Oil cooling your hub- NOT snake oil!
- Thread starter Spicerack
- Start date
-dg
1 kW
ian.mich said:
I'm looking forward to your video.
Why can't you use hubs with separate wire exits (I'm thinking Bafang/8-FUN SWXK style here)? I assume they leak somewhere, but where? And why can't it be sealed?
itchynackers
100 kW
Any liquid (water or oil) will leak through the easiest point of exit (least resistance). Believe it or not, it can/will leak between phase wire insulation, and the metal phase wire itself. Doesn't seem likely, but I've seen it. My attempts at a solution have been to find a very small pressure valve that opens at a preset psi (maybe 1 or 2 psi). This should allow heated gases to exit. Preventing oil from getting into the valve is another consideration, so placement of the valve is crucial.
Sancho's Horse
1 kW
itchynackers - was it you that used the ebay motorcross (I believe) breather valve? I know I have seen that on somebody's thread.
bionicdan - not totally sure I can accurately picture what you are considering. I think there is some good possibilities for using centrifugal force to pump oil out of the motor for remote cooling. I am still trying to get a grip on whether introducing a hole will also introduce cavitation issues, or no, or whether the ATF may be protective. I think ATF is chemically mostly fine for winding varnish. Over a period of years, it may be a good idea to replace, because eventually it will be less than optimal chemically. Mechanically, I would need to do more research, but it seems mostly fine.
Just thinking, but in stop and go situations, having a setup where oil is removed to a higher surface area (I haven't posted on piping, but I like some of your thinking on that) for remote cooling, and then when the motor stops, gravity feeds the cooled oil back into the motor just when it is needed for a start seems like a good idea. I am not sure if I would use less oil though. My thought is that it provides room for more oil, and if I can have hole coverage while spinning it may allow for convection through the piping. Not sure if the amount of oil is as significant in preventing ingress as methodology.
bionicdan - not totally sure I can accurately picture what you are considering. I think there is some good possibilities for using centrifugal force to pump oil out of the motor for remote cooling. I am still trying to get a grip on whether introducing a hole will also introduce cavitation issues, or no, or whether the ATF may be protective. I think ATF is chemically mostly fine for winding varnish. Over a period of years, it may be a good idea to replace, because eventually it will be less than optimal chemically. Mechanically, I would need to do more research, but it seems mostly fine.
Just thinking, but in stop and go situations, having a setup where oil is removed to a higher surface area (I haven't posted on piping, but I like some of your thinking on that) for remote cooling, and then when the motor stops, gravity feeds the cooled oil back into the motor just when it is needed for a start seems like a good idea. I am not sure if I would use less oil though. My thought is that it provides room for more oil, and if I can have hole coverage while spinning it may allow for convection through the piping. Not sure if the amount of oil is as significant in preventing ingress as methodology.
ian.mich said:
I'm looking forward to it too. Constant drippage is something that has prevented me from experimenting with this.
Which motors wouldn't qualify because of their wire exit, though? I think there is a bafang motor that falls into that category, but i'm not sure what else would.
Spicerack
10 kW
Mine only drips if overfilled and the seepage is very minimal. Well worth the fact that I can now use the motor at my desired power level- 2kw, not the rated safe level- 500W!
itchynackers
100 kW
Yes, I am currently using the motocross valves. They work, but you still have to stop once (after you've heated the oil) to release the pressure. I'm just looking for the ideal solution. This is better, but not the best. I tried the pinhole method at first. It worked ok. I would get about a drop per ride coming out the cover. Not even enough to get on the brake disc. Still had to do a wipe down every couple rides though. I'm looking for a small, automatic release valve. No luck so far.
Also, I'm currently running 650ml of oil (takes a very long time to heat up the motor, and the peak temp is MUCH less). This is exactly half the open volume of my 9c motor, so the oil comes right up the the axle. I've had it squeeze out of the wires. You can actually watch it happen if you stop the bike, and wait a minute for the oil to seep. Once the motor begins to cool, it sucks back inside the axle. I thought I did a pretty good job of sealing within the motor where the wires enter the axle. Guess not. Still trying though!
Also, I'm currently running 650ml of oil (takes a very long time to heat up the motor, and the peak temp is MUCH less). This is exactly half the open volume of my 9c motor, so the oil comes right up the the axle. I've had it squeeze out of the wires. You can actually watch it happen if you stop the bike, and wait a minute for the oil to seep. Once the motor begins to cool, it sucks back inside the axle. I thought I did a pretty good job of sealing within the motor where the wires enter the axle. Guess not. Still trying though!
itchynackers
100 kW
Where is your hole located on the motor? Min is about 2" from the axle, wire side.
Kepler
10 MW
Decided to do the oil cooling mod on Bafang powered Fighter. Main reason was to quieten it down a bit but also with a view to turn up the amps a bit too. 
I started with adding 80ml of ATF and running it for about 5km. I then opened it up again to see how well it had coated everything. I was surprised with just how much oil the stator soaked up with very little actually draining out when pulled down.
Re assembled the motor sealing the motor case with some gasket silicon. Opted not to install a vent hole at this point as I figured the wiring through the axle would provide enough relief. Will see how this goes.
