Have we gone that long without a heated discussion about cooling?
It is a big deal, and it is often problemmatic.
more to come,
Dean P.

As far as I know the importance of cooling goes in this order

ESC
Motor
Battery
Timer (which doesnt really need any)

Cooling concept that will be in corporated in the REvolutions project. A small centrifugal pump that is built in the backplate of the spinner and it channels the flow directly in to the motor.

But a centrifugal pump tends to fling the fluid out to the edge of the pump, never in to the center.

Why not just round the back of the spinner for laminar flow, then make the spinner ring a hair larger and perhaps with a sharp lip to separate the airflow into fuselage parts and cooling parts, with the rest of the assembly as you show?

Sounds good. The centrifugal compressor will pull the air in depending on the fin angle and direction of rotation. You are right although it is very effective when you go out from the center.

Does anyone have any pictures of how their plane is ventilated?

This is one of my big hurdles in convincing myself to try an electric setup. I don't have the faintest notion of how to build the fuse so it's properly cooled.

Guys,
One thing that has worked for my Stuka is to open a rear fuse vent that allows airflow through the cowl up over the motor and ESC then out the cowl or thought the fuse and out the back.

Best,          DennisT

The reason I was asking about the rain issue is that the esc in my R/C car goes haywire if it gets even a hint of moisture on it-driving the car in any sort of rain, or even over wet grass or a small puddle is an impossibility.  And, sometimes at the contest you have to fly in the rain.  Plus, I have on good authority that the guys in tropical areas like Tampa can take off in perfectly clear conditions and have a pop up shower completely soak them before they get to the square 8.  Thats kind of tough to avoid......  I didn't really think it would ruin the motor, but I wonder about those timers and speed controllers.....

Hi Guys,
Hunt and I were discussing this just the other day. It looks like waterproofing is in order for the entire motor/esc/battery/cooling passages bay. Fortunately, it is water, not nitro, so nitrate dope will work nicely. Heck, add color and really wow 'em all!

Motors shouldn't care about the wet, but I'd squirt some lube on the bearings after a drenching just to displace any unwanted moisture in them.

Properly cleaned electronics shouldn't care about clean rain water ... but 
There are water-based fluxes used in some PCB manufacture that are great both environmentally and in terms of the circuit board cleanliness that is possible,
but if they are inadequately cleaned off, then moisture makes them conduct again.
There are also "no-clean" fluxes that don't get appreciably conductive when wet, just corrosive.

ESCs and TIMERS and such really ought to be cleaned and conformally coated with a Humiseal, silicone, or Pyralene coating, but now I am being fussy and overly demanding.
Good PCB cleaning in manfacture solves almost everything. Conformal coating would make circuit repairs almost impossible.

Good stuff coming up in this thread,
Dean P.

Charles Berry told us long ago that rain water ingestion beneath a hood is beneficial to a motor.  He thus apprehended Maybelline at the summit.

Was this the same guy that couldn't get the seatbeat loose from his girl?


Randy

Real airplanes with round motors have small spinners, ingest air through a round cowl and control the outlet size/flow rate with cowl flaps.  The classic stunt look with a big spinner has its origins in cowling a single cylinder IC  engine, plus the Mustang/Spitfire look of WW 2.  We need to switch to the Hellcat/P-47 Look.  See Adamisin's Mythbuster. Another way that seemed to work well for me was the setup on my Panther, which sort of mimicked the light airplane flat engine look. Notice the big outlet in the bottom.

John

My biggest problem is preventing dirt from getting in my motors. 

John

Sounds good. The centrifugal compressor will pull the air in depending on the fin angle and direction of rotation. You are right although it is very effective when you go out from the center.

Awhile back Dean offered up the idea that we might be able to cool by pulling air forward through the motor, that is, pressurize the motor compartment ahead of the firewall then somehow force the air through the back of the motor and out the spinner.  Traian, your centrifugal fan concept could do such a thing, pulling air forward through the motor then venting it around the perifery of the spinner.  The inside to out flow would work to the strength of the centrifugal style fan too.

