RUST: DIY Hub Motor Repair & Restoration

[Kingfish]

EDIT: Formerly titled "eBikes/EBikeKit Hub Motor Compatibility" - however this thread has turned into a rust-related R&R. The hope is to repair my hubs, AND also to test if the stators can be swapped between these suppliers.

Greetings –

Admittedly I am a bit embarrassed to confess that my trusty bike has gone kaput this past month and I’ve been bussing it nearly two weeks now. The original problem could be traced back to my road trip: The phase/signal wires to the rear hub motor were frayed due to rubbing by the left-side pannier and causing shorting. The repair was made in the field and that was the end of the problem until I returned to the rainy Pacific Northwest when one day the rear hub cut out altogether (about 4 weeks ago).

No problem – I’ve got a 2WD, er… um now a FWD – and it got me home fine. I figured it could be that the wiring needed a redo: The front hub got the phase-wiring upgrade before I made the road trip although not the rear: Planned work Item for some dreary (I almost said rainy but that’s all the time) weekend.

Meanwhile, the FWD was holding up just fine – until two weeks ago on the way home approaching the summit of the last hill before home when that hub motor outright quit on me. Lovely, right when it’s chucking down big-drop rain, in the dark, 100 feet to go to the top, cars backed up behind me... I pushed the bike over the hill and coasted on down to the base of my hill and walked it back to the secret urban bat cave.

I have spare motors: 9C 2806s & 7s, all but one are front hubs; the one rear 9C has a disc on it but I hates it. Anyway – there are parts available to test with. I did modify my present EBikeKit hubs to use the USB Mini-B Connector for the Halls connection so I could slip the nuts & washers & torque-arms on and off, although none of my other motors have that feature. With no spare cables for testing, I ordered up a few and waited.

Today I finally got around to fabricating a test harness to positively diagnose that the issues were with the motors and not the controllers (tiny but very important detail). I removed both hub motors and rotated the axles with a 10mm wrench: Rear Axle feels like there’s a little bit debris hitting, nothing gigantic, however the front hub definitely has profound grinding problems, and gets stuck – which leads me to think that I have a moisture problem and likely rust.

I took one of my spare mint-condition 9C front hubs and mounted it on the front fork, hooked up the test harness and tried it on both controllers: It spins smooth as glass, and thus concluded that the controllers are not at fault. (Good news if any could be had)

OK – so now the question:
I am going to presume that the stators are suffering from moisture and likely not recoverable. Both hubs came from EBikeKit last spring and they have the disc brake option which after some effort, figured out how to make work.

Have any members swapped stators between 9C sold by EBikes.CA and the EBikeKit variation? Are they Apples = Apples - or am I looking at Pippins verses Fuji - not an exact match?

Looking forwards to getting back on the road soon.
~KF

[amberwolf]

It's more likely that the problem is magnets: They might have moisture ingress behind them in the epoxy, letting them come off the ring and stick to the stator instead. This is easily fixable as long as the magnets are intact. If not, you'd just need new magnets for the broken ones.


As for stator fit, well, I have a motor from Icecube57 that has an old bell-housing E-bikekit.com rotor and covers, with a GM 1000W stator/axle. Worked fine for him, and appears to work fine here though I don't yet have the bike finished to actually test it in (it's probably going to be the middrive motor for my CrazyBike2 replacement). And they are "totally different" manufacturers.

[neptronix]

I was wondering how all that pacific northwest riding was gonna treat those 9C-esque hubs.
I'd love to see your motors if/when you get them apart.

When i had my MAC motor open, which i had ridden all over the place in the Portland area... even though maybe a few drops of rain hit it.. the friggin' cover plate bearing was bound to the axle O_O ... so i can only imagine..

[Kingfish]

I was wondering how all that pacific northwest riding was gonna treat those 9C-esque hubs.
I'd love to see your motors if/when you get them apart.

Ask and ye shall receive Aye laddy, after some strong coffee I felt most motivated to discover the truth, and I fear the worst. Decided to do both wheels in parallel. First, the dog & pony:


Rear Hub


Front Hub

We’ll start with the RH first since I was the most optimistic about its’ status. Using the wheel-pullers, once it cracked open and I could see inside, I knew differently. Pictures are worth a thousand words. This first series is a little blurry, though I did better on the FH.


