Help please! Horrible rasping sound from 9c

[Xanda2260]

Hey guys, hoping you can help me out.
I have dome several searches to no avail, and would appreciate any assistance, even if it's just a link to decent thread in the subject.

Ive been cruising around on my trike (see sig) for a while now, and having a great time. Recently however, it has started making a horrible rasping sound when a lot of torque is required (accelerating, hill climbing etc.) it only seems to happen once the motor has warmed up. It sounds like gears slipping, but the 9c is direct drive. I thought it might be the stator slipping around on the axle, as I believe they are just pressed in, but that would wind the phase and hall wires up causing damage, there isn't any,
My second thought was maybe a dodgy hall sensor or connection, but then why only after the trike has been run for a bit?
If anyone has ever had this symptom, any info/advice would be greatfully recieved.

Thanks in advance guys

Alex

 

[hydro-one]

could be your tire rubbing on the frame? is there any side to side motion of the wheel? could also be your phase connections? is the sound only under load? run the bike with the tire off the ground can you make the noise? when?

 

[Kingfish]

• Tire rubbing frame: Looking at your cool framework, the clearance is tight there. Inspect that part first for rubbing.
• Second to that, test the tension of the spokes to ensure tightness. Perhaps they’ve stretched a bit since installation so that when under load the wheel is warping.
• Hub to frame contact: The color differences would make it easy to spot. Something to rule out.
• Phase wiring: Good point! That happened to me on my road trip. I had issues at the connectors as well as where the wires pass through the axle. The wire gauge was also a bit small for the current passing through – and acted like a heater melting the insulation. Upgrading the wires fixed the latter two issues and improved my bottom-end.

If there are no external sources then we could suspect the bearings in the hub covers are allowing for rotor and stator contact. They are not the highest quality… but that shouldn’t be an issue. Still, it’s a relatively easy thing to inspect and replace (upgrade to the best if you do). This also offers an opportunity to inspect the motor for moisture, and confirm or deny other physical wear. With bearings, check for wobble, axial thrust movement, and actually - any sort of looseness in any direction: There should not be any play of the sort, and they must turn smoothly like silk within their confines.

Happy trails, KF

 

[nicobie]

I'd guess that something is screwed up with your hall/phase wiring. I wouldn't ride it until you get it figured out.

 

[dogman dan]

Assuming it's not just a mechanical rub, I would look into it being the phase wires. I once cut a phase wire down to all but two strands. It worked great at low speed, low load still. But when it was asked to climb a hill, it made a very loud clacky sound we call a motor stutter.

Basicly, under bigger loads, the motor only ran on 2 wires, instead of 3. So it did a thing somewhat like an engine not firing on all cylinders. No power, runs rough etc.

If it's stutter, chances are it's quite loud under heavy load, and produces a lot of vibration you'll notice. It could be a cut wire, or any kind of bad connection, from the solder inside the motor, to the plugs and thier contacts, to the solder in the controller. Look at the plugs first, and any other possibilities for a cut wire. In my case, a wire had rubbed the tire.

It could be halls wiring, but the way it runs good at low load makes me think phase wires. Halls is more likely to stutter at all speeds and loads.

 

[Xanda2260]

Thanks guys! Greatly appreciate the help.
I've checked for wheel rub etc. but found nothing, wheel runs fine off the ground (and indeed for the first 5-10mins of a ride), and I only get the grinding vibration under large loads. Will inspect phase connections and report back.

Cheers!

Alex

 

[hydro-one]

if it only happens after 10 min of riding, and then only under load. first is a phase connection , mabye heating up and warping, making bad contact. then i would replace the hall sensors ive had them fail intermittantly due to heat, and all the motor wiring (mabye a melted wire shorting). if that dosent fix it, replace the controller, , if that dosent fix it then your motor is screwed, phase winding is shorting to ground due to moving under heat.

also could be the bearings , or tolerances in the motor causing the stator to contact the magnets. these change when its hot. take motor apart to check for rubbing marks

also try wiggling the wires around to reproduce the fault, it hate ebike gremlins!!

