The first smoked Cromotor?

[Doctorbass]

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."

130kmh.. Yeah right!

they use the max speed measured by the C-A ... not too accurate on the max speed display.. mine show often 170-180km/h or more every time i go over 90kmh... it's a glitch

I have seen the video on yooutube and the max power in the motor is 11-12kW wich only allow around 65-70mph GPS from my own test with similar bike aerodynamic unoptimized etc....

130kmh woudl require like 15-20kW input ( if the motor dont saturate...)

Doc

 

[Philistine]

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."

Thanks for the update, I thought it sounded a little worse than a bad hall in the video, it sounded like my 9C after I melted it. To be honest I am amazed it lasted as long as it did after watching what they were doing in some of their videos. Who would have thought a bicycle hub motor would not like going 130kph. :lol:

 

[neptronix]

Only 80mph!?!
Zombiess, what gives? this motor's weak! :lol: :lol:

That's gotta be well over >20kW continuous to fry the damn thing..

 

[zombiess]

Only 80mph!?!
Zombiess, what gives? this motor's weak! :lol: :lol:

That's gotta be well over >20kW continuous to fry the damn thing..

Lol. I want to see the video that led up to the frying. They should have brought an egg to fry on it. High speed shouldnt really be done with large diameter wheels. Also it needs a proper cooling setup, those holes won't help much as mentioned.

If it was only 12 kW I don't know how they could kill it on such low power, hope they post more details. I regularly do 12kw and it hasn't cared or gotten very warm after lots of abuse andmine is stock, but I'm in a much smaller wheel. I can probably do 70 MPH when I up my voltage to 145v. Wonder what baterries they were on, last ones in their videos were sag city.

 

[John in CR]

If it was only 12 kW I don't know how they could kill it on such low power...

That's my problem with all the wild claims. Your stock motor was near the verge of meltdown on Saturday at only about 3000W average (88wh/mile at a guesstimated 35mph average), but you don't understand how an inadequately ventilated motor died at 12kw. The motor melted because they created more heat than it could reject for too long a period of time, which is actually quite easy when pushing 12kw into it. Extreme speed attempts require proper tuning, ie correct voltage, current, and gearing. Even Luke is still having problems with the gearing part, and all he has to do is change a sprocket. With hubmotors changing the gearing isn't so easy. Plus the high power is pushed for long enough that you really have to look at it as continuous operation, so comparisons to peak input in regular riding with a light load are invalid. The wind at high speed is a huge load, which creates the requirement of continuous power conditions.

 

[MadRhino]

True performance on the long run with hub motors does require a liquid cooling system. They can take amazing bursts of power, but continuous performance needs efficient cooling. That has to be the next step, and will make possible to use lightweight materials in their construction.

 

[auraslip]

We really are in the stone ages of hub motor tech. Maybe the bronze ages.

Just look at what kenye accomplished with his oil cooling and weight reduction. Not all of us want to take a grinder to our motors and cut out extra material between spoke holes, make our own carbon fiber covers, and run oil to a radiator though. Those mods are gonna be expensive, but stuff like that will be a huge game changer. In 20 years we'll have motors that weigh as much as the cromotor pushing full sized motorcycles. Imagine that on a bicycle.

 

[John in CR]

I definitely agree that brushless motor design is still in its infancy, but I believe the answer lies in more efficient motors so the waste heat is low enough to be dissipated by simple air cooling. Maybe my opinion is clouded by the fact that I already more than doubled a hubmotor's continuous power limit with fairly straight forward air cooling, and that I have a sub 20lb motor that has half the % heat losses of typical hubbies, which through electrical trickery is able to haul my big load up the steepest roads I can find as well as go faster than I like to go on the flats. If the ultimate answer ends up being a larger than currently available geared hub design, then of course an oil cooling system makes sense, because the transmission needs lubrication anyway and you lay out the design so the oil also cools the motor section.

 

[sn0wchyld]

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 :^)

its been done, though I cant find the thread now... basically a guy made his motor into a radial fan. 2 problems arose, 1 that the motor doesnt have the rpm to be a very effective fan, and 2 the blades eventually broke off, leading to some pretty major damage!!

using laptop fans internally works pretty well (speaking from experience :wink: ) but from what I've read so far oil cooling might be the next big thing... particularly with modified 'heatsink' side covers. I think its burtie who's running a hs at 5kw with peak temps of like 65. even my forced air ht got to 90 a few times on just 4kw!! maybe not the best for the super powered hubs, as the magnets might get a bit too warm though. either that or liquid cooling, pumping it out to a radiator.

 

[zombiess]

If it was only 12 kW I don't know how they could kill it on such low power...

That's my problem with all the wild claims. Your stock motor was near the verge of meltdown on Saturday at only about 3000W average (88wh/mile at a guesstimated 35mph average), but you don't understand how an inadequately ventilated motor died at 12kw.

I understand if your stupid and continue to push things beyond their limits without giving them a chance to cool you'll kill them.
I understand trying to go fast with a hub motor in large diameter wheel will hurt efficiency and create more heat.
I understand that if you don't have cooling holes setup correctly it won't work well.
I understand once you get past the saturation knee point your efficiency starts to drop and you start making more heat.
I understand the Greyborg motor in stock form has been proven reliable in stock form through multiple races which really punishes them.
I don't understand your constant jabs at me and Greyborg when we clearly state the motor is rated for up to 4KW continuous use in stock form.
Anything else I'm not understanding?

Speaking of wild claims, what are you taking about my motor was near the verge of meltdown on Saturday?

My 9c 2806 with cooling holes lived and still lives after doing several 10 min sessions racing cars at 125v 60a battery 145a phase going 50-55mph GPS. It got way hotter than my Hubzilla did at the race. I couldn't even touch the ventilated covers on it and the windings were measured at around 140C, the hottest I ever got that motor and it still looks new. Even my 9c 8x8s covers get hotter than my Hubzilla did at the race. I can and have burst over 16kw into my 36 fet controller for a few mins of playing around doing 30 MPH power wheelies (need the longer swing arm) and the motor was only a little warm afterwards even after sitting for a few minutes. It pulled hard, similar to Farfle's 2Pi I rode at the race which had awesome acceleration. It was really nice to ride with a fully predictable throttle response and amazing acceleration.

Jeremy

 

[zombiess]

130kmh.. Yeah right!

they use the max speed measured by the C-A ... not too accurate on the max speed display.. mine show often 170-180km/h or more every time i go over 90kmh... it's a glitch

I have seen the video on yooutube and the max power in the motor is 11-12kW wich only allow around 65-70mph GPS from my own test with similar bike aerodynamic unoptimized etc....

130kmh woudl require like 15-20kW input ( if the motor dont saturate...)

Doc

Yup, I want to see video leading up to this too, their batteries were sagging more than an 80 year old woman's boobs. It takes my bike ~8KW input (120V@67-72A) on a fresh pack just over 125V that will sag about 7V from 125V until coming back up to around 120V under load once I reach BEMF to hold 57-60 mph on GPS and 10-12KW to get it there in a decent amount of time and that's just 60mph with me tucked good. Just going to 70mph will require me to hold at least 14KW input minimum (probably past the saturation knee point so it could take more) into the controller which means I need to put about 18-20KW into the controller if I want to get there in a decent amount of time.

When I make an attempt at the 70mph club I'll post up the results, not sure if I'll get 70mph, but mid to high 60's shouldn't be a problem. If I had my motor built into a 17" moped wheel then I could reach 70mph a bit easier because the tire height will be a bit taller than my current setup. Personally I want more acceleration than top speed so I want to get my longer swing arm worked out.

I use this bike for testing, fun and commuting. Most of my riding is done between 20-35mph.

