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:

here are the Tlogs

this is the equipment list:

Techpod Kit

Foxtech 370kv motor

APC 12*8 prop

Castle ice2HV 40 ESC

2x Zippycompact 6s 5000 mah lipo

APM 2.5 + telemetry + airspeed sensor

AttoPilot 45A current sensor

6x Hitech 65-hb servos

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

 

Views: 8662

Tags: flight, techpod, time, uav

Comment by Weiliang on July 28, 2013 at 5:10am

Hi Wayne,

Did you observe the average Amps drawn? How many kilometers was covered in 170 minutes?

Comment by Jonathan Arad on July 28, 2013 at 6:09am

@Weiliang

He wrote on another site that the airplane covered 123 km (76.5 miles).


100KM
Comment by wayne garris on July 28, 2013 at 7:15am
When I was flying it seemed to average about 2.8 amps. The tlog when converted to kml shows 76.5 miles traveled.

Moderator
Comment by Nathaniel Caner on July 28, 2013 at 7:52am

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

Comment by Hein du Plessis on July 28, 2013 at 8:44am
Wow would you say it's more efficient with a high volt battery and low kv motor vs the other way around?

Moderator
Comment by Nathaniel Caner on July 28, 2013 at 9:34am

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

Comment by Martin on July 28, 2013 at 9:37am

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.


Moderator
Comment by Gary Mortimer on July 28, 2013 at 10:06am

Cool thing to do on your birthday.............

Comment by Tommy Larsen on July 28, 2013 at 10:32am

How many watt is specified for your engine?

Br

Tommy


100KM
Comment by wayne garris on July 28, 2013 at 11:23am

Thanks Gary!

@ Nathanial

here is the log file from the ICE2HV . there are inherent electrical efficiency gains from running with higher voltages. The power diodes in the ESC are non linear resistors, they have a constant voltage drop across them. however you are correct in saying the most efficient set up for a given Kv may be a lower voltage and bigger prop however instead of lowering  the voltage, lower the Kv. best of both worlds.And as for a solution for climb vs cruise performance, that's why I am looking into a variable pitch prop set up. choose your cup wisely ;-) 

@Martin

 I chose the foxtech motor for those very reasons. To be honest the foxtech is a very good engine however it was a bit of an experiment. The biggest problem is the large air gap. I am getting at best about 85% efficiency out of it. I am going to order a inrunner with a gear drive. You can easily get 95% out of one.

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