Hub motor maintenance?

[Returnformer]

What exactly does a direct drive hub motor need in terms of maintenance? I searched and found lots of pages saying that they're low maintenance, but couldn't find what that low maintenance is.

In particular, what about the axle? I don't have indoor space to keep my bike, unfortunately, and need it ro commute etc, so I ride in all weather, rain, snow, e.t.c. The salty kick up from the roads in the winter is particularly corrosive, I need a new freewheel pretty much every year by the end of winter, although that shouldn't be getting inside the motor. It does get on/ in the axle, and likely as a result of that and/ or rain, the axle on my first motor seized up. It was ok for a while when used every day, but if I remember right, when we came back from a vacation it started having issues after having sat unused for a bit.

Anyway, how to I get in to grease the axle? I know how to remove the axle on a regular wheel, but I'm guessing it's not the same on a hub motor, with the wiring running through it.

What other maintenance does the motor itself need?

Thanks.

 

[MadRhino]

The axle is safe as long as it is firmly held in the dropouts to prevent it to spin. Torque plates, pinch dropouts, any mean to hold its torque, is a must.

The only maintenance required for a DD hub is to replace bearings. We don’t grease them, they are sealed bearings that will last many years.

Then, if you beat it to overheating, you may have to replace the hall sensors, or fry it dead. That is why serious builders with fast and powerful bikes, are using temp cut off or at least, temp monitoring.

 

[Returnformer]

The axle is safe as long as it is firmly held in the dropouts to prevent it to spin. Torque plates, pinch dropouts, any mean to hold its torque, is a must.

on that bike, i didnt have torque arms, i didnt realize i needed them yet. once i saw that it had dug out the dropouts, then i did research and realized i needed.

so, it wasnt rust that killed it, it was something else? spinning uncontrollably or something? why would that cause the axle to seize up and no longer rotate? and is there any way to salvage it?

 

[MadRhino]

When the axle does spin in the dropouts, it happens that it does twist or bend. This could explain the bearing seizure. Normally, bearing wear does make it loose, creating a lateral play that can’t be missed when fixing a flat, replacing tire or trueing the wheel.

The repair in your case, is to replace axle and bearings. That is likely to cost more than a new motor, unless you have access to a machine shop to make an axle yourself.

 

[markz]

Once the axle of the motor starts to spin from no torque arms, wires get their insulation stripped off and conductors touch and you get a fried controller. Rewiring the motor is easy, but the hole through the axle shaft is quite small. I'd stuff the largest wires you can through, and go with a sensorless controller. The larger wires can handle more power. While your in the motor, painting the inside with a insulating varnish is a great idea, lots mentioned here on ES about that. Hall sensors need to be glued in with a small dab of epoxy, then might as well throw in a temperature gauge too. Bearings are easy to replace and you can buy some Ferrofluid/Statorade to help cool the internals, again that info is well documented here on the ES forums.

I like to clean the hub, I usually have a cheap bottle of generic windex around to clean the hub, spokes, between the flanges and the rim. I like to inspect the spokes and see if any have poked through the rim strip.

Direct Drive motors have no moving parts inside, like geared motors gears. DD's last the longest, and with Geared motors you might want to replace the grease, Mobil 28 aviation is a good choice, but something similar is good too.
https://www.exxonmobil.com/en-US/Aviation/pds/GL-XX-Mobilgrease-28

 

[miro13car]

only maintenance on my hub motors is couple of droplets of oil on bearings
I have to put my ebikes on their sides on the floor so oil would get into bearings.
motor bearings must be kept wet with oil all the times.
I also drop some oil where cassette is.

 

[MadRhino]

only maintenance on my hub motors is couple of droplets of oil on bearings
I have to put my ebikes on their sides on the floor so oil would get into bearings.
motor bearings must be kept wet with oil all the times.
I also drop some oil where cassette is.

I don’t know the motor that you have. All of them that I have seen are made with sealed bearings. This means that you can’t get oil in there without breaking the seal. If you manage to push some oil between the seal and the crown, it can only be light oil that will lower the bearing tolerance to heat and hits. That is because sealed bearings must be filled with grease, not oil.

A sealed bearing is meant to last, then be replaced. There is no maintenance required, and if one would still want to do some, it could only be done properly with a new replacement seal and the matching die to press it in after greasing with graphite or silicon, heat rated grease.

 

[miro13car]

I use syringe to get some synthetic motor oil into bearings,
but even without syringe such oil seeps into bearings.
no way
those bearings are like water sealed after thousands of kilometers.
also factory grease ages for sure , drays after years of use
it is not the same grease as like new.
after over 10 000 kilometers - no slightest free play .

 

[MadRhino]

I have replaced bearings because they had slight play at 20000 km. Big bearings on 30 lbs motors, that never had been lubed since manufacturing. One of my motors once, shorted the windings on the casing because of bearing play, after 30+ thousand km, never serviced. I don’t believe that pushing oil in a sealed bearing can make it last longer. I would bet on the opposite but that’s your bike so...

 

[Tolkano]

You can grease sealed bearings just pick off the seal

My motor covers had 1 good bearing and 1 shit bearing that had alot of resistance when i tried to spin it, which improved alot after i repacked it with proper grease

 

[dogman dan]

If the seal fails enough to grease them, replace them. Get the new ones at a good bearing shop local, or on line. Fairly standard bearing. Get some oil in there temporary makes sense.

Re the original post. In your climate, its possible for water to seep into the motor as vapor, then condense inside. This can rust a motor, or in worst case, enough water can freeze and then the motor won't turn with the chunk of ice inside till it thaws.

This takes some time, so my advice would be to open the motor once a year. Same time you swap the freewheel. Just open it up, and look for rust, let some moist air out. If you actually drain out liquid water, then look at painting the inside of the motor for next year, and possibly open the motor to dry it out more often.

 

[markz]

If the seal fails enough to grease them, replace them. Get the new ones at a good bearing shop local, or on line. Fairly standard bearing. Get some oil in there temporary makes sense.

I found my MXUS 3kw bearings at a parts store for transmissions.
https://transmissionsupplies.com/
I would have never have guessed, but for some reason, some person I called directed me there and it was a good price. I prefer to buy local if I can, but it is easier to press the mouse button and wait.

I rode around with a loud, noisy bearing for a few days. It got peoples attention, no bicycle bell needed

 

[Returnformer]

If the seal fails enough to grease them, replace them. Get the new ones at a good bearing shop local, or on line. Fairly standard bearing. Get some oil in there temporary makes sense.

Re the original post. In your climate, its possible for water to seep into the motor as vapor, then condense inside. This can rust a motor, or in worst case, enough water can freeze and then the motor won't turn with the chunk of ice inside till it thaws.

This takes some time, so my advice would be to open the motor once a year. Same time you swap the freewheel. Just open it up, and look for rust, let some moist air out. If you actually drain out liquid water, then look at painting the inside of the motor for next year, and possibly open the motor to dry it out more often.

how do i open it up, the bolts on the sides? anything special to do to get it open?

thanks.

 

[markz]

how do i open it up, the bolts on the sides? anything special to do to get it open?

https://www.ebikes.ca/learn/troubleshooting.html

What I do is take the bolts off the cover plate, then take a flat head screw driver(s) to insert ever so slightly then twist to lift the cover plate. Insert too far and you would end up damaging the laminations on the stator. Then lightly tap the axle on the ground to get the stator out of the magnetic force and it comes out like a breeze. You might need a jaw puller from Harbor Freight to get the cover plate off.

 

[flat tire]

If it doesn't fail catastrophically they generally don't need maintenance. For perspective, car wheel bearings usually last 200k+ your bike will probably do 20K+ which is longer than nearly all users will ride a given bike.

If you want to open the motor to remove water, it's probably both too late to prevent rust and you should only do it when nice and hot, so all the water is sure to escape. And try to seal it up before you close the covers.