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oil cooling info needed please

J

jimmyhackers

Pedelecer
Feb 18, 2015
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few things i need to run through really.

im prefer oil over air cooling as with my pc i went from fans to water cooling and id never go back again. super cool and quiet.

i get air cooling is as easy as drilling holes. but as per another thread my hubs limit will be around the 2kw mark with air cooling. so oil is where im at for a 2kw plus increase.

please note i wont be pushing near 2kw on it... yet :)

either way i have some questions about oil.

what oil should i use?
how full should the hub be?
i figure i will have to make some gaskets/silcone seals to keep the oil in. will it still seep through bearing etc?
will the oil unbalance my hub sloshing about?
i get that the hub faces inside and out are the main heat transfer limitations(oil to metal to air). will grooving the inside and out faces so i increase their surface areas make any noticable difference to heat transfer?
i know that when metals gets hot their electrical resistance increases. how will keeping a motor cooler effect efficency or performance? i.e will a cooler motor use less amps/volts? if so will this change torque or top speed?

finally what kind of temp drops have people seen on their bikes with oil cooling

thanks in advance for the help
jim
 
S

selrahc1992

Esteemed Pedelecer
Dec 10, 2014
559
218
jimmyhackers said:
few things i need to run through really.

im prefer oil over air cooling as with my pc i went from fans to water cooling and id never go back again. super cool and quiet.

i get air cooling is as easy as drilling holes. but as per another thread my hubs limit will be around the 2kw mark with air cooling. so oil is where im at for a 2kw plus increase.

please note i wont be pushing near 2kw on it... yet :)

either way i have some questions about oil.

what oil should i use?
how full should the hub be?
i figure i will have to make some gaskets/silcone seals to keep the oil in. will it still seep through bearing etc?
will the oil unbalance my hub sloshing about?
i get that the hub faces inside and out are the main heat transfer limitations(oil to metal to air). will grooving the inside and out faces so i increase their surface areas make any noticable difference to heat transfer?
i know that when metals gets hot their electrical resistance increases. how will keeping a motor cooler effect efficency or performance? i.e will a cooler motor use less amps/volts? if so will this change torque or top speed?

finally what kind of temp drops have people seen on their bikes with oil cooling

thanks in advance for the help
jim
Click to expand...
completely noob question - but are you sure you need it at all? I know someone who routinely runs a BPM 500W at 1.5 kw in a hilly area witrh significant climbs without any additional cooling for i guess more than a year now with no heating problems whatsoever (and at a guess he weighs 100kg plus)
 
Stalkingcat

Stalkingcat

Pedelecer
Jan 24, 2015
193
28
are you sure you need it at all?
Click to expand...
Probably not, considering OP is planning on increasing the volts to gain the extra wattage. Heat come mainly from the amps so prob no need to cool, unless you want to experiment that is?

Maybe take the motor apart, stick a thermistor in there and see if any need to cool?....
 
J

jimmyhackers

Pedelecer
Feb 18, 2015
91
14
36
have read a fair way into the post on ES fair few pages, im have a fair idea of what to do :)

jist of it is...... oil works loads better, but can get messy. added drag seems to be more with air cooling less with oil. either way its negligible.especially when compared to gains in safer/cooler running aspects. either one is a viable option.

one post said he noticed a lot of drag with air cooling. and many comented on how full their hub was is critical to tempretures/drag etc

ive had a thought on oil cooling. people say that sealing it and expansion due to heat causes problems (messyness). depending on how good a seal i can create i could put the internals under a vacum which would negate expansion and possible keep the oil in for longer.

the irony is.... i dont think ill need anywhere need the full capacity of the cooling system im goign to create. but i dont think it can hurt
 
Stalkingcat

Stalkingcat

Pedelecer
Jan 24, 2015
193
28
How would you put the internals under a vacuum?

If any oil can escape due to not sealing well, then air would be sucked in the same way, if put under vacuum.

The cover seal is easy.
The main problem is oil getting down the wires.

The best solution to this that I have found, is to strip back the coating of all the wires and solder the strands up where they go into the axle. cover in heat shrink and then resolder onto the halls and phases.

Then seal the axle hole with a load of high temp silicone.
 
