Do rear hub motors fail

[powersupply]

Do rear hub motors fail under normal use?

No overclocking or overvoltaging etc, just regular use.

I have a g-bike and was wondering if it is possible that the motor is failing?

http://www.shopgbike.com/products/city/yellow.html

We checked the controller, used another one, checked wires, batteries etc.

So it really boils down to the motor.

I read that the magnets within the motor might fail when hot.

Considering the heat here in SoCal and my weight, could that have happened here?

How could I check that??

Thanks!

 

[el_walto]

Yes, they can fail.

If it was a magnet the motor would still move ad make horrible grinding sounds, or have less power than before.

Could be shorted windings, or busted hall sensor. You need to describe in more detail what the problem is. Does the motor move at all? Does it make sounds?

 

[jateureka]

According to the Tech Specs the motor is 750W, 48V brushless DC running 48V 20Ahr lead acid batteries with 48V 25A controller.

There is plenty of info here on testing brushless systems, so maybe use the search function.

Like the other posted said, you haven't described the fault sufficiently - is it totally dead as in no lights or battery indication, or does the motor judder or has it no power but turns the wheel when you lift it off the ground?

 

[cal3thousand]

There's a G=bike being sold for $350 in So cal right now because it has a bad hub motor. Was very tempting to buy and fix.

I guess it is fairly common to have this issue.

 

[powersupply]

Thanks for your replies!

The bike is slower and seems to miss a step or two.
Looking at the innards of brushless motors, It is as if some of the magnets are dead.

It makes no grinding sound or so, it's just as if it has a hickup.

We hooked up a different controller, actually another bike next to it, but with just the motor wires going to my bike.

Exactly same thing.

So battery, controller, even the accelerator are excluded as possible failures.

When lifted up, it seems to run fine, but under (even slight) load does it do this jitter.

I tried to locate such a motor, but it seems to be really unique, none would fit either because of the brake used, or because of the chain spoke on it's axis. It looks like this one but even that does not fit:

http://scootersupport.com/motors.htm#MOTORHUB750

Is it possible to repair such a motor at all?

I mean the magnets look glued/fixed in those pictures
http://endless-sphere.com/forums/viewtopic.php?f=30&t=26012

Thanks!

 

[powersupply]

There's a G=bike being sold for $350 in So cal right now because it has a bad hub motor. Was very tempting to buy and fix.

I guess it is fairly common to have this issue.

Must be sold, search comes up empty.

Sad to see this is common, ha dhopes it was a fluke of some sort.

 

[cal3thousand]

There's a G=bike being sold for $350 in So cal right now because it has a bad hub motor. Was very tempting to buy and fix.

I guess it is fairly common to have this issue.

Must be sold, search comes up empty.

Sad to see this is common, ha dhopes it was a fluke of some sort.

It's still there:

http://losangeles.craigslist.org/lac/bik/3916345410.html

It was $550 a few weeks ago. $300 now.

 

[powersupply]

It's there indeed. Could swear I put in g-bike and nothing came up.

Seems to be the same issue I have.

That shopgbike company is a bunch of crooks. They have a google voice number which they never pick up or reply to, emails same thing.

And nearly none of the vendors they have listed on their webpage deals with them anymore.

I tried to find a repair shop but none would have it.

The bike is not really driveable in this condition, and I fear to ruin whatever is left.

I searched this site and found a few things on how to repair a motor, but it is still unclear if a magnet (or a group of) could fail just like that.

So please, if anybody has any input on this subject, please LMK.
Thanks!

 

[Ykick]

Doubtful magnets have gone bad. More likely Hall sensor failure either wiring or the part itself inside the motor. I'd make sure the connector containing small wires exiting the axle is assembled properly and no pins backing out the housing.

If it's Hall sensor component then you'll need the ability to open a motor and rework the components. Which aren't that expensive but skill/labor is required.

 

[cal3thousand]

I would offer to work on it but I don't have the space for something like that.

 

[dogman dan]

90% of my experience is that a plug gets a poor contact, or some other wiring issue happens. Wires get cut at the axle, or rub a tire and wear through. Plug contacts often back out of the housings, or the wire may break at the point where the contact attaches.

Hall sensors sometimes fail, but I never had any of mine fail, unless I cooked the crap out of them. "Normal" use can cook off a motor. If you weigh enough, and climb hills slow enough, it can overheat a motor. If you tow kids on skates up hills, you will surely overheat a motor. Bike trailers can overheat a motor.

It's fairly simple to test halls, without opening the motor. See the wiki for how.

 

[jateureka]

That is a pretty heavy scooter at 155lbs (inc 52lbs of SLA battery), plus the weight of the rider and anything else they are carrying - that's quite a load for a 750W hub motor to haul around, esp in a hot climate. I'm inclined to think something overheated/melted.

