Life span of a hub motor?

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Paul T   10 mW

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Life span of a hub motor?

Post by Paul T » Apr 02 2012 4:24am

I have a 500w front hub motor set up on my bike; I lost my licence for 2 years hence this mode of transport. It’s been great I’ve had it about ten months now and have done over 4000kms on it, It’s had the controller replaced and the hall sensors, but they may not have needed to be replaced as it was the controller, but my question is how long will the hub motor itself last? I’ve ridden it through countless downpours I cover the controller and battery off course but the hub just ploughs through rain hale or shine. What wears out in there? It’s not the geared type of hub motor.

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Re: Life span of a hub motor?

Post by miuan » Apr 02 2012 4:28am

The motor will eventually get rusty inside and the bearings will fail first. Other stuff is pretty much fail proof in direct drive motors. Golden Motor once stated their DD motors should last for 50tkm, but of course it varies with too wet weather conditions.

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dogman dan   100 GW

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Re: Life span of a hub motor?

Post by dogman dan » Apr 02 2012 6:09am

Yeah, rust can kill a motor early. Drying out the inside from time to time will help. Water can get inside in amazing ways, but a few holes drilled in the hub cover can let the vapors out on a dry day. You can keep the holes covered most of the time with some amuminum duct tape. The all metal tape designed for hot ducts is what I mean.

Kept dry, the bearings tend to last a lot longer but are easily replaced. As you know, replacing halls is not a huge problem too. So other than a motor getting so rusty it siezes, only abuse kills a brushless hub. You can break the case in a crash, or melt one with too much watts.

One option to consider if this is your only transport for awhile is a second bike, or at least having spares like another motor kit handy. So you don't have weeks of downtime if something does break.

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Re: Life span of a hub motor?

Post by ZOMGVTEK » Apr 02 2012 11:14am

A DD hub should last almost forever. The bearings will eventually fail, but they should be fairly easy and cost effective to replace. Keep the windings dry and cool, and it can last you a lifetime.

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Drunkskunk   100 GW

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Re: Life span of a hub motor?

Post by Drunkskunk » Apr 02 2012 11:44am

Only wear part is the bearings, and those should last at least 20 years of constant use before the seals might get old and possably leak. But then I have some 30 year old wheel bearings on my motorbike that are in pristine condition. YMMV. But I'd say the motor will out live your grand kids
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Kingfish   10 GW

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Re: Life span of a hub motor?

Post by Kingfish » Apr 02 2012 11:58am

I’d have to agree with all the above.

My first DD motor still works, however the second pair used in my 2WD both suffered/failed from rust within a couple of weeks of each other. Once that occurs you are in for a complete R&R which includes rust treatment, plating, varnishing, venting, finally seal- and bearing replacement.

An interesting idea is to add a tiny vent hole near the axle to equalize the pressure and prevent vacuum from sucking the moisture, and perhaps a threaded drain hole near the periphery on each side to bleed off the condensate. There’s another thread going around using an oil-cooling bath which in the right circumstance along with the vent/fill hole could be enough to assuage heat & rust.

Beyond that, as long as the motor doesn’t overheat, it should last a good long while. :)

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MadRhino   100 GW

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Re: Life span of a hub motor?

Post by MadRhino » Apr 02 2012 12:01pm

Yep, the only ways to kill a DD hub are water and heat. Well, they don't really kill it, but can make it more expansive to repair than buying a new one.
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Re: Life span of a hub motor?

Post by Kingfish » Apr 02 2012 12:09pm

MadRhino wrote:Yep, the only ways to kill a DD hub are water and heat. Well, they don't really kill it, but can make it more expansive to repair than buying a new one.
Except that getting a new one doesn't solve the inital design flaw: Mine wasn't even 6 months old before it crapped out rust-solid. :cry:

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dogman dan   100 GW

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Re: Life span of a hub motor?