If people want to keep chasing higher and higher speeds, go right ahead. I've already got what I want... for now 8)

 

[John in CR]

Zombies,

You're the one who said the motor was too hot for your overly sensitive fingers, and if you didn't think that was running up near the limits then why worry about the fan? You had the settings right and your bike did great, so why are you struggling with the difference between peak power, continuous power, and average power. The course looked like the bike seldom needed to slow down below the rpm required for peak power at WOT, which is right were you want to be, because then you stay up in the beefy portion of the efficiency curve. That's why I maintain that average power is pretty much in line with continuous power under those conditions. If my estimate of 35mph average is significantly off, please correct me. There's nothing wrong with my math in that 35mph consuming 88wh/mile is 3080W average. Do you believe the manufacturer's 3000W rating for the motor now?

Peak input is an almost meaningless number. I can take a 1.6lb Hammerdrill motor and pump almost 7kw into it...big deal. I have hubmotors with much more copper on each turn, so I could safely pump 20-30-40kw into them, but making those kinds of statements will simply result in burned up motors, just like happened with much more frequency in the past year.

Do yourself a favor and help avoid melted motors for your customers. Help people gain a better understanding of torque, since that's where the motor you sell has a real advantage. If you keep making those wild power claims, it will come back to haunt you. Find someone with a dyno and put your bike on it, and prove me incorrect if you think I'm wrong. Otherwise match the motor with a tuned controller as a package deal, and give people a warranty.

Zombies, I'm truly only trying to help, not hammer on you. Our ebike drive systems should have absolute reliability for years, only needing to change the bearings after we bang on them too hard for too long, and there's no reason the Cromotor can't be tuned to a ton of fun and still be absolutely reliable. If you sell this thing on 10kw+, then it damn sure better be capable of it for near continuous operation. Until you know what the real limits are you need to test it with real loads just like you did with Saturday's race and about 3kw average input.

John

 

[zombiess]

What customers do with their motors is their issue if they decide to push it beyond what they are rated for. Motors are rated at 4KW. I put a fan on the motor because we thought we had only 15 mins before the next race and I wanted it cooled faster. Is wanting to make sure the bike is in optimal race condition for racing a bad idea? There was enough charge left in the pack to complete the next race too, should I not have charged it either? The answer to both is of course no, this is racing. You try get everything as optimal as possible. I wanted my bike to have a top place finish as it's a win for ebikes, hub motors and proof the motor can take some pretty hard abuse. I doubt few will ride a motor this hard on the street for as long as these races were.

I'm pushing my motor harder than most to show that when you run it within the rated power you won't have any problems. If I kill my motor you'll see me posting about it and what I did to do so. I'm not making any wild power claims, neither is Greyborg. I'm simply posting what I myself am doing. I'll repeat the same thing here as I have many times in other threads, this motor was brought to market not for speed but for the torque and hill climbing capability it has. It just so happens almost everyone buying them wants to go fast on them.

I don't have a temp probe in it yet so I can't give real temp readings, but this hasn't gotten anywhere near as hot as either my ventilated 9C 2806 or stock 2808 motor has (I couldn't touch either).

If you got a company to make one of your motors to fit a bicycle drop out people would do the exact same things with it as you see being done with the Greyborg motors, including me It's just the nature of the beast.

Let me get back to you on the math, I need to figure it out. A 12 lap race is 9.6 miles.

 

[zombiess]

Ok, I just calculated it.

On the 12 lap race where he averaged 88KW/Hr he traveled 9.6 miles. That's an average speed of 34.3 MPH. I wonder what the median speed was (speed reached most frequently) because the racers need to slow way down in a lot of those corners, way less than 34mph and then hammer it coming out of them. I know his peak speed on the CA was 52MPH which should be accurate because I calibrated it by GPS and I reset the CA before each race and he hit over 50MPH on the straight away in every race according to the CA.

Track has some nice fast section and some tight slow sections. It's a fun track and I'd love to get on it in a Kart. I'm not the greatest on 2 wheels and am much more comfortable racing on 4 (unless the front two are off the ground in a wheelie from a hard launch).

