Mysterious gold spacer in KS 18XL

[rumpel]

Hi, during a change of a bearings in my Kingsong 18XL I found a small gold ring on a floor. As I realized it was on the motor axle and fitted rather the side where the power cable goes into the engine. Is it a proper place for it ?

[alcatraz]

Looks like it could be a shim.

They're normally used to release axial pressure on the bearings and at the same time take the play out.

If it's squeaky clean it was probably behind the motor covers on the inside. You just need to figure out which side.

It's a very important part. By forgetting it or installing it wrong you can seize/bind up the motor assembly after tightening everything up. Listen for noise and enaure it spins smootly before finishing the job.

If you don't know which side, have a look at the rotor when you drop it in. It should be centered with the magnets on the rim side.

[rumpel]

It fitted the axle on a side where the power cable goes in although I saw it somewhere on YT that a guy had it on an other side ( sensor cable one ) which confused me and I’m not shure about it although motor spins normally and everything is working.

[alcatraz]

Did you swap the bearings?

That could change the shim requirement. Some bearings have more play than others.

I'm not sure it is the purpose of it. It's just a theory.

Also the binding I'm talking about could happen after you tighten down the axle nuts. They press against the bearing inner races and if there's too much axial play inside the motor the bearings could bind as the internal bearing play is reduced to zero. This internal play is usually very small. It's good if the replacement bearings have a similar level of play (measured by a C number ranging 1-5 I believe). It's hard to guarantee equal play because the OD tolerance being off by a little will impact the internal play when the bearing is pressed into and compressed by the bearing seat in the motor cover.

[Funky]

It's very, very thin.. About 1mm thin.. I can't see it be used as shim. That 1mm thickness does nothing.

 I also had that gold ring. I simply put it on what ever side. As i don't remember which side it had it. I doubt it does anything anyways.

[Funky]

Just now, alcatraz said:

Did you swap the bearings?

That could change the shim requirement. Some bearings have more play than others.

I'm not sure it is the purpose of it. It's just a theory.

Also the binding I'm talking about could happen after you tighten down the axle nuts. They press against the bearing inner races and if there's too much axial play inside the motor the bearings could bind as the internal bearing play is reduced to zero. This internal play is usually very small. It's good