ElectroSurf3r
10 W
Here is the Super V and Clown video thread:
http://endless-sphere.com/forums/viewtopic.php?f=6&t=39986
http://endless-sphere.com/forums/viewtopic.php?f=6&t=39986
Hubmotor Ventilation John's new (now old) approach
- Thread starter John in CR
- Start date
I firmly believe that oil-cooling will prove to be the ultimate for a race-hub, but for a true daily commuter geared-hub / DD-hub that could use some extra cooling, I think air-cooling will provide the best "trouble-free" effect. I have some experiments in mind, and there is a 9C headed my way.
The proven centrifugal aircooled component is the enshrouded front disc brake (two plates with radial vanes in-between). For most builds I don't think a rear disc brake is vital, especially if using a front disc brake and the well-regarded Salmon pads on the rear rim (perhaps adding a rear-hub regen braking system?). With the sideplate of a 9C acting as one half of the enshroudment, a second aluminum plate with some vanes can be added.
Since such a device would be unidirectional. The average-performing true radial vanes can be curved (harder to make) or simply angled. I believe angled vanes would improve air-flow (rather than curved) and be easy to implement. Something very similar to Matts RC airfan larger diamer though, and attached to the 6-hole disc brake mount on the left side of the hubs.
I'm glad to see so many builders developing better cooling. I cannot imagine a modern engineer designing an industrial motor without a fan, and the air-cooling / oil-cooling will provide very real and measurable improvements, once the optimum details are finalized through experimentation...
John, would it be possible for you to video a "smoke test" of your hub, to make the flow more visible?
Graphic by oofnik
http://endless-sphere.com/forums/viewtopic.php?f=28&t=10560&start=15#p162010
The proven centrifugal aircooled component is the enshrouded front disc brake (two plates with radial vanes in-between). For most builds I don't think a rear disc brake is vital, especially if using a front disc brake and the well-regarded Salmon pads on the rear rim (perhaps adding a rear-hub regen braking system?). With the sideplate of a 9C acting as one half of the enshroudment, a second aluminum plate with some vanes can be added.
Since such a device would be unidirectional. The average-performing true radial vanes can be curved (harder to make) or simply angled. I believe angled vanes would improve air-flow (rather than curved) and be easy to implement. Something very similar to Matts RC airfan larger diamer though, and attached to the 6-hole disc brake mount on the left side of the hubs.
I'm glad to see so many builders developing better cooling. I cannot imagine a modern engineer designing an industrial motor without a fan, and the air-cooling / oil-cooling will provide very real and measurable improvements, once the optimum details are finalized through experimentation...
John, would it be possible for you to video a "smoke test" of your hub, to make the flow more visible?
Graphic by oofnik
http://endless-sphere.com/forums/viewtopic.php?f=28&t=10560&start=15#p162010
John in CR
100 TW
SM,
I disagree. Unless a radiator gets introduced to the mix like Doc has done, oil fill will never live up to the hype. It's really no different than taking the radiator hoses for a car and connecting them together, leaving the radiator out of the equation. As proof of oil fill's lack of effectiveness, simply look that the unacceptably high temps GCinDC is reaching going up hills.
As proof of the superior results achieved by air cooling simply look at the mountain climbing videos my son posted. The motor he was running is little different than GCinDC's H35, just 5mm more stator width. While I'm sure there are improvements we could make to improve the flow rate, it's hard for me to get excited about trying something new when we've yet to get a ventilated hubbie hot. If it ain't broke, why fix it?
I hope you come up with something easy that's even better that what I've been doing, though an extra plate outside the motor seems like an unnecessary complication. Where did you plan on having this added contraption sucking it's air from? If it's anywhere other than at the exhaust holes at the perimeter of the motor, then I suggest you head back to the drawing board, because that would be drawing air out of the motor before it even has a chance to flow over the stator and do any cooling.
In the meantime, I'm working on attacking the heat issue from the other end. The first point of attack is using more efficient motors that have less than half the heat losses of common hubbies. Half the heat generated means half the heat to reject.. The second is proper tuning of controllers. I learned a lot about how motors and controllers react to each other during the process of tuning Hubmonster's controller up to over 30kw peak. I've been running at that level for a month, and the motor still doesn't get hot or anywhere close to hot, and the controller is running cooler than it was at 12kw peak, though still significantly warmer than the motor ever gets.
