CX2 Motor Heat Study
 

I’ve seen a lot of posts regarding the Extreme 180 motors and how they run cooler and longer than the stock motors, but I have not seen any hard data on the subject; just people’s gut feeling after switching. I also got to wondering about the aftermarket heat sink, and whether it really did some good or was just 3.6 grams of dead weight.
Since I work in a test lab, I decided to run some tests to see if I could quantify the differences.

I won’t go into the details of how I ran the tests: that would take too much room and bore the heck out of most of you. If you are interested in the details of how the tests were set up and run, send me your e-mail address and I will send you a copy of the test report.

A very small temperature sensing device was attached to each motor, and the motors were run for 10 minutes using two power supplies to maintain a constant voltage to each motor, so that each run would be identical and not dependant on the battery discharging identically on each run. Four runs were performed. One with stock motors without heat sink, one with stock motors with heat sink, one with Extreme motors without heat sink, and one with Extreme motors with heat sink.

The data showed that the heat sink did in fact make a substantial difference. The motors ran about 14 degrees F cooler with the heat sink installed. But the Extreme motors did not run cooler than the stock motors. The stock motors with heat sink saw a rise in temperature over 10 minutes of 42 degrees F, while the Extreme motors with heat sink saw a rise of 43 degrees F.

Based on this information, I am tempted to install two heat sinks on my motors. If the added drop in running temperatures will make the motors last longer, it might be worth the small 3.6 gram penalty I would pay for adding it.

RE: CX2 Motor Heat Study
 

Great info! Thanks!

RE: CX2 Motor Heat Study
 

Good information. So you are a genuine lab rat. It's good to have a couple in our midst. You guys take the discussion and opinion out of anecdotal evidence. Of course that takes a lot of the fun out of things, but good information is good.
You sure found a bunch of heat rise! I have no idea at what temp the motor is nearing the limit of it's comfort zone. A ball bearing motor should be quite happy running pretty warm. It should be far more heat tolerant than a bushed motor, depending on the design of the bearing races.

I was wondering about the ball bearing heat rise and the value of heat sinks on the Xtreme motors. Looks like the heat sink stays. Nuts.
If I cross drill the heat sink to remove some mass, do I loose the ability to dissipate heat? Or does the turbulence as the air moves through the drilled holes actually slow down and collect more heat?
Does color matter? I thought that flat black will dissipate more heat than a metallic color.
And I certainly expect that the thermal paste does transfer more heat.

Thanks for the info. Good stuff.

RE: CX2 Motor Heat Study
 

Great info WXUP! Good to see some 'technical' info! Please keep us posted on your findings/measurements with the second heatsink! We all be very interested i think.

Also, do you have any tips on how to improve heatdisipation other than airflow? I guess the downwash is about as much airflow as one would get, so like soloboss says; (cross)drilling (to increase surface-area?), other materials (like copper?) or maybe heatpipes (like some PC's use? i have several of them lying around :))? Currently my PC is liquid-cooled, but i guess that's not an option for the lil' CX2 ;).

RE: CX2 Motor Heat Study
 

The catch22 of RC flight.

There will come point where added weight (2nd heat sink) will cause the motors to work harder, to get lift, thereby causing the motors to heat up faster and to a higher degree. Not to mention shortened flight times.

What is that point? I don't know.
And the problem is that a static test will not yeild results because the heli will not be lifting that weight unless it is flying.
And if it is flying, then other variables come into play like throttle control inputs.

Try dissipating heat at 8,000 ft above sea level. It's not easy. [:@]

RE: CX2 Motor Heat Study
 

Here was my study cut and pasted from a thread about 20 days ago.


The purpose of This experiment is to determine if the temperature of the XTREME brand Motor s with properly broken in Carbon brushes, will run at the same Temperature 'Naked', (meaning without any heatsink of any type) as the Stock E-Flite brand motor s WITH the heatsink upgrade; which Most agree is almost a must. The test is using E-Flite's aluminum and paste heat sink.

HYPOTHESIS: The Extreme 180's run cool enough to not need the aluminum heat sink for average flying.

