fan with a reverse pitch model. Or, maybe delete the mechanical
fan and use one or two electrical radiator fans.


TIA,

Ed

 

[Ken Chambers]

Ed,

The current May/June 2002 issue of the IAOC Newsletter has a Member Spotlight
article by Dieter Harre and his beautifully restored Amphicar. He describes
the modification where, "the engine fan was removed and two electric 9" fan
motors were neatly housed in rear of the radiator in the "pull" mode.... The
engine runs a nice cool 145-155 degrees and never overheats."

Perhaps Dieter would like to elaborate in more detail the electric fan
conversion for an upcoming Tech Center article.

Ken Chambers, CA
'64 Red


> I would like to get your thoughts about why the Amphi radiator fan pulls air
> through the radiator and into the engine compartment. Is there a good reason
> for this air movement direction, or did Trippel just follow automotive
> convention?
>
> I've made a list of the pros and cons of each direction.
>
> Through radiator and over engine:
> 1. It's the standard convention, and the Triumph fan pitch dictates that.
> 2. The coldest air flows through the radiator.
>
> >From engine compartment and through radiator:
> 1. The engine vapors would be expelled from the compartment, rather than
> being pushed back toward the bilge and passenger compartment.
> 2. Hot air would not be pushed toward the rear seat.
>
> I don't think it matters much which way the engine compartment louvers
> point, since the current direction has the air intake in the low pressure
> area formed by the top or windshield. Besides, the air ram effect is pretty
> low at 8 MPH.
>
> Where all this leads is the question of whether it would be a good idea to
> replace the fan with a reverse pitch model. Or, maybe delete the mechanical
> fan and use one or two electrical radiator fans.

 

[David Chapman]

Amphicar gave a lot of thought to the air flow in the engine compartment, a
modern technology electric fan would be good and give a number of benefits, it
would be much quieter and give an extra few HP. I'd prefer to fit it in the same
position as mechanical fan (mechanical fan removed) mount it in that circle, I
think it would be about 16inch diameter. I was looking at some the other day,
the latest generation fans are very quiet, use hardly any power and are rated
for a 20year plus life. The problem with a fan directly on the rad is it misses
the oil cooler so I don't think I'll go that route.

The mechanical fan on the engine is an Amphicar design, not Triumph, it moves a
lot more air than the one on a Triumph. It would be good to know what the
standard CFM value is (so you can get an electric one to match) but I haven't
got anything to measure it.

The airflow is designed to slightly pressurise the engine compartment and air is
sucked over the engine then pushed back down the sides so on the left side of
the car the last think it passes over is the exhaust on it's way out, works
well. It is important to try and make the area around the rear seat as airtight
as possible.

Also, in rough water, the airflow coming out the side louvres stops water coming
in and although it is more likely to come in the centre louvres, the water is
deflected by the radiator to go past the oil cooler and into the bilge, all very
clever.

If you do temperature measurement then everything around the engine (and
particularly the carburettor) gets much hotter if the back seat is removed.

Note also the air intake (which for best performance should be cold as possible)
is above the radiator so gets air before it is heated by the rad.


David Chapman.