I've got a new monster hubbie coming in, so after I apply my basic ventilation strategy it would be a perfect time to demonstrate air flow. I need something that will generate some serious smoke but won't leave a nasty residue in my motor. Any ideas? I picked up a cheap cigar and tried that before, but it really wasn't enough smoke for much of a demo. You could clearly see smoke getting drawn in, but that was about it.
John
I disagree. Unless a radiator gets introduced to the mix like Doc has done, oil fill will never live up to the hype. It's really no different than taking the radiator hoses for a car and connecting them together, leaving the radiator out of the equation. As proof of oil fill's lack of effectiveness, simply look that the unacceptably high temps GCinDC is reaching going up hills.
As proof of the superior results achieved by air cooling simply look at the mountain climbing videos my son posted. The motor he was running is little different than GCinDC's H35, just 5mm more stator width. While I'm sure there are improvements we could make to improve the flow rate, it's hard for me to get excited about trying something new when we've yet to get a ventilated hubbie hot. If it ain't broke, why fix it?
I hope you come up with something easy that's even better that what I've been doing, though an extra plate outside the motor seems like an unnecessary complication. Where did you plan on having this added contraption sucking it's air from? If it's anywhere other than at the exhaust holes at the perimeter of the motor, then I suggest you head back to the drawing board, because that would be drawing air out of the motor before it even has a chance to flow over the stator and do any cooling.
In the meantime, I'm working on attacking the heat issue from the other end. The first point of attack is using more efficient motors that have less than half the heat losses of common hubbies. Half the heat generated means half the heat to reject.. The second is proper tuning of controllers. I learned a lot about how motors and controllers react to each other during the process of tuning Hubmonster's controller up to over 30kw peak. I've been running at that level for a month, and the motor still doesn't get hot or anywhere close to hot, and the controller is running cooler than it was at 12kw peak, though still significantly warmer than the motor ever gets.
I've got a new monster hubbie coming in, so after I apply my basic ventilation strategy it would be a perfect time to demonstrate air flow. I need something that will generate some serious smoke but won't leave a nasty residue in my motor. Any ideas? I picked up a cheap cigar and tried that before, but it really wasn't enough smoke for much of a demo. You could clearly see smoke getting drawn in, but that was about it.
John
REdiculous
10 kW
Large smoke bombs would probably work for visuals. Or a gang of smaller smoke bombs. Might find 'em on sale since the 4th just came and went.
A special-fx smoke machine would be a bit more expensive up front, and it might lack the volume you're after, but refills are cheap. *shrug*
A handful of leaves makes a fair amount of smoke ... low-tech and free.
A special-fx smoke machine would be a bit more expensive up front, and it might lack the volume you're after, but refills are cheap. *shrug*
A handful of leaves makes a fair amount of smoke ... low-tech and free.
gensem
100 kW
What do think about the placement? I ll probably use a 6mm drill and a wide angle.
I ll try to do the blades tomorrow. (hope they are not hard to do)
I ll try to do the blades tomorrow. (hope they are not hard to do)
John in CR
100 TW
REdiculous said:Large smoke bombs would probably work for visuals. Or a gang of smaller smoke bombs. Might find 'em on sale since the 4th just came and went.
A special-fx smoke machine would be a bit more expensive up front, and it might lack the volume you're after, but refills are cheap. *shrug*
A handful of leaves makes a fair amount of smoke ... low-tech and free.
Smoke bombs were my first thought, but I remember stains on concrete lasting for years, so I'm leary of that in my motor.
Keep in mind that I already know how well it works, and real world demonstration of the results blasting up steep mountain roads is better to me anyway. Next time I'll bring a thermometer with me.
John in CR
100 TW
gensem said:What do think about the placement? I ll probably use a 6mm drill and a wide angle.
I ll try to do the blades tomorrow. (hope they are not hard to do)
I can't see the pic. With a center punch I put dimples within a few mm of the root of the lip that locks into magnet backing ring. My goal has always been to end up with my holes as close to perimeter of the inside of the motor as possible, so as close to that lip as possible. Air could literally flow right off the surface of the magnets and out the exhaust without somehow fighting against centrifugal force to get to the exhaust holes. That's why I make them so small too.
For blades, my easiest were Hubmonster's for which I used 1mm AL sheet cut with tin snips. It's great for enclosing batteries too, because it's thick enough to hold its form, and thin enough to easily bend, so a full sheet will find good uses. I've also cut up the cheapest thinnest AL pot I could find.