So test 2 today. Added only 40ml of oil considering the stator was previously saturated. Rode for about 5km. Motor was marginally quieter and importantly, no oil had leaked from the motor.
I have just added another 40ml to take it 80ml plus the original saturation. Probably closer to 120ml in total as an estimate. Still need to take it for a spin but the main aim is to find a balance of useful cooling and noise dampening without any significant oil leak issues.
I have read right through the thread but couldn't find too many references to gear hub motors and how much ATF worked best for them. Please share if you have any experiences with the amount of oil used in geared hubs.
I started with adding 80ml of ATF and running it for about 5km. I then opened it up again to see how well it had coated everything. I was surprised with just how much oil the stator soaked up with very little actually draining out when pulled down.
Re assembled the motor sealing the motor case with some gasket silicon. Opted not to install a vent hole at this point as I figured the wiring through the axle would provide enough relief. Will see how this goes.
So test 2 today. Added only 40ml of oil considering the stator was previously saturated. Rode for about 5km. Motor was marginally quieter and importantly, no oil had leaked from the motor.
I have just added another 40ml to take it 80ml plus the original saturation. Probably closer to 120ml in total as an estimate. Still need to take it for a spin but the main aim is to find a balance of useful cooling and noise dampening without any significant oil leak issues.
I have read right through the thread but couldn't find too many references to gear hub motors and how much ATF worked best for them. Please share if you have any experiences with the amount of oil used in geared hubs.
Kepler
10 MW
Ah huh. Thanks for that. :?
I am trying to work out what is the optimum amount of oil to add to a geared motor. Too little, and although I think it will lubricate fine, you wont benefit from improved heat transfer or sound dampening. Too much and you may risk placing unnecessary drag on the motor and even more annoyingly, start pushing oil out of the motor.
This is obviously an optimum amount to add. Hopefully I can figure this out with a bit of experimentation. However, it would be nice to gt a feel for what is working for others.
I am trying to work out what is the optimum amount of oil to add to a geared motor. Too little, and although I think it will lubricate fine, you wont benefit from improved heat transfer or sound dampening. Too much and you may risk placing unnecessary drag on the motor and even more annoyingly, start pushing oil out of the motor.
This is obviously an optimum amount to add. Hopefully I can figure this out with a bit of experimentation. However, it would be nice to gt a feel for what is working for others.
I'm just messing with you, motors can take a suprising amount of oil, and the drag is not significant at all. can never go wrong with 150-200ml in a 9C/1000w hub, which i think is plenty for your gear motor. you're bound to leak a little bit thru the bearing, and wiring i guess since you didnt seal that up and drill a pinhole.
itchynackers
100 kW
I found that for a DD motor, no-load current didn't rise after putting in more than 150ml. See the data here... http://endless-sphere.com/forums/viewtopic.php?f=30&t=38039&hilit=+650ml&start=30
It does leak out the axle more though.
It does leak out the axle more though.
Kepler
10 MW
My findings experimenting with oil level in a Bafang geared hub.
So baseline approx 100ml of oil. No leaks and a reduction of noise of maybe 50% at full throttle. Hard to judge temp but the motor seemed be getting as warm was it normally did for similar style of riding.
Went 150ml. Maybe slightly quieter. Again temp felt similar. Close inspection revealed a bit of oil weeping from side of the motor at the shaft. Not good but possibly acceptable.
Next was 200ml. Motor noise and temp the same as 150ml. However this time I noticed my back brake was no longer working too well. Looked down and sure enough, there was oil all over the place. Bugger, just what I was trying to avoid.
Spent the next 2 hours stripping down the motor, draining and cleaning up the mess. I stink of ATF.
So this is where this experiment finishes for me. Perhaps I would have seen better results by sealing the axles and adding a vent hole but I am not interested in risking anymore mess. I will leave the motor oil lubed by adding 50ml back into the motor but I doubt if this will be enough to aid in cooling.
My personal opinion is that its not worth the mess.
So baseline approx 100ml of oil. No leaks and a reduction of noise of maybe 50% at full throttle. Hard to judge temp but the motor seemed be getting as warm was it normally did for similar style of riding.
Went 150ml. Maybe slightly quieter. Again temp felt similar. Close inspection revealed a bit of oil weeping from side of the motor at the shaft. Not good but possibly acceptable.
Next was 200ml. Motor noise and temp the same as 150ml. However this time I noticed my back brake was no longer working too well. Looked down and sure enough, there was oil all over the place. Bugger, just what I was trying to avoid.
Spent the next 2 hours stripping down the motor, draining and cleaning up the mess. I stink of ATF.
So this is where this experiment finishes for me. Perhaps I would have seen better results by sealing the axles and adding a vent hole but I am not interested in risking anymore mess. I will leave the motor oil lubed by adding 50ml back into the motor but I doubt if this will be enough to aid in cooling.
My personal opinion is that its not worth the mess.
Kepler said:My findings experimenting with oil level in a Bafang geared hub.
So baseline approx 100ml of oil. No leaks and a reduction of noise of maybe 50% at full throttle. Hard to judge temp but the motor seemed be getting as warm was it normally did for similar style of riding.
