Suntour HESC Rear Hub Motor rotating on axle?

legin

Finding my (electric) wheels
Aug 24, 2019
5
0
I have had a Crossfire -E for 3 years now. The bike is presently unusable.
Basically, when climbing steep hills where I live ( 15% to 20% or higher) on full power, the hub motor connection to the battery is wrenched loose, thereby losing all power because of rotation of the cover from which the connecting cable emerges from the motor and with it the cable itself.
When this first occurred, I thought perhaps I had forgotten to tighten the wheel nuts, but having tightened them "properly" but without a torque wrench, the same problem happened again -and again, the distances travelled before the problem occurring being progressively less each time. I have had the rear wheel off this bike quite a number of times and have reasonable experience, admittedly from years ago, in bike disassembly and reassembly, though of course, not of E Bikes.
Just to put a fly in the ointment, there is a lugged washer which fits over flats machined into the axle on the cassette side, , the lug then fitting into the bottom of the dropout to enable the wheel nut to be tightened so that the dropout does not bind on the cassette and to anchor the axle. This washer broke in two within the first year but could still be slotted into place. The cassette still revolves freely round this washer.

I decided to mark the axle, axle nut, wheel and motor cable cover to see what was actually rotating and test the bike again. On cutout,, the motor cable cover had rotated 180 degrees anticlockwise as usual from bottom to top, the axle was where it was when I set out, or had rotated 360 degrees and the left hand axle nut had moved from 6 oclock to 8 oclock but had partially unscrewed itself. I am a bit perplexed about the wheel nut because as long retired petrolhead, as well as the bike experience, I know how to tighten nuts and bolts.

Looking at whether the (now fractured) lugged washer is responsible for anchoring the axle in place, I find it difficult to believe that this is solely responsible for preventing the axle from turning, given the huge torque which the axle has to cope with on full power up hill. It is brittle poor quality metal. And I am wondering if the internal part of the motor through which the axle is threaded has come loose in some way. I know obviously that the motor in general revolves round the axle.

I am sorry this seems a bit complex, but has anyone else had this problem or has anyone any ideas about it? Or is it me, probably, not seeing the wood for the trees?
 

joelectric

Pedelecer
Feb 22, 2019
61
37
Motherwell
I had the same problem after my dropouts were filed down but an over zealous incompetent bike mechanic. I now do all my maintenance myself on my bike. I fixed the issue of the axle slipping inside my dropouts by fitting 2 anti rotation washers on each side of My axle and fitting a torque arm on both sides as well. I got the anti rotation washers from whoosh and the heavy duty torque arms from hammer ebikes. Slight overkill but the axle has never slipped since.
 
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vfr400

Esteemed Pedelecer
Jun 12, 2011
4,875
1,753
Basildon
Stick a torque arm or two on the axle. problem solved. Next!

These are quite good - laser cut:

These are stamped out. I don't know thw quality:
 

egroover

Esteemed Pedelecer
Aug 12, 2016
456
227
53
UK
There should be of those 2 chromed lugged washers, one each side on the Crossfire (well there is on mine). The HESC motor is pretty torquey (50Nm) so you do need them or as mentioned a torque arm

36660
 
Last edited:

vfr400

Esteemed Pedelecer
Jun 12, 2011
4,875
1,753
Basildon
There should be of those 2 chromed lugged washers, one each side on the Crossfire (well there is on mine). The HESC motor is pretty torquey (50Nm) so you do need them or as mentioned a torque arm

View attachment 36660
That could be the cause of the problem. If the two tangs touch, you won't be able to tighten the nut to the frame. Those tangs are not enough to stop rotation. 90% of the resistance to rotation comes from the friction when the nut is tight.
 

legin

Finding my (electric) wheels
Aug 24, 2019
5
0
Many thanks all. First, I did not know, and I should have- that there are castellated spacers, I'll call them, on each side of the rear wheel. Maybe the bike was wrongly assembled with only the one, which is why it has broken. Interestingly, though, on my bike the rear axle is chamfered only on the cassette side so that the spacer fits neatly over the chamfer, but not on the nearside. Looking up anti rotation washers, these are in fact the "spacers" I have been taIking about, with 2 flats on them to fit over the axle.. The Carrera ones are brittle, so some heavy duty ones would be better. Looks like torque arms would provide a fail safe , but having looked them up, I can't figure out at all how they are fitted.
 