The magnet ring is completely crusted over smooth with sweaty scale on the inside. At about 8:00 you’ll see a tiny chip out of the edge of the magnet: This damage likely occurred on disassembly because of the fresh break and lack of distribution.


The stator was nearly drippy with sweat; the dark blotches indicate dew. The smell was very irony and dank metallic; quite unpleasant.


Rotated stator slightly to give a better view of the damage. Note the crusty bits where the shaft merges with the stator. Lovely ain’t it? Dig that pumpkin crusty rust all over the unit.

Next the FH. With optimism completely tempered, I methodically proceeded to unwrap this present.


Wow, what a surprise!


Again, I think this damage occurred upon disassembly. In review, I suspect that the durability of the magnets was greatly weakened by corrosion. Stepping outside the box for a moment, this hub’s destruction is like a form of art.


The FH stator was not as wet as the rear and I think likely fared better.


Again, the close-up reveals the delicate nature of the corruption.

Conclusion:
I inspected the bearings of both wheels and they rotated freely without indication of damage. Clearly the grinding I felt beforehand was caused by the impertinent growth of rust. The sad part of this story is that I acquired these hubs in May, just 6 months ago. The FH I can sort of understand cos I opened it up to size-up the phase wires, though I did not on the RH. The seals have clearly failed. Frustrating because my 9C hub did not display this sort of problem and it’s been through two winters. I’ll have to review this up with EBikeKit cos I don’t want to drop $600-$700 worth of parts and labor every 6 months.

As for the adaptability of 9C stators with EBikeKit hubs, at this point I don’t wish to proceed. I think I am looking at replacement. On the bright side, I won’t have to get the spokes remade.

Fun, huh? KF

[DAND214]

KF, so what's wrong with them. A little rust. Can't you just clean it up.

Are the mags still attached to the ring? I would guess it's the halls. Or have you tried a sensorless controller already?

Put some of the rust remover sealer on it and see what happens, It worked on the BBQ.

Dan

[Kingfish]

Dan, you are getting me to laugh about this more and more. The issue I fear is that the magnets’ plating is compromised. Although… after some reading I learned of the CorrosionX stuff. DoctorBass also posted a repair to his rusted hub, so my despair is somewhat less. It is certainly cheaper to attempt a repair than go through the complete replacement.

ADDENDUM: Here's another thread on the CorrosionX stuff with a warning not to use it prior to painting: CorrosionX for waterproofing?

As for the OP, I have both new front and rear stators ready to insert, well – the rear is ready with the 10-AWG upgrade:



I created this modification during March 2010 but never had the courage to follow through with the installation after struggling for 8 hours with the wiring. The front hub that I modified last May went much faster using 12-AWG, and I’ll try that again for the FH stator. But before I get that far, I’ll need to buck up and remove the rust.

Thanks for the words of encouragement
Back on board the Repair Party, KF

[John in CR]

That stuff should clean up fine. Before you do though, did you put alignment marks on the covers and magnet ring to get the holes lines back up the same during reassembly? 9C are notorious for rubbing if you don't get them back on the same. If you didn't, use the glue and corrosion splotched to figure out the original alignment and make your marks before cleaning.

[DAND214]

KF, you can do it! Following your west coast trip, tells me you can fix just about anything, if you try.

The rust is just a coating on the mags. On the stator it's a little more. The windings look fine to me, but I'm not there to really see it.

I still say it can be fixed. GET TO IT!.

Dan

[Kingfish]

Dang John, good point however I didn’t mark the covers. My bad.

Thanks for the encouragement Dan

Home treatments:
I did some reading last night and found some cheap rust removal remedies using a combination of the following:

• White Vinegar (Acidic acid)
• Cream of Tartar (Potassium hydrogen tartrate, also called potassium acid tartrate)
• Baking Soda or Powder (Sodium bicarbonate, forms carbonic acid when mixed with water)
• Lemon Juice (Citric acid)
• Hydrogen peroxide (oxidizer used to reduce Iron further)
• Borax (Sodium tetraborate decahydrate; forms Boric acid)

Solid products can be combined with liquids to create a paste, or the rusty items can be immersed in the liquids for a period of time. I don’t have a bucket large enough to treat the magnet ring whilst mounted to the wheel, but can do for the stators so I think I shall try the paste method on the former and the immersion method on the latter.

I have decided to change the title of this thread to reflect the repair, although I will still test to see if the stators are swappable if nothing more than for edification because I am not certain the R&R of the stators will work.

Off to the store (fitting that it's chucking down rain)...
~KF

[neptronix]

Holy ********************************, batman.
This confirms my fears of destroying motors by running them in a the humid and rainy pacific northwest climate. That's exactly why i would only ebike ride for about 4 months out of the year when i lived in Portland.

Many people have stated that running DD motors with open covers is actually better for the motor.. because moisture is never allowed to remain. I'm starting to wonder if that's true now.

Your hubs do have great patina, but it hurts to look at those!!

If those don't work out, hit up cell_man for some new MXUS DD motors. They're basically knockoff 9C's that ampedbikes and some other kit sellers put out there. At $160 a kit, they're less painful to throw away if they go bust.

I wish you the best of luck, and do think that an experiment with some kind of rust-proofing material in your climate would be interesting to see.

[Kingfish]

Thanks Nep I didn’t rush off to the store just yet without following up on more details.

Direct Stator Swap:
The 9C stators that I have probably won’t be directly swappable without small changes. Evidence by this thread: Nine Continent Disk Motors.

Having read that, I took a good look at the bearings on my current flanges; I can feel water damage in one of them – and that’s enough for me to warrant replacement. I found these premium-grade bearings at McMaster-Carr:

• 6002 - Disc-Side of the FH, Freewheel-side of the RH
• 6202 – Blank-side of FH, Disc-side of RH

These are spec’d out to be double-sealed steel ball bearings loaded with solid polymer greas, having operating parameters far-exceeding our needs. Mainly I just wanted the best-sealed bearings money could buy. The stock 6202 bearings are sealed, however the 6002 are not and they definitely show it: The outward-facing seal rings of the 6002-flanges are worthless beyond being simple dust protectors; mine are grimy. Double-sealed bearings cost up to 3X over the General Purpose bearings we find used on these motors, and it is to our benefit to upgrade if given this opportunity.

More Debris & Hall Sensors:
I had to pull the other flange off the axle to read the bearing part number. One of the wheels still had moisture on the back side – even though the stator has been removed in a dry climate for nearly a day. This proves to me that it’s not enough to have it statically air-dry; it must be exposed to circulation. I took another look at the rotors and noted something odd on the FH:



The spring-metal washer had corroded into bits, part of it is shown here (I used my fingernail to put it out a bit more for viewing). This obviously was the cause of the stuck-axle symptom. Note where the rusty water appears to have collected on the right side. Like John said, I think perimeter holes are required, however I really fear grim entering into this environment.

With camera in hand, my attention returned to the Hall Sensors for a close-up: The picture is worth a thousand words.


Front Hub


Rear Hub

Once I have the rust removed (if successful) it might do to place a call with one of those electric motor-rebuild places and find out how they seal the windings. Surely an automotive engine compartment is full of nasty residues and these types of folks have sorted it out.

Now to scourer the ventilation threads, KF

[Kingfish]

D'oh! I found the other bit of that spring-washer looking at this photo:



See it off a little to the right, behind the chipped magnet?

Sheesh! KF

[neptronix]

This is too much to bear, kingfisher.

You know, you do have a good idea with the car motor theory. How do alternators last dozens of years on the coast, in the pacific northwest, the south, etc? how do iron and ferrous magnets survive out in the open like that? hmmm.. maybe some sort of coating is involved.

http://www.tercelreference.com/articles/rebuild_alternator/rebuild_alternator.html



Looks like they're using some reddish goo on the tercel alternator..
But most pictures of alternator stators online don't show a coating.
I wonder if the heat of the motor and open air prevents condensation from really sticking..

[Hillhater]

Are you sure you have not been using that thing as a coffee grinder ??

[dnmun]

naval jelly will cut the rust off, or you can use dilute phosphoric acid like they use for auto body rust treatment before priming. you can get it at the places where they sell auto paints.

did your motor fail because the hall sensors were damaged by the metal circlip? i thought you drove through rain during your trip last summer which may be when that started, imo.

[Kingfish]

The hubs have never been immersed in water; only exposed to rain. On the road trip, the only rain they saw was on the day I left and the day I returned. It’s been raining almost nonstop since then – but then in Seattle, three consecutive days of sunshine during July or August is called “summer”.

EBikes.CA spells out a good explanation about how water can enter a hub motor (search for "waterproof" question). I had a pleasant conversation with Ebike-Kit and suggested how to mitigate this problem in the future by sealing the stator with varnish as Doc had done. I think the next trick is to vent the disc covers in such a way that the accumulated moisture could spin out – although I do not want big whopping holes that can expose my motor to road grime; something to think about whilst the rest of this saga comes together.

Update & Progress:
For rust treatment, I went to my local supermarket and snagged:

• One gallon of White Vinegar @ 5% acid @ $3.39
• Box of Baking Soda @ $0.89

For parts, I turned to McMaster-Carr:

• PN: 2349K414, Double-Sealed Metric Perma-Lube Steel Ball Bearing #6002 @ $19.62 each, Qty-2
• PN: 2349K421, Double-Sealed Metric Perma-Lube Steel Ball Bearing #6202 @ $13.88 each, Qty-2
• 15-1/4 oz Net Weight, Green Insulating Varnish @ $7.45, Qty-1
• Polyurethane Caulk, 10.1 Ounce Cartridge, Black @ $6.60, Qty-1

Rubber Seals:
I desired to replace the rubber seals and went to EBikes.CA to see if they had stock but were not offered – although the bearings could be had. It’s not a high-priority, although it would make good sense to replace them regardless. I’ve calculated the bore and shaft to be 25mm x 15mm, with the seal width between 5-7mm, though I am not certain this is accurate.

Found a site online where I can order up just about any configuration from SKF. Here’s the table of available sizes, materials, and shapes. Either V or R/RG will work, and I was leaning on the HMSA10 V w/ Stainless Steel garter spring, P/N 563024.

Ebike-Kit & 9C disc covers appear remarkably identical and presumed the same, though I could be wrong. Before making the plunge, does anyone have knowledge on replacing the seals on these hubs

Thanks, KF
EDIT: Added McMaster part numbers to the bearings.

[Kingfish]

No replies to my question; I'm on my own

Status:
Ordered the SKF seals (HMSA10 V w/ Stainless Steel garter spring, P/N 563024) from a local dealer; about the same price each as those spendy bearings! Should arrive in a couple of days. Once I get around to prepping the covers I'll send them off to the machinest and hav ethe new bearings pressed in; don't have that ability within my hidden urban bat cave.

~KF

[amberwolf]

I guess I missed the question part.

Are you referring to the bearing seals or the cover seals?

The latter on my bell-style 9C covers appear to just be a very thin layer of silicone used to glue the cover shut.

The former I'm not sure about, but some time back I considered how I would replace mine if I had to, and decided I would use a thin plastic "washer" against the bearing face on the inside of the axle/bearing hole, then a very very thin layer of wax (like rubbing a candle or crayon) on the axle itself at that point. Then just slather silicone into the hole to fill it and let it cure, sticking to the metal of the hub cover and the plastic "washer", with teh wax keeping it from sticking to teh axle, so it can still rotate there as the covers turn.

[Kingfish]

Friend AW ~

I’m off silicone cos of what my bodywork guy had said:

Some years ago I pulled into my local bank; it had that angular parallel parking. I pull in with my nice well-kept 4x4 and dashed into the bank to take care of a deposit; nothing fancy about the task – just 5 minutes and done. When I came out, the bugger parked next to me collapsed my driver-side door when he pulled out and jaunted off ( grrr and double grrr). I had to take the truck into a body shop on a no-fault claim. Boss moss supervising the work explained that silicone is hydroscopic, and instead I should use polyurethane (which is not).

Ever since, I've using PU for all my moisture sealing issues.

My ½ watt, KF

[amberwolf]

Ah, that is interesting. I wonder why it is used for water seals on so many things, then?

[Kingfish]

Silicone sealer is easy to remove; comes off like a rubber band. Polyurethane is tough stuff; quite durable and not influenced by most environmental & road agents. I have no idea why it is so popular with bathroom fixtures: I mean, how many times have we cleaned the mold and mildew beneath, on, or around it? My gosh, it is a natural harbor for all sorts of biota! However – for gaskets & engines, the RTV version is perfect!

Back to the repairs…


Photo for reference...

I need to draw up some plans to modify the hub covers for the machinist. My thinking was 6 to 8 equally-spaced 1/8th-inch holes at the perimeter right where cover bends meets the magnets (see image). This way any accumulated moisture could spin out. (Overheating is not a problem for my use). That should do it wouldn’t you think?

Cheerios, KF

[Doctorbass]

here is the thread i made for the BionX motor restoration:

Using the best epoxy for magnets, the DP-420, some aceton and isopropylic alchool to clean and a bit of patience!

http://endless-sphere.com/forums/viewtopic.php?f=2&t=16776&hilit=bionx+epoxy


I also used this special high grade red varnish for motor:
Sprayon A00601A00 Red Insulating Varnish








5305 rebuilt after rust damage

Here is the thread: http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=24830&hilit=varnish


Doc

[dnmun]

alan, i think the rust on the magnets may be permanently magnetized to the magnets so it is a real problem since it is not gonna just release if the rust is scrubbed, but i wondered if the conversion of the rust to iron phosphate by the metal prep would make it soluble so it would be dissolved into small enuff even molecular so that there can not be a sustained magnetic interaction to keep it on the magnets.

i think it just grows on the outside of the stator and is blown off as the hub spins around the stator and ends up stuck on the hub magnets, this coulda been some of your drag too, as it piled up in places maybe.

[Kingfish]

Yeah Dennis, I figure it won’t be easy. Somewhere I have a map-magnet that I might use to coax the material off. Map magnets were made for the petrochemical industry to hold large heavy drawings on the sides of metal walls, such as drilling platform. I ordered up a box when I first became an engineer and still have a couple pieces floating around today.

Doc – that is some epic recovery you did there with that motor; I am in awe and inspired by your efforts!

~KF

[Kingfish]

Status:
I’ve cleaned the rust off the rotors best as I could. They have some damage to the finish and will never look pretty again. It took a lot of scrubbing. I used the Baking Soda/Water mixture to scrub them down with a toothbrush, then squirted them down with Vinegar which rapidly went to work at a second level of cleansing, and finally with soapy Five Star PBW (the brewer’s caustic). Still, there was residue left. After drying the moisture out with a heat gun, I rubbed the finely crusted surface with my finger, lurking for any flakes and particles which I was able to drag off with my fingernail. After that – I wiped down this residue with cotton balls soaked in isopropanol. And it still looks crappy, but at least I can see the surface and know that it is nearly free. I’ll probably wipe it down one more time with alcohol before sealing, although I wouldn’t mind taking a plastic scrubby to it one last time – dry, without water.

The stators came next. The stator that came out of the Rear hub motor, the one that was factory-sealed, the one that I didn’t touch or mess with until this inspection, has green corrosion on the windings. It’s a light patina, and appears to be limited in nature, and yet – I am worried that the windings might be compromised.

The Front hub stator didn’t have that problem, and I stuck it in a bucket, and dumped a gallon of vinegar on top: It’s fizzled away briefly like a witch’s caldron… OK – I lied, it didn’t fizzle THAT much, but it was neat to see it was actively working right away! I let it soak for about 10 minutes and then began to work on it. Surprisingly, this went very quickly and cleaned up very well. All the sloppy silicon goop from manufacturing came off, as did the cheap paint. The wires to the Hall Effect sensors are brightly tinned and picture-perfect! The crud between the teeth took some effort with a toothbrush, but it’s mostly gone now, and there is just a tiny bit left to scrub off. The oven is set to 170°F (lowest setting) for drying after I give the stator its’ last rinse.

I don’t know if I should try it though with the Rear hub stator that has the minor wire corrosion. It looks like it just started to oxidize and might be able to wipe it off. I’ll try to get picture posted shortly. Those that have cleaned off the stators before, would this be an issue? Should I still try? I fear it could be a short.

Concerned, KF