Wheel hubs and air vents/good idea?

Amish David

Active Member
#1
@Court you may have heard of this before as others have, I have read several post that stated and even one person said I build bikes and I know what I'm talking about which for some reason made me laugh, anyway I was told to drill holes in my rear wheel hub so it would vent and help the heat Escape. however my response to that is if you get caught in the rain you're kind of screwed are you not? I would assume water would get into the wheel hub causing it to Short Circuit or rust up after a while and stopped working. Any thoughts?
 

JRA

Well-Known Member
#5
@JRA would I have to drill a small hole to inject it then seal it with silicone? To be honest I had to get my neighbor to look this stuff up. Thanks for the advice.
Yes, you will need a place to get it in there but you can use one of the disc brake rotor bolt holes that will then be filled with a bolt. Just use a somewhat smaller bit and try not to bugger the threads. Mark it so that you will know which one as I have found it does need some re-upping about once a year.
 

Amish David

Active Member
#6
Yes, you will need a place to get it in there but you can use one of the disc brake rotor bolt holes that will then be filled with a bolt. Just use a somewhat smaller bit and try not to bugger the threads. Mark it so that you will know which one as I have found it does need some re-upping about once a year.
Than you for the info. I will order some soon
 
#7
First, it depends on whether or not you have overheating problems NOW, and also whether or not your hub is geared, or direct drive.

I was quite surprised to learn that water inside the hub is not really a problem, unless huge quantities. Waterborne grit and rocks and such are issues, most put screens over the holes. Long-term corrosion is a problem, most who drill the covers use a spray on varnish on the coils. The electrical short is apparently not an issue at all. Didn't make sense to me either, but 10 or more experienced riders all saying the same thing, and no disagreement from anybody, well, OK. This stuff is for direct drives motors, for the most part, and mostly only hot-rodders require these modifications.

The statorade is effective, though this may evaporate over time, and really should be combined with some heat sinks between the flanges, as what it does is transfer heat to this area, where the magnets are, which can be permanently weakened by excessive heat. The holes have the benefit of getting the heat OUT of the motor.

Again this is only needed at high power levels, for most users these techniques are not at all necessary and could actually do more harm than good.
 

Amish David

Active Member
#8
First, it depends on whether or not you have overheating problems NOW, and also whether or not your hub is geared, or direct drive.

I was quite surprised to learn that water inside the hub is not really a problem, unless huge quantities. Waterborne grit and rocks and such are issues, most put screens over the holes. Long-term corrosion is a problem, most who drill the covers use a spray on varnish on the coils. The electrical short is apparently not an issue at all. Didn't make sense to me either, but 10 or more experienced riders all saying the same thing, and no disagreement from anybody, well, OK. This stuff is for direct drives motors, for the most part, and mostly only hot-rodders require these modifications.

The statorade is effective, though this may evaporate over time, and really should be combined with some heat sinks between the flanges, as what it does is transfer heat to this area, where the magnets are, which can be permanently weakened by excessive heat. The holes have the benefit of getting the heat OUT of the motor.

Again this is only needed at high power levels, for most users these techniques are not at all necessary and could actually do more harm than good.
@Nelson37
I live in the mountains so yes it's getting hot, also I guess you called it direct drive only one gearing faster you hit the throttle the faster it goes. It will do a little over 33mph
 

indianajo

Active Member
#9
I've seen one hub motor with external heat fins, it was from Switzerland and cost over $2000. Trying to buy one, seems to have disappeared. Was stocked at sdebike.com but not now.
direct drive hubs drag the same backwards as forwards, geared hubs have in internal one way clutch and don't drag at all forwards. Pushing it around with no power should tell you which kind you have. Geared hubs are better for conquering grades theoretically, but heat capacity levels vary. I bought a serious dud.
 
#10
I've seen one hub motor with external heat fins, it was from Switzerland and cost over $2000. Trying to buy one, seems to have disappeared. Was stocked at sdebike.com but not now.
direct drive hubs drag the same backwards as forwards, geared hubs have in internal one way clutch and don't drag at all forwards. Pushing it around with no power should tell you which kind you have. Geared hubs are better for conquering grades theoretically, but heat capacity levels vary. I bought a serious dud.
It's a 10 speed mountain bike it rolls forwards and backwards just as easy as it did with a stock wheel
 
#11
That would indicate geared and not direct drive. The gears are internal to the motor, basically a small direct drive with a set of gears around it. Definitely make no holes. Statorade much less feasable. Light oil fill, or ATF, and/or, heatsinks. Hubsinks (TM) are available for several models that bolt together, also you can cut some aluminum C channel to size, cut some fins in it, and use an epoxy with good thermal transfer. These may help, but with a geared motor not so much. There is no good thermal path from the hot parts to the case. The real answer is pedal more, or put the motor in a smaller wheel. You have too high speed a motor for your application. The heat is because the motor cannot spin as fast as designed, the smaller wheel lets it spin faster and generate less waste heat.

