Al Gietzen wrote:

That could be right.  There is nothing optimum about Tracy's core, or

the

inlet ducting; but I guess the important thing is that it works.

Al Gietzen

It sort of works. Tracy complains about the oil temp getting too high
when we climb for too long or make some top speed runs. Tracy lives
in flat country. It is never necessary to climb out at max angle.
In fact it is rarely necessary to climb over 500 feet but he does it
slowly anyway when he goes on a long cross country.

With one simple cowl flap down under the engine I think it would
work a lot better and he could make those inlet holes a lot smaller.
Tracy is not convinced. He was mumbling something about getting the air

warmer

by keeping it in the AC core longer or something like that. :-)>
He also does not think those big inlet holes are hurting him on drag

either.

His argument there is external diffusion. Top speed is about 205 MPH
but I think with some cooling drag improvements it might reach
215 MPH with the same power. We have sort of agreed to
disagree :-) I left the water manometer with him and I hope he finds
time to make some improvements and do some more tests.

BTW the water manometer could measure the flow through the
rad if you set up some pito tubes in back of the rads.

I did measure the flow velocity at the exit from the core with the
anemometer.  The little fan in the instrument is about 1 1/4" so it is
measuring the "average" flow from the face of the rad; the flow in the
channels is about 20% higher.  The fan is shrouded, and probably distorts
the flow pattern more than a pitot tube would.  I did a couple of
measurements with the manometer which were consistent, but the dynamic head
is relatively low, and the accuracy suffers.

At 1300 cfm the measured "average" flow velocity was about 15.5 mph (22.7
ft/sec).  Velocity in the channel is about 27 ft/sec.  This is all nicely
consistent with my design point of 2600 cfm at a climbout speed of about 120
mph and a diffuser ratio of about 4 : 1.  I didn't bother with further
measurements of flow and pressure drop for the rad because the pressure drop
is very low and the design should work fine.  Some day I'll know for sure.

Al Gietzen

 
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