 

[Xanda2260]

it hate ebike gremlins!!

I hear you there!

Cheers

Alex

 

[Xanda2260]

Right guys, I I fiddled with phase connections to no avail. Went for a lovely ride round the block, 6mins in and brraaaaaaaap. It really does sound like metal slipping against metal. So I opened the motor and found this:

Looks like the stator and rotor are rubbing! There are similar marks on the stator, and the magnets shifted when I pulled the stator out. Do you guys agree? This is the first time I've opened a hubby.

On the plus side, the windings look fine...

Thanks in advance guys

Alex

 

[Ykick]

Are those bearings okay? In one photo it looks rusty where the bearing is pressed in.

Any recent accident or overtightening spokes which might've deformed the rotating hub?

These motors are not known for precision manufacturing tolerances and if none of the above I suspect it's a case of Chinese crap manufacturing.

 

[Xanda2260]

Bearing spin fine, no grating or crunching, in fact the motor works great until it warms up, and even then it works fine in low torque situations.
I'm totally stumped, and I don't mind admitting, but it certainly seems like the stator is rubbing on the magnets. The fact that it's the edges of the magnets that are worn, makes me think the stator is tilting under the torque, suggesting there is play in the bearings, but I can't feel any by hand (hardly conclusive though).

Still, any and all opinions greatfully received!

 

[Kingfish]

I’m confused: You say the bearings are fine, no grating – but here I see a bearing on the spindle by itself. That is a problem. Bearings are press-fitted into the hub covers and should not be easy to remove without likewise pressing them out.

As long as they are out – replace them with superior quality. Just get that one thing behind you and try again. Here’s the link to what I used:

• RUST: DIY Hub Motor Repair & Restoration

Best of luck, KF

 

[Xanda2260]

I’m confused: You say the bearings are fine, no grating – but here I see a bearing on the spindle by itself. That is a problem. Bearings are press-fitted into the hub covers and should not be easy to remove without likewise pressing them out.

As long as they are out – replace them with superior quality. Just get that one thing behind you and try again. Here’s the link to what I used:

• RUST: DIY Hub Motor Repair & Restoration

Best of luck, KF

I think you just found my problem! I didn't realise the bearings were meant to be such a tight fit to the covers. I popped the cover using the old 'bang the axle on a block of wood' pages trick, the cover popped, the bearing stayed put. I guess that the bearing was jamming as it warmed up, and the grating I was hearing was the bearing sliding past the cover. Sound possible?
If so, any recommendations for replacement bearings? And what gear do I need to press them in?

Thanks SO much KF, I'm forever in your debt!

 

[Kingfish]

Gosh <blush>
Lot's of people here have helped me - too many to count!

Also I suggest a good tool to purchase that is relatively inexpensive is a wheel puller. :wink:

Mine has 7-inch jaws, and I got it on sale < $20 USD. Amazon has one for about $21 + shipping.

I also had a machinist do the pressing for me; didn't trust myself for that job.

Might be a good time to do a little R&R on the hub motor whislt it's out for service for anti-rust treatment/small bleed hole, etc.

ADDENDUM: Bearing replacement suggestions are in the previous post; you have the link - click it and you will see what I ordered from McMaster-Carr.
Best of luck there friend, KF

 

[Xanda2260]

Oh yeah, my bad. Must stop scan reading.
Thank you!

 

[mat h physics]

Tight tolerances make for better eff, but when something is a little off, thermal expansion of the stator becomes an issue. Neither race (inside/outside) should turn in/on it's support, if it does, the wear is taking place on those surfaces.
If you are going to use a damaged cover, have it cut to a larger diameter OS bearing by a machine shop. Take the entire set up, they will need to observe the covers function to get a proper setup.
Should you "attempt" to epoxy, it will not be centered correctly.

PS The bearing race is case hardened and will not wear like the cover material, ie I doubt you will get away w/ just replacing the bearing. BUT, sometimes a slightly Over Sized OD can be found (like .002") which would work if not much wear has taken place.

PPS Thermal expansion can be used in your favor, put the bearing in the freezer and/or heat the cover b4 installing.