How much space there is between the end windings at their thickest point and the side covers will dictate what you can do with the blades. I hope you come up with something I can borrow for my next ventilation. My only input is epoxy AND a small bolt, both done together in one step after some surface prep, along with not straight radial blades (they're to push air away from the covers at the stator) You can bend and shape the blades after the epoxy is cured.
John
gensem
100 kW
I hope I did not went too far... 
I have 2mm aluminium sheet at hand and a clearance of about 15mm, will see what I can do!
I have 2mm aluminium sheet at hand and a clearance of about 15mm, will see what I can do!
John in CR
100 TW
As Hancock would say, Good job. The motor should love you for the effort.
gensem
100 kW
Hancock might be happy but im not so happy on the shape that the blades should have.
Im trying to imagine how could I shape the blades in a way to push the air to the perimeter... The way your blades are John the air will probably flow to everywhere inside the hub eventually reaching the outtake holes.
A simulator would be so helpfull...
Im trying to imagine how could I shape the blades in a way to push the air to the perimeter... The way your blades are John the air will probably flow to everywhere inside the hub eventually reaching the outtake holes.
A simulator would be so helpfull...
John in CR
100 TW
gensem said:
Centrifugal force pushes it to the perimeter. That's not want I try to use the blades for. El Steak so no improvement in cooling when he added straight radial blades, so I think we can reasonably assume that at the perimeter the air is essentially spinning at wheel rpm. I use the blades to deflect air away from the side covers toward the stator iron and end windings. I believe without them the air flow will mostly just follow the relatively smooth side covers and go to exhaust with little turbulent flow at the stator, where it is needed the most. With the blades, at least some of the air is forced away from the cover and if the lifted trailing edge of the blade passes close to the stator, it gives it a small puff of air all around the stator. Multiply the little puffs by the number of blades and the rpm and it turns into a lot of turbulence right where turbulence does the most most good.
No doubt some little blowers could make more turbulence there, but my issue with fans is that I would never know if one isn't working and then that section of the stator wouldn't get nearly the same cooling. With the blades I know they're all always working and providing the same effect all the way around the stator. Hubmonster is in a smaller wheel, do higher rpm, and it's cooling is highly effective with only 5 blades in each cover. It looks like you have better intake than I do, which should offset most of the diameter advantage mine has, but since you're at lower rpm with the bigger wheel, I think going to 10 blades in each cover makes sense. It's not that much work, especially if you can recruit a pair of helper hands for the epoxy and bolting in one step phase. Mine was pretty quick curing, so I had to be really quick to do 5 in one mix. Definitely do a test fitting with the bolts first.
To me the big question is where does saturation start to occur, because once you get into saturation (a gradual thing, not a definitive line), cooling efforts will have less and less effect. Sure I'm running 425A/550A peak, but that on a 1.5 turn per tooth motor wound with effective 8ga wire. Even with my last step up in current I still felt a substantial increase in thrust, so if Hubmonster is in saturation, it's not by much. Saturation is what you'll have to be most alert for in tuning for maximum performance. Do it in gradual increments, and start with a low battery/phase limit ratio and try different ratios to see what's best. I'm all but certain that the usual 2.5:1 or so, won't be the right answer for you. I settled on 1.3:1 with mine. As low as possible, while still reaching the same max speed is what worked for me. Any higher is just a waste, because it already takes lots of throttle care not to get flipped on my back.
John
Actually John, phase current in a three phase motor is 1,41 x batt current. So if you have a 1:1.3 ratio, I would hyphotize that your phase currents drop off once you are up to speed (The battery current limit kicks in). The more I think of this ratio, the more confused I am. This ratio should not affect the 'lift the front wheel effect' at all. Phase current alone decides the maximum torque you'll witness. Battery current only regulates how much power you can possibly feed the motor. By increasing this, if you have the batteries for it, you can gain more high-end torque - where it isn't the phase current - but the battery current that limits power.
So; recap:
Phase current limit: Torque limitation.
Battery current limit: Power (Torque x rpm remember?) limitation.
Limiting phase currents is what's effective. These chinese controllers employ a static variable that makes sure the phase current rise wont blow the controller at low speeds, still they have massive current rise at low speeds. Employing current limit I see phase currents in the 200A region while drawing 1-2-5A battery side at startup from standing still. The maximum battery current peaks at 110A, stays there for a bit, and then falls off as speed increases. This gives a constant torque feel up until the 110A limit (it then drops), as opposed to the nonlinear torque of most china controllers. If you have to take throttle care not to flip over, lower your phase currents - keep battery current where it is.
As for saturation; your air gap, magnet area, and stator area could be analyzed, I believe, to give you an answer to this. I've read a brushless design handbook where this was discussed, but I do not remember the how to's - maybe Miles could give you some pointers? Saturation is linked to phase currents, so maybe a simple dyno test to find out at what phase currents the motor siezes to produce torque would give you the best and fastest results? Shave some amps off and you should have a good setpoint.
Edit: gensem, I'll 'go out on a limb' and state that those holes being angeled won't make much of a difference compared to regular holes. It will create a different effect, I'm not sure wheter it is positive or negative. Picture speeding air, at the top it will either be forced in or sucked out. At the bottom you have the opposite effect. You will therefore have a constant downwards stream (or upwards) of air inside the hub. Could actually be a good design I have to say. The holes in the middle won't do much if I'm correct. Remember that air passing past the hub will have many times the speed that the hub holes moves at.
So; recap:
Phase current limit: Torque limitation.
Battery current limit: Power (Torque x rpm remember?) limitation.
Limiting phase currents is what's effective. These chinese controllers employ a static variable that makes sure the phase current rise wont blow the controller at low speeds, still they have massive current rise at low speeds. Employing current limit I see phase currents in the 200A region while drawing 1-2-5A battery side at startup from standing still. The maximum battery current peaks at 110A, stays there for a bit, and then falls off as speed increases. This gives a constant torque feel up until the 110A limit (it then drops), as opposed to the nonlinear torque of most china controllers. If you have to take throttle care not to flip over, lower your phase currents - keep battery current where it is.
As for saturation; your air gap, magnet area, and stator area could be analyzed, I believe, to give you an answer to this. I've read a brushless design handbook where this was discussed, but I do not remember the how to's - maybe Miles could give you some pointers? Saturation is linked to phase currents, so maybe a simple dyno test to find out at what phase currents the motor siezes to produce torque would give you the best and fastest results? Shave some amps off and you should have a good setpoint.
Edit: gensem, I'll 'go out on a limb' and state that those holes being angeled won't make much of a difference compared to regular holes. It will create a different effect, I'm not sure wheter it is positive or negative. Picture speeding air, at the top it will either be forced in or sucked out. At the bottom you have the opposite effect. You will therefore have a constant downwards stream (or upwards) of air inside the hub. Could actually be a good design I have to say. The holes in the middle won't do much if I'm correct. Remember that air passing past the hub will have many times the speed that the hub holes moves at.
hillzofvalp
100 kW
gensem said:I hope I did not went too far...
I have 2mm aluminium sheet at hand and a clearance of about 15mm, will see what I can do!
I did holes like that to my original 9C... Now that I have CNC access I doubt I will ever do that again to a motor. I will upload revised cromotor cover design here. I'm interested in have the design fully critiqued and improved in this thread before I yank apart my motor again
gensem
100 kW
Got it John! Will do saturday, even tho i dont think I ll have the bike ready this saturday (job takes most of my time)
gensem
100 kW
hillzofvalp said:
Its not likely that everyone has a CNC in his drawer, hehe...
To be truth if you could make quality covers from a graded aluminium with angled holes, blades, etc... i think there would be a market to for it! (we are not talking about cromo only, think of all the 9 continents)
hillzofvalp
100 kW
Being a student run, academically funded Lab, it would be practically against the rules to do that... But manufacturing personal covers to spec and then having someone else manufacturing them in numbers externally would work. In fact, I could probably build a mini CNC that would put out two-three covers per day for under $1600.
Milling out 10" lovers from 1.25" thick aluminum stock would be expensive, though our lab has countless aluminum drops that could easily make 4 covers from a single piece....
It would be more viable in reality to just modify existing covers, and then I would only need a $900 machine
Milling out 10" lovers from 1.25" thick aluminum stock would be expensive, though our lab has countless aluminum drops that could easily make 4 covers from a single piece....
It would be more viable in reality to just modify existing covers, and then I would only need a $900 machine
John in CR
100 TW
Teh Stork,
These controllers may work like that in theory, but not in operation. If I raise only the battery side current limit and don't increase the phase current limit too, then top speed decreases despite the high limits I'm running and despite the bike being nowhere near either current limit a top speed. Another odd effect while I was incrementally increasing the current limits, from peak settings in the 16kw range through about 22kw, the bike had a quite pronounce surge in thrust right around the transition point of switching from current limiting to BEMF limiting the current. I've yet to see any plausible explanation for that effect. I tuned this controller through countless iterations of different current limits and going for short rides. I settled on limits that were as far as I was willing to take the controller. With focus and aggressive riding I can hit 30kw input at between 25 and 30mph.
