|Aug 12, 2003, 09:57 AM|
Buffalo Intl, New York, United States
Joined Feb 2002
Hangar 9 T-34 Mentor E-conversion
Well the time has come to toss in a motor/gearbox/batts into the ARF box and shake it around and pour out the T-34 .
I am planning on retracts for it but not at this time, I want to fly it on the fixed gear for now.
Here is the motor/gearbox/batts that I plan to throw into the box:
2.5:1 Gearbox (?? which brand yet - suggestions)
16 - 1950 faup's
Hacker Master 77 OPTO
I know that there are other motor combinations out there but this is what I already have - and since its waiting for a different big edf to be finnished I might as well use it on something fun.
MotOpinion - Hangar 9 T-34 Mentor
1500ft above Sea Level, 75°F
Motor: Mega AC 22/30/3; 1270rpm/V; 0.032 Ohms; 1.46A idle.
Battery: Sanyo HR-4/5FAUP; 16 cells; 1800mAh @ 1.2V; 0.006 Ohms/cell.
Speed Control: Generic Brushless ESC; 0.006 Ohms; High rate.
Drive System: Generic 13x11in Prop w/2.5:1 Gearbox; 13x11 (Pconst=1.25; Tconst=0.956) geared 2.5:1.
Airframe: Hangar 9 T-34; 555sq.in; 111.4oz; 28.9oz/sq.ft; Cd=0.048; Cl=0.46; Clopt=0.59; Clmax=1.11.
Stats: 82 W/lb in; 70 W/lb out; 27mph stall; 37mph opt @ 51% (19:17); 42mph level @ 55% (17:06); 1400ft/min @ 25.4°; -323ft/min @ -5.7°.
Possible Power System Problems:
The steady-state motor temperature at the best lift-to-drag ratio airspeed (218°F) is very high, which will significantly affect efficiency and motor longevity. A lower current would decrease the temperature.
The steady-state battery temperature (approximately 188°F) is higher than the suggested maximum temperature for this cell type (140°F), which can result in battery pack damage. A lower current would decrease the battery temperature.
Current can be decreased by using fewer cells, a smaller diameter or lower pitched propeller, a higher gear ratio, or some combination of these methods.
Power System Notes:
The full-throttle motor current at the best lift-to-drag ratio airspeed (37.4A) falls between the motor's maximum efficiency current (22.5A) and its current at theoretical maximum output (174.6A), thus making effective use of the motor.
The voltage (15.4V) exceeds 12V. Be sure the speed control is rated for at least the number of cells specified above.
Possible Aerodynamic Problems:
The diameter (13in) to pitch (11in) ratio is less than 1.5:1, which will result in reduced propeller efficiency at low speeds (the propeller is stalled). Although this is not likely to affect flying characteristics, it may make take-off or hand launching difficult.
The static pitch speed (73mph) is within the range of approximately 2.5 to 3 times the model's stall speed (27mph), which is considered ideal for good performance.
With a wing loading of 28.9oz/sq.ft, a model of this size will have flying characteristics suited to an experienced pilot. The plane will fly fast, and be readily able to handle fairly strong winds.
The static thrust (76oz) to weight (111.4oz) ratio is 0.68:1, which will result in short take-off runs, and no difficulty taking off from grass surfaces (assuming sufficiently large wheels).
At the best lift-to-drag ratio airspeed, the excess-thrust (47.6oz) to weight (111.4oz) ratio is 0.43:1, which will give steep climbs and excellent acceleration. This model should be able to do consecutive loops, and has sufficient in-flight thrust for almost any aerobatic maneuver.
This analysis is based on calculations that take motor heating effects into account.
What do you guys think - doable
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