Air Cooling my x5

[vanilla ice]

But cooler = more efficient right?

[itchynackers]

I plan to monitor the motor case heat via the hand method for a bit. If it feels too hot (whatever that is) then I'll air cool. Just trying to decide on the best configuration for the holes. I'm not convinced the previous discussions/placements are optimal since the placement seems to be based on non-representative air movement over the outside of the motor.

[El_Steak]

I compiled some test data with different hole patterns here:

viewtopic.php?f=2&t=9791&start=405#p278852

I also did an additional run (after RUN "E") for which I double the size (surface area) of all the holes around the perimeter. The results where pretty close to RUN E (no improvement).

If you have other ideas for hole patterns, try it out and share with us, but if you want to end up with a meaningfull data set, you definately need to install a temp probe inside.

Like Icecube, I stopped worrying about it. On my commute, the motor will reach 130-135C but will not climb higher, I guess it reaches some sort of equilibrium at that point. I have 3000km on it and it still runs great. Should

[itchynackers]

Yes, your data seemed to be the most meaningful, as it used real conditions, not smoke on a bench conditions. Also, your hole patterns were symmetrical (cover to cover). I just had a hard time believing that asymmetrical patterns (holes near axle on right, holes near perimeter on left) had any meaningful purpose.

You seemed to have fixed the cooling. Do you think there is anything that can be done to improve exposure to the elements (sand/water entering holes)? Based on your data, would placing bits of screen over the holes be a good comprimise between cooling/exposure?

[El_Steak]

I opened up the motor after about 1500km with the holes in the cover and didn't see any dirt or rust inside. I don't go offroad with my bike, but I rode through a few nasty storms.

Having all those holes in the covers can let some water in the motor but it also offers good ventilation for it to quickly evaporate (especially when the inside temps reach 130C !)

With the type of riding I do (commute on the road), I don't feel that its necessary to install any screen or mesh on my covers.

Those 9c motors are so cheap that I consider them semi-expendable. If I end up killing it after a season or two, I'll just buy a new one

[John in CR]

El Steak,

Thanks again for your efforts re air cooling. You really went the distance effort wise.

The results still have me confused. Other than the heat created directly in the magnet backing ring, almost all of the heat of a sealed hub motor must be transferred from the stator through a fairly turbulent layer of air, then through the covers to the environment. Heat transfer is a pretty slow process. Air has a low specific heat capacity, so transferring heat to it quickly heats it up, which means in an unmodified hubbie we've got a hot stator creating hot air to transfer the heat out through the cover.

The rate of heat transfer from the stator to the air is inversely related to the temperature of the air. That's why on a hot day a car can much more easily overheat even with a well functioning cooling system. ie The temp of the air flowing over the fins of the radiator is warmer, so the car is less able to shed waste heat.

What this means all means to me is that to the extent we get fresh ambient temp air flowing through our motor by ventilating them, that the motor should cool noticeably better. That's exactly what I've seen, though not quantified, with the ventilated hubbie I have, however, El Steak didn't see the same results. The only potential explanations I've come up with are that either the motor isn't getting air flow through it while in motion due to the outside air flow, or the air flow through it is mostly bypassing the hot stator making the airflow on the stator somehow less turbulent than with a stock sealed motor.

I don't have an answer, but hopefully I'll come up with one soon, because I'm going to try to take a 9x7 9C up to 8 or 9kw running it as a mid drive at 130v nominal with the motor ventilated in a housing with intake air directed at the intake holes in the cover and spitting the heated air out through the rear of the housing.

John

[itchynackers]

That seems like what I'd like to do. Based on the flow lines in this video... http://www.youtube.com/watch?v=sY3r0EGqmRE it seems like the air wants to enter the hub at the very front (perimeter), and exit at the lower rear (also perimeter). So I thought I'd drill all my holes as close to the perimeter as possible.

[The Mighty Volt]

what's the name of that conical tool used to drill the holes? Thanks.

[John in CR]

what's the name of that conical tool used to drill the holes? Thanks.

I just used a center punch to make evenly spaced dimples so the drill bit wouldn't walk around. I just used a drill bit and a hand drill to make the holes.

[TylerDurden]

what's the name of that conical tool used to drill the holes? Thanks.

"Step-drill."

[adrian_sm]

what's the name of that conical tool used to drill the holes? Thanks.

Do you mean a step drill? Here is a link to the one I used.

[The Mighty Volt]

what's the name of that conical tool used to drill the holes? Thanks.

Do you mean a step drill? Here is a link to the one I used.

That's the one. Thanks Adrian!

[John in CR]

I don't see how a step drill is useful for shaping these holes. To maximize air flow through any hole you want a smooth and rounded radius transition to minimize turbulence. Also, for the perimeter holes I've made in 3 sets of covers there wasn't clearance for a step drill, because they butted up against and into the bolt flange to position the hole as close to the perimeter of the interior air space as possible. Those aluminum covers are so soft that it's really easy to do with a hand drill, and the same bit works well to taper the holes by taking your time and an angled circular movement with the drill. The only challenge I found is to get uniform placement of the perimeter holes, because my preference is to make lots of small holes to reduce the size of debris that could enter. eg On my most recent set the holes are quite angled and small enough diameter compared to the material thickness that when viewed directly from the side the hole is only a small slit to the interior, so a rock much smaller than the hole will just hit metal and bounce off unless it flies at the motor at just the right angle. Add that the holes are moving and the rock has to have perfect aim, perfect angle, and is coming at the perfect speed.