Regarding in at the top and out at the bottom is not at all what happens with a ventilated hubbie. They would make a chuffing sound, and the air would have to fight against centrifugal force. There have even been some who accidentally angled the holes in the wrong direction, resulting in a scooping type effect at the top where the holes are moving fastest relative to the outside environment, and the result was a hot motor. This happened because it turbulence at what should be the exhaust holes and flow was stifled.
The approach I use attempts to minimize the effects of the exterior air flow. I know for a fact that it works quite well as evidenced by being able to climb mountains running extremely high power with no heat issues. In fact I did one several mile climb where I was riding hard enough to get 6% regen on the way up from braking to slow for the curves, and the top half of the climb averaged almost a 20% grade. At the top of the climb the motor temp was 37°C. If you believe you have a better hubmotor cooling approach, let's see it in action, because we'll all want to use it. FWIW, that was with a hubbie that has a peak efficiency of only 84%, not Hubmonster HE which has a peak efficiency of 94.6% . Imagine the power it will be able to run with this ventilation approach.
John
These controllers may work like that in theory, but not in operation. If I raise only the battery side current limit and don't increase the phase current limit too, then top speed decreases despite the high limits I'm running and despite the bike being nowhere near either current limit a top speed. Another odd effect while I was incrementally increasing the current limits, from peak settings in the 16kw range through about 22kw, the bike had a quite pronounce surge in thrust right around the transition point of switching from current limiting to BEMF limiting the current. I've yet to see any plausible explanation for that effect. I tuned this controller through countless iterations of different current limits and going for short rides. I settled on limits that were as far as I was willing to take the controller. With focus and aggressive riding I can hit 30kw input at between 25 and 30mph.
Regarding in at the top and out at the bottom is not at all what happens with a ventilated hubbie. They would make a chuffing sound, and the air would have to fight against centrifugal force. There have even been some who accidentally angled the holes in the wrong direction, resulting in a scooping type effect at the top where the holes are moving fastest relative to the outside environment, and the result was a hot motor. This happened because it turbulence at what should be the exhaust holes and flow was stifled.
The approach I use attempts to minimize the effects of the exterior air flow. I know for a fact that it works quite well as evidenced by being able to climb mountains running extremely high power with no heat issues. In fact I did one several mile climb where I was riding hard enough to get 6% regen on the way up from braking to slow for the curves, and the top half of the climb averaged almost a 20% grade. At the top of the climb the motor temp was 37°C. If you believe you have a better hubmotor cooling approach, let's see it in action, because we'll all want to use it. FWIW, that was with a hubbie that has a peak efficiency of only 84%, not Hubmonster HE which has a peak efficiency of 94.6% . Imagine the power it will be able to run with this ventilation approach.
John
hillzofvalp
100 kW
That's insane. I almost don't believe that small temperature figure, but if it's true..well, then... Great.. Screw water cooling. Are you sure that your thermistor isn't being rapidly cooled by the air? Is it buried deep within the winding with arctic alumina or something similar?
What is the diameter of the hub and what is the average rpm at which cooling is most effective.
Sometime when I have time I'm going to ask some grad students how they would approach the vent designs. They can be very willing to help out on a new challenge!
What is the diameter of the hub and what is the average rpm at which cooling is most effective.
Sometime when I have time I'm going to ask some grad students how they would approach the vent designs. They can be very willing to help out on a new challenge!
John in CR said:
Ah, sounds like you've found a system that works for your controller. 30kW bursts is insane.
But about the top and bottom ventilated with angled holes - there really are no wrong direction in my opinion here. Say the perimiter is traveling at 50kph, the hubmotor has holes 15cm from the center - the holes would move really slowly compared to the outside air. Turning the direction of the vents only changes the way the air flows in the motor. This was certainly not the cause for the motor heating. Remember that the scooping effect is as strong on the bottom as if on the top.
John in CR
100 TW
TehStork,
At the lowest point in the rotation, the holes are moving at a speed of zero relative to the outside world. Also keep in mind that it's not a tremendous air flow, so things like angling the holes the wrong direction can have a very significant detrimental effect on flow. If you take the time to think about the air flow circuit from intake to exhaust, you'll quickly realize how impossible it is to intake at the top and flow out at the bottom with that spinning motor shell, and that's before considering that hot air rises and that there's no way it has sufficient pressure to fight against centrifugal force. The only time the air moves like that is when a ventilated motor is stationary, but it flows in at the bottom and out at the top as hot air rises.
