View Full Version : 1300 kv motor getting hot

08-21-2011, 11:14 AM
I have 6S setup with Kontronik Jazz 40. After about 2 minutes of flight (hovering - just setting the new bird up) my brand new 1300 KV motor is getting very hot. I can touch but it is very hot. I loosened up motor end of the belt all the way - it is not sloppy but by simply touching it I get deflection of 2-3 mm. Everything seems to be ok - no binding anywhere, no slop or loose screws. Heli is brand new so all the bearings just installed and checked prior. I wonder if my ESC is not powerful enough (40A versus YGE's 60A). Battery is also getting hot (never did on my old 450 Sport). Thanks in advance for any suggestions.

08-21-2011, 01:00 PM
Hot is relative. Unless you can take some measurements, there's no way to really tell say if you have an issue or not. But an overheated motor will be untouchable, so I'm guessing maybe not. Remember... Higher power systems do more work and so, generate more heat. It's the law of thermodynamics. You went from a 3S to a 6S, you're burning more power and everything should get hotter.

08-21-2011, 01:42 PM
My bad - I did not get a temp. Will do next time. I think that higher voltage would actually reduce heat associated losses hence would run cooler and that is why even wires for 6s systems are thinner than 3s. My concern is that I use jazz 40 amp versus stock 60 amp yge escape. I am new to miniprotos and also wondering if it is normal to run motor hotter than for example 450 pro? Perhaps to relatively more drag losses due to unusual design.

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08-21-2011, 03:03 PM
ESC suitability depends on how much current you are pulling - if you are Kyle Dahl running 4000HS and flying the way he does, you are probably pulling 50 or 60 amps most of the time. If you are an average recreational flyer running 3000 - 3500 HS you are totally fine with that ESC. The 450 Pro comes with an Align 35A ESC, and Kontroniks are conservatively rated, so I would be totally comfortable with that ESC up to 3500 rpm.

Even if it was near its limit, it would be the ESC getting smokin hot first - how hot was that after flight?

This heli is so quiet you may have a really high HS and not realize it - have you tached it?

08-21-2011, 04:22 PM
ESC is ice cold but battery and motor are hot. I will tach it as soon as i can get my batteries recharged. So could it be that i just have to much drag somewhere? The heli is brand new and I do not have any feel for the miniprotos. I have Furion 450 and it is so smooth everywhere - head, tail. You could spin bare main shaft by hand and it will keep turning. Miniprotos does not feel that way at all. I guess the next step would be tear it down and look for he culprit.

08-21-2011, 11:58 PM
If ESC is cool then it's fine. Your batts are obviously working fairly hard, although 'hot' is fairly subjective.

I found that the apparent drag in the drivetrain seemed unusual too - when I spin the head by hand I only get a turn or two out of the main blades, even with blades on. I was worried about that too, but in the air I seem to get better consumption than I used to on my 450 Pro which spun easily. I guess the heli is lighter but whatever it is, it seems to be normal. I was told to loosen my belt on the motor side to the point where people would tell me it's too loose - I took this to mean about 5-6mm deflection on the front side with moderate force. It is a bit of an art to balance the tension between front and rear portion, but I am running my belt what I consider to be fairly loose, but not loose enough to get slapping in the boom or any slippage. If yours is set up like that you should be fine - it works for me.

Thunder Fighter
08-22-2011, 12:30 AM
As you go from 3s to 6s with the same wattage being drawn you reduce your amperage by half so a 40A ESC is more than enough. If you can keep your finger on the motor for more than a couple of seconds then it is not running too hot.

The battery getting hot is more of a problem, are they old packs or low C rating? Usually by going to 6s packs on a 450 your pack should run cool as again you are halving the current draw from them. The belt tension on the front belt can be set vey loose, mine moves several mm with just a very light touch and doesn't slip with my 4s setup.


08-22-2011, 06:35 AM
My batteries are 5-10 cycles old so I do not think they are a problem and in combination with motor being hot - seems like they both are working extra hard trying to overcome too much drag. I think in my case belt tension is a culprit. I did loosen it up on the motor end so it is almost sloppy. I also slacked the tail portion of the belt and it seems to spin much better. I could not try it again yesterday because of rain but will try today. Like Ausant mentioned - belt tension is an art just like pinion mesh on regular helicopters. Thanks

08-22-2011, 10:01 PM
I think that higher voltage would actually reduce heat associated losses hence would run cooler and that is why even wires for 6s systems are thinner than 3s.

It can reduce parasitic losses. Higher voltage means the same Power at a lower Current, and parasitic dissipation increases with the square of Current. It's why high-tension power lines run really high voltages, sometimes greater than 1000 KV. At high voltage, they don't have to carry a lot of Amps, because when that high voltage gets stepped down to 120V the available amperage increases.

But.. Power is an expression of work, force exerted over time. The Power that is dissipated in doing the work is converted to heat. Do more work, expend more Power, generate more heat. Thermodynamics.

Even if a 6S power system is more efficient, it's still consuming more power than a 3S system. If for no other reason than the heli itself is larger, it requires more energy to make it fly, and that generates more heat.

08-22-2011, 10:08 PM
Ran it today after adjusting tension - what a difference - motor and battery are muuuuuuch cooler. Thanks for your advices guys!:thumbup: