The first smoked Cromotor?

Philistine

100 kW
Joined
Aug 15, 2010
Messages
1,736
I don't speak Italian, and maybe this has been discussed elsewhere (apologies if so), but is this Esoria and those crazy Italian guys with the Cromotor? Looks like some magic smoke coming out of the holes? Certainly isn't sounding too good. Having said that I was scratching my head at some of their videos as to how far they were pushing the motor. Is this video old news and I missed the discussion?

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No dicks cut into the side covers? Shame.
 
If you're going to open your motor to the environment to run it at higher power, at least get the hole placement correct or it does little good. Then you still have to find the limits of your system with gradual increases and maximum loads it will see. Even just using your hand to monitor temps after hard runs is a big help learning the limits. Running to failure is expensive and doesn't really tell you much except that you passed the failure point.
 
Just sounds like a hall sensor. I have have smoke coming out of the X5 lots of times and it was ok.
 
If you're going to open your motor to the environment to run it at higher power, at least get the hole placement correct or it does little good. Then you still have to find the limits of your system with gradual increases and maximum loads it will see. Even just using your hand to monitor temps after hard runs is a big help learning the limits. Running to failure is expensive and doesn't really tell you much except that you passed the failure point.

John, (sorry if this is a totally inane question), where should the holes go? I have not got around to venting my hubs, and I see you on multiple threads pointing out the stupidness of others venting placements. Maybe you have done this in a wiki I don't know about (apologies if everyone is groaning at me on this), but please tell us where the venting holes should go and how they should be placed? I really want to vent my hubs but I see a bunch of different info on the forum...?
 
Just sounds like a hall sensor. I have have smoke coming out of the X5 lots of times and it was ok.
Yep. Pump 100+ volts into a motor, take it to 80+kph, cause smoke to billow out, then, when it makes a sound like a chunk a steele being smashed into a cheese grater..... Probably a blown hall..... my thoughts exactly.... :lol:

EDIT: That would be what was creating the smoke, the blown hall.... :lol:
 
I think the holes should be located exactly in front of the winding. At least, worked for many persons from now and is a sinple mod to do. Keeping hot air is never hood for lowering the temp of the motor.

By doing that, a bigger portion of the radiating IR energy from the winding can exit directly without being reflected by the side cover. Not most of the energy but it help.

What i mean is that it is not JUST a question of air cooling, but also it is a question of radiating heat.

I'm pretty confident about the way i placed the holes in my 5403.

I'm also thinking about adding some angle to force the air to exit thru these holes but i will also need to add some holes on the lower diameter to allow cold air to enter.


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Doc
 
Philistine said:
Just sounds like a hall sensor. I have have smoke coming out of the X5 lots of times and it was ok.
Yep. Pump 100+ volts into a motor, take it to 80+kph, cause smoke to billow out, then, when it makes a sound like a chunk a steele being smashed into a cheese grater..... Probably a blown hall..... my thoughts exactly.... :lol:

EDIT: That would be what was creating the smoke, the blown hall.... :lol:
Nope I have had smoke coming off the windings but they were/are still ok. I have done this ~30+ times each time they are just getting a little blacker. The failed hall was the solder melting off on of the hall sensor legs.... Im still riding my X5 buddy its works just like the day I got it.
Edit: BTW it doesnt matter how many volts you push a motor with. Voltage determins speed, its the amps that kill motors. The more amps you flow through the windings the hotter they get.
 
I was told they either went or tried to go 100mph in that video and that was the result, not sure if they made the number or not.

My own opinion, sounds like a blown hall sensor and I'm guessing the motor is OK. I was hoping to see flames not a few wisps of smoke needing forced air to force them out :( or :) I guess :lol: These guys could be the mini Italian version of Luke when it comes to destroying stuff from things I'm hearing :D

I can get my bike to 100MPH I've already figured the numbers I need to do it. If they actually did reach 100mph or even got over 90mph on that setup and the motor didn't explode into a giant plasma ball it would be pretty amazing. In a 26" wheel with the normal 4 turn Hubzilla in a 26" wheel it would take 190V @ 250A to attain 100mph unless some aero work was done. That's almost 48KW into the hub motor and 7KW of that is going into heat! I'll try to find out more details.