When I'm dumping over 100A into my motor it can't ever stay there for longer than a few seconds at most because it reaches the BEMF range pretty quick. I'm doing it to see what the motor can take. I'm the guy selling them and want to be able to tell people what's safe to do on them and what isn't, therefore I personally need to test the envelope of what they can take before I make solid recommendations on operating range.

I've done the same thing with the controllers I'm working on and I tell people all the time to turn their settings down on the high voltage controllers or risk blowing the FETs, because I've found what I consider the safe limits.

 

[gensem]

The motor is a beast compared to 9c that no one can deny.
But yet I dont feel confortable pushing over 6kw on my cromotor without having some sort of airflow between the magnets and the winding. In a hot day with traffic even 6kw might kill it. On thoses day I use my motor at 4kw and max speed of 60km/h. (3speed middle position)
I really want to use 10kw on my cromotor but I ll only raise the current after having the covers drilled and the airflow measured.

 

[zombiess]

The motor is a beast compared to 9c, that no one can deny.
But yet I dont feel confortable pushing over 6kw on my cromotor without having some sort of airflow between the magnets and the winding. In a hot day with traffic even 6kw might kill it. On thoses day I use my motor at 4kw and max speed of 60km/h. (3speed middle position)
I really want to use 10kw on my cromotor but I ll only raise the current after having the covers drilled and the airflow measured.

I'm going to do the same because it's the smart thing to do if you want to push the limits. I'm eventually going to ventilate my motor covers as well because I want to be sure it stays cool at the higher power levels but I wanted to push it in stock form first since that's what I'll be selling. If I get similar results to my 9C 2806, it's should be great. Biggest difference with this motor I've noticed is that when it does get warm I barely notice a drop in the performance. My 9C motors get really boggy when they get hot which means it's time to stop and let them cool.

I think I'm going to leave this motor as is through summer here so I can see how it does. I'm going to hit up ebay and find a K type probe with a long lead so I can use it with my thermometer while riding. The hottest days of summer here are 45-47C which means the black top road surface temps can reach over 60C. At our drag strip they shut down the track if the surface temp exceeds 60C due to safety because of tire blow outs from the extra heat.

Here is a great example of our summer heat.
[youtube]T9hFnB6KvYE[/youtube]

 

[John in CR]

The motor is a beast compared to 9c that no one can deny.
But yet I dont feel confortable pushing over 6kw on my cromotor without having some sort of airflow between the magnets and the winding. In a hot day with traffic even 6kw might kill it. On thoses day I use my motor at 4kw and max speed of 60km/h. (3speed middle position)
I really want to use 10kw on my cromotor but I ll only raise the current after having the covers drilled and the airflow measured.

No doubt. It's essentially twice the motor at less than 50% more weight compared to a 9C. Something I found out when crunching cooling numbers that hadn't dawned on me before is that once the motor is well ventilated the ambient temps don't play nearly as big a role as when it's sealed. That's because since the heat exchange is directly with the stator the temperature differential is much higher than rejecting heat at the covers. That means changes in ambient temps are a much smaller percentage of the temperature differential. Sure cooler air is better, but we don't have to worry about the hot days.

 

[oatnet]

130kmh.. Yeah right! they use the max speed measured by the C-A ... not too accurate on the max speed display.. mine show often 170-180km/h or more every time i go over 90kmh... it's a glitch

I have seen the video on yooutube and the max power in the motor is 11-12kW wich only allow around 65-70mph GPS from my own test with similar bike aerodynamic unoptimized etc....

There has been a lot of funny data coming from the Italian "testing" of the cromotor. Accountant originally used their results to advertise this motor as doing 160kph on 134v(120v nominal). Of course, that would require a 13kv motor, and we all know the Cro turned out to be a 9kv motor. Here is the link to that post:

http://www.endless-sphere.com/forums/viewtopic.php?f=31&t=20321&start=120#p479085
72 V 50 A after one hour drive motor temperature 40 C
84 V 100 A after one hour drive uphill very hot.
134 V 250 A max speed achieved 160 kmh, and no more driving because record was achieved.