Post by dogman dan » Apr 02 2012 1:59pm

I've never worried too much about water, living in the desert like I do. But oddly, we got a few snowstorms this winter, and I took a few spins in the snow as it melted away. Later this spring, a hall sensor failed in my motor, so I replaced it with a spare I had around.

I was a bit suprised to see how much rust I had inside, for just a few wet rides. No other motor I've owned has had a trace of rust before. Not wanting a lot of dirt getting inside a dirtbike motor, I ended up drilling vent holes in the cover, but 1/8 inch ones. The idea is humidity will always get driven out when the motor gets hot, but larger sand particles will still be excluded.

We'll see if this approach works.

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amberwolf   100 GW

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Re: Life span of a hub motor?

Post by amberwolf » Apr 02 2012 5:19pm

That Fusin I got from you was nearly spotless when I got it, and it's not seen very much moisture here in Phoenix, only some sprinking rain, yet when I opened it roadside to kludge up a fix for the cracked clutch, it was pretty rusty in there. Not like Kingfish's motors, but a lot worse than I'd expected.

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LegendLength   100 W

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Re: Life span of a hub motor?

Post by LegendLength » Apr 03 2012 10:19pm

By the time the motor dies there will be cheaper, lighter, more powerful ones around :)

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Re: Life span of a hub motor?

Post by lcyclist » Apr 09 2012 4:59pm

I rode a 1kw BMC direct drive hub for over 10,000 miles (16 kms) until it was stolen. I think it would have lasted 10,000 miles more. I rode it conservatively at maxing 500-1200 W
in hot/shine weather in Phoenix. I replaced parts of the bike (controller, battery, a set of chain, pedals, flat tires) but the motor kept going. On the other hand, my 600W BMC geared motor only lasted 6000 miles before the gear clutch started to malfunction. So now I am riding a Crystalyte HS direct drive, sensorless and still going after 5000 miles.

If rode conservatively, I think a direct drive motor will last a long time. Great for commuting.

Paul T wrote:I have a 500w front hub motor set up on my bike; I lost my licence for 2 years hence this mode of transport. It’s been great I’ve had it about ten months now and have done over 4000kms on it, It’s had the controller replaced and the hall sensors, but they may not have needed to be replaced as it was the controller, but my question is how long will the hub motor itself last? I’ve ridden it through countless downpours I cover the controller and battery off course but the hub just ploughs through rain hale or shine. What wears out in there? It’s not the geared type of hub motor.

ColinB   100 W

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Re: Life span of a hub motor?

Post by ColinB » Dec 04 2015 8:33pm

Bringing back an old thread....

I've got a Crystalyte HS3548 that I've used for 2 years so far, and 11,000kms. I wonder how long it might last. I am not able to remove the motor cover (can't get the screws out without stripping them) to see how it is doing inside, if it is getting rusty. For removing the screws, I've tried heating them to release any lock tight, and using a manual style impact driver. No luck. It's not budging!

I do ride in the rain and on wet roads here in BC. I at least have the motor wires in a drip loop, which should help a little. And I don't leave the bike out in the rain. Should I pick up a spare motor soon? It still "feels" like it did when it was new. If it is getting all rusty inside, what would occur? Bad hall sensors? What would happen to my controller and battery? I don't have a fuse in my system.

Thanks for any thoughts. Colin

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Chalo   100 GW

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Re: Life span of a hub motor?

Post by Chalo » Dec 04 2015 8:45pm

As others have said, the bearings will fail first. When that happens you'll be able to feel a slight amount of play when you push the wheel from side to side in the frame. Any perceptible play at all should be taken as a sign of deteriorated bearings. To replace them, the side covers have to come off.

If a magnet comes unglued, there will be a horrible racket and enough consequent damage that a new motor will be the easiest solution.

You are lucky to live in the same region as Grin Technologies. That should reduce your turnaround time getting back on the road if you have a show stopping problem.
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dogman dan   100 GW

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Re: Life span of a hub motor?

