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Old Sep 28, 2004, 02:22 AM
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Silverstreak328's Avatar
Tampa St Pete, Florida, United States
Joined Dec 2003
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How hot is TOO hot for a bl motor?

After test running my T-rex 450 for a FEW minutes, the Mega 16/15/3 motor was pretty hot. I could hold my finger on it for 4 seconds before it really hurt. How hot can I let this motor go and do they sell heatsinks for this size motor?

BTW it has amazing power and thrust!
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Old Sep 28, 2004, 04:31 AM
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dankers's Avatar
Melbourne, Australia
Joined Apr 2004
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Its too hot. Tried this motor, its no use on 3S, its heavy and draws a lot of amps which means you need bigger cells which adds weight.

On 4S its get needs a 9T pinion and there is should be ok. Running this motor on 4S is outside the motor's specs though.
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Old Sep 28, 2004, 09:25 AM
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Spring Valley. MN
Joined Jun 2000
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Quote:
Originally Posted by dankers
Its too hot. Tried this motor, its no use on 3S, its heavy and draws a lot of amps which means you need bigger cells which adds weight.

On 4S its get needs a 9T pinion and there is should be ok. Running this motor on 4S is outside the motor's specs though.

Dankers, what is out of spec for this motor on 4s? max rpm is listed as 55k rpm 4s only has it spinning 44k, 5s has it up to 56k. The problem as I see it is the efficiency is too low and going up to 4s makes it even worse

Silverstreak, This is exactly why I sugested you to wait till people had sorted out the power system on the T-Rex before you started to order components, often things that look good on paper turn out to be a duds in real life and unless you have access to a bunch of motors or really deep pockets it can get very frustrating before you find the right match. In the mean time you can try a heat sink the hacker B40 sinks will fit as will the GWS sinks for a speed 400 motor.
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Old Sep 28, 2004, 10:07 AM
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Joined Dec 2003
418 Posts
I have accepted the risk when I ordered a Hacker 18L and some light weight 1050mah cells. On paper or on the spreadsheet rather, the results seem excellent.

Many think the motor does not have the muscle for the job my views are its no more proportionally smaller than the razor V2 was for the hornet. And I plan to get the bird as light as possible regardless.

What are your thoughts guys on my motor and cell choice ?
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Old Sep 28, 2004, 10:37 AM
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Spring Valley. MN
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The 18l looks surpizingly good efficiency wise, but the head speed looks a little high unless there is an 8t pinion available on a 9t pinion the head speed is up around 2400 and from what I've heard the tail getts crazy on high head speeds. I have also read that Align was working on a differant gear ratio for the tail. If you can knock 2-3oz off the AUW it looks even better(what motor wouldnt ).
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Old Sep 28, 2004, 11:03 AM
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Melbourne, Australia
Joined Apr 2004
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Quote:
Originally Posted by buzzsaw 46
Dankers, what is out of spec for this motor on 4s? max rpm is listed as 55k rpm 4s only has it spinning 44k, 5s has it up to 56k. The problem as I see it is the efficiency is too low and going up to 4s makes it even worse
Buzz, you are correct its within specs. My bad. Looking at soo many motors getting mixed up. Trying to stay within specs now, this is costing money :-)

Hacker 18L does look very good on the right pinion. Nice and light as well.

T-rex tail is nuts.
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Old Sep 28, 2004, 11:30 AM
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San Carlos, California, United States
Joined May 2002
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I'm really surprised the 16/15/3 becomes that hot on the T-rex.

I fly Coronas which weigh 1200 grams on that motor, and the motor doesn't become that hot. For some reason, your T-rex is eating a lot of power. Do you know what the headspeed is on the 16/15/3?

From what I've heard, the T-rexes are already heavy, so you want to avoid adding more weight. This kinda rules out the next larger Mega (16/25/2).

If you can get pinions large enough, then some sort of outrunner might be a good choice, because they dissipate heat fairly well.