There are also various ways to direct additional airflow to the hub with airscoop type arrangements.
 
#12
That would indicate geared and not direct drive. The gears are internal to the motor, basically a small direct drive with a set of gears around it. Definitely make no holes. Statorade much less feasable. Light oil fill, or ATF, and/or, heatsinks. Hubsinks (TM) are available for several models that bolt together, also you can cut some aluminum C channel to size, cut some fins in it, and use an epoxy with good thermal transfer. These may help, but with a geared motor not so much. There is no good thermal path from the hot parts to the case. The real answer is pedal more, or put the motor in a smaller wheel. You have too high speed a motor for your application. The heat is because the motor cannot spin as fast as designed, the smaller wheel lets it spin faster and generate less waste heat.

There are also various ways to direct additional airflow to the hub with airscoop type arrangements.
Will try hubsinks, I am doing about 50 percent of the work going up the large hills to my house. After a 30min. Ride I can keep my hand on the wheelhub but its pretty warm, thanks. I also only ride at about 15mph, im in no hurry.
 
#13
First, that's not hot at all, BUT, the windings inside are a LOT hotter than the outer shell. You really need an internal temperature sensor to have a good idea what is going on inside. Around 180F and above is when bad things start happening.

What is your speed on the hill, and what is top speed on the flats? Rule of thumb, maintain over 50% of top speed while hill climbing, or time to overheat can be from 1-2 up to 5-6 minutes, based mainly on the total mass of the motor.

Whoa, Nelly. Sorry, I re-read your top speed of 33 mph. YOU _ HAVE _ THE _ WRONG _ MOTOR.

Unless your are maintaining around 18 mph on the hill, that will seriously overheat. Need your motor make and model, preferably pics and a currently active link. Also battery voltage. And Wheel size. Those performance numbers point to possibly Direct Drive, where Statorade or ATF and hubsinks may be the best answer.
 

J.R.

Well-Known Member
#15
David,

Since you "are in no hurry", slow your throttle speed, lower the bike gear to make spinning the cranks easier (your effort) and spin faster. The only time I ever had a hub overheat was with my direct drive, slogging uphill in the snow.

Same hills in summer up to 95° never overheated with direct drive or geared hubs. The most simple, cost effective solution is to lower your speed, bike gear and pedal faster.
 
#16
David,

Since you "are in no hurry", slow your throttle speed, lower the bike gear to make spinning the cranks easier (your effort) and spin faster. The only time I ever had a hub overheat was with my direct drive, slogging uphill in the snow.

Same hills in summer up to 95° never overheated with direct drive or geared hubs. The most simple, cost effective solution is to lower your speed, bike gear and pedal faster.
I go about 15mph up hill but peddling for 3 min. Doing half the work getting up the hill I will buy a temp gage, I can put my hand on the motor and leave it their but feels hot to me.
 

J.R.

Well-Known Member
#17
Sounds warm if you can put your hand on it.

The reason I suggest spinning faster in a lower gear is that's how humans and low torque motors like ebike motors generate power. You'll be generating more power easily by spinning faster, not harder.
 
#19
First, that's not hot at all, BUT, the windings inside are a LOT hotter than the outer shell. You really need an internal temperature sensor to have a good idea what is going on inside. Around 180F and above is when bad things start happening.

What is your speed on the hill, and what is top speed on the flats? Rule of thumb, maintain over 50% of top speed while hill climbing, or time to overheat can be from 1-2 up to 5-6 minutes, based mainly on the total mass of the motor.

Whoa, Nelly. Sorry, I re-read your top speed of 33 mph. YOU _ HAVE _ THE _ WRONG _ MOTOR.

Unless your are maintaining around 18 mph on the hill, that will seriously overheat. Need your motor make and model, preferably pics and a currently active link. Also battery voltage. And Wheel size. Those performance numbers point to possibly Direct Drive, where Statorade or ATF and hubsinks may be the best answer.
My bike will easily go 18mph with no help, but I try to do as much PAS. . Up the hills Asia can because some are pretty steep for 3 min. At 15mph. I am running a Voilamart 1000w rear hub. Battery is 52.2 fully charged. 10spd. 26" My first build and i read a lot of good reviews on the motor, I am not going to spend 3k+ on a bike. My little 850.00 does fine for the most part, and my main transpertaction is horse & buggy, this is just a Sun. Church bike.
 

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