I can tell you that after Ebike Stig raced my bike for 13 laps at 88WH/mile in one of the final races at grange and my motor got pretty warm, what I consider hot, after sitting for about 5 mins (I could still barely hold my fingers on it so pretty warm for a person without hyper sensitive fingers like me, guessing internal temp was over 100C, but this is the same temp the side covers on my stock 9C 8x8 get to in daily riding so I knew it wasn't too hot) as everything started to get to the same temp. Put a blower fan on it for 10 mins and it was back down to ambient and never got warmer.

I found a 300V 300A capable BLDC for about $1700 USD. I could use that to probably go 100mph on my setup with ventilating the motor but I'm not going spend $1700. Power wise with a 20.2" tire like I have it would take about 220V at 200A for a total of 44KW, but I'd get to top speed way faster and would produce less than 5KW of heat.

If I only had $1700 I didn't care about....

P.S. I might have one time or another spied a water cooled version of the Hubzilla, but it was a custom one off job if I did see it and not for general consumption (get a real motorcycle you suicidal maniacs!) :mrgreen:
 
Doc,

Didn't you run any calculations first? Even if your windings had an emissivity of .9 (I doubt it's even close), and they completely filled your hole area and were able to radiate the full 180° from that surface, that's still only 162cm2 of radiating surface area (.0162m2). That means even if your windings were at 300°C you would only radiate 88W of energy from those holes, and that includes both side covers. Even at 400°C, way past motor failure, you'd only radiate 167W. It just doesn't get hot enough and doesn't have enough surface area to radiate significant amounts of energy, and you need to dump way over 10 times heat as can radiate through those holes.

As further evidence that radiation is minimal, the ventilation holes I make in covers have almost no line of sight exposure to the windings, because I use small holes at the extreme perimeter cutting almost into the lip for the magnet ring. If radiation was significant, then my covers would get about as hot as they do with a sealed motor. Even at double the power that starts to overheat my sealed motor, the ventilated version of the same motor has covers that get only warm. The area between the spoke flanges gets only slightly warmer than the covers. These great results can only be explained by a significant fresh air flow through the motor, and the shape and location of the holes can have a drastic impact on the flow.

John

Doctorbass said:
The holes Should be located exactly in front of the winding nowhere else.

By doing that, a bigger portion of the radiating energy from the winding can exit directly without being reflected by the side cover.

What i mean is that it is not JUST a question of air cooling, but also it is a question of radiating heat.

I'm pretty confident about the way i placed the holes in my 5403:

Doc
 
Your calculations seem realistic Zombiesss.

The question remain, wich motor will reach the highest output power .. well .... the fastest speed.. the 5400 or the Cro 8)

That will be interesting to see any developpment about that :mrgreen:

Doc
 
John maybe i forgot to mention something important. Evacuated radiating heat is certainly not as important as air cooled you are totally right abot that. But i might try the idea that Lowracer did few years ago with a high pressure blower that was blowing air in the side cover holes. Having larger holes like i did, might help having more airflow input thru a really close exit of a air blower..

About the hall sensor that have the solder that melt, i think that using the heat shrink might help "keeping the solder" in place, helping to keep electric contact between the wire and the hall sensor lead. But probably that making a little loop aroun dthe hall sensor lead migt help.... or maybe spotwelding the wire to the hall sensor lead would eliminate that problem?..

Doc
 
Holes help, particularly with quicker cooling once you stop, so you can go out for another heat. But at some point, all they really do is let the smoke out. If you are way over the like, it's going to take more than some holes to help. You start needing not just air blowing in those holes, but something like a liquid nitrogen spray.

One thing I haven't seen done yet, is set up a mister nozzle to spray the winding through the holes. Likely wouldn't work at high speed, but maybe usefull on the cool down run?
 
Dog,
I have a functional water misting system. I really don't know how much it helps yet though. I planned on using it at Pikes, but I'm not sure I need it now.
 
Misting the covers, or misting the windings? Misting the covers works good for cooling a hot motor that nearly overheated faster. Not sure though, if just misting the covers would do any good if you are really pushing a motor. But it surely would extend the run time of a motor that is close to the line, but not really past it much.
 
Someone needs to make a side cover that is a big fan. One side intake,one side exhaust. Constant airflow when running, or if you get in the red, prop up the rear and just run it under no load to push air over it. I know this would work well, as I push my RC heli electronics past design parameters easily when there is a big "fan" above them :^)
 
dogman said:
Misting the covers, or misting the windings? Misting the covers works good for cooling a hot motor that nearly overheated faster. Not sure though, if just misting the covers would do any good if you are really pushing a motor. But it surely would extend the run time of a motor that is close to the line, but not really past it much.

