Hey everyone, so I don't have the APM tuned very well but at least its hitting waypoints and holding altitude and airspeed. I decided to get it flying and see just how long it would go. Here it the result:
this is the equipment list:
APC 12*8 prop
2x Zippycompact 6s 5000 mah lipo
APM 2.5 + telemetry + airspeed sensor
So whats next for the techpod? well, I will refining the gains. After I have it flying smoothly, I have a setup in the works that will be pushing flight times over 5 hours. Stay updated on the lated techpod news @ hobbyuav.com
Comments
Get the biggest prop you can mount on your plane, get a low kv motor (around 200-500). Then find a voltage that will make the prop spin close to the maximum allowed rpm. Just take a look at what the multicopter guys are using. There have been multiple posts about high efficiency multirotors here. The same rules apply to airplane propulsion.
No, not necessarily, once we achieve cruising speed the demands can be quite low to maintain flight. However before we can achieve cruise, we must achieve our cruise altitude. This is where compromise needs to enter the equation. In general terms for any given motor you have a range of acceptable voltage and prop sizes. Lets say as an example you have a motor that will run on 4-6S LiPo, and it can use from 13x8 to 15x8 props at 800rpm/kv. If we were to power your motor on 6S you would choose a prop at the lower end of the range like the 13x8, and at the higher end like the 15x8 when using 4S. In the latter configuration you would get less top end speed but more thrust. Personally I usually like to fly like this with slow turning low kv motors turning a bigger prop at a lower pitch for maximum thrust. Tuning a given combination for maximum duration requires some empirical testing to determine the best combination for a given application.
So for maximum duration we want a combination that provides enough thrust to achieve altitude comfortably while not being too inefficient. In other words...the holy grail!
Regards,
Nathaniel ~KD2DEY
Wayne,
Did you save the logs from the Castle ice2HV 40 ESC? That would give you the best data on current and performance. It would seem that you are getting more than twice the performance in your Techpod than I,m getting in my Super Sky Surfer in Watts/Lb but about 2.7 times the flight time. Presumably due to a cleaner airframe and a good airfoil selection. Your only consuming about 11Watts/lb in sustained flight as compared to my SSS at about 24Watts/Lb. Of course motor/prop combination/performance is another big factor here.
Regards,
Nathaniel ~KD2DEY
@Weiliang
He wrote on another site that the airplane covered 123 km (76.5 miles).
Hi Wayne,
Did you observe the average Amps drawn? How many kilometers was covered in 170 minutes?
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