Cool - Warm - Hot - Whaaaat?

[Fluid]

I read almost daily on OSE that so-and-so's motor ran "cool". To most normal folks, "cool" means an object is not above ambient temperature - to some it means the object is below ambient. So to say that you ran your boat for five minutes in the summer and the motor came back "cool" is really deceptive - tell me it didn't gain any temperature during that run time! Yet, the term "cool" is used so often it is now about meaningless.

I guess it has become a matter of status to say your setup runs "cool", but in reality what was the actual motor (or pack or ESC) temperature? 50*F? 75*F? 100*F? 120*F? What is "warm? 100*F? 120*F? 140*F? What about "hot"? 120*F? 150*F? 180*F? I strongly suggest that we start using a temp gun and report the actual temperatures instead of meaningless words. Any serious FE boater has a temp gun, they're not expensive and one can save you a lot of $$$ in damaged parts.

http://www.offshoreelectrics.com/pro...od=dh-DTXP3100

I suggest that we start using real data when we describe our setups, not guesses and meaningless terms.


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[Tamelesstgr]

What I love is datalogging. I have a temperature probe for my ESC and one for the motor. My motor temp probe is pushed through the endbell and rests right up against the windings (I used to record the temp on the outside of the water jacket with the temperature gun). I saw the graph and could see the ambient temperature of the motor at the start of a run, and you can see the motor temperature rise during a run. It's also interesting to see once the run is over and water cooling stops, how much heat soak increases the motor temperature.

On 9/4/16 this is my Leopard 4082 - 1450kv on 6s with an X442 prop on a 3 minute run

Ambient motor temp at start: 78 degrees
Motor running temp with cooling: Peaks at 90 degrees
After run stopped motor temp (heat soak): Peak at 102 degrees

Ambient ESC temp at start: 78 degrees
ESC running temp with cooling: Peaks at 102 degrees
After run stopped ESC temp: Gradual cool down

NSR 32 Leopard 1450KV 6S X442 Prop 9-4-16 Temp Chart.jpg

On 11/16/16 this is my Leopard 4082 - 1450kv on 6s with an X445 prop on a 3 minute run

Ambient motor temp at start: 76 degrees
Motor running temp with cooling: Drops to about 60 degrees
After run stopped motor temp (heat soak): Peak at about 80 degrees

Ambient ESC temp at start: 66 degrees
ESC running temp with cooling: Peaks at 97 degrees
After run stopped ESC temp: Gradual cool down

You can also see in the graph that I stopped around the 5 minute mark and the heat soak started creeping up and then dropped again when I started running. Water temp in my pond was probably 50 degrees?

NSR 32 Leopard 1450KV 6S X445 Prop 11-16-16 Temp Chart.jpg

20160523_220426.jpg

[srislash]

Nice work, big difference based on the season.

[Doby]

My setups run cooler in the winter, warmer in the spring /fall and sometimes hot in the summer...my temperature gun confirms this.

[ray schrauwen]

You could also factor in the time to get the boat open after a run. If it was stuck out there for 5 minutes and still reads hot or about 150F there is more heat that has dissipated.

[T.S.Davis]

can save you a lot of $$$ in damaged parts. .

I'd like to add to that statement. Giving real numbers might save someone else some money too. People read this forum. If I say it "ran cool" it may not mean the same thing to me as it does to someone else.

I think too that it's frustrating for experienced guys that know what should and shouldn't work to hear "came in cool" when we know damned well there is no way the setup came in cool. Cool how? Like the shrink didn't melt off the wires? It didn't de-solder?

[Tamelesstgr]

Prior to datalogging my newb self thought increasing KV and prop size would get me going faster. Much to my dismay I learned that on one of my setups I couldn't touch the motor it was so hot after a run

Since then I'm much more methodical in paying attention to hull size, motor size, prop size, battery selection and of course data!

[Newboater]

I always use a temperature gun to measure ESC and Motor temps. It is safe to say that if your setup can maintain a safe temperatures in the summer heat then you should be good all year round, as the ambient water temps will only be cooler after the summer.

[RandyatBBY]

double info.

[Lone-Wolf]

I'm guilty of using the terms "cold...warm...hot". I guess when we put info out there for anyone to read we really should have a valid number beside it. Time to pick up some batteries for my temp gun. Now I'll be paranoid when using the word cold.

[NativePaul]

Maybe I am not normal, but to me cool or warm has nothing to do with ambient temperature, but everything to do with my temperature. The same object at ambient temperature will feel cool or cold to me in winter, but will feel cool or warm in the summer. Where I live the ambient temperature varies wildly but my temperature is much more stable at 37c. It makes more sense to me if I call things under blood temperature cool and over blood temperature warm, as this can easily be felt with an uncalibrated hand and no equipment or mathematics are required, whereas basing it on ambient temperature requires a temperature gun to measure the object, either something of low mass that has been in the shade for a while or some research to find the ambient temperature, and a little simple maths to find the difference.