J

jimmyhackers

Pedelecer
Feb 18, 2015
91
14
36
i used to be an aircon engineer. my oil inlet would more than likley be a schraeder type valve. id remove the internals of the valve for filling with oil. then put them back in and stick my vac pump on the valve. pull a few torr and see if it holds a vacum. if it does gravy :) if it doesnt, i still have an oil filled hub that may leak a teensy bit.

my friend has a 2d laminate sign cutter. i might see if hes upto making me a set of gaskets with it. Then like you id gunk up the axle and also look and see if any flappy wires inside the hub can be secured with a high temp silicone.
 
Stalkingcat

Stalkingcat

Pedelecer
Jan 24, 2015
193
28
Fair play for experimenting with this, would be great if it worked....

On a separate note, I have seen pressure release valves used before but its hard to get one perfectly suited to the amount of pressure before opening. maybe there are adjustable ones around or different release settings?

You maybe hard pushed to get the pressure high enough at 2000w though?
 
D

Deleted member 4366

Guest
I wouldn't use gaskets. The motor is shimmed to eliminate sideways movement. You'll have to re-shim it if you add gaskets. A bit of sealant shoild be sufficient to seal it, but you need to think about the whether you'll be able to dismantle the motor again.
 
Stalkingcat

Stalkingcat

Pedelecer
Jan 24, 2015
193
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Also no real benefit of playing with gaskets as sealing the cover isn't a problem that needs solving.
I used rtv instant gasket sealer and am able to get the covers back off if needed. Unlike polyurethane and others, which will seal them shut for good.
 
T

trex

Esteemed Pedelecer
May 15, 2011
7,703
2,671
how often you need to open the motor cover? not very. I'd like to know how much farther you can push a standard 1kw DD motor with oil cooling. 48V 35A continuous?
 
Stalkingcat

Stalkingcat

Pedelecer
Jan 24, 2015
193
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Hi Trex, at 48V 35A continuous, i don't think you would need to bother with cooling, at least that's what it says on the motor simulator.
 
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trex

Esteemed Pedelecer
May 15, 2011
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at what power level do you think that the bike will be better equiped with a DD motor than a geared hub motor?
 
Stalkingcat

Stalkingcat

Pedelecer
Jan 24, 2015
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I think it depends on which motors are being compared, the riding being done and where abouts the watts are being used? Geared motors are more efficent at accelerating, but less efficent at crusing speed. So hard to know exactly, as a geared motor accelerating and sucking 2000w's would provide better acceleration than a non geared at the same power. The non geared would do a better job going faster and pulling 2000w than the geared would.
I think that's how it works, confusing myself now:(

Im just about to oil cool my new BPM motor, which so far, I love, running at 3000w.
 
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trex

Esteemed Pedelecer
May 15, 2011
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would you post your findings with the oil cooled BPM motor? that would solve the noise problem as well as increasing the pulling power.
 
Stalkingcat

Stalkingcat

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Jan 24, 2015
193
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Yeh apparently the BPM's are the perfect motor for cooling.

I've put it on an oldish carbon build, to try to get as light as possible..
20150328_163747.jpg
 
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selrahc1992

Esteemed Pedelecer
Dec 10, 2014
559
218
Stalkingcat said:
I think it depends on which motors are being compared, the riding being done and where abouts the watts are being used? Geared motors are more efficent at accelerating, but less efficent at crusing speed. So hard to know exactly, as a geared motor accelerating and sucking 2000w's would provide better acceleration than a non geared at the same power. The non geared would do a better job going faster and pulling 2000w than the geared would.
I think that's how it works, confusing myself now:(

Im just about to oil cool my new BPM motor, which so far, I love, running at 3000w.
Click to expand...
Which controller do you use? I just finished building a BPM with s12sh from bmsbattery which must give circa 50a because the LCD says 2300w on 12s/44v lipo,I'm light and its a primitive build (very good,but nonetheless,v brakes), I can't imagine upping power more without upgrading brakes,tyres and suspension,and becoming neurotic about the lovely community support officers
 
S

selrahc1992

Esteemed Pedelecer
Dec 10, 2014
559
218
selrahc1992 said:
Which controller do you use? I just finished building a BPM with s12sh from bmsbattery which must give circa 50a because the LCD says 2300w on 12s/44v lipo,I'm light and its a primitive build (very good,but nonetheless,v brakes), I can't imagine upping power more without upgrading brakes,tyres and suspension,and becoming neurotic about the lovely community support officers
Click to expand...
Sorry s12sm
 
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