When I built it, it was for a vented 8x8, so it was misting the covers and the windings. Now I have a liquid cooled 6x10, so its just the covers. But that is good, since the covers are now hotter than they would be without the liquid oil.
 
With no air intake holes there is no real air flow, just a bit of extra turbulence in the area of the holes. With intake holes closer toward the center, the flow that goes through the motor will follow the path of least resistance, which is hugging the insides of the covers. With holes located over the windings like that the flow will mostly bypass the windings on the way out. To combat that effect I put curved blades right where Doc put his holes, and those blades deflect the spinning flow of air away from the covers directly at the windings. These blades also ensure that as much air as possible gets up to full rpm near the perimeter to maximize the centrifugal force pushing it to the exhaust holes at the extreme perimeter.

I'm sorry Doc but I believe "exactly in front of the winding nowhere else" should be retracted, since many others follow your example.

In addition to as close to the perimeter as possible which requires smaller and more numerous exhaust holes so the air doesn't exhaust prematurely, the exhaust holes should angled and shaped to minimize the negative effects of the holes moving relative to the outside environment as well as actually enhance the flow by creating a low pressure region inside the leading edge of the hole without creating a high pressure region at the trailing edge that would cause turbulence which is extremely disruptive to flow, since our centrifugal fans (the motor shells themselves) don't have an outer housing to protect and direct the flow like a typical blower has.

Just like I couldn't expect to build a controller simply assembling some of the parts required, air flow systems and heat transfer require a lot more design effort than just putting some holes in the side covers. Unlike a controller, which will either work or not, opening the motor at all will have some beneficial impact. Unfortunately that has lead many to settle for horrible air flow designs....drilling round holes in a pizza pan doesn't make it an effective fan blade. Why open the motor to the elements only to achieve 10-20% of the cooling effect possible?
 
shock said:
Someone needs to make a side cover that is a big fan. One side intake,one side exhaust. Constant airflow when running, or if you get in the red, prop up the rear and just run it under no load to push air over it. I know this would work well, as I push my RC heli electronics past design parameters easily when there is a big "fan" above them :^)

That's exactly what my ventilation approach tries to optimize, but not in the manner you are describing. An axial fan might move some decent air at the wheel rpms we run, however, the flow with axial fans is very easily disrupted by influences of air movement in the environment not in line with the direction of flow, AND flow restrictions have a major impact on flow because a low speed radial fan can't generate pressure.

OTOH, a hub motor is very easily turned into a centrifugal fan. In factory form the hubmotors I've been using for years hit their thermal limit at 4-5kw continuous turning almost 600rpm or more and moving through the environment at 35mph or higher. My son uses one that I turned into a centrifugal fan, and we haven't hit it's power limit yet even running over 10kw up a few miles of steep mountain road. He's being a puss and doesn't want to let me mod the controller to push it well past the 137A battery side current limit it has now.

I just finished a larger diameter scooter hubbie and I'll post a thread with pics of how I modded the motor once I test it in real world use. The stator has about twice the surface area of the one my son uses, so as long as I can get enough air flow through it I'll be able to run it at twice the continuous power. The greater diameter will be a big help in getting more flow, so it's not unreasonable. I'm also trying something new to get significant air flow through the magnetic gap, but I want to run the motor first before I share since the hype and unsubstantiated claims and wild predictions of some in the forum go too far.

John
 
John in CR said:
With no air intake holes there is no real air flow, just a bit of extra turbulence in the area of the holes. With intake holes closer toward the center, the flow that goes through the motor will follow the path of least resistance, which is hugging the insides of the covers. With holes located over the windings like that the flow will mostly bypass the windings on the way out. To combat that effect I put curved blades right where Doc put his holes, and those blades deflect the spinning flow of air away from the covers directly at the windings. These blades also ensure that as much air as possible gets up to full rpm near the perimeter to maximize the centrifugal force pushing it to the exhaust holes at the extreme perimeter.

I'm sorry Doc but I believe "exactly in front of the winding nowhere else" should be retracted, since many others follow your example.

In addition to as close to the perimeter as possible which requires smaller and more numerous exhaust holes so the air doesn't exhaust prematurely, the exhaust holes should angled and shaped to minimize the negative effects of the holes moving relative to the outside environment as well as actually enhance the flow by creating a low pressure region inside the leading edge of the hole without creating a high pressure region at the trailing edge that would cause turbulence which is extremely disruptive to flow, since our centrifugal fans (the motor shells themselves) don't have an outer housing to protect and direct the flow like a typical blower has.

