Dangers of oil cooled BDC hub motor?

Hey everyone, I'm new to the forum but have been lurking without a username for some time now. I know that this has been a topic of discussion in the past but was hoping to get some more information from the wonderful people here

I have a direct drive hub motor/wheel combo that I purchased from ebay a little while back. I recently started overvolting it (from 36v to 48v) and love the additional speed and power, but I'm concerned about the heat that is generated. I have read that there is really no point to oil cooling a hub motor without gears because there is no need for the lubrication, and that drilling holes in the side covers is just as, if not more effective. I would really rather put oil in the motor though because I'm concerned about the moisture that may get inside if there are holes in the side covers. Is there any reason that it would actually be worse to put oil in a direct drive hub motor vs a geared hub motor?

There seem to be lots of cure-all stories revolving around oil filled hub motors, but there have to be some horror stories out there too. Does anyone have some that they would like to share? I'm most concerned about the oil ruining whatever adhesive is used to attach the magnets to the wheel hub especially if automatic transmission fluid is used. Is this a legitimate concern?

Thanks in advance!

You should look up the still-in-use thread about oil cooling such motors. It's FULL of all the information (and stories) you're after.

"Oil cooling your hubmotor, it's not snake oil" (20 pages)
http://endless-sphere.com/forums/viewtopic.php?f=2&t=37972

Sorry man, but to post your 1st OP about a thread that has 35+ odd pages, seems kinda..."trollish" in internet slang.

Anyways, WELCOME TO ES! The hardest part of having liquid coolant sloshing around in the hub is actually keeping it there 1st. A close 2nd is monitoring it's level just as anyone would do a car's fluids (you drive a car or are familiar with the process I'm assuming). You'll find hidden in that thread quite a few posts about a "spigot hole" that is used to refill the oil in case any does leak out.

That's my 2 cents of it. Harhar, I kinda joined near or about the same time that thread started. LUCKY ME

Thanks for the welcome . Sorry, I can see how my post might seem a little trollish. I read through a good chunk of that thread, but somehow I didn't notice that it was 20 pages. It looks like I've got a lot more reading to to!

The reality is, the folks that committed to the process haven't said otherwise that it wasn't helping. No utter failures reported from my observations.

*still busy reading* So no one thinks that atf dissolving the adhesive is a significant concern?

I'm just wondering why you need to oil cool a dd motor being run on 48v? Unless you give it 60 amps or more, or climb crazy steep hills, you aren't going to melt that motor. Normal riding on hills up to 8% are not a problem at 48v 20 amps.

I did learn how to melt motors, but always did it with 3000w, not 1500w or less.



http://endless-sphere.com/forums/viewtopic.php?f=4&t=18921&p=276344&hilit=Heat+test#p276344

The motor is rated for 800 watts @ 36v and I'm running ~50v through it. I wouldn't be terribly concerned except that there are a lot of relatively steep hills in my area. The motor gets pretty hot to the touch. If you think this level of power doesn't warrant additional cooling though, by all means tell me I'm wrong. I just figured it would be a good idea.

if you can hold your hand on the motor indefinetly, its ok. if water boils on the magnets after 10 minutes of "heat soaking" (sitting after a hard ride, or hill) then its too hot and u need to lower amps, cool, or get a smaller wheel........ :wink:

Exactly what he said...

At 48v.. I highly doubt you are getting even close to hot enough to cause problems