Hubmotor Ventilation John's new (now old) approach

[hillzofvalp]

could you post some measurements of everything you can measure on the motor some time? So I can start modeling the vents...

 

[Emoto]

I've actually cut angles slots as exhaust vents in a set of side covers, but it was expensive in the form of using many dremel disks and it was very time consuming, so I never recommend it. The end result looked quite nice though.

You'll find the resulting shape to be angled slots with sharp edges (the leading edge on the inside and trailing edge on the outside). Be careful in the programming, because angle in the cuts for these slots depends on whether the cover is for the left side or right side, and if you get it work flow will suffer drastically, because they will try to scoop air in at the same time centrifugal force is pushing it out.

For the intake, instead of slots parallel to the axle like for the exhaust, I would cut even narrower slots (to keep debris out which can obviously flow in the intake easier than into the exhaust and whatever grit and sand does get in can flow right out of the exhaust). The goal of intake is to allow free flow of air into the motor. That means as much cross sectional area as possible, and to the extent the holes can be shaped like blades that "scoop" air into the motor it is a good shape. Again, the angle is important, because it is opposite on the left and right sides. I would cut many slots running radially from the axle, and stagger the roots of the slots to make room for more of them.

John

John im very close to machining ventilating my covers, i saw in another thread you posted this photo.
I like this a lot! from a structural perspective over traditional drilling/milling holes/slots , and small debris protection, any more pics., i think im going to use this method for slotting.

 

[burningwings]

Cooling at the lever you describe is ASTOUNDING . Pulling 150 wph at 30 degree grade and only 20c above ambient . How do you measure temperature ? My motor 3540 cry gets 37c sitting in the sun. Thermodynamics is being violated methinks.

 

[John in CR]

Your motor is just a toy in comparison. No laws of thermodynamics broken here. The over 30% grade section of the climb is short, but the primary reasons for the low temp increase in that 2012 climb are:
-Very low resistance windings
-A very heavy motor with much of it aluminum.

While interior blades and intake on one side and out the other is far more effective than the more common approach of big holes in a plate, the exterior bladed approach used on HubMonster noted late in the thread far exceeds all of my previous hubbie ventilation. For a year and a half I've been running that motor at 27kw peak input. I measure temperature at the stator, and I've only pushed the motor to 100°C twice during quite extreme riding. The motor stays cool enough that the only times I even turn the temp gauge on is out of curiosity or to set the temp alarm before extreme riding. Any hubmotor I ventilate from now on will include exterior blades on the exhaust side.

 

[burningwings]

Sounds good to me. My toy could use some cooling its a cry 3540 . Your suggestions would be MOST welcome. I get up to 100c almost around the block. 60v 100amp peak on flat ground. You must forgive my doubting your results , but this might explain why I questioned you. Keep up the GREAT work you are doing we can ALL benefit from it!

John Henry Dumbelton III

 

[John in CR]

100C just going around the block??? With what kind of performance and how much total load (rider and bike)? That sounds more like a wiring config issue running a false positive. What current settings, phase and battery? What's your no load current and speed?

While my 6 phase HubMonsters have no equal, I'll give you an idea of what low stress running with good heat management can do. There's a Home Depot-like hardware store I frequent, and getting there is a 200m+ net increase in elevation, which is 4km of street level road (I stay well in front of traffic at 70-80kph cruising speeds and a few stops, and then it's 8km of highway with a 250 climb over a hill and down and then gradual incline the rest of the way. I never get passed on the lower roads and almost never on the highway portion, with commonly showing off the torque accelerating well past 100kph on the climb and staying mostly in the 90-100kph range the rest of the way. The last time I remember turning the temp sensor on for that ride, and I know I didn't baby it more than usual, I arrived with the stator at 68°C. I checked it again after locking it up and answering questions to someone who saw me on the hwy, and without any more air flow the temp climbed to 70°C and held there. BTW, that's running 111V nominal, pushing a 190kg+ total load, using a tire with an OD of 19.25".

One thing to keep in mind about temperature is that each degree C increase in copper temperature increases copper resistance by about 0.4% . That doesn't sound like much, but for the guys running their undersized motors too hard and increase motor temp by 100° above ambient, that's a 40% increase in resistance in their motor, so 40% more heat for the same current with a motor they were already pumping too much current into.

 

[burningwings]

Hi John. I weigh 190 lbs. The bike is about 80 lbs. Flat streets of Sacramento. I run 65 volts at max 99 amps setting on the CA, Lyen 18 fet 100 amp controller. No load current 2.45 a @ 50 mph. Don't know the phase current. By the way , how can the phase current be higher than the battery current source ? I do believe it is though. My motor does indeed slow when hot .Your HubMonsters motor sounds far out. Do have pictured of your bike ? I would love to see it !