Oil cooling your hub- NOT snake oil!

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John in CR   100 GW

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Re: Oil cooling your hub- NOT snake oil!

Post by John in CR » Aug 17 2019 4:45pm

FranBunnyFFXII wrote:
Aug 17 2019 3:21am
...high RPM where the cooling will be most necessary.
Extra cooling is most needed at low rpm with high load, which equates to high torque needs (high current) and low power output (power = torque X rpm), so it is low efficiency (lots of heat). At high rpm the motor runs lower current and has better cooling due to higher velocity and turbulence at the surfaces where heat is transferred. The exception would be big scooter motors with high pole counts, which have high no load current. Those can create significant heat just to spin the motor at high rpm even without producing any positive torque to move the vehicle.

FranBunnyFFXII   100 µW

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Re: Oil cooling your hub- NOT snake oil!

Post by FranBunnyFFXII » Aug 17 2019 5:02pm

John in CR wrote:
Aug 17 2019 4:45pm
FranBunnyFFXII wrote:
Aug 17 2019 3:21am
...high RPM where the cooling will be most necessary.
Extra cooling is most needed at low rpm with high load, which equates to high torque needs (high current) and low power output (power = torque X rpm), so it is low efficiency (lots of heat). At high rpm the motor runs lower current and has better cooling due to higher velocity and turbulence at the surfaces where heat is transferred. The exception would be big scooter motors with high pole counts, which have high no load current. Those can create significant heat just to spin the motor at high rpm even without producing any positive torque to move the vehicle.
My bike's motor only heats up when it's doing high speed riding, not when I'm doing stop and go traffic.

This is where my concern for cooling is coming from in the first place. The motor heats up the most when I'm cruising along uninterpted at 30mph for long periods of time.
It gets warm enough right now to physically feel the heat bleeding off the motor case. But it doesn't really warm up even to the touch after doing a good few miles of stop and go traffic where it's having to accelerate hard to keep up with cars and keep me from getting rear ended.

Since my goal with the build is to get higher top speed, much longer cruising speed range, and better acceleration, this is where the concern for cooling is coming from.

John in CR   100 GW

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Re: Oil cooling your hub- NOT snake oil!

Post by John in CR » Aug 18 2019 2:54pm

At those power levels it's probably just getting warm not hot. For some extra cooling add an air deflector on each side to direct more airflow toward the side covers.

FranBunnyFFXII   100 µW

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Re: Oil cooling your hub- NOT snake oil!

Post by FranBunnyFFXII » Aug 18 2019 4:25pm

John in CR wrote:
Aug 18 2019 2:54pm
At those power levels it's probably just getting warm not hot. For some extra cooling add an air deflector on each side to direct more airflow toward the side covers.
Less than 5$ of oil 3$ of silicon caulk and my friend's drill would still be cheaper and more effective. :lol:

Punx0r   100 GW

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Re: Oil cooling your hub- NOT snake oil!

Post by Punx0r » Aug 19 2019 4:04am

The biggest drawback of oil-cooling for most people is keeping the blasted stuff where you want it - inside the motor. It can be surprising the number of places warm oil can find to escape: it will travel along inside stranded wire. While the ferrofluid seems expensive for a small amount of oil, it largely solves this problem by simulataneously only requiring a small amount of oil and because it's held in place by the magnets.

John in CR   100 GW

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Re: Oil cooling your hub- NOT snake oil!

Post by John in CR » Aug 19 2019 11:47am

FranBunnyFFXII wrote:
Aug 18 2019 4:25pm
John in CR wrote:
Aug 18 2019 2:54pm
At those power levels it's probably just getting warm not hot. For some extra cooling add an air deflector on each side to direct more airflow toward the side covers.
Less than 5$ of oil 3$ of silicon caulk and my friend's drill would still be cheaper and more effective. :lol:
Owning an EV that drips oil is what's :lol:

Except to the extent that using oil makes the outside shell of the motor get hotter, a sealed motor can't shed heat any faster without doing something to improve the outside air flow. I bring fresh cool air into motors where I push performance using blades on the exhaust side and holes and/or slots on the other. That's why I'm able to push hubbies at up to 30kw peak input with no cooling issues, especially at high speed. The only way I'd go the messy oil route is for a beach bike, and the oil would be more to keep water out andd corrosion resistance than for cooling.

I was one of the earliest to use ventilated cooling and have never had an issue despite riding in rain and roads with lots of magnetic dust from volcanic eruptions. Granted, I do ride strictly on raods, but I wouldn't use a hubbie for offroading anyway. For effective and durable vented cooling, don't follow the followers. Instead use the smallest holes or slots and on the exhaust side put holes only at the extreme perimeter with blades outside to create a centrifugal fan effect. My start drawing air through the motor at about 10mph that I verified with a smoke machine.

Ohbse   10 kW

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Re: Oil cooling your hub- NOT snake oil!

Post by Ohbse » Aug 19 2019 10:58pm

It's been 2.5 years since i posted that little blurb on sealing your hub.. for anybody new to this now, much has changed - just go buy some statorade and enjoy the same result with no mess!

Solar-E-Cycles   1 µW

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Re: Oil cooling your hub- NOT snake oil!

Post by Solar-E-Cycles » Aug 28 2019 9:41am

I understand that statorade (ebikes.ca) is a ferromagnetic fluid that is attracted to the magnets and therefore fills the gap between the electric windings and improves transfer of heat through the magnets to the outside hub into the air.

qwerkus   1 kW

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Re: Oil cooling your hub- NOT snake oil!

Post by qwerkus » Aug 28 2019 2:01pm

Ohbse wrote:
Aug 19 2019 10:58pm
It's been 2.5 years since i posted that little blurb on sealing your hub.. for anybody new to this now, much has changed - just go buy some statorade and enjoy the same result with no mess!
Actually statorade still requires proper motor sealing if you don't want the stuff to leak through the edges of the side panels at high rpm.

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