Cooling a hub motor with small fans inside and some question

I have seen somewhere in a forum that someone installed mini computer fans inside his huge 10k motorcycle
hub motor and drilled a few holes in the hub motor sides and said that it never over heated on him.

I was wondering if it will work without drilling holes in the hub, what do you think?

Also, Do you think i can fit two or three 4cm square fans inside a 1500w motor? (never had it open)

Next question, When people upgrade the phase wires to thicker ones, why don't they upgrade the hall
wires? they are extremely thin, don't they burn?

I need power for my 12v temperature monitor and i was told to use a DC/DC converter.
I checked on ebay and there are plenty that cost about $2.5 but they say that the output is 4.5v to 30v
but there is no knob or switch to set it to a fixed voltage...How does that work? Here is a link to one:
http://www.ebay.com/itm/60V-Input-D...801?pt=LH_DefaultDomain_0&hash=item43bde15bf9

Last question, Do you guys know if the cycle analyst temperature indicator can be programmed to beep
at a certain temperature level?


Roy.

The three phase wires to the motor flow the amps. If you upgrade the phase wires to something fatter, they can flow even more amps than the stock wires without overheating. It is not uncommon for a Cromotor to use 100A.

The hall wires only use a small 5V signal at very low amps, regardless of how many amps the motor is using. Whether the motor is big or small, the hall wires never produce much heat.

On the dcdc converter the blue rectangle with the brass screw is the voltage adjust knob.

Using fans inside a sealed motor is pointless. You need the holes in the case to remove the heat to somewhere else otherwise you're just recirculating hot air.

Oh i thought that the main issue with over heating is the heat of the motor itself that is melting the wires...

One DC/DC converter on the way thanks!

How do people make their hubs work with holes? I can't imagine what will happen after one day riding
on a dirt trail not to mention rain and puddles...am i missing something?

Would like to hear from you people who know the cycle analyst well about my last question.

Thanks alot.

Lots of posts on the subjects Roy. Ill admit it's a bit daunting at first , but so much knowledge here it's time well spent.

The only way that I have been able to cool motors is with air flowing through the internal guts was to use a pressure type blower, what I found works well is a brush less motor fan (if you can't find one, a air bed inflate type will do but with brushes will have a short running life) that will push out air out with inches of water pressure (like a vacuum cleaner impeller type) using the output end. On a hub motor I would drill a series of holes on both sides of the covers, then use the output of the blower with a close nozzle and 100% shroud to make sure the air flow is through from one side to the other.

ES member bluefang adapted an existing centrifugal fan to the shaft of a non-hub motor. I believe that this idea could be adapted to a hub-motor, with the fan attached to the disc brake flange, and if you add stand-off spacers, a disc brake could still be used.

My idea is that holes would be added to the hub on the disc brake side near the axle, and holes would be added on the other side near the rim. This is just my opinion, I have not run experiments yet.

If i drill holes in my motor than i would go with the mini fans idea inside the motor.

BUT, why doesn't anyone talk about the problems of having holes in the hub motor?
If for example i go off road the whole inside on the hub would be filled with sand and rocks
and i didn't even get into the water problem in winter, off road puddles....sounds like a short life for the poor hub.

It depends on the hole size and placement. Water isn't normally a problem unless it stays in there. And you'll want to coat the inside with a protective armature coating. Rocks shouldn't get in but you can put a screen material over the holes if that is an issue for you. Dust and dirt goes in one side and out the other.

But before you take the motor apart, do you know you need more cooling yet? Cooling is only done by those people pushing the motor beyond it's design limits. Its not something 99.999% of the motors need. Many here do it because this forum is sort of where the insane and power mad ebikers congregate, and many of us are shoving unreasonable amounts of power into our motors. So Many of us need to cool them just to keep them running. A normal motor shouldn't need cooling. If it does, you're probably using the wrong motor for the job.

If you need really extreme cooling for the hub, you might be better off trying to somehow increase the surface area of the hub in combination with oil cooling. I don't know if putting oil into the hub is an option for you, but I think it is something worth considering if you haven't already. There is only so much air you can have blowing through the hub. You might also look into a higher capacity hub motor or a chain drive of some sort with an even bigger motor. Oil cooling your hub sounds like the biggest bang for your buck to me. Maybe look into the cost of a little automatic transmission fluid and appropriate sealant.