Toshi
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Old Sep 28, 2004, 03:07 PM
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Seattle, WA USA
Joined Jul 2004
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I'm new to brushless motors. I'm running a Himaxx 2015-4100 in a HB FP elite and I have another one for a Hornet 2. The power has been great and they also seem to be quieter then brushed motors. I'm amazed how quiet the HB is with the Himaxx. They do seem to run quite warm, though. All of the searching I've done on this subject seems to verify that. Is it true? Does a brushless motor run warm to hot even when properly set up? Is it just the way they are?
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Old Sep 28, 2004, 04:14 PM
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Somerset, PA
Joined Feb 2004
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Seattle,

I was just searching for threads about hot 2015-4100s. mine is setup HB elite FP with piccolo blades 3S 1100, and gy240. brushless tail.
I'm hovering at about half throttle.
It was quite warm with the 10t pinion almost to hot to hold. So, just today I went down to 9T pinion and its better, still warm but not hot. I was thinking of going down to a 8T pinion. does anyone use an 8T pinion with this setup?
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Old Sep 28, 2004, 04:19 PM
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Tampa St Pete, Florida, United States
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My azfai BL cdrom motor doesnt even get warm when I fly my aerohawk with it. it is incredibly effecient. I even hooked it up to my trex450 and hovered around and it just BARELY got slightly warm!
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Old Sep 28, 2004, 05:29 PM
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Seattle, WA USA
Joined Jul 2004
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Interesting. Maybe I'm over stressing my motor by running a 10t pinion. I'm also using the M24 blades which have quite a bit more mass then stock HB blades. (BTW, the M24 blades are one of the best things you can get for a HB.) I have a Sparrow heat sink on the Himaxx, and after a good 15 minute flight (w/ a TP 1320 3-cell LiPo) it's hot enough that I can not comfortably hold on to the hink sink for more then five to ten seconds. Does this mean I'm running inefficiently and/or hurting the motor? Persistant, if you try 8t pinions, please post your results.
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Old Sep 28, 2004, 07:42 PM
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Somerset, PA
Joined Feb 2004
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Seattle,

I would say thats too hot. I wont be trying the 8T pinion for another week of testing out the 9T. You probably will shorten the life of the motor running that hot.
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Old Sep 29, 2004, 12:56 AM
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Joined Aug 2004
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I'm using the HiMaxx 2015-4100 on my Aerohawk with a 2S TP 1300 LiPo. I too was concerned about the temp, and was looking for longer flight times. Below are the flight times (hovering) and motor temperatures that I measured for each pinion. Note that I am using Like90 blades. The 8-tooth pinion took about 60% throttle for hovering. The 11-tooth was somewhere less than 50%.

8-TOOTH
Flight Time=15.5 Minutes
Motor Temp= 111 Degrees F.

9-TOOTH
Flight Time=14.5 Minutes
Motor Temp= 123 Degrees F.

11-TOOTH
Flight Time=13 Minutes
Motor Temp= 136 Degrees F.

The above data seems to indicate that motor stress increases as you increase pinion size, which makes sense. I've since moved off of the 8-tooth pinion in favor of a larger pinion with more power (I'm doing less hovering and more FF now).
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Old Sep 29, 2004, 03:12 AM
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Seattle, WA USA
Joined Jul 2004
262 Posts
Nice data, MrBruiser. I would of guessed that the temperature differences would be greater between pinions... However, maybe 136 degrees is not so bad. The Himaxx documentation lists the maximum allowable motor temp as 212 degrees F.

I ran a few flights with the canopy off and it did make a difference: the motor was only warm instead of hot. I didn't think the canopy would restrict cooling that much but it seems that it does. I'm going to try mod'ing the canopy to let more air get to the motor and electronics.
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Old Sep 29, 2004, 04:43 AM
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Spring Valley. MN
Joined Jun 2000
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I typically try to stay under 160F so 136 isn't bad, for comparison the B20-22s in my hornet after 20 min of hovering and slow circuts is only in the 126-27F range. the H2 gets the motor a little hotter and cuts into the flight times but I think the heat was still in the 130-135F range after a 15 min flight.
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