This Experiment will help determine if it is prudent, (for those who care) to sacrifice the 3.7 Grams (more with the paste) ballast the aluminum upgrade brings; with weighing the benefit of better motor cooling, (if any) on one side, to the redundancy of the upgrade to supposedly cooler running motor s to begin with. If the Hypothesis is correct, then this heavy feature is not needed other than for asthetics, and the offset of the significant weight loss of removing this redundancy, will allow other upgrades that may serve the heli more effectively; I.E. aluminum grips for stiffer blades, etc.

This experiment was conducted indoors with the ambient air temperature being the same for both CX'S. Both helis were placed on the floor and the ambient air temperature for each run was the same at 74 degrees F.

Both canopies were removed for this experiment.
Both batteries are the same age E-flite stock batteries charged to match 8.4 volts output.
This was a static test timed at precisely 7 minutes, at the half throttle position and the throttle trim verifyed at the furthermost down position.
The heli's were run 1 at a time.
The temps were measured with a clean probe at the outer cans of both motor s at the middle.
After the run, 1 minute was allowed to equillibrium the core temp to the outside can temp.
Temp readings written down were the temps that held steady after a 5 second lapse on the meter.

Here We go:

CX-2 # 1 with stock motor s and heat sink w/paste.

before run:
Left Can = 74 F Right = 74 F

After run and 1 minute:
Left Can = 105 F Right = 104 F average: 104.5 Degrees F.

CX-2 # 2 Extreme motor s w/ aluminum heatsink/paste.

Before run:
Left Can = 74 F Right = 74 F

After run and 1 minute:
Left Can = 98 F Right = 100 F average: 99 Degrees F.

CX-2 #2 With heatsink/paste removed:

Before run:
Left Can = 74F Right = 74F

After run and 1 minute:
Left Can = 103F Right = 105F average: 104 Degrees F.

Variables;

CX-2 #1 has all stock parts with only the aluminum upper head upgrade.
CX-2 #2 has all aluminum upgrades except grips.
Both have stock blades, flybar.

Conclusion:

The EXTREME 180 motor s DO run cooler than the stock motor s. So much so that they run at the same temperature naked (without any added heatsink) as the Stock motor s do with the heavy upgrade.

I do understand that the heatsinks benefit the Extreme's as well; having them run cooler, but if weight reduction if first on Your mind, then You don't need them, with the understanding that You may have to monitor the motor temps. (with your finger) a little closer.

RE: CX2 Motor Heat Study
 

Soloboss:
I would love to get some heat specifications from the motor manufacturer. But I'm guessing they are all made overseas and getting that kind of information would be difficult to impossible. I'd hate to stress over keeping the motor temperature under 120 degrees F only to find that they are perfectly fine to 150. But in the absence of specs I prefer to error on the side of caution.

Heat sinks are all about surface area. The more surface area exposed to ambient air, the faster the heat transfer. Although you need enough metal between the motor and the fin area to transfer the heat to the fins. Knowing where to place the holes is the art and science of designing heat sinks.

I'm not sure about your color question. I believe car radiators are painted black for that reason, but I don't know the details on that. I will ask the mechanical engineers at work and see if I can get an answer on that.

The thermal paste makes a great deal of difference. When you put two "flat" surfaces together you assume there is a lot of contact area to transfer heat. That is really incorrect. If you looked at the surfaces microscopically, you would see lots of tiny ridges and vallys, and the real contact area is at the points of the ridges. The paste fills in the spaces and magnifies the contact area immensely.

shufflez:

Other materials such as copper might work better, but I believe aluminum is one of the best heat conductors, and since it is very light weight, one of the best choices for our particular application. The "heat pipe" concept is an excellent one because of the tremendous surface area it offers. But I haven't seen anything adaptable to our motors. If you have any ideas, let me know and I will test them. I do plan on testing some other heat sinks (designed to cool transistors) to see if they do a better job than the e-flight one.