You are lucky Doc because you are getting the 13kv winding that could actually achieve 100mph on standard 144v, and be quite streetable on 72v. I was an early adopter who repeatedly asked for the same motor, but all I was offered as a future used one after it was thrashed for testing. So much for the 5403/13kv Cro comparison.

I definitely agree that brushless motor design is still in its infancy, but I believe the answer lies in more efficient motors so the waste heat is low enough to be dissipated by simple air cooling

I agree that stopping the heat generation is far more effective than cooling. Effeciency like your hub motors is definitely key, I hope I can buy one some day. Another way to reduce heat generation is to get increase watts by using a higher KV motor so you can increase volts, not amps.

-JD

 

[zombiess]

No doubt. It's essentially twice the motor at less than 50% more weight compared to a 9C. Something I found out when crunching cooling numbers that hadn't dawned on me before is that once the motor is well ventilated the ambient temps don't play nearly as big a role as when it's sealed. That's because since the heat exchange is directly with the stator the temperature differential is much higher than rejecting heat at the covers. That means changes in ambient temps are a much smaller percentage of the temperature differential. Sure cooler air is better, but we don't have to worry about the hot days.

That's great info to know since summer is brutal here and coming soon. Ventilating my 9C in a way that promoted air flow is probably why it still lives and runs strong.

Did you happen to post your numbers anywhere? I'd love to see the difference. How big of a difference are we talking when going sealed to ventilated such as the standard radial technique which has become popular?

Anyone done an air vs oil cooled on the same hub motor yet?

I also want to see more videos from these Italians backing up their speed claims because I know it takes massive amounts of power. I always carry a GPS when I'm testing top speed and like to video as well if possible. I want to see exactly what they were doing that led up to the frying of the motor.

*edit*
Just found these, he's going really fast for sure but no GPS. Certainly has a large battery pack though.
126V at the end on the cycle analyst and I saw a peak amp reading of 200A on the CA screen. Let's say he was 130V fully charged. With 26" wheels that means he'd have to supply about 130A battery current to reach the BEMF zone and be topped out at 73mph which is 117km/h. A very high speed for sure, but not the 132km/hr / 82.5MPH indicated. To reach that speed in a 26" wheel you would need at least 150V and be able to supply the motor with about 165A.

On my bike if I wanted to go 132km/hr / 82.5mph I'd use the same 20.2" tall tire I have now (to keep efficiency higher) and would need 175V @ 130A.

Basically you need to output 18KW to the ground no matter how you get there and that's a whole lot of power for a 4KW hub motor to put out. You also need a controller that can handle at leat 25KW input because I'm pretty sure the motor isn't going to be in the 80% efficiency range at this speed.

This isn't to knock down his achievement, I believe he hit at least 112km/hr or 70mph which is really fast for a hub motor, it's just not 132km/hr with what's shown unless they other hard evidence backing it up. Sure looks like a fun ride.
[youtube]FkjtwHCuWME[/youtube]
[youtube]BjbbkUjPSZY[/youtube]

 

[Doctorbass]

With the 5303, what i did is 113km/h GPS. Power draw was 12kW

was with kelly 220A 120V 30s lipo.

Yes a 5303 can continuously draw 12kW and give 113km/h on a DH MTB with 24 x 3.0 tires... and a crazy driver like me

Once my original 5303 is reconditioned or that my 5403 modifications are finished i will post new results

I should be able to get the 115-120km/h GPS... caught on camera

I will raise the speed bar that bicycle hub motor can do for you guys :wink:

Doc

 

[zombiess]

I'm looking forward to see what you can do doc. Video + GPS FTW

How do you like the Kelley controller? I'm sucking down a little over 8KW once I'm up to about 60mph on my bike. If I can ever get it to go 113km/hr or 70mph I'll report back how many watts I'm using to hold the speed. I can easily make it draw quite a bit more by just sitting upright, at these speeds aero is everything. It would be a big jump for me to go from 60mph to 70mph, I have the batteries to do it, just not sure I want to try yet since I'm pretty happy with what I have. I'm sure the bug will get me eventually.

