<VV> Electric cooling fan results
Tony Underwood
tonyu at roava.net
Mon Jul 30 12:41:25 EDT 2007
At 05:10 AM 7/30/2007, AeroNed at aol.com wrote:
>
>In a message dated 7/30/2007 3:13:12 A.M. Central Daylight Time,
>JVHRoberts at aol.com writes:
>
>Well, if you drove a Corvair at 200 MPH, it might work!! It's not prop
>wash,
>its ram air that cools aircraft engines.
>
>
>
>Not totally true...you can run an airplane engine on the ground for as long
>as you want with out anything but prop wash for cooling, BTDT.
>
That's not totally true either if you get into some of the larger
engines. Many larger radials have serious cooling issues when
running at low speed or idling on the ground. The BMW 14 cyl radial
installed on later variants of the "pre-D" FW190 had a secondary
multi-bladed fan mounted behind the prop which pretty covered the
entire front of the engine to help keep it from overheating while
idling. The Convair B-36 had some serious heating issues as well
when on the ground idling for any extended time... as did many
airplanes that used the 28 cyl PW-4360 corncob engines, only the B-36
was worse being pusher-prop with nothing from the prop blowing into
the air intake.
And a B-17 with cowl flaps left closed by either oversight or error
will overheat bigtime, not unlike the "cowl flaps" on a 'Vair engine
if they get jammed shut for whatever reason (seen that in a couple of
'Vairs).
Now, for sake of considering your argument, a boxer-6 civil aviation
engine usually won't overheat. It will cool well enough with what
the prop blows through it what with all the cooling fins on it.
A Corvair engine with no shrouds or fan (removed to clean out all the
cotton batting rats nests and seed husks) will idle for ~20 minutes
sitting on a pallet (waiting for all the valves to pump up) without
overheating if there's any sort of breeze blowing across the
patio... BTDT too... :)
Getting the air around and through the fins goes a long way towards
improving engine cooling... this is why deflashing the heads is
important, particularly on a 'Vair engine that's likely to be run
hard either for performance aps or climbing long stretches of hills
or towing something etc.
tony..
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