Wolfpackin:

You are correct about more weight causing the motors to work harder, thereby generating more heat. But you are incorrect in your assumption that this cannot be compensated for in a "static test". The same issue is true of the two motors, since the stock motors are a bit heavier than the Extreme motors. If the Extreme motors run at a different voltage to hover the helicopter than the stock motors, this will generate a different amount of heat. In order to compensate for this in "static" testing, I connected four very fine wires to the motors, so that I could measure the voltage to each motor while the helicopter was hovering about three feet off the ground. This way I can simulate the helicopter at any weight, with any set of motors, and simulate how hard the motors will need to work to hold a hover. Now I can run the motors statically, with power supplies instead of battery packs, to exactly simulate the helicopter hovering at it's current weight. The power supplies also eliminate the variables caused by battery packs not performing exactly the same between runs, or differences in throttle settings.


goldslinger:

Accurate testing is all about eliminating variables. If you can't compare apples to apples, you don't have a valid test. There are just too many variables here not accounted for. Using two helicopters with two different battery packs: no way to know if the two drive trains are identical in terms of drag, rotor pitch, etc., no way to know if the two battery packs discharge exactly the same. Using "half throttle position": are they the same between the two different transmitters? Can you be sure the motor voltages were exactly the same just because both throttles were at the same position? In testing it is important to create a baseline and then change just one variable at a time. Everything else must stay the same, or your results are tainted by the sum of all the other subtle changes.

RE: CX2 Motor Heat Study
 

I want to know if your Xtreme motors were broke in or new????? My Xtreme motors run way cooler now than they did when they were new. I fly a battery and they only gain 10 to 12 degrees and battery stays cool also. I uused an infrared heat gun to check mine. But when the motors were new, I got like a 20 to 30 degree gain over the same time, and the battery got hot also. I also run my motors with the heat sink and removed the stickers so they wouldn't retain heat eaither.

RE: CX2 Motor Heat Study
 

This is getting good.

My experiment was to see if the difference was substantial enough to toss the heat sink on the XTREMES, to conserve weight; Others and I already knew that they greatly benefitted the stock motors, so I didn't want to re-invent the wheel on that.

ONE MAJOR FLAW in Your experiment; You are ACTUALLY TESTING an apple and a pear. The fact that these two are brushed motors are where the similarities end. You said Your experiment was based on 'if XTREMES ran cooler and longer' but You didn't play the XTREME'S strong suit, 'You apple to apple' in that there was no moving air running over them that the blades do. You'll see that the open ventilated can of the XTREMES will keep the motor cooler MUCH better than stock BECAUSE of the introduction and exploitation of air convection from an external influence! It's not the internal impedance, friction, etc. so much as it is the ventilated properties relying on the external force of good old prop wash! I think You pretty much have to test it in the heli for that, or it's like taking what We learned from NASA'S whole space exploration data and using it to see if the Moon is really made of Cheese.

What You DID prove is that the ball bearing motors weren't necessarily a plus for temps. I think they are to a small degree for less friction, and for longevity. Under load, the ball bearings offer less resistance, but when pushing their own pinion gears against air, would test the same as stock.

IN THE HELI, (real life situation) the stock run MUCH hotter than the ventilated XTREMES. One of the variables on my experiment was an actual HEAVIER load with the aluminum upgrades on the XTREMES and they still ran cooler.

Here's a very Unscientific experiement; run the stock without a heatsink full bore for 9 minutes; touch them for 20 seconds. After applying burn cream to Your fingers, do the same thing with the XTREMES. I think Your findings will be pretty conclusive.

I wouldn't have even submitted my findings if the results were too close to call because of the variables, but it was a test to merely confirm my suspicion that One didn't need the heat sinks on the 180's, if You chose not too; and Yes, the stickers were removed, of course. E-flite's tolerances are amazingly good and consistant. So are my building and lubrication techniques.

I'm not going to fly the motors around the room without a heli attached to it, so I left them in the helis which, coincidentally, were both CX-2'S !

I don't think any motor manufacturer saved my test to their 'favorites,' but I think it was Scientific enough and accurate enough to benefit Me and this Community on weight issues.

