Jay,
So if I read you correctly at any speed between 500 and
6500 or so RPM on a Tiger, and you want to cool a Tiger with
the maximum air flow, the more blades the better? Unless of course
your Tiger has room for a 3 foot radius single blade fan.
"Optimum efficiency" can mean two different things.
1. The minimum power to flow n cfm/minute at any fixed RPM.
2. The minimum power required to cool a Tiger with a limited
fan diameter.
I believe that most Tiger owners will opt for #2.
Most of the automotive fans are very poor aerodynamically
with the simple pressed out "U" shape on the blades. If you
examine the better electric add on fans you may note that there
are a lot of blades and the blades appear to be aerodynamically
designed much better than the simple stamped auto fans. I assume
that the electric fan maker is attempting to get high efficiency
with limited diameter and 12 volt power.
Now is there any way one could use one of those plastic
"electric fan blades" on the snout of the waterpump? The question
is, what is the maximum RPM the plastic fan can handle compared to
the Tiger's redline?
If any Tiger Owners have an optical Tack plus an electric
fan on their Tiger, the maximum RPM data would be handy to those
with overheating problems.
On my 351C Tiger, I have a 14" 5 bladed poor aerodymamic
fan. I added a 360 degree shroud attachment to the original
fan shroud and had the radiator recored with a late model core
(brass). The radiator is 4" wider than most. I also run the
stock Tiger II oil cooler. I can set in traffic for a 15 minutes
and not get above 90 degrees C in 95 degree F, 90 % humidity
weather.
I also have a 2.8L V6, with automatic trans in an Alpine
with a modified original Tiger radiator and an aftermarket
multiblade aluminum fan. The blades are much smaller than on my Tiger.
It runs at 86 degrees C above 35 MPH and attempts to peg the
gauge after 5 minutes of traffic. There is presently no fan
shroud on the Alpine. There is an after market oil cooler
for the auto transmission and the stock Alpine Oil cooler
(single row) on the Alpine. The heat inside the Alpine is much worse
than in my Tiger, even though the Tiger burns a lot more gas than the Alpine.
In town driving,I get 12 to 13 MPG in the Tiger and 18-19 in the Alpine.
I do normally accelerate more briskly in the Tiger than the Alpine
when in traffic. The 2.8 Alpine can not accelerate briskly with the
small 2 barrel carb, C3 auto, 3.5 rear gears and 195-50-15 tires.
At 08:04 AM 7/1/99 -0700, you wrote:
>
>
>
>Here is something I'm sure Bob and my dad will not leave untouched. In
>today's LA Times, in the "Science" section they had the following:
>
>"Q: Is a fan with five blades more effective than one with three blades?
>A: The more blades a fan has, the less efficient it becomes because each
>blade is moving in the turbulent wake of the blade preceding it. But a fan
>with fewer blades has to turn faster to move the same amount of air, so it
>will have a higher tip speed and thus be noisier. The same principles
>apply to airplane and ship propellers. The optimum efficiency is achieved
>with a single blade attached to a suitable counterweight, and some planes
>have actually flown with such a design. The primary reason for multiple
>blades is to reduce the diameter and the noise."
>
>
>Jay
>
>
>
James Barrett Tiger II 351C and others
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