Water cooling information

[Shooter]

Here a picture of these jackets:


regards,
manuel

Just something to think about with these jackets. It seems that if the ID of the jacket was a close fit to the motor can, we could get transfer of heat from the motor to the jacket by direct contact (heat sink). Advantage here is that the water flowing through the spiral passages takes heat from both the motor directly (bottom side of flow) and the jacket (top side of flow). One step further, making the jacket out of a better heat sink material (Cu?) would further help. I'd be curious if anyone else agrees. I could machine up one of these, but Cu is extremely expensive, and it would probably take me an easy 3 hours.

[ManuelW]

Hello,

well the ID of that water jacket is not that tight. I'd guess the gap around 0.2-0.3mm or something like that. I think a tight fit is almost impossible as when the ID is a little too big there is no direct contact but also no real space for the water to flow and if its a little to small you can simply not mount it.
So I think a style like the one I showed is the right one. Aluminium is in my eyes also the material to go. Easy to machined, excellent heat conductor and way lighter than copper.

regards,
manuel

[1945dave]

Just something to think about with these jackets. It seems that if the ID of the jacket was a close fit to the motor can, we could get transfer of heat from the motor to the jacket by direct contact (heat sink). Advantage here is that the water flowing through the spiral passages takes heat from both the motor directly (bottom side of flow) and the jacket (top side of flow). One step further, making the jacket out of a better heat sink material (Cu?) would further help. I'd be curious if anyone else agrees. I could machine up one of these, but Cu is extremely expensive, and it would probably take me an easy 3 hours.

Shooter I really think this comes under the heading if it ain't broke don't fix it. Any small additional gain that could be derived by refining the basic cooling jacket design is so marginal that it doesn't make the effort worth it. For example, the heat sink concern. This jacket like most others have two "O" rings holding the jacket and breaking the direct contact that would be required to qualify as a heat sink. I have made a cooling clamp chamber that would come closer to what you seem to want. Essentially it was a clamping cyclinder that had a split down the middle and when tightened it physically gripped the motor tightly and with a little dielectric heat transfer compound qualitfied as a heat sink. Then to further assist the transfer of heat I had four tubular paths through the clamp that water passed through. It worked well but was rather heavy compared to traditional cooling jackets so I doubt if the gain justified the design.

Dave

[martin]

This is why the good old fashioned coiled tube cooler works so well, you have every coil touching the motor transfering heat from the motor to the pipe along with the water cooling the tube, add to that heat transfer compound & youve got pretty good cooling.None of these coolers with o rings transfer heat directly from the motor they only disapate heat from the water & not direct heat from the motor can.

[1945dave]

I find it interesting that you seem pretty convinced that coils (with transfer compound) are better than water chambers. You know that the big problem with our electric brushless motors is we are cooling the wrong component. The can is just the part we can cool the easiest. The heat is generated at the armature inside the motor can and ofcourse never actually touches the motor can. Just the same The out runner design is conceptually better at heat transfer than inrunner styles. But there are limitations in size and space. I think you need to look into a freon cooling system that works inside the can. <SMILE>

dave

[jcald2000]

Dave, the heat is generated in the wire windings (resistence) and they are next to the can in an inrunner, so the water in the can is next to the heat source with a good conduit. Out runners are backwards, windings are in the middle and the heat conduit is thur the shaft and bearings.

[Shooter]

Shooter I really think this comes under the heading if it ain't broke don't fix it.

Yep, yep...... I hear ya. Just grasping at straws at this point. No matter what I tried up north resulted in temps in the 140-150's. Speeds were 52-54 (spec power UL-1 motor, esc, props M445, M545, 645 cut down to ~43mm, etc...). Turns out I might just have to prop down and live with slower speeds when the water is hot (ran a few times at the club pond with smaller props 42x55 that someone loaned me, about 49mph and achieved 130° motor temps).

I did try a small container full of (4) ice cubes and it actually worked well on the bench. Ice remained for nearly 140 seconds at 10cc/s water flow and 90° inlet water temp. Outlet temp started at 68° and worked it's way up to 88°. I can share the data if anyone is interested. Essentially it does prove to be feasible if you are willing to deal with the extra weight of water (after the cubes melt), the 'sloshing effect', and the extra complexity. I ran it in the boat once today and my temps came back in the high 120's with the bigger prop, but there was some water in the boat most likely due to a bad connection and/or condensation from the ice. Fun stuff.

[srislash]

Just to throw this in there for the racers in the crowd,I used to use a container of ice and water with a 12V pump between races to get my motor ice cold before running.This was the old brushed days in the Puget Sound but it did keep my temps within reason for the duration.Just had to mention it as Shooter was talkin ice.

Shawn

[1945dave]

No matter what I tried up north resulted in temps in the 140-150's. I can share the data if anyone is interested.

Shooter, are we talking motor temp and ESC temp? What is your ESC running? I agree 120 degree motor is better than 150 degree motor but if the ESC and batteries are okay how bad is a 150 degree motor?

Dave

[Shooter]

Roger that. A guy at our club mentioned the same thing, except with a syringe.

Regarding the ice canister, here is the data I collected. (4) cubes seems to be adequate capacity for a 6 lap race. The cubes will be gone by lap 4/5 or so, but the temp differential achieved early on is very beneficial for motor/esc temps at the end. The test was somewhat conservative because my flowrate is probably a bit high (10cc/s). If anyone has actual measured flow rates with a single rudder intake, please chime in.

Thanks,
Pete

IceCooling.pdf

[Shooter]

Dave, I was referring to motor temps. Measured on the windings near the wires coming in (found to be the hottest in my experience), 30sec after the run.

[ray schrauwen]

I've seen Terry Davis add a homemade wire cooler. just block of aluminum with 3 holes for wires drilled through it, then cut so 2 bolts can clamp it to the wires and a last hole with a tube to flow water through. It was pretty neat. I might make a pair.

[1945dave]

Dave, I was referring to motor temps. Measured on the windings near the wires coming in (found to be the hottest in my experience), 30sec after the run.

Shooter, I agree with you. I sometimes wonder if many of the guys that respond to these discussions ever read the original post. A while back I asked how should you align the cooling jacket on a can that is longer than the jacket. I expected at least one serious answer that took a position and justified what they suggested, yet, not one ever came forward. I slide the jacket as close to the wire lead endas posible and leave any gap on the shaft end principly because the shaft end almost always has a water cooled end mount so why not try to cool the other end? Works for me.

Dave

[ray schrauwen]

There is also debate about where you exit the water from the jacket. I say the exit should be at 12 o'clock and as far back as possible so it fills up completely. SOme have said if the water exits the side the jacket does not fully fill up and cool the topof the motor. I have nno idea but, I do it because Lehner does it (I think) and it seems like the right thing to do.

[1945dave]

There is also debate about where you exit the water from the jacket. I say the exit should be at 12 o'clock and as far back as possible so it fills up completely. SOme have said if the water exits the side the jacket does not fully fill up and cool the topof the motor. I have nno idea but, I do it because Lehner does it (I think) and it seems like the right thing to do.

There should be no debate on this. You are 100% correct the exit needs to be at the highest point of the jacket possible. To do other wise is just lazy or careless. There would be no justifiable reason to on purpose place the exit anywhere else.

Dave