vfr400

Esteemed Pedelecer
Jun 12, 2011
4,875
1,753
Basildon
The torque arms above fit on 12mm axles that are milled to 10mm wide with two flats. I can't remember whether the Suntour axle is like that, so you have to check. basically, the axle has ro be the same shape as the 12x10mm hole in the torque arm. There is no exact way to fit them, but you should aim for the arm to be at right angles to the piece that goes on the axle. after that, you have to think about how to anchor the arm so that it is held fast. they provide a jubilee clip to go round the frame, but I've seen those snap. I prefer to screw the arm to a fixed position, like one of the caliper screws. Some people drill their frame and just use the piece that goes over the axle.

Instead of using the supplied arm, I made my own tie-bar out of a piece of scrap steel. You can just see the piece on the axle underneath it:

36677

Here's a front one that had a convenient screw on the fork leg for the arm:
36678

Here's one where I ground down and re-drilled the supplied arm to fix it to a caliper screw:

36679

here's one where a guy was able to drill his frame and use just the axle piece. it only works if your frame is flat:
 

vfr400

Esteemed Pedelecer
Jun 12, 2011
4,875
1,753
Basildon
In the old days, before torque arms were commercially available, people had to improvise:

Here's one of my self-made ones. Made with a file an angle grinder and welded out of scrap steel:

36681

and these front ones are hard to spot sitting in front of each fork leg:

36682
 
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legin

Finding my (electric) wheels
Aug 24, 2019
5
0
Thanks vfr 400 for the information and particularly the photos.
I still have one problem which I haven't managed to find an answer to.
My Suntour rear axle has flats only on the cassette side and adjacent to the top gear cog and not extending to the outside of the dropout. So looking at yours, and a video I found somewhere, that's the only side I could attach a torque arm to. The other side of the axle is round so no flats for a torque arm to hold that side. Same with anti rotation washers. Presumably torque arms have to be fitted to both sides in order to equalise the torque on the axle. I am slightly puzzled by this as I would have expected Suntour to put chamfers on each side. The bike is only just 3 years old and so not one of those early ones when manufacturers were experimenting with E bikes. And if they attached just one anti rotation washer to cope with the motor torque, maybe it's not surprising that mine has fractured
 

vfr400

Esteemed Pedelecer
Jun 12, 2011
4,875
1,753
Basildon
One torque arm should be enough for your motor. The tab-washers do nothing if they don't fit on a flat part of the axle, so I'm not sure what your saying is right. Anyway, assuming that the.

I'm still missing something. If you do up the nuts tight, the friction alone should be enough to hold the motor for the test you did, but the motor turned. That means that for whatever reason, you haven't got enough friction. You have to find out why. My suspicion is that your frame has got worn dimples where the tab-washers sit, which has allowed the tabs to meet each other in the middle, and when you tighten the nuts, all it does is press the washers hard together without clamping tightly on the frame. I must admit, when I did some repairs on one of those bikes, I looked at that arrangement and noted how close the tabs were together, and I thought it was a bit dodgy, but the nuts tightened OK, so I didn't think any more about it.
 

legin

Finding my (electric) wheels
Aug 24, 2019
5
0
Thanks. The bike came with only one tab washer in total which goes on the inside of the dropout in order for it to locate on the flats in the axle. As the axle nut is torqued up, the non tab side of the washer bears on the inside of the cassette but its diameter means that it does not bind on the top gear cog. The tab obviously faces outwards so as to locate in the dropout. I can't recall one being on the other side and, as you say, it would have done nothing because there are no flats on that side of the axle. I've got a torque wrench ( for cars)and it starts at 28Nm so should be fine for the 40-45Nm recommended by Suntour, although I have never used a torque wrench on any bike and have been tightening these rear wheel nuts for the past 3 years with just a ring spanner and have had no trouble up to now.
From what you say, I'm just wondering now whether Suntour have modified the axle since I bought mine so that there are now flats on both sides of the axle rather than one and maybe even introduced 2 tab washers each side. There's a post from a guy above which says that there is one tab washer on each side of his Crossfire.
Hope this makes sense.
 

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