Jumpjet101

I have an Axe CP and have been learning how to fly it. I've got to the point where I can hover it for the full 10 mins using my 1350 LiPo's. I have four of these batteries (2 MegaPower, 2 EPYAYA) and I ran through two of them back to back the other day and burned out my main motor. After replacing the main motor, I decided to try it again back to back and this time I burned out my tail motor. The motors get very hot after a 10min flight. Is this normal for these motors to burn out or am I just over doing it without a cool down period. If I have cool down period between flights, how long do you recommend?

How long have you ran your Axe CP back to back using LiPo's?

sammy64

The main motor has a fan inside and the heat sink is covering the Exhaust holes
http://www.rcuniverse.com/forum/m_55...tm.htm#5548156

this MOD helps a lot with the cooling down of the main motor...

s_mcflurry

The longest I've gone is one LiPo pack (~9 minutes) and am wary about running it any longer than that because of this reason. Even at that stage the main motor is sweltering...so I'm considering upgrading to brushless motors to address this. A rule of thumb I've heard floating around here (if I remember correctly) is to cool your motor down for as long as you run it - if you ran it for 10 minutes, let it cool down for 10 minutes.

nicadflyer

I would like to thank the person who figured out the cooling mod for the Axe CP.
I just modified the heat sink on mine. I have been practicing hovering from a stand (landing skids loosely tied down). Before the cooling hole mod the motor was 135 degrees after 5 minutes. After the mod I ran two stock 650 mah batteries. Batt # 1 for 5 minutes/ motor 105 degrees. Five minutes later, batt 2 for 5 minutes/ 111 degrees for the motor. Roughly 25% better cooling. The battery temps were the same for all runs, 106 degrees.
Now I need some Lipos so I can practice longer.

mrasmm

do you have a link to the mod, or how did you end up doing it?

nicadflyer

IF you look closely at the motor, you can see the two cooling holes. Mark where the cooling holes are on the heat sink and then just pop it off. I used a Dremel to cut out the two slots. Pop the heat sink back on. Be careful NOT to remove the white grease, its for transferring the heat from the motor. It took about 10 minutes.



Closer view.

Whirley Bird

My Feedback: (1)

Thanks for the pictures.
I have a dremel tool but my concern is the metal filings getting inside the motor but I have a box of spare motors and a big tube of the heat transfer past.
Many thanks
Vegas./

nicadflyer

I took the heat sink off and did the cutting away from the helicopter.

nicadflyer

Double post

Whirley Bird

My Feedback: (1)

Guess what I just found out.
If you put the motor to your mouth and try to blow air through it it feels restricted.
But if you put the top on the motor in your mouth and blow ir into it the air feels like it has no restriction at all
GEE 2 more slots cut on the othe rside on the motor may even lower the temps another 10 more degrees.
Vegas/

Jumpjet101

When you all measure the the motor temp, Are you looking at the motor or the heatsink? I have a digital thermometer that I use to check the temps. After a 10min flight, I get around 120 degrees on the main motor from the front. But checking the temperature from the side aiming it at the heatsink, I'm getting temps in the 170's. Does the heatsink usually get hotter than the motor or is the motor actually getting 170 degrees under the heatsink? I have did the mod and cut open the the vents on the motor.

I have a couple Lipo 1350's and after a 10 min flight, the hottest part of the battery is reading approximately 140 degrees which is the bottom of the pack. Is this normal or to high? I am using Mega Power 1350's.

Whirley Bird

My Feedback: (1)

First question.
On base board heat the fins are of a different metal and heat is attracted to the thin fins and the air around the fins are cooler and heat is attracted to the cooler air,so the fins are cooler then the pipe their attached to.
But the fins are stationary and air is always flowing from the bottom out the top.
It sounds like the heat sinks (although a different application) is doing the job.
As for the battery 140* is just about maxxed out.
Some guys velcro the whole bottom of the battery.
Not good because it acts like an insulator.
I keep mine in place with one of the nylon/velcro reusable straps and keep it vertical.
Any material between the battery and the surface it's mounted to will hold heat.
Vegas/
PS: Small holes drilled in the heat sink fins may make them run cooler.
If you can, mount 1 heat sink 180* out from the other one so heat from the lower heat sink doesn't get absorbed by the one above it.

Whirley Bird

My Feedback: (1)

If you open up the slots you may get more air going through the motor but the velocity of the air will drop off to close to nothing
It will slow down the flow and heat the cooler air/
You want to get the cold air inside that motor, absorb the heat and discharge it as fast as you can

mrasmm

some people think that the motor is actually cooler than the heat sink, or that the alum heat sink sucks all the heat out of the motor because it conducts it better, but this just rankly isn;'t true =)

The truth of the matter is the optical thermometers work on the principle of emmitted infared light, or heat energy. So if we are talking about light here, let me give you some examples. If we are in a dark room and you shine a flash light off a mirror, you are going to get alot of light comming back at you, but if you shine it off other opbjects like paper or something you're not gona get near as much back, and if you shine the light on something black with alot of space inbetween it like a prefilter you're gona get almost no light back.

So the basic just of the story is that the temps aren't actually that different, but rather the amount of infared light they shine back is less, so the temp prob reads less.

I personally take my temp probe and put it on the max function and go all over the motor and find the max temp, and then go with that reading. After a few reads you'll know where the hot spots on your motor are =)

170F for the main is a bit hot, and 140F for the lipo's is the absolute max you want to be at. I would go over you heli and make sure that everything is spinning real freely, that it takes 7 or 8 seconds or longer to spin down, that the gear mesh is not too tight, ect.

Thanks for the post on the heat sink mod =) that is good to know that a little space will cool down the motor alot =)