Jim It's not the motor temperature at full throttle you need to consider, you need to worry about motor temperature at hover especially when its warm out over 65 degrees IMO. I would look at the current numbers at hover as one sign of how much heat the motors will have at hover but its also a component of Load (weight) and overall design.
50% hoover and low temps are the first thing I'm looking at in ecalc as well as hoover time. I've never used ecalc this much, so I'm not sure how accurate it is. My quad flies longer and cooler than ecalc says it should, so there is a bit of uncertainty in my mind on this. 8kg is is a little over my average flying weight (with 2 large batteries) which gives me more leeway for longer flight times or a little more camera gear. As you can see, @19.8 lbs, hoover is 47%, temp is 29C or 82f # hoover, and efficiency is 90.4. With 18,000 or 20,000 total mah, 15-20 minute easy flying is a good prossibility. I'm using 5-6 lbs for battery weight in my auw, and the 18-20lbs is my sweet spot with ability to push a few more lbs on it.
and also change your battery charge state to full and it even gets better. For all calculations I used Norm to be conservative. Jim it looks like if you use 2 batteries it takes your hover throttle to 40% and if you use full charge state it take its it to 35% and your flying itme over 12 minutes.
There is anecdotal posts that it isn't advisable to go much below 40% at hover. Easy fix in this case, drop to 15x5 props. Seems like the setup described is over propped for the weight.
Thanks for the heads up. Looks like I have some eCalc learning todo. I don't understand if I have my weight in eCalc set to 8kg including drive with auw showing 8kg, why my hoover throttle % would change just by going from 6000 to 12000mah, but not changing the auw or cell or c rating of battery? I'm confused or uneducated regarding this. My earlier post show 47% on hoover throttle, but when I go 2p @ 6000mAh and have 12,000mah, it drops. I don't get it as my auw stays the same. I can't get 8,000 mah or 10,000 mah to work in eCalc. I swear I used tried 8 and 10,000 before. I used eCalcs resistance from 3200, 4000, 4000, to take a wild guess at what to use for 8000 and 10000mAh resistance and used custom for batteries. mAh resistance actual 3200 0.0064 yes 4000 0.0053 yes 5000 0.0042 yes 6000 0.0035 yes 8000 0.0025 guess 10000 0.0015 guess I went ahead and ordered the Avroto 3515's today along with the 16" props and 2 8000 mAh batteries. I plan on ordering some 15" and 14" props. I may play with seeing how long I can fly with a light gimbal and camera just for the sake of it. It may turn out the 16" props will only be used when I carry a heavier load if eCalc is correct. One thought came to mind is I could put a smaller fixed camera on and have it shoot a frame every second or two just for the sake of having some good aerial photo shots.
More power can flow from a 2 battery setup. If you want to change the voltage, ex. QC 6200 to a QC 10000, do the first pass a 6000mah 25c and after the settings are there change the battery back to custom and adjust the mah to match your battery. It will get you close enough. eCalc says it is a +/- 10% and that seems to be pretty close to my experience in real life.
Avroto 3520's just came in! We got the last set in the states! I have to say they are smaller than I thought but when I compare the windings woah! What a difference! Should have them in the air mid next week. Can't wait to feel them in flight!