MICRO - Engine Test Results (And REGULAR class propeller Recommendation)
Stephen
4 propellers where tested on the static thrust tester from the mecE
shop on the .46ax os engine by Andrew, Brandon and I. These where the
11x5, 11x4, 12x5 and 12x4 (diameter in inches x pitch in inches). the
12 x 4 prop was chosen and gave 18.8 N of static Thrust. The runner up
was the 11 x 5 giving 17.7 N. More tests are recommended on a greater
variety of prop sizes. A 1/4 inch hole in the center of the prop was
needed to fit onto the shaft of the .46 engine while the .61 engine
shaft used in regular class was something bigger than 1/4 so we where
unable to use any of the props tested last year.
A better understanding of "leaning" the fuel mixture is recommended
for further testing. This friday we used a slightly conservative
mixture because the engine was brand new and we didnt want to have the
mixture too lean which would have over heated the engine (permanently
reducing performance). Last years testing of the .61 engine gave 22.6
N thrust from the 12x5 prop which leads us to believe that the 13x4
prop may be better suited for the regular class. Others worth testing
for the regular class engine are the 13x5, 13x3, 14x4, and 14x3. Check
the blue bag with orange straps in the cage to see what props we
already have but hopefully you wont find any of the 13 or 14 inch
props listed above becaues then we know they werent tested last year.
If they where tested last year then they probably werent better than
the 12x5.
sat Jan 16
Brandon and I tested the fuel consumption of the engine. There was
inaccuracy in the results due to throttle not being 100% (was about
80%), not having a good pen to mark off where the fuel was at the
beginning and the end of testing, and again not knowing how much to
lean the fuel. But, we did get a number. Based on the flight time of
48 seconds (viewed from a video taken in L.A. last year), accounting
for the possiblility of having to make another lap if we missed our
landing (ie another 48 sec), and accounting for 30 seconds from when
the engine starts till after we let go of the plane on the runway, a
maximum of 3.8 oz of fuel (this includes a safety factor of 2) is
needed for the microplane flight.
In conclusion, the 4 oz fuel tank will be used for the microplane
because the 0.46ax engine consumes 0.015 oz/s.