John

[The Mighty Volt]

That's what DB uses, he holds up a small conical bit in the video and says he hopes that whoever invented this bit deserves a lot of money!!!

The thing of the step bit is that it allows you to start the hole smack-dab where you want the hole to "finish" so to speak.

[icecube57]

Would scoops like this help force air into the hub.

[John in CR]

Would scoops like this help force air into the hub.

No. Jeremy did a calculation in the other thread. Forced air like Arlo1 did with fans on the stator spokes to suck air in from the outside on one side, or a centrifugal fan approach are really the only options. That is unless you have a drum brake on one side whose stationary cover could be used to mount a powerful ducted fan to blast air into the motor, but I'm the only one around here using motors where that is viable. The last option is modding the one side cover to take a bearing with a much larger ID, and using the extra area between the axle and the bearing to force more air through. Someone did that with good success though I've lost the link to that video.

The moral of the story is trading an X5 for a 9C was a big step down in power. Sure your 5303 was hard to drive, but no way a 12fet was going to do it, and 18fets cuts it thin on the hard to drive motors. What you needed was the big 24fet like I'm using to drive my even harder to drive hubbies without issue.

You're a big guy like me, and we need manly motors or higher speed motors with a gear reduction to make them manly. Do you want me to tell you how I plan to dependably run my lowly 9C at 4kw continuous and 7-9kw peaks?

[icecube57]

The 9C is a step down from the x5. I dont regret it at all. That was a big weight hit. I had the GM before which was a 9x5 and that thing was hard to cool but I finally got it to take 4k continuous. This being a more appropriate winding should run cooler than the GM. Im chasing after that same type of build i had previously with the Gm. I expect some performance but not stellar. With the 9C Im looking for 88v 65A possibly more consevative than that. I got the GM to do a hard 15 miles without overheating after the bugs were worked out but that was high speed 40mph riding. It did have the same holle pattern as I have in my 9C now. I honestly dont have the on the road playground that many of you have. I dont do technical riding like methods did with his bike recently. I dont tackle alot of steep grades unless i have a good running start.I have to survey areas and plan rides that I think the bike can handle. The topography of Georgia sucks to where its a challenge to go anywhere on my bike with out being under full power and wasting whs. I can run to the store and get small bit of groceries and stuff but thats still a challenge with the terrain, topagraphy and nature of the drivers around here makes a street rod less appealing and my life more valuable. The build is shifting to be recreational riding with the ability to hold my own when i need to. I do feel i could hange with GinDC if i ever had to tag along on one of his rides. But I can do that type of riding here not even in a wet dream. Id like to take my bike to several areas and explore the city or town. The weight of the X5 is an advantage but its very unappealing when transporting my bike. But please do tell me your secrets.

[icecube57]

Just an idead a friend and are are fooling around with.

[El_Steak]

i took a different approach to cooling for next season. I lost 20 pounds since november and i will probably be under 150 before next season starts.

this should help reduce heat generation while climbing and accelerating. It will also increase my range, improve performance and reduce tire wear

my girlfriend thinks i am loosing weight to improve my health and looks, but its all about the ebike baby !

[John in CR]

Good job El Steak. Nothing beats increasing that power to weight ratio. Congrats on the hard work. Hopefully I'm not far behind, but I'll never see 150, but low 190's sure would be nice.

[El_Steak]

thx, I'm just 5'7" hence the 150 pound.

It wasn't too hard actually, I'm just counting my calories using a little ipod application.

[oldpiper]

thx, I'm just 5'7" hence the 150 pound.

It wasn't too hard actually, I'm just counting my calories using a little ipod application.

That's why I find it so hard to lose weight,I don't have an iPod! Thanks, El Steak!

Cameron

[John in CR]

thx, I'm just 5'7" hence the 150 pound.

It wasn't too hard actually, I'm just counting my calories using a little ipod application.

That's why I find it so hard to lose weight,I don't have an iPod! Thanks, El Steak!

Cameron

I'll pounce on that excuse too, though I know the real excuse is too much time at the keyboard much of which was taken away from activities involving physical movement without adjusting caloric intake. If anything I take in less calories than 15 years ago.

Computers and video games are the primary cause of greatly increased obesity, yet McDonalds and Whoopie pies get the blame. This misguidance has given Big O, the 1st Lady and others the idea that they somehow have the right to tell you what you can and can't eat, and they actually believe it's their responsibility to do so.

[docnjoj]

Hey John
I don't care to debate the Healthcare politics but I do know that Obesity and Diabetes are the two fastest growing killers in America. Maybe the Gov't shouldnt get involved, but you and I ( I'm 6'2'' and 230 lbs) have weight problems. It is considered an epidemic by CDC. Our bikes may be the only thing that save us from sure death or disability. Sorry to get into this but I teach Health Care Administration for a major university and have to rehash this sh*t every quarter.
Warm personal regards
otherDoc

[Hyena]

I reckon a big blower mounted to the chain stay and pointed at the largish holes would be just as effective at cooling and easier to implement than playing with fins and internal fans. When I get time to actual make and test something is another issue...

Our bikes may be the only thing that save us from sure death or disability.

Good for you guys, my bike will CAUSE me sure death or disability