Holes work, but only marginally, because no fan design in the world consists of holes in a relatively flat plate. Debris is a surprisingly small issue. First, mount your motor properly so the hall sensors are at the top and less likely to get west. That's the intake side. Exhaust side requires holes at the extreme perimeter to dust, water and sand getting in can flow right out. Small holes is the way to go for good reasons, to get the cooling air where you want it and to get exhaust holes closer to the perimeter as well as prevent anything large from getting in no matter what.

To get flow:
Active-
Zappy uses fans with good success, sucking air from the intake side and blowing to the exhaust side. I would use small blowers instead of the little axial fans, since axials really need freely flowing air without disturbance or restrictions unless you go to high power and noise. Plus the blowers can take air from the intake side and blow it at 90° at the stator. Going active with fans makes sense for slow high load riding like off road, and Zappy has little problems even in mud and riding through small creeks and stuff. Toolman2 who also rides in the dirt uses a noisy leaf blower type motor to force air into his motor.

No Active fans-
Holes alone permit some minimal flow, so it does help cool to a small extent, several hundred watts max with no blades. I've used blades both inside and out to stimulate more flow. Interior blades on the covers make sure the air is spinning well and allow you to direct it at the stator, to help more heat be carried out of the motor. I've never had a heat failure and have run up to 12kw through hubbies with interior blades. Flow is still not strong though. I have gone to exterior blades on the exhaust side, which fling air away from the motor shell like any centrifugal blade. Exhaust holes should be behind the blades, which is the low pressure region and sucks air out of the exhaust holes. I run a hubbie with less surface area than typical at 26kw peak with this approach, and the only way to get it hot is extreme loads like a nearby 20% grade mountain road with many low speed accelerations due to the curves, and by hot I set my alarm at 105°C and it's only tripped once. No high pitched fan noise and hundreds of CFM of air flow at healthy street rpms are why I go with blades. Plus there's no wiring or fans to break and replace.

Oil,
It's messy and drips. Sure it helps get heat quicker from the stator to the shell, but then what? It still has to be transferred from the shell to the outside air, so it accomplishes very little for continuous running. Plus the inside of hubbies isn't made to withstand hot moving oil. It's probably of greater benefit to geared hubbies which suffer the insulating affect of air, since the spinning motor is inside and separate from the shell.

No direct drive hubbie with oil has run anywhere near the same power that ventilated motors have run. Just don't follow the crowd putting big holes in the side covers not even close to the perimeter. It helps cool, but only marginally, and no real thought or planning or testing went into the size or placement with that so often copied strategy. An EE who is good with electronics came up with that approach, but air flow design and thermodynamics is the domain of ME's, and except for LFP who excels at both, they mix about like oil and water.

Well thanks alot, i guess i will wait and see the temp of the motor while pumping max juice to it
and see how hard i need to go with my cooling system.

Roy.

rg12 said:

Well thanks alot, i guess i will wait and see the temp of the motor while pumping max juice to it
and see how hard i need to go with my cooling system.

Roy.

Click to expand...

That's best, since cooling needs vary so much with load, terrain, how you ride, etc. Just don't go pushing your motor to 130°-150°C or higher like some foolish members seem to believe is ok.

I'm planning on trying this on the disc brake side of a hubmotor:

http://endless-sphere.com/forums/viewtopic.php?f=30&t=62658

All that sound too complicated.
Why not take a windshield washer pump, place the nozzle on the chain stay aimed towards the motor and activate it with a button.
Would only work at low-speed, at a high speed I suspect most would be lost to the wind

spinningmagnets said:

I'm planning on trying this on the disc brake side of a hubmotor:

Click to expand...

No need to build something that big, but yes exterior centrifugal blades are the cat's meow for cooling. That's how I keep my Hubmonster 20-30°C or more cooler than HOV's who has nearly identical ventilation as mine, but he never installed the blades, instead choosing to suffer motor heat problems.