Need help with propellor sizing

[LeeT]

When I first got my DJI 450, I was using the stock 10 x 4.5 props with a 2200mah 3s battery. The stock motors were barely warm when landing. After experiencing the infamous DJI prop break I added some bling and made changes to the frame. I added extra upper and lower frame plates, a BEC for the LEDs and a bunch of LEDs. Unfortuneatly I did not get an AUW of the stock F450 before the changes. After I made all the changes I switched to GEM FAN carbon filled props, which are much stiffer.. The AUW with a 3300 3s battery is now 1502gms. I am using GenAce batteries rated at 25C. The motors are hot when landing, but the ESC and battery are only slightly warm.

I found a deal on SunnySky Angel motors for $13 each (sorry they are sold out). The motors are 2216 880KV. I tried the 10 x 4.5 and the motors are moderatly warm. I went up to 11 x 4.5 props and the motors are hot, although I got a 9:30 flight with 80% discharge.


I plan on adding a gopro which will take the AUW up to 1669 gms. I have a collection of props (GEMFAN carbon filled or APC) 11 x 4.5, 10 x 4.5, 10 x 3.8, 9 x 6 and 9.4.7. I tried using ecalc, but I am afraid the numbers don't mean a lot to me.

The props are ballanced and the bearings were removed and oiled.

Based on the info above, what size prop should I be able to use with out the motors heating up? Could the C rating of the battery contribute to the heating problem?

 

[jes1111]

The logical conclusion is that 11x4.5 is too much prop for that motor with that AUW. With respect, you need to persist with eCalc - all the answers/understanding you need are in there. Try posting a screen shot of your numbers in eCalc and I could point out where you might have gone wrong.

 

[LeeT]

The logical conclusion is that 11x4.5 is too much prop for that motor with that AUW. With respect, you need to persist with eCalc - all the answers/understanding you need are in there. Try posting a screen shot of your numbers in eCalc and I could point out where you might have gone wrong.

The main issue I have is that neither the DJI 2212 or the SunnySky 2216 are listed in ecalc. If I knew a close equivalent then I could plug the numbers in, and ask specific questions.

 

[jes1111]

Yeah, that can be tricky. According to http://www.foxtechfpv.com/sunnysky-221611-kv800-motor-p-383.html these are a straight knock-off of this: http://www.rctigermotor.com/show.php?contentid=143, so select Tiger MT2216-12. The DJI is possibly an OEM version (or knock-off) of the Tiger MT2212: http://www.rctigermotor.com/show.php?contentid=145

Try it with these motors - massage the numbers (in a logical way) until the Hover Throttle and Flight Time agree with your reality - then you can change components to play "what if".

 

[LeeT]

Yeah, that can be tricky. According to http://www.foxtechfpv.com/sunnysky-221611-kv800-motor-p-383.html these are a straight knock-off of this: http://www.rctigermotor.com/show.php?contentid=143, so select Tiger MT2216-12. The DJI is possibly an OEM version (or knock-off) of the Tiger MT2212: http://www.rctigermotor.com/show.php?contentid=145

Try it with these motors - massage the numbers (in a logical way) until the Hover Throttle and Flight Time agree with your reality - then you can change components to play "what if".

I entered information from the T-Motor and SunnySky (based on my best guess), Clearly I am not doing something right. When I tried to change the hover times, it went back to a predetermined value.

Is there an FAQ or similar on how to get the proper values into ecalc, and what the values mean? I appreciate your help, and if you can point me in the right direction.

View attachment 6544


View attachment 6545

View attachment 6546


View attachment 6547

 

[jes1111]

The only help available is http://www.ecalc.ch/calcs/help/xcoptercalchelp.htm

Take a step back - you can only change values in the top panel, the first five lines. The second panel and the graph below that show you the calculated results for those "input values".