Just like I couldn't expect to build a controller simply assembling some of the parts required, air flow systems and heat transfer require a lot more design effort than just putting some holes in the side covers. Unlike a controller, which will either work or not, opening the motor at all will have some beneficial impact. Unfortunately that has lead many to settle for horrible air flow designs....drilling round holes in a pizza pan doesn't make it an effective fan blade. Why open the motor to the elements only to achieve 10-20% of the cooling effect possible?

John, I agree and i also corrected my statement.

This is tempting me to retry what i did 2 year ago for my giant with the 5303. but that i never ahd the gain in cooling effect due that i made the holes in the opposite angle after i swaped both side cover when i made the holes :roll: :roll:


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Doc
 
Hey Doc,

I'm just happy we're back on the same page. In that pic, what is that gray ring on the hubbie cover between the ring of holes and the brake disc? I don't remember seeing that before.

I've been spending some time today running numbers, and using some conservative but I think reasonable estimates of stator surface areas and convective heat transfer coefficients, and limiting stator temps to 200°C, it looks like our 200mm motors are going to be limited to somewhere around 2500W in heat rejection. Hopefully my estimates were overly conservative. Your X54 will be somewhat more capable due to a lot more exposed copper surface, but definitely do your stress testing incrementally if you're able to run a continuous load at those levels. Also Zombiess' idea that he's going to be anywhere near peak efficiency at such high power isn't realistic at all, since peak power will be more in the mid 70's in efficiency.

On another note, I was running numbers on oil cooling, and it's simply not the answer, not for maximizing continuous power from our hubmotors. The reason is because the magnets have such a low thermal limits and the outer shell can't be allowed to exceed that limit. Since the external surface area is unchanged and the heat is dissipated to the environment the same, then the continuous power limit is virtually the same as from the factory with only air sealed inside. We don't typically operate continuous, so oil cooling will provide some benefit, but I certainly don't see it being better than air cooling, which I've proven to double the continuous power handling of my motors. I get on the highway running at high speed, and I have to climb mountains, so I have to build for continuous operation, and I have no interest in running motors past stator saturation.

John
 
John in CR said:
Hey Doc,

I'm just happy we're back on the same page. In that pic, what is that gray ring on the hubbie cover between the ring of holes and the brake disc? I don't remember seeing that before.

I've been spending some time today running numbers, and using some conservative but I think reasonable estimates of stator surface areas and convective heat transfer coefficients, and limiting stator temps to 200°C, it looks like our 200mm motors are going to be limited to somewhere around 2500W in heat rejection. Hopefully my estimates were overly conservative. Your X54 will be somewhat more capable due to a lot more exposed copper surface, but definitely do your stress testing incrementally if you're able to run a continuous load at those levels. Also Zombiess' idea that he's going to be anywhere near peak efficiency at such high power isn't realistic at all, since peak power will be more in the mid 70's in efficiency.

On another note, I was running numbers on oil cooling, and it's simply not the answer, not for maximizing continuous power from our hubmotors. The reason is because the magnets have such a low thermal limits and the outer shell can't be allowed to exceed that limit. Since the external surface area is unchanged and the heat is dissipated to the environment the same, then the continuous power limit is virtually the same as from the factory with only air sealed inside. We don't typically operate continuous, so oil cooling will provide some benefit, but I certainly don't see it being better than air cooling, which I've proven to double the continuous power handling of my motors. I get on the highway running at high speed, and I have to climb mountains, so I have to build for continuous operation, and I have no interest in running motors past stator saturation.

John


The grey "disk" you see is the machined side that i needed to do because of the clearance for the brake caliper !.. I needed to machin this area AFTER i have painted the motor :lol:

But i kept it since it look cool 8)

As usuall i will test it gradually as well :wink: it's not my goal to burn thing that i pay $$$ and dozens hours in modifications!

Doc

Doc
 
It's toast. Here's the requiem as posted on the Superbaics forum by Stealthman. Loose translation:

"Yes, the Greyborg has left us, it didn't stand up to 70 kg of bike at 130 kph. Rest in peace, it immolated itself for the good of research, and made us understand that this beast of 70 kg will require something BIGGER. There will be more developments in the future . . . ."

Other posts say the motor is "fuso" (fused, a/k/a melted).

As usual, this heroic death sounds better in Italian. So raise a glass of cheap Chianti and repeat after me: "Riposi in pace, si è immolato per il bene della ricerca."
 
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