Post by dogman dan » Dec 05 2015 7:09am

Might work to use an allen head inpact driver on those screws. the kind you smack lightly with a hammer. The hammer tap keeps the wrench seated so it doesn't tend to strip as much. But that could just twist the heads off the screws.

Just saying, if a hall sensor dies and you must open the motor. Or, maybe Grin could service it for you. Once open, you can spray it with high temp paint.

Re visiting the motors I drilled tiny holes in.

They did rust lightly right away, but in my climate, even rode through all the rain we get, those off road motors never got seriously rusty. The tiny holes totally prevent an accumulation of water inside. Every use, the hot air expands, driving out some moisture with it. And the air sucked in each cooling cycle is not always that humid here. So my motor would completely dry itself. It's the motor sitting there, with a half inch of accumulated water submerging part of it constantly that makes a motor rust itself to death IMO. Or, freeze and be unable to rotate till thawed.

You can safely drill some tiny 1/8" holes in your cover. Just do the drilling near the axle so it cannot possibly hit the halls or coils. Use a drill stop to limit the depth of the penetration of the drill bit to about 3/16 inch.

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Re: Life span of a hub motor?

Post by ColinB » Dec 10 2015 5:18pm

I have tried to use an impact driver - no luck.

I do ride the bike in all weather, so water and rust probably will be it's downfall. Not overheating. I've got the power turned way down to be kind to my batteries.

I hesitate to drill any holes through the cover plate without removing it - I'd be concerned about any metal shavings getting in there. It would be handy - squirt in some sort of rust preventer every few weeks just as preventative maintenance. I like the idea of a few small holes - normally cover with tape, but able to open it up and air it out.

I think in my case my only choices are:
- watch for the bearings starting to go.
- get a controller that can do sensorless or sensored operation (to bypass any issues with the halls failing.)

I've had it two seasons now - should I consider starting to shop for a spare?

Colin

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Re: Life span of a hub motor?

Post by Eskimo » Dec 11 2015 1:46am

You can try to drill those screws out. When you drill that cap off, rest usually comes out lightly.
My other hubbie seems to have developed a slight free play between the bearing inner surface and the axle. I replaced bearings once and bearings were quite loose on the axle.
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dogman dan   100 GW

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Re: Life span of a hub motor?

Post by dogman dan » Dec 11 2015 6:46am

True, one or two small shavings of aluminum could drop in if you drill it. 99% would be pulled up by the drill to the outside. But at least not magnetic, so they wont clog the space between the magnets and the stator, and cut up the windings. But the risk is small, once you get to a point where you can hear the water sloshing in there. Some humidity in there will take some time to ruin the motor. But once you can hear liquid inside, I'd drill the cover.

As for the halls, I've never had halls fail on a motor I treated nice. Only abused motors have gone up in smoke.

Spare everything is not a bad idea, if you really rely on this bike for transportation.

Only when a spare motor is in hand, would I go to the extreme of drilling out the cover bolts. I wonder what they did with this thing, epoxy instead of locktite? I've never had that much trouble with any cover bolts.

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Drunkskunk   100 GW

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Re: Life span of a hub motor?

Post by Drunkskunk » Dec 11 2015 9:47am

Don't drill the covers without removing them. the metal shavings would eventually destroy the motor, but the bigger worry is hitting the coils of wire just under the cover. The copper windings on the stator are in some cases are so close to the cover that you couldn't fit a sheet of paper between them. hit those with the drill bit, and it would end the motor. even scratching the varnish off could cause them to start arcing to the cover, shorting out the motor.
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dogman dan   100 GW

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Re: Life span of a hub motor?

Post by dogman dan » Dec 12 2015 5:37am

That's why I said drill tiny 1/8 inch holes near the axle, using a drill stop. Minimal size hole for minimal shavings going in, no drill penetrating to the wires or coils.

And I did say only do that, if you actually can shake the motor, and hear water sloshing around in there.

Or just forget about it, and have a spare motor handy when it does eventually fully lock up with rust.

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