Advice on motor upgrade for CineStar 6

[bson]

Hi!

I need some advice if I should go for a motor upgrade on my CineStar 6 or not. I'm having a reasonably good working CS6 with FFS-3328 motors (700 kV), which I think is equivalent with Tiger 2814-11. The AUW is 7 kg so it puts ~1.2kg on each motor. It hoovers around 55% throttle with 2x6000mAh 4S batteries and the flight time is approximately 7 minutes with 20 - 25% charge margin left. The props are APC 14x4.7.

I'm pleased with it except that the motors are running really hot. They smell "burnt electronics" after 6 - 7 minutes flight time and I can touch them but barely hold them with my finger tips. Now I have two questions to all you experienced guys out there:

1) How hot can a motor get before there is a risk of failure?
2) Would it be a good idea to upgrade to Tiger 2826-6?

Many thanks in advance for any kind of help!

/Bjorn

 

[bensid54]

I have some questions first what is the load rating for those motors? Are they being used within the specs recommended? The motors sound like the next flight could be their last because if they are too hot to touch on the outside then likely the wiring and or insulation is damaged which equals a risk every time you lift off. I can't recommend a motor but I can give you a bit of advice to use when choosing a motor, make sure you don't use a motor to it's maximum capacity. Eighty percent of motor capacity is as high as you want to go and a drop of light oil but no more than one drop per bearing. Try lubing your present bearings and see if that helps bring down the motor temperature.

 

[Vojec]

I have MT2814-11 710KV motors and my AUW is 8.5kg. I fly with Xoar 13x6.5 and 3x 4S 5800mAh (7 min of flight). Recenty switch to MT (MN) 3520-11 400KV, with same reason as you. Well summertime knocking on the door, and air is condense and motors push to their limit... first I will try to lowered props from 14x... to xoar 13x6.5 or graupner 12x6 better for summertime, link to kopterworx: http://kopterworx.com/shop/propeller-mounts.html. second put the 3rd battery on board and see results. My feeling is 7-8 min of flight for sure...
With these electric props motor will run cooler (try ecalc- and see results) not fight with condense air... If you have AUW 7kg and same motor spec as you describe then I see no problem. I have the same 7kg setup for 2 years with no problem...

 

[bson]

Thank you bensid54 for your input!
I'm a bit puzzled. My accs 12000 mAh 4S, which gives me an absolute max flight time of 10 minutes (calculated of course). This gives an average of 80A, which in turn a power consumption of 80 x 15 / 6 = 200W per motor. The QC-3328 is rated for "Mechanical power: 350 W", which then should be safe. I have carefully inspected the windings with strong light and magnifying glass and the all look good. Maybe I have sensitive finger tips. I'll try to find a way to measure the temperature after next flight.

 

[bson]

Thank you Vojec for your very valuable feedback! Is yours a hexa (not octo) as well? So you think a Xoar 13x6.5 will put less stress on the motors than APC 14x4.7?

 

[Vojec]

oh I miss that important notice... octo, sorry. And Yes you have a problem with 6 motors

 

[bson]

You are so right! After 7 minutes calm flight the outrunner is 88 C degrees!!! Will stay on ground until I get my 2826-6 :-(

 

[bson]

Did a similar 7 minutes flight with new Tiger 2826-6 motors and the warmest ended up at 47 C degrees immediately after flight.:nevreness: Another side effect was also that it felt more responsive and stable in gusty, wind which it was today during the test.

 

[bensid54]

Still seems too warm when you consider the amount of air cooling those motors get. I read in another thread that the recommended maximum weight should be 5.8kg for this model which may be why the first set of motors fried due to the amount of weight they carry. I found when I keep under the maximum weight rating, my motors hardly get above ambient air temperature. Not sure if this helps but I found that with any powered craft the lighter the load the less stress on motors and less heat generated. People tend to think that maximum means recommended when what it really means is that's all the machine can tolerate.