Das-kit Rear hub Motor Lateral Play

Matt Jones

Finding my (electric) wheels
Oct 13, 2013
20
2
A, A
My NCM Prague is now about 2 weeks out of warranty (Typical!). Today I noticed a good few mm of lateral play on my rear wheel. It’s enough that if you grab the rim while the bike is on the ground, you can feel it move pretty easily on the axle.

I took the wheel off and noticed nut on the non drive side, I tried to tighten this and it immediately sheared, which isn’t surprising as its barely a couple of mm thick!

So, I wonder what my prognosis is here? Is it likely that a replacement nut, (perhaps a marginally thicker one?) would tighten and solve the problem, or is it likely to be a bearing issue? I am sure I have read that bearing in these motors just aren’t designed to be user serviceable, and that a motor would be more cost effective?

if it comes down to that, where can I buy a plug and play replacment wheel and motor, do I have any options in terms of compatibility?

Any help greatly appreciated!
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
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Does the hub axle actual have play in it , I doubt it as they are pretty rigid.
Most hubs tend to be serviceable, the bearings are sealed and are generic with the type number written on the casing. If bearings are worn one can hear them when riding.
The wobble could be the nut being loose is the rim out of true ?
 
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vfr400

Esteemed Pedelecer
Jun 12, 2011
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There are a few different versions of those motors. You don't need to scrap it. There is a way to take out the play. It's not a worn bearing, and even if it was, they're dead easy to relace and cost about £2 each.

I can't understand what you broke, can you show some picyures?
 
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Matt Jones

Finding my (electric) wheels
Oct 13, 2013
20
2
A, A
There are a few different versions of those motors. You don't need to scrap it. There is a way to take out the play. It's not a worn bearing, and even if it was, they're dead easy to relace and cost about £2 each.

I can't understand what you broke, can you show some picyures?
Hi
Sorry can’t show the actual nut, but its back on the bike at the moment, but its basically the nut you can see on the axle here inside the rotor holes.. bare in mind that this one looks decent, whereas mine is barely a couple of mm thick, similar to the one you can see on the drive side in the photo.bb as soon as I tried to turn it, it sheared with barely any effort.

I’d try simply replacing that and see what happens, but I ordered an M12 locking nut assuming it would do the job, but turns out the thread isn‘t M12.

On a positive note, when I approached NCM asking if they’d do me a decent price on a replacement motor as its only a few weeks out of warranty, they corrected me and told me warranty on the motor was actually 2 years, so fingers crossed might get it sorted that way. D389FA8C-A20A-492C-9B80-4E3876FF1D0C.png
 

Matt Jones

Finding my (electric) wheels
Oct 13, 2013
20
2
A, A
Does the hub axle actual have play in it , I doubt it as they are pretty rigid.
Most hubs tend to be serviceable, the bearings are sealed and are generic with the type number written on the casing. If bearings are worn one can hear them when riding.
The wobble could be the nut being loose is the rim out of true ?
Hi,
There is no noise at all.

The Rim was a little out, but I had it trued a few weeks ago, and I know for sure there was no play then.
 

vfr400

Esteemed Pedelecer
Jun 12, 2011
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It's a standard 12mm thin nut, also known as a jam nut, that you can get from Ebay, screwfix or anywhere. As you nearly always need a washer on that side to get the correct caliper alignment, you can go a bit thicker on it, but not too far.

You need 12mm x 1.25 and 3mm or maybe 5mm thick. I think I'd try 5mm:
 
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Matt Jones

Finding my (electric) wheels
Oct 13, 2013
20
2
A, A
Thanks! Ordered.

I actually did have a small spacer, when I got the bike I wasn’t impressed by how close the smallest cog ran to the dropout, so I dropped a small washer in each side to keep it central and give a couple of mm clearance.

I am hoping that I can take the washer and existing nut out and just replace it with the slightly thicker nut. Hopefully this will do the trick. that way if the thin nut has damaged the thread, rather that just itself, the new thicker one might be able to “straddle” the damaged part and still get some purchase on good thread.. assuming I can get it off without doing more damage?

Thanks for the reply.
 
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Matt Jones

Finding my (electric) wheels
Oct 13, 2013
20
2
A, A
Just an update...

NCM have taken details of my weight and riding habits, and sent me a picture of How the nut/washer arrangement should look, Which is nothing like mine really, thicker nut AND a washer between the Nut and shoulder of the hub. They've now gone away to confer or something, which is great, but at the end of the day I need the bike, so I continued my experiments..

So I got the new nut. Which looks remarkably similar to the one that NCM insist should have been there in the first place (see picture of my old nut, and the one I have now fitted.

In light of NCM's photo, I also opted to place a thin washer, not only because that's apparently as it should be, but also in the hope that it would move more of the new nut away from the thread the old one damaged.

This has reduced the play by around 75%.. there is still a little wobble but it's marginal. I might be able to tighten a little more, but obviously terrified of stripping the thread further. On the negative side, this has reduced the the freespin of the wheel somewhat, where before if you gave it a tug, it would spin forever before gradually slowing to a halt, now it seems to only do so for about 5-7 seconds or so, so not sure everything is perfect.

The interesting thing is that this feels far more "right" than before. The scope of brake adjustment is far better now, and I always felt like the whole wheel was slighly alligned to the brake side a few mm too much (seems obvious now,.but I put it down to all manner of other things, cheap Chinese frames, poorly built wheel, the fact I had put a tiny washer either side to make up for the chain virtually touching the dropout on the drive side...

My conclusion here is that NCM have been really sloppy on this. And I suspect my bike should have left the factory with the adjustments I've now made.
 

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vfr400

Esteemed Pedelecer
Jun 12, 2011
9,822
3,993
Basildon
As I said in my earlier post, there are different versions of that motor used bu Das Kit. That's why you have a thin nut and some have a thicker one. The differences on the outside are slight, and the differences inside are significant.

The lateral play is controlled primarily by that nut being tight. There is also a shim on the inside, which makes the width of the core correct between the two bearings.

The bearings are very cheap. You can get them from Ebay, or you can get upgraded versions from bearing suppliers for not a lot of money. They're dead easy to fit. They're standard sizes and the designation is marked on them. I can't tell you the designation because the different versions use different sizes. You have to check what you have.
 

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