 

[el_walto]

Bad hall sensor, hall sensor wire, or bad connection on a phase wire.

 

[powersupply]

Thanks for your input!

We hooked up the motor to another bike, I remember we were hooking some very thin wires, too, they were probably for the hall sensor?

As mentioned it worked but when I'd put load on the free running wheel, it would show the same pattern.

Will read the Wiki reg hall and check it just to make sure, but I doubt that.

I must admit that I would drive with a passenger sometimes, but that was month ago.
Never thought I might overload something.

This strange behaviour only started about 10 days ago.

Will try to get in touch with the Craigs seller, let's see if he has the same problem and maybe found a replacement for this somewhere.

 

[jateureka]

There's some info here on testing the motor and halls. http://endless-sphere.com/forums/viewtopic.php?f=2&t=21832

If it is a geared motor (not sure?) then it could have stripped teeth on the planetary gears as this fault could also give similar symptoms to what you have described.

 

[powersupply]

Here are some pictures.
I went to a few shops and none have ever seen this, especially the brake is a problem, as most are disk based (or so).
Measuring the width and palcement of the chain, none of the goldenmotor or others would fit.
HAs anybody here seen such a motor?





View attachment 3



View attachment 1

 

[powersupply]

There's some info here on testing the motor and halls. http://endless-sphere.com/forums/viewtopic.php?f=2&t=21832

If it is a geared motor (not sure?) then it could have stripped teeth on the planetary gears as this fault could also give similar symptoms to what you have described.

thanks for that link!!

I have no idea if this is geared, at least it is not visible from outside.

Can those planetary gears be repalced?

 

[cal3thousand]

Why don't you buy a Hub motor from John in CR and make this thing a BEAST? IT will FLY!

 

[fechter]

I don't think those motors are geared. I'd suspect a hall sensor problem. Like Ykick says, a poor contact on the connector is common, but the sensor itself can die, especially from overheating.

If you can reach the hall sensor connector and poke some meter probes in there with the power on, you can test them like the threads indicate. There are 3 sensors, and it sounds like one is not working.

 

[powersupply]

Why don't you buy a Hub motor from John in CR and make this thing a BEAST? IT will FLY!

Who is John in CR?

I'd love to buy a motor just to be done with it, but the brake mechanism of this bike seems special.
And it is hard to break with this thing as it is, don't want to lose the rear brake.

Edit:
Sorry, just saw "John in CR" is a nick here.

Thought it is a John in Costa Rica...

 

[dogman dan]

He is in Costa Rica. He has a supply of very strong scooter motors.

But chances are, if you haven't found a fault in your wiring, it's the hall sensors going bad. You might be running on just two of the tree magnets, with one sensor not working.

Or, if you have a bad contact or cut wire to the big wires to the motor, not enough power flows then. So it will run fine slow, but under load it chatters and balks.

Again, check all your wiring. If nothing obvious is found, then test your hall sensors. See how to do it in the wiki, or go buy a motor and controller tester on ebay. They are cheap, and quite a time saver.

My bet is that you melted something. It could be the halls, it could be some of the wiring inside the hub, or it could be where the wires go into the axle that cooked. Two people, if you went up enough hills, could definitely do it. The scooter is designed for a population where two people is 200 pounds. In the west, that can be 3/4 of one person.

You can heat up a motor till the magnets fail. Iv'e done it twice!!! But those were brushed motors that really run hot, and I romped on them very hard. In one case, the magnets would no longer stick to a fridge. In the other, they just came unglued over and over. In the end, they weakened enough to really slow the motor down, and make it run even hotter.

I've never seen this happen with brushless motors, not even ones that flames poured out of. But halls cook off pretty easy, at much lower temps.

 

[powersupply]

Sadly it is not the halls.
At first we'd get no changes on any of them, and thought they were all dead.
Which could not be because the motor is running in fact.
So some more reading and we added an opposing resistor (pulldown/pullup??) and they all worked!

However, we went through a whole turn, very slowly in order to see which magnets could be bad/low, but could not identify any change within the highs and lows.

So both halls and magnets seem to be fine.
I sent John a PM, hope he has something for me.

We've exhausted the testing I guess, it is really very difficult to get to the wires and all.

 

[Ykick]

Test Halls while connected to the controller, pull-up resistors are already in circuit, if wiring is good.

If Halls test good you may have a Phase FET issue inside the controller.

Spin the motor by hand, connected and not connected to the controller - any significant resistance?

 

[powersupply]

We disconnected the halls totally from any circuit (i.e. controller).

We hooked up some 5V and then the resistors.

Will check the spinning thing later, thanks!

Hoiwever, as mentioned, we tried a controller from another bike, and it had the same symptoms.

 

[dnmun]

it does not sound like you know how to test the hall sensors properly so you may wanna read up on it before saying they are ok.