BTW, Carbon brushes were freshly broken in at 100 percent, Stock motors (one can only guess) had 3 hours on them; so should have been seated.

What started the experiment was a discussion on weight issues; that the heat sinks, although will help under any circumstance; wasn't mandatory on the 180's like they are on the stock; and I gave evidence to the affect that what others already knew in their 'gut' was probably correct.

I have found that peoples 'gut' feeling is correct nearly; no, 100% of the time.

NASA can't even start on a proper Space Capsule without a Pilot's input for a good reason; there is NO better eperimentation than actual experience, and that is where the 'gut' comes in. That and good ol' common sense.

I'm not going to trash 10 sets of motors, and spend weeks to get microscopic consistancy on something; only to Fart and have to start over because I added another variable to the ambient air temperature or something like that, and then forget the blatant obvious that they WILL behave radically different in the helicopter and THE HELICOPTER'S cooling affect.

If I were testing consistancy on the longevity of stock motors, then it would have had to be done much more 'Scientifically.' with a power supply, and all. Or I could simply ask someone who's flown the heck out of these things, and I bet it would be just as accurate as in Very consistant, kinda consistant, not very, etc. but without the charts and graphs. ;)

I think Your experiment was VERY WELL DONE.
I think Your experiment was VERY BENEFICIAL.


I think it's cool that You have access to some neato equipment and am looking forward to hearing from You again.

Thanks,
Gary

RE: CX2 Motor Heat Study
 

I agree, Wolf.

And the supposed stronger magnets will increase the effieciency, the ball bearing spindle reduces friction. The ventilated upper benefits can't be tested with the pinions pushing air, without the benefit of prop wash which is the reason for the ventilated cap in the first place. You know this to be true, because for any passive convection air circulation to work, there needs to ba an inlet, AND at least a twice as large outlet, and You don't have that on the XTREMES.

You may have consistant voltage, but what were the RPM's of each? What is the torque? Stronger magnets equate to more torque, so less amperage draw, so less heat. . . so the differences between the weaker stock and the XTREME will be magnified under load because of the 'snowball' affect of what You are talking about. It's been echoed here, by many people.

You won't have to ask these questions if they are subjected to a 'reasonable' constant that a near identical load of a CX-2 for both; an experiment that has lesser degree of variables than testing them 'static' under no load conditions, when they behave so radically different in a heli.

RE: CX2 Motor Heat Study
 

Apparently there is a misunderstanding about what my “static test” consisted of. Let me see if I can clear this up. I was not simply running the motors with nothing connected to them. Picture the helicopter in a hover. Now picture carefully reaching up and pinching the body of the helicopter between your thumb and index finger. The helicopter is supporting its own weight, your hand is simply preventing lateral or longitudinal movement. This is exactly how the helicopter was tested. The only difference is the motors were being driven by power supplys instead of a battery pack and variable speed control. The air movement across the motors was identical to when the helicopter was hovering. Goldslinger, in your test I believe you stated your helicopters were sitting on the ground with the canopies removed. I’m quite certain the airflow in my test more closely simulated a natural hover than yours.

Blk822:
You made an excellent point about the break-in time on the motors. I would guess the Extreme motors had about 40 minutes or so run time on them when the test was conducted. I have no idea how long it takes to seat a new set of brushes, so if this is not considered long enough I will have to repeat the test once the motors have more run time on them. What length of time would you suggest is necessary to fully seat the brushes?

RE: CX2 Motor Heat Study
 

I broke mine in for over half an hour then after about 10 or more flights is when I noticed the heat difference and the battery being so cool after a long flight.

RE: CX2 Motor Heat Study
 

Goldslinger,

I have not done any serious scientific testing of my motors, but I can tell you that the X180 motors run cooler than stock; at least with MY helis.

I have 2 CX2's. One of them has the X180 motors and the other is stock. I have a thermocouple attachment for my Fluke multimeter, so I know the tesperatures are good.

Anyway, anecdotal evidence suggests that the X180 motors with heat sink will be between 90 and 105 degrees F after a 10 minute flight. The stock motors uner identical conditions run much hotter, say between 110 and 125 degrees F.