Went 150ml. Maybe slightly quieter. Again temp felt similar. Close inspection revealed a bit of oil weeping from side of the motor at the shaft. Not good but possibly acceptable.
Next was 200ml. Motor noise and temp the same as 150ml. However this time I noticed my back brake was no longer working too well. Looked down and sure enough, there was oil all over the place. Bugger, just what I was trying to avoid.
View attachment 1
Spent the next 2 hours stripping down the motor, draining and cleaning up the mess. I stink of ATF.
So this is where this experiment finishes for me. Perhaps I would have seen better results by sealing the axles and adding a vent hole but I am not interested in risking anymore mess. I will leave the motor oil lubed by adding 50ml back into the motor but I doubt if this will be enough to aid in cooling.
My personal opinion is that its not worth the mess.
Yeah takes some real planning and definately a pinhole/valve and tons of silicone.
Sancho's Horse said:
Im not great at explaining things and more often writing my thoughts as they happen. What I was trying to suggest is you would have less free oil in the hub at any one time. So it spends most of its time in the pipes being cooled and then transfered exactly to where its needed on the coils etc. So rather than have 300ml+ trying to escape your hub you might only end up with 50-100ml pooled up before it hits the out exit hole on the body. You might still have 500ml in the system but it will be in a more controlled environment ie sealed pipes with no points of exit.
When I mentioned gravity I meant at 0-10mph there wont be any centrifugal forces really. So if you wound the coil from inside(hub) to outside (rim) in the correct direction (clockwise/counter cw) as you slowly turn the wheel any small bubbles trapped in the pipes will buffer the oil around. Then over ten miles per hour the force exerted outwards will take over this job. So even though its slow at 10mph it never stops completely
I opted for the temperature sensor so I may not need any cooling over my short 20 minute ride but worth keeping in mind. I would love oil cooling and three of the metal gears in mine so I could test out my 40amp controller properly but will most likely stick to 25a max on nylon.
http://www.youtube.com/watch?v=3K3XfpNmdK0
Still havnt received my mac motor from Em3ev and its been nearly 1 month when i selected sal-uk 2-4 week delivery before christmas. Ok christmas may have delayed it by a week but its still taking ages and it says status pending on the website :? . Will give an extra week for the holidays and keep my fingers crossed
*its here, took 4 weeks over xmas. Just gotta build my headway pack onto my frame then go test it in the snow wooo (so pending just means on it was on its way on the em3ev order status) It was very well packaged too.Sancho's Horse
1 kW
bionicdan -you know the problem of picturing it was my fault. I am working on a mid-drive setup, so the extra gearing allows it to ramp up to optimal speeds a lot faster, and at a lot slower speeds...so, I think in your configuration gravity would be a much greater contributor to overall dynamics.
Th oil will still build up pressure, so, a pressure release valve, or a well placed pinhole still seems like a critical element. I just don't have any data to release on how the oil will behave in the piping. I agree about the large bubbles being less of a problem, but under pressure, and without a release, they will behave differently.
Usually, there are better minds who have examined problems and crossed things off the list. However, there are also many of the greatest breakthroughs in science, which involve people making mistakes, or just doing things they are often themselves skeptical of and finding out that they were wrong.
Th oil will still build up pressure, so, a pressure release valve, or a well placed pinhole still seems like a critical element. I just don't have any data to release on how the oil will behave in the piping. I agree about the large bubbles being less of a problem, but under pressure, and without a release, they will behave differently.
Usually, there are better minds who have examined problems and crossed things off the list. However, there are also many of the greatest breakthroughs in science, which involve people making mistakes, or just doing things they are often themselves skeptical of and finding out that they were wrong.
Hi
I did a little research on ATF oil and other oils that would be suitable for hub motors.. based on the data provided on this blog.. the stator temp can get over 200 degrees F, and it seems to be around 130 C with 4kw input power..
it seems ATF breaks down above 200 degrees F or 100 C . thermal stability is important. a good oil in hub motors would have these qualities:
1. high dielectric
2. non corrosive
3. high thermal stability (so it doesnt break down into carbon or sludge)
4 good thermal conductivity
I would think a good candidate would refrigerant oil either mineral based or alkybenzene oil those oil have all those qualities .. grater than 300 degree before break down. does not attack the enamel on the motor windings.
and some oil go as high as 400 degrees..
great work on this site..
newbie (retired aerospace engineer)
salty
I did a little research on ATF oil and other oils that would be suitable for hub motors.. based on the data provided on this blog.. the stator temp can get over 200 degrees F, and it seems to be around 130 C with 4kw input power..
it seems ATF breaks down above 200 degrees F or 100 C . thermal stability is important. a good oil in hub motors would have these qualities:
1. high dielectric
2. non corrosive
3. high thermal stability (so it doesnt break down into carbon or sludge)
4 good thermal conductivity
I would think a good candidate would refrigerant oil either mineral based or alkybenzene oil those oil have all those qualities .. grater than 300 degree before break down. does not attack the enamel on the motor windings.
and some oil go as high as 400 degrees..
great work on this site..
newbie (retired aerospace engineer)
salty
