Definitive Tests on the Heating and Cooling of Hub Motors

[Arlo1]

Just bead blast them and maybe machine slight groves into them.

 

[izeman]

If you had the patience you could turn a series of small grooves in the face of the covers, say 1mm wide x 1mm deep spaced 1mm apart. That would double the surface area.

Wouldn't it be even tripled?

 

[Punx0r]

It was late-night logic, but as far as I could see, the space between the groves and bottoms of the groves is the area you had anyway, but you gain the area of the two sides of the grooves. As it's all equal dimensions you get 1mm+1mm (original) plus 1mm+1mm = double. I could well be wrong.

Alternatively you could fix an aluminium torroidal plate to the face of the cover with loads of intersecting hacksaw (or chopsaw) cuts across the face to make a pin-fin heatsink. It wouldn't be pretty but it could be done from a random piece of scrap with basic tools.

Or CNC something nice like Luke suggests

 

[izeman]

yes. you're right. i'm wrong. i didn't take the bottom into consideration the grove makes it 3 times the surface, but the bottom is unchanged. so it's doubled...

 

[Punx0r]

I guess the real answer is to have a motor that's more efficient, but working with the motors we have, getting more heat to the case via oil and then increasing its disipation seems like a neat idea to increase power handling.

Drag losses from the oil would be interesting to know. I know convention is to reduce wheel size and volt up, but with oil drag I imagine there's a compromise somewhere for optimum efficiency. Rather than resistive Vs. hysteresis losses it's resistive Vs. hysteresis + drag

 

[izeman]

I guess the real answer is to have a motor that's more efficient, but working with the motors we have, getting more heat to the case via oil and then increasing its disipation seems like a neat idea to increase power handling.

Drag losses from the oil would be interesting to know. I know convention is to reduce wheel size and volt up, but with oil drag I imagine there's a compromise somewhere for optimum efficiency. Rather than resistive Vs. hysteresis losses it's resistive Vs. hysteresis + drag

imho efficiency if quite good already. most of us are just pumping way too much power in this small motors. that makes them less efficient. but even if you ride it on a moderate level you still can overheat the motor if it's no able to rev up to it's healthy rev zone. and then you would need cooling as well. that's why my latest build it a mid drive. i live in a hilly neighborhood and with the mid drive i allow the motor to run at almost full rpm most of the time.

 

[sardini]

Sardini: I don't know my phase amps, but I run 24s LiPo and pull about 30 to 45Adc on my extended climb of about 11 Km. I try to keep the speed at around 30Km/Hr without stopping. I'm just reaching the 90DecC point at the top of the hill on a warm day (just in time to head down and cool off). Obviously stopping and starting a lot, will heat things up a lot quicker. I do a total 42Km loop of ups and downs on shingle forestry roads and use about 13AH of my 15AH pack (first 11Km is the longest climb and uses most of the packs power) .

We all have different requirements, oil is a simple option to give a go and see if it suits you.

Oil generally has many disadvantages , but, if you want to go a simple as it gets, replace oil with deionized water and you will have a lot more fun!

 

[alsmith]

Over time, ALL coolant will turn conductive.

From THE BEST HEAT TRANSFER FLUIDS FOR LIQUID COOLING

Deionized water is water that has had its ions removed, including sodium, calcium, iron, copper, chloride, and bromide. The deionization process removes harmful minerals, salts, and other impurities that can cause corrosion or scale formation. Compared to tap water and most fluids, deionized water has a high resistivity. Deionized water is an excellent insulator, which is why it is used in the manufacturing of electrical components where parts must be electrically isolated. However, as water’s resistivity increases, its corrosivity increases as well. Deionized water will pH at approximately 7.0 but will quickly become acidic when exposed to air. The carbon dioxide in air will dissolve in the water, introducing ions and giving an acidic pH of around 5.0. Therefore, when using water that is virtually pure, it is necessary to use a corrosion inhibitor. When using deionized water in a recirculating chiller, special high purity plumbing is needed. The fittings should be nickel-plated and the evaporators should be nickel-brazed. When using deionized water in cold plates or heat exchangers, stainless steel tubing is recommended.

 

[parabellum]

I have to guess about no oil loses, and it is not worth relying on my memory.
But have measured this right now.
At 35C I have 210W no load on 795rpm (CA calculated)
At 100C I have 140W no load on 795rpm

Should I ride a hot motor for efficiency?

Mxus 500w 8.36kv(calculated from CA data) 300ml Quacker State ATF about 3cm under axle level (temp sensor between lams and winding)

 

[liveforphysics]

Sardini: I don't know my phase amps, but I run 24s LiPo and pull about 30 to 45Adc on my extended climb of about 11 Km. I try to keep the speed at around 30Km/Hr without stopping. I'm just reaching the 90DecC point at the top of the hill on a warm day (just in time to head down and cool off). Obviously stopping and starting a lot, will heat things up a lot quicker. I do a total 42Km loop of ups and downs on shingle forestry roads and use about 13AH of my 15AH pack (first 11Km is the longest climb and uses most of the packs power) .