I can't easily test them anymore as I just upgraded my stock motors to X180's in my second CX2.

I know it's not scientific, but my personal experience shows that X180's, combined with proper canopy ventilation, do run cooler than stock motors. What net effect this has is yet to be proven, though many claim to have reduced yaw problems and greater longevity with the Xtreme motors.

RE: CX2 Motor Heat Study
 

You said in Your experiments that the 180 XTREMES did not run cooler than the stock.

I think You will have a hard time convincing a single person on this forum, to that finding.

You need to go back and see what You did wrong.

RE: CX2 Motor Heat Study
 

I agree. I have not had a single person tell Me to the contrary, until now.

I think He needs to fly them and touch them. Can't get any more proof positive than that.

RE: CX2 Motor Heat Study
 

Three hours run time is the norm or You can look inside the XTREMES and see when they are seated. Your experiment is looking more and more flawed. (just returning the favor).

My 180's were broken in with no load for 1 hour, 30 minutes, at 10 minute increments, with increasing voltage input on an ice pack.

They were freshly seated when I tested them. The stock motors were broken in in the same manner.

If You didn't break them in properly, the commutator is damaged and they will run hotter and arc all the time; like any other motor.

And Who gives a rat's butt how You hover it; airflow is over the motors and BOTH were subjected to the same kind of airflow, be it on the ground or tethered. Everyone here that I know ventilates the canopy; so off they came. (eliminating various types of canopy ventilation). I bet You didn't ventilate Yours, again, not playing the strong suit of the XTREMES.

So now You say You DID test them in a heli? Why didn't You mention that? that's kind of important and how did You tether them? You told Me it was unreliable to have 2 cx-2's; so did You replace the motors on the same heli? Did You get the gear mesh the same? Did You let the 4 in 1 cool for 30 minutes like I did, so they won't draw more amps; same with the moving parts? I smell too many variables of what You accused me of having. The variable/s I had was in the stock motors favor; so with a 4 degree or so cooler temperature than stock; I would have had to have something very major (seized bearing) to affect it by enough to say what You are saying, which is just the opposite.


My experiement was to see if the 180 XTREMES ran so much cooler than the stocks (which is a given) that the fins were redundant, and as a byproduct; re-affirmed what Everyone already knew, but gave insight that You don't have to have the heatsink on the XTREME'S if You don't want to, therefore saving alot of ballast.

You did an experiment and said You are going to put heat sinks on Your motors; well good for You; I guess You are emulating what everyone has done for months on their helis, cars, boats, airplanes, etc. without the labcoat and diploma.

But saying the XTREMES do not run cooler than stock is just plain wrong; and that is an opinion of many people here Whom You apparantly don't respect enough to take at word value. You want raw data and won't have anything to do with the unparalleled supercomputing skills of the Human mind in which the byproduct is common sense. "I burn my finger on the stock ones after a battery pack, and I don't with the XTREMES, I better do an experiment to see if the stocks run hotter."

I wasn't on a rant until You started telling Me how I wasted 5 hours of my valuable Free time, and picking apart My experiment that I so carefully conducted; only to see it is becoming more clear that You have far more variables than I did.

I guess One shouldn't be so quick to judge.

Gary

RE: CX2 Motor Heat Study
 

I appreciate Your input Bry,

I think it's as credible as anything on this thread. ;)

Gary

RE: CX2 Motor Heat Study
 

whew this is getting scientific and heated =P too much for my blood.

