Thread: Discussion HK Radjet 420
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Old Sep 12, 2012, 04:44 AM
Ben D Wing is offline
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The Peak District
Joined Dec 2006
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As an addition to my last post: With the CG set at 220mm back, the left elevon has approx +0.5mm reflex and the right +1mm, but even so I think the balance point could benefit with going slightly further forward as the RJ is slightly pitch sensitive and does not pull out of a dive and this of course indicates a neutral CG.
After balancing the prop many times, my RJ has always displayed a resonance at full throttle with the dome prop nut looking very blurred. After trying many different props, I decided to swap the prop nut with a standard hex alloy nut from my spares box, and guess what, the vibration issue was cured! Now the motor is smooth through the whole rev range and this can only be good for the motor, Rx and servos as in my experience long term vibration usually causes some sort of failure. It seems that the supplied dome nut is not very accurately machined, but then I've also found this phenomenon with larger dome nuts of varying makes.
Finally, having never bothered to measure the motor's output before, I dropped my Wattmeter across it and at WOT it's drawing 3.1A with a power level of 23.5W (in). This may not sound much, but it does have a PWR of about 173W/lb and gives the RJ excellent vertical performance. And talking of performance, it's uncanny that this little RJ has almost identical flying properties to it's larger cousin, the original Multiplex Funjet. Well done HK!
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