Also, note that the only new thing I tried with this motor is intake on one side, and exhaust on the other to get more flow through the gap. The holes and their placement and angled cuts along with interior blades have been used successfully on multiple motors for the past 2 years, so there's really no question about how it works. Way back when I did a smoke test and starting at about 100rpm the motor clearly draws air in through the intake holes. This motor definitely runs the cooler and at much higher power with the same efficiency, but it's impossible to tell how much is the approach and how much is caused by the larger diameter motor, which has greater centrifugal effect. Also, the very large opening space in the stator spokes allowed me to get the blades closer to the end windings, since I was able to adjust them after the fact by removing only one cover.
John
At the lowest point in the rotation, the holes are moving at a speed of zero relative to the outside world. Also keep in mind that it's not a tremendous air flow, so things like angling the holes the wrong direction can have a very significant detrimental effect on flow. If you take the time to think about the air flow circuit from intake to exhaust, you'll quickly realize how impossible it is to intake at the top and flow out at the bottom with that spinning motor shell, and that's before considering that hot air rises and that there's no way it has sufficient pressure to fight against centrifugal force. The only time the air moves like that is when a ventilated motor is stationary, but it flows in at the bottom and out at the top as hot air rises.
Also, note that the only new thing I tried with this motor is intake on one side, and exhaust on the other to get more flow through the gap. The holes and their placement and angled cuts along with interior blades have been used successfully on multiple motors for the past 2 years, so there's really no question about how it works. Way back when I did a smoke test and starting at about 100rpm the motor clearly draws air in through the intake holes. This motor definitely runs the cooler and at much higher power with the same efficiency, but it's impossible to tell how much is the approach and how much is caused by the larger diameter motor, which has greater centrifugal effect. Also, the very large opening space in the stator spokes allowed me to get the blades closer to the end windings, since I was able to adjust them after the fact by removing only one cover.
John
Good to see this thread finally started, have you seen this motor
On the smoke test to demonstrate air flow, would be good to find a small spy camera, plenty of cheap ones around and hack it so you could mount or remotely fit lens inside the motor to observe flow,[ from cold static test of course] What do you think
On the smoke test to demonstrate air flow, would be good to find a small spy camera, plenty of cheap ones around and hack it so you could mount or remotely fit lens inside the motor to observe flow,[ from cold static test of course] What do you think
Attachments
John in CR
100 TW
If I was selling the mod, then I'd be inclined to go to to great lengths to demonstrate how it works, but I'm just giving the approach away for free. I put a significant effort into research before cutting into my first cover, and I've revised and refined my approach with real world usage of these motors for over a year. I climb steeper grades at higher power hauling a heavier load than anyone I know of. The motors I've used aren't magic, and aren't any more efficient than those most use (excluding those who push their motors into saturation, which no amount of cooling will cure). That means I'm generating more heat, and since my vented motors have no heat problems whatsoever, that's proof enough for me that the approach works quite well. Even if I did a smoke demonstration, that wouldn't really be proof anyway, because the dynamics of the ventilation holes relative to the outside environment while a bike is moving is completely different than a stationary spinning wheel, though what goes on inside the motor is mostly unchanged, especially if you intentionally design your strategy to minimize those outside influences and use them to your advantage.
John in CR said:
Well, with this as a reference, the top holes move twice the speed. You need to have the center of the motor as the reference for speed. You are using the ground as the reference - and this gives you the zero speed.
Rememer that in a 26" wheel the edge of the wheel travels ~5 times faster than what the hub does. The sorrounding air speed flows at this speed. Any static smoke test wont be realistic.
hillzofvalp
100 kW
Discuss: (the other side would get the intake holes)
-improvements? I did this in 5 minutes but Iw ant you guys to get the ideas flowing so I can make optimized vents
the thing I like a lot about the idea of more Holes on the perimeter too is that it also adds more surface area for the covers themselves to cool.. but is probably very insignifcant.
GOOD NEWS: the cromotor already has the bolts and nuts on the freewheel side. I plan on making fins that attach to this for easy securing
-improvements? I did this in 5 minutes but Iw ant you guys to get the ideas flowing so I can make optimized vents
the thing I like a lot about the idea of more Holes on the perimeter too is that it also adds more surface area for the covers themselves to cool.. but is probably very insignifcant.
GOOD NEWS: the cromotor already has the bolts and nuts on the freewheel side. I plan on making fins that attach to this for easy securing
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