One thing that I do think that could be resulting in the differences is the PWM of the stock ESC vs a nice steady output of a PSU. My guess is the PWM would make the motor run hotter because of the voltage spikes. Also alt (air density), humidity, ambient air temps, the percentages and cooling capacity of all the gasses that make up the air might be different, not to mention the inconsistancies in mfg of these little motors. you can get a hotter running motor by just the way it's wound. If it's not would correctly you can get what is basically a short caused by counter acting EMF feilds because the motor windings were not properly overlapped. There's a bunch of things like that to contend with too =)


here's a pic of some brushes in a 370 sized motor after 90 min just to give you an idea of what the brushes look like after a certain time period in seating. it's been a while so I can't remember all of the details, but I think I started probably around 1v and then stepped up by 0.5v increments until I got to 6v with 10 min increments. This is out of my motor break in thread here http://www.rcuniverse.com/forum/m_5628228/tm.htm

http://image2-7.rcuniverse.com/e1/fo...99/Je99887.jpg
http://image2-2.rcuniverse.com/e1/fo...99/Db84002.jpg

These brushes have a thin edge to seat faster, but even they are not fully seated. If you look at the two brushes you will also see that one side is more worn than the other side. The more worn side is magnetically attracted into the commutator, where as the less worn side is magnetically repelled by the commutator, so you also have that factor to deal with. I believe the negative side is attracted and the positive side is repelled.

To me it looks like alot of good work from everyone here =) I personally would just like to see things a bit more constructive. That way people feel better, and the data is more accurate =)

lol, anyways, I'm off by box now ;)

RE: CX2 Motor Heat Study
 

Hey, mrasmm,

Nice illistration.

Yes, I agree, and Altitude would affect it somewhat, as well; but as long as both motors were tested in the same environment; yes, You might get different temperatures, but the spread will still be there; I guess.

When it comes to accuracy, I'm going to fly; therefore test, my heli with the ESC and not a power supply with it's guts hanging out following it around, so I guess If You are going to study how a Dolphin behaves, You better get wet to study them and not pull them out of their environment and onto the dock and study them; I guess is the point I was making. ;)

Thanks for the unbiased input.

Gary

RE: CX2 Motor Heat Study
 

yeah, no problemo =)

I definately got where you were comming from and the advantages from that way of testing, and I can see the direct application as well. I also see that with the other way. I can see what you are both saying about how one way isn't maybe quite 100% in the way of testing and how there are things that can be improved, there are always things to improve in any scientific method, so that's a good thing. I'm just wondering what the inconsistancies were between the two types of testing to get the different results. Obviously in the end the question is, does upgrading the motors make sense, and things to consider are efficiency (motor temps, amp draw, flight time), as well as power of the motors, as well as cost effifiency in replacement of just the brushes vs the whole motor, longevity and a bunch of other factors, and once you determine that, is it worth it for the heat sink. Do the motors benifit from whatever temp drop, will it make the motors last longer and be worth the weight in leu of performance.

That's a really complicated question =P For most people to complicated to care about, but from the sounds of it we have two people who are very interested in figuring it out, and seem to be NASA quality researchers here [8D]

my personal guess is the Xtreme motors would be better, and the heatsink would be better, and it might have some advantages in drilling it out in the right way to allow for more heat dissapation, and a ever so slight reduction in weight. I guess we'll see what the two of you end up finding out in your lab type tests =)

RE: CX2 Motor Heat Study
 

I was under the impression that one brush weres faster due to the fact that one is positive (voltage traveling to the comutator , arching to the comm.) and the other negative( voltage coming off the comm. and arching to the brush)

RE: CX2 Motor Heat Study
 

you can have right or left hand electrical theory, and both work just fine in figuring out how things work. This may be a case of that phenomina.

Electricity is the flow of electrons, and electrons have a negative charge, so electricity in the real world flows from negative to positive, so it will actually arc from the negative brush to the comm, and from the comm to the positive brush.

Same phenomina can be seen with lightning. Lightning actually strikes from the ground up to the clouds =)

Not sure about the actual arcing causing the wear differences, it definately could be. The way it was explained to me though was the magnetic attraction and repelling of the brushes based on their charge. If anyoneis a [sm=49_49.gif] and knows for sure, lets hear it =)

RE: CX2 Motor Heat Study
 

How can a copper comm. be magnetic with a corbon brush. Neather are magnetic?

RE: CX2 Motor Heat Study
 

The whole theroy on the way electrons flow is still hot topic in many areas. I'm an automotive tech and the engineers designing cars fight about it.

RE: CX2 Motor Heat Study
 

LOL. . . they only thing they agree on is that it works! :)