In none of m installations have I made any preparaton for rain - perhaps I need to think that through a bit more!  Unfortunately I have also been looking at new ways to improve ESC cooling that would also distrub the integrity of the shrink wrap.

Igor mentioned that even with triple sealing some water gets through.  My concern is that slightly ineffective sealing would also make it difficult for water to escape.  A little humudity trapped inside the ESC and heated by the ESC could become bad for the electronics.

It would not even have to be rainy - just humid.  As the ESC heats up it expands the ari around it inside the shrink wrap - that air flows out through what ever leak points exist.  As the ESC cools the air inside the ESC Wrap shrinks and draws in outside air. If that outside air is humid then it brings that water into the ESC.  Water needs to be kept out, and any water that gets in must be purged.
 

For a moment lets consider the other extreme.  What if we were to:
* Do all the good things Igor described to prevent any direct hits from large water droplets
* REMOVE the shrink wrap
* Rely on a free flow path, and the heat generated by the ESC to help keep it dried out.
* Of course in case of immersion...... PUNT!

I might "sacrifice" one of my Turnigy's to some testing...

Maybe there is a simpler solution. 

Why not wrap the ESC with its shrink wrap loosely in aluminum foil.  Seal both ends where wires come out.  The foil dissipates heat and is an effective barrier to moisture.  By loosely wrapping the ESC would always have room to breath.

If there's someone out there with an extra ESC kicking around, stripping off the shrink wrap and seeing if it'll run a motor when it's in a glass of water would be a very educational exercise.  I'd do it, but I've got engines running out of my ears and just enough electronics to fly the electric planes that I already have.

Now why didn't I think of that!  I'll supply the glass but you will have to pay for shipping.

Hi Scott,
Let's see ... the motor and ESC are always best when kept cool as practical, and the battery is happiest between 100F and 120F.
All your other aspects are highly dependant on how well the cooling paths are laid out and built.

Properly ducted tightly around and through the motor, 1/4 square inch of inlet (as seen from directly in front of the plane) is adequate, even plenty, for a 60 ouncer that consumes 350 Watts on average. I'll bet 1/3 of a square inch would do if done properly.
The ESC probably only needs half that.
The battery probably needs maybe 1/3 of a square inch of inlet, for the same power levels.

Exit area? The temps we see cannot possibly lead to more than a 10% increase in cooling air volume as a result of heating. If the outlet hole area (AS VIEWED FROM DIRECTLY BEHIND THE MODEL) is 10% greater than the inlet, you are golden. If it looks like a static port (big hole on the bottom) then you are back to the 2X or 3X inlet area rule of thumb, and you are making lots of drag without actually controlling the cooling outflow. Heck, with a big hole on the bottom, a series of continuous inside loops might choke the airflow and cause overheating.

Of course, if you just blow some air into a cavern full of parts and then just let it spill out, you are in terra incognita.

I remember the Melmouth 1 construction/design articles!
take care,
Dean P.

Sounds good. The centrifugal compressor will pull the air in depending on the fin angle and direction of rotation. You are right although it is very effective when you go out from the center.

I have been thinking ever since you said that and now I am strongly considering reversing the airflow from the back to the front.

How about some temperature readings? We are running Plettenberg 25/12 motor, Schulze 18.46 and 18.61 ESC with Thunderpower 5s 3900 Mah batteries.

Average temperatures after 6 minute flight:

Motor: 120 degrees Fahrenheit
ESC: 115 degrees Fahrenheit
Battery: 110 degrees Fahrenheit

We are flying in the HOT Florida sun (92-95 ambient air temp) and measurement of the temperature is accomplished with a laser temperature gauge directly on the components immediately after flight.

Does anyone have recommended safe temperature ranges?

Jim Smith

How about some temperature readings? We are running Plettenberg 25/12 motor, Schulze 18.46 and 18.61 ESC with Thunderpower 5s 3900 Mah batteries.