There is no defined temperature of cold and hot, which is an issue. For me cold is under about 15c and hot is above 50c (sorry, I do usually do imperial conversions as I know it is an American forum and I know my weight and length conversions off hand, but C to F isn't a linear ratio and I never learned the conversion chart). The further something is from blood temperature the harder it is for me to tell how hot it is, I can tell 20c from 30c, or 40c from 50c very easily, but I doubt I could tell 100c from 150c or -10c from -60c. I find 55c uncomfortably hot to hold, and while nearly all of my stuff runs cooler than that, I do have a temp gun, and if I think something is over 50c I will use it, I also use it to reach into places that I cant feel like through the cooling holes into the windings if a motor is warm.

It is definitely possible to run a boat without gaining any motor temperature, I have had many that lost temperature when running, where I live ambient temperatures at the start of the season will be about 20C and water temperature will only be about 7C, and through most of the summer air temps will be 25-33c but the lakes will only peak at about 17c in late summer, all of my Naviga Mini Hydro class boats (450mm (17.5") averaging about 200w powered by 72g 28x35mm Mega 16/15/2 on 2s or 16/15/3 on 3s)) be they cats or riggers will have their motors come back noticeably cooler than they left on most race days during the season (I don't have any measured temps as it is so obviously safe that there is no point in measuring them), it tells me that the motors are to big and I could save some weight by going smaller, but smaller cans don't have enough torque, so the actually lose out. I ran the same 16/15/2 on 3s in my Mini Hydro sprint at about 400w for 6 laps plus half lap mill with no cooling and it came back in the low 60Cs during summer (OK, but plenty hot enough for me to want to measure).

[Shooter]

Ask a group of people to feel a 'piece of wood' and a 'piece of metal', both at room temperature. 90% of them will tell you the piece of metal is cooler. 20% will insist it is cooler even after you've measured the temperature.

[properchopper]

I remember " back in the day" the safe operating standard was "if you can grip the motor for five seconds you're O.K." Now with the ready availability of laser temp measuring devices and onboard data logging (as well as real time databroadcast) way better accuracy is available. But what defines an acceptable temp range on all the components (motor, ESC, batteries) is a good question and I wholeheartedly agree with Jay that there's no standard semantic describing what's "cool" or the like. Each component and it's variants has its "let the smoke out" thermal breakdown threshold. A lot of where you set the critical point depends on what you do " A back and forth zoom-zoom run for a few seconds to get a max GPS pop has a different "go/no-go" point than a heat/oval racer who needs a mill + six + penalty lap runtime. Accurate temp monitoring (including, as Ray says, getting readings as quick as possible after the run) is critical to accuracy.

Lots of smoke can be avoided if the "one minute test" convention is routinely applied. It's surprising that one of the largest Q & A topics for discussion : "which prop should I use " fails to routinely bring this up for mandatory enforcement. Even if one boater knows what prop works on his rig, the same prop on an exact same boat might cause unacceptable & destructive temps if the second boat has a different weight distribution (runs wet) or substantially more runtime.

Test, check, test.

If all else fails, use one of these :

odor meter.jpg

[NativePaul]

Ask a group of people to feel a 'piece of wood' and a 'piece of metal', both at room temperature. 90% of them will tell you the piece of metal is cooler. 20% will insist it is cooler even after you've measured the temperature.

Metal is more thermally conductive than wood, if you are somewhere hot and that ambient temperature is above blood temperature, the metal piece will feel warmer than the wood instead of cooler, you are just getting a more accurate feel for the temperature. Luckily I have no wooden motors, so it is not an issue for me.

Lots of smoke can be avoided if the "one minute test" convention is routinely applied. It's surprising that one of the largest Q & A topics for discussion : "which prop should I use " fails to routinely bring this up for mandatory enforcement. Even if one boater knows what prop works on his rig, the same prop on an exact same boat might cause unacceptable & destructive temps if the second boat has a different weight distribution (runs wet) or substantially more runtime.
Test, check, test.
If all else fails, use one of these.

Sound advice there Tony, and I love that odour meter, I didn't know such a thing existed, but I bet a burned ESC would read over 9000.

[Tamelesstgr]

That's a great point Tony, and I've seen something kind of funky happening in my 32" Deep-V. I've been trying to build up a nice collection of S/B props and have an X442 that seems really nice, balanced, sharp, thinned. Then I bought an X445, balanced, but not as sharp, probably not thinned. The difference between the two props from the different folks who worked them had me scratching my head.

Example:
The X442 over 5 runs logged an average of 102.09 amps, 2346 watts, and gps speed ranging from 44-48 mph
The X445 over 6 runs logged an average of 77.79 amps, 1870 watts, and gps speed ranging from 41-44 mph (All values dropped)

The X445 which has greater pitch should draw more amps etc and reach a higher potential speed. Makes me start to question if the X442 was a better prepared prop?