Hello,
I would like to share the results of my tests hoping for advice and friendly critique.
I am not sure where the subjects to be presented fit. If they fit here - so be it; if not - please advise.
Results:
I have run the ground tests of my two models:
1. Intrepid XL ( called Great White as it is almost entirely white and flies great )
2. A monoplane called Parrot, as it is covered with green, red, yellow, black and white U-cote.
The purpose of the ground tests was to find the static thrust and the torque of glow engines used in my models.
Great White (GW) uses Jett 60 with Windy's carbon composite pipe and the exhaust extension ( not deflector but extension ), the Parrot is powered by Evolution 36 with my own tongue muffler and the exhaust extension too.
Comment: the exhaust extensions have been made using the aluminum pipes having the cross section areas larger than the exhaust opening areas of the engines.
I have tested their influence on the RPM, power and heat distribution/overheating for both engines and the only impact is extra friction of the exhaust gases.
The amount of this friction ( synonyms: energy loss or exhaust gases flow resistance ) cannot be measured using a very simple test setup that I have used but the RPM, torque and the temperature of the engine heads was not affected. Simply put: when the exhaust extensions are removed, the RPM, torque and the engine heads temperature remain the same on the ground.
The only adverse effect of the exhaust extensions is extra weight: 20 grams for GW and 16 grams for Parrot but both models needed some tail weight anyway.
After trying many props, two different venturi and two different fuels ( 10 and 15% nitro, both with synthetic and castor mixture, 47/53 ), the selected combinations were as follows:
Ad.1 12.5" x 4", 2 blade, Zinger wooden prop. ( cut from 14x4 to obtain wider blades), 10% nitro fuel with the oil mixture like above, black RO-Jett C/L venturi drilled to dia. = 0.225" ( from original 0.185") and to 0.100" fuel line diameter (from original 0.060"). Jett 60 received also new piston and lining after it lost its compression in the Summer of 2014 ( the reason why this happened was never clearly identified. Perhaps some rust was lurking somewhere...?).
Jett 60 static thrust: 2450 grams at 9600 RPM ( max. RPM) with the pipe set at 17.75" ( glow plug to the baffle ).
Jett 60 static torque: 6,900 gram x inch resulting in the power of 2.3 HP.
I have flown GW ( 2024 grams dry weight, launch RPM 9300 and 8900 respectively) on 66' lines next day with average lap time 5.4 - 5.5 seconds and excellent tension overhead ( I have to build a little gizmo to measure the lines tension during flights ). Yes, yes, I know...the model is a bit heavy but it was my first stunt plane finished in 2009 and it still flies with the engine exhibiting 4-2-4 break on pipe.
Ad.2 11x4, 2 blade, scimitar style APC grey prop, the same fuel as GW, 5.7 mm ( 0.224" ) dia. venturi.
Evo 36 static thrust: 1450 grams at 10,000 RPM.
Evo 36 static torque: TBD ( I still have to calculate it from the existing data).
I have flown Parrot ( 1084 g dry weight, launch RPM 9200 ) on 58' lines next day with average lap time 5.1 -5.2 seconds.
There is no 4-2-4 break with 9200 RPM, therefore I would have to throttle the engine down to, say, 8,800 and watch the line tension overhead.
Again, I have to build a piezoelectric addition to my handle and collect the line tension data.
Has anybody build anything like that before?
Greetings from Toronto, Canada,
Matt
Topic: Ground tests and flight tests (Read 1824 times)