Average temperatures after 6 minute flight:

Motor: 120 degrees Fahrenheit
ESC: 115 degrees Fahrenheit
Battery: 110 degrees Fahrenheit

We are flying in the HOT Florida sun (92-95 ambient air temp) and measurement of the temperature is accomplished with a laser temperature gauge directly on the components immediately after flight.

Does anyone have recommended safe temperature ranges?

Jim Smith

Hi Jim,

Considering your high OATs, your system temps are very good. They are all within safe limits.

In answer to your question, the rough rule of thumb for all three items is:

IF YOU CAN TOUCH IT FOR SEVERAL SECONDS WITHOUT PAIN THEN YOU ARE OK.
       
      (I suggest using your left hand if your right handed, please don't ask how I came to this conclusion  )

BTW: Normal human touch without pain is roughly somewhere between 115 to 125

The temp numbers are:

MOTOR 

The Ideal world for our motors would be somewhere colder than 100 degrees below ZERO.    ....... For our purposes up to 130 F is still OK without doing any serious damage to the magnets or epoxy. When you pass between 150 to 180 you are shortening the life of the motor and lowering it's performance permanently. When you pass 180 to 220 there is a high risk of epoxy failure and having one or more magnets cause some serious damage inside your motor. It should come as no surprise that there is a wide variance between the very cheap motors and the higher quality motors like Plentenberg, Hacker, AXI, etc. when it comes to temp. tolerance. 

ESC

These magical wonderful devices should be kept under 120 F. Best is as cool as possible. They will tolerate higher temps, but they are subject to problems/failure if they overheat. Over 140 to 180 and trouble is sure to follow.   

BATTERY

The opposite from the above is true here. They like to be "warm". Their ideal world is somewhere between 90 F to 115 F.  If they are below about 50 to 55 F you should try to warm them up. (search this site for methods guys use to do this). You will NOT have full power available if your batteries are below 50 to 55 F, and it goes down fast from here.
This means that, for many, they may have to make sure the airflow to the battery is decreased during cold WX flying to keep the battery above this 50 to 55F temp. At the higher end, our batteries do not like high temps either. Above 130 to 140F and you begin to shorten their life span. Above 150 to 160 F and they become very unhappy.

Easy gauge:  If it hurts to touch it, it is too hot ...... If your tongue sticks to it when you lick it, then it is too cold. 

MEASURING TEMPS

Scotts suggestion is excellent. In addition to mail-order, these inexpensive temp gauges can be purchased at most LHS that carry RC Cars. They are usually more accurate than the hand held gauges. (The hand held gauges are OK for our use, the other is just a little better.) If you are really interested in monitoring and controlling your systems temps, then you may want to use the outstanding "Eagle Tree" onboard system. Many on this site have used it. It records ALL temps, RPM, Amps, A/C speed, etc. and plays them back on your computer and or plots a graph for your entire flight.

The temp #s I have given above are from reading many mfg. sites, and talking with my ERC flying friends who are aerospace engineers, and from personal experiences and experiments.  ..... Of course, your milage may vary. 

Regards, 

Randy,
Thanks, now if I could find someone to build one of these with two thermocouples one for the inlet side and one for the exhaust with an RPM sensor for testing on my F2C gear in a less than 30 gram package.

     

Scott

I can say 2 things:

1/ Once I spoke with Mr. Vaclavik (AXI boss) on field when we wanted push him to AXI 2826/13. And one of points he wanted to know was the temperature. My AXI 2826 had after flight 60degrees Celsia AT BEARING ... we measured it by infra thermometer. The rotor was ~10-15 degrees colder. He told us that it is temperature on edge. Motor survived ~400 flights and when retired, bearing does not show any wear.

2/ Scorpion 3020 which I had this seasone and which is clearly overloaded goes regularly to 90 degree Celsia, in hot days up to 100, need new bearing, it is clear when I turn the prop.

sorry

60deg C = 140F
100deg C= 212F

That is right, just remember that bearing is much warmer than surface of the motor. I was abble to get in to the bearing, because I have an adjustable adaptor between firewall and motor (I had there OS LA47 mounter on firewall before) so the back bearing is on eyes.

Do not you know what is preservative for? ... to preserve from unwanted drops