 

[John in CR]

Did you happen to post your numbers anywhere? I'd love to see the difference. How big of a difference are we talking when going sealed to ventilated such as the standard radial technique which has become popular?

By popular, if you mean what I call big holes in a spinning pizza pan, no. I think most people get maybe 20% of the flow possible with a more considered approach. I just finished another motor trying a new twist on ventilation, and I'll share full details and pics once I get some results.

As far as numbers for heat rejection, I was playing around mostly with the calculator for convective heat transfer located about half way down the page here http://www.engineeringtoolbox.com/convective-heat-transfer-d_430.html

If you give it a go, let me know what you come up with as the stator surface and we'll compare notes afterward.

John

 

[Beachcruzer]

This isn't to knock down his achievement, I believe he hit at least 112km/hr or 70mph which is really fast for a hub motor, it's just not 132km/hr with what's shown unless they other hard evidence backing it up. Sure looks like a fun ride.
[youtube]FkjtwHCuWME[/youtube]

The driver in the Test 2 video says "cento dieci" (hundred ten) three times, presumably reading about 110 kph off the speedometer in the car. I can't make out what the rider is saying though. My Italian is pretty bad these days, especially when I'm not drunk on red wine. Maybe Esoria can shed some more light.

This story is about to start a new chapter with a 6 kw Kelley hubmotor in a 13" wheel.

 

[zappy]

Hi, I think its funny when people on here on ES are cynical about Chinese supplied specifications i think they are more realistic than some give them credit for. With hub motor output it comes down to duty cycle. The generic conservatively rated 1000w hub motors can put out around 4 times that at high speed in the efficient zone and only 1/3 of rated power at crawling speed. Heavy built motors like the X5 maybe 6 times ,lighter built like 9C maybe 3 times.
I encourage people to buy a cheap digital cooking thermometer(4$ on ebay the one that can measure to 1 decimal place) carfully cut the end off and install the pickup in the copper windings with super glue and then a smear of silicon over the top. This can be helpful for the back of mosfets in the controllers as well. This will help you understand the effects of any mods ,phase amps, wheel size, day temp, cooling options etc and motors can be pushed closer towards their max potential more safely. Although a hot hub side plate shows the windings are obviously very hot. When you are doing very low say 50rpm or 5km/hr the controller phase amp multiplcation can smoke windings/halls with near cold side plates. Just for an example i consider the cromotor to be roughly twice the size as the magic pie and from testing the magic pie motor it was really quite depressing how little heat a hub motor can actually get rid of (no airflow) loaded up on the dyno until the windings reach a safe steady state max of 150 degree C, it can only dissipate around 350W of heat! Four small internal fans increased this by about 45% for 10W consumption. A large increase in power density at 100% duty cycle. At higher speeds say 4000w 80km/hr steady state the fans make almost little difference but in the bush on single track the difference is huge. For example a magic pie with 4000w in at 80 km/hr a hub can get rid of the of 800w of heat(at 80% efficient) but with 4000w in at 5km/hr and 3200w of heat (20% efficient) it will have a duty cycle of seconds. I think we should talk measured winding temps in degree C, phase amps, and actual duty cycle not blisters on hands and eggs etc. As these hub motors get pushed towards their flux limits the watts in is also very differnt to watts out! Above 150 phase amps my pie makes pathetic little extra torque.
Hub cooling options?
For impressive peak bursts minimal effort use heavy motors
For fast commuting drill side plates to maximise centrifical air flow out of the hub(quiet and cheap can be artistic :wink: )
For fast commuting with lots of trafic lights or slow hills drill side plates to maximise centrifical air flow out of the hub and internal fans
For max effort spraying water directly onto the windings turning it to steam and having a closed loop to your controller for phase amps/winding temp limit. (may need big mudguard for this :wink: )
Oil filled wet bath would improve cooling to a point but armetur temps will be limited to close to max magnet temps only 80 degree C with out doing damage and loosing torque, and at very high speed adds drag and oil shear adds heat. (I dont like the idea of an EV dripping oil)