We all have different requirements, oil is a simple option to give a go and see if it suits you.

Oil generally has many disadvantages , but, if you want to go a simple as it gets, replace oil with deionized water and you will have a lot more fun!

Water is one of the very best heat transfer fluids on the planet.

However, it would be a terrible choice in this appliction. It would work only if you could keep the water only in contact with an ion-free surface (no metal contact) and in an environment with no atmospheric CO2 (because it instantly dissolves into deionized water to make carbonic-acid.)

 

[sardini]

Nevertheless, the first video shows how fast the temp goes from 84c to 67c at the stator (down left screen) .


[youtube]UiGO8RffovI[/youtube]

[youtube]LchBIXH5PXY[/youtube]

 

[cal3thousand]

Nevertheless, the first video shows how fast the temp goes from 84c to 67c at the stator (down left screen) .

I couldn't see anything in that video... too busy trying to recover from vertigo

 

[sardini]

Nevertheless, the first video shows how fast the temp goes from 84c to 67c at the stator (down left screen) .

I couldn't see anything in that video... too busy trying to recover from vertigo

You are right i will make a better one but the number are right it needs 30-40 sec from 84c to 67c

SORRY!

 

[agniusm]

Or you could just piss on your hub, will save you a syringe and tubing :lol:

 

[hydro-one]

That works!!!! just dont piss on your battery wires!!!! i will ask my bother about water, he is a boiler chemist, one of few apparently.... id rather have water dripping out of my motor than oil although mineral oil seems a ok compromise,....

 

[Hyena]

Lol, that reminds me of a story my uncle told me once about the time his car broke down in outback Australia. It overheated and blew the radiator cap so he lost alot of water. There was no water around but he happened to have a bottle of wine in his car. Rather than waste the wine by tipping it straight into the radiator he drank it then half an hour later pissed into it :lol:

 

[alsmith]

Or you could just piss on your hub, will save you a syringe and tubing :lol:

That would be restrictive for cooling unless you get a radical cystectomy so flow would be more continual. Probably not for everyone. Or anyone?

 

[John in CR]

Just let me know when you guys get a liquid cooled hubbie ready to race, so my air cooled hubbie can embarrass it hauling a fat rider. This talk about the oil filled messes being so great has gone on for over 2 years now, but no one has run one at higher power than I run a stock sealed motor purchased in 2008. It's time to put up or shut up. If the best it can do is help a low power geared hubbie run at moderately higher power, that's fine, but just admit it, so we can stop hearing the endless speculation about liquid cooling without a motor specifically designed for it.

I may actually put oil in a hubbie some day, but it won't really be for cooling. Instead it will be to prevent corrosion and to keep water out.

 

[liveforphysics]

Your motors are a level above my friend.

Massive and well designed. That's tough to beat for high performance and reliability.

It wouldn't be a good fit for my next roadbike build though, because I'm shooting for ~35-40lbs total vehicle with battery weight.

 

[Punx0r]

Air-cooling wins for simplicity but water ingress is a problem for me (at least). It rains ocassionally here and local flooding of paths/trails means I sometimes ride through water upto the axle (I'll handbag the bike if it's deeper than that).

 

[Spicerack]

Air-cooling wins for simplicity but water ingress is a problem for me (at least). It rains ocassionally here and local flooding of paths/trails means I sometimes ride through water upto the axle (I'll handbag the bike if it's deeper than that).

I rode my air cooled large slotted 9c through quite alot of water last week. I had prepped it a bit with some spray oil before riding and the water was only surface and moderate puddles but it went fine. In fact on a run where it normally gets to 40-55 celcius it ran at 21 celcius due to the water spray passing through it constantly. So there you go. Air cool your motor then ride it in the rain- no overheating problems! :wink:

 

[cal3thousand]

Air-cooling wins for simplicity but water ingress is a problem for me (at least). It rains ocassionally here and local flooding of paths/trails means I sometimes ride through water upto the axle (I'll handbag the bike if it's deeper than that).

That's why mine is air-cooled. It was super easy to varnish the windings/stator and drill holes in the sideplate while I had it open for repairs. I'm not at all worried about water ingress since I have the varnish, but I'm beginning to worry about other things such as sand and gravel.

I think I will just make it a point to spray out the motor afterwards if I'm in really sandy conditions and run it until dry.

Anyone think that's a bad idea?

(BTW, for anecdotal fun, the motor is only barely warm to the touch after a 13.5 mile commute at ~30mph with bursts to 40mph)

 

[Merlin]

What Motor did you drive?
Iam thinking again to open a bit my 4080...

 

[cal3thousand]

What Motor did you drive?
Iam thinking again to open a bit my 4080...

3525

 

[sardini]

I have to say that i use drops of water, which quickly evaporate, when needed. The downside is that my range went from 80 km to 50 km....hahaha

My 200euro hubbie have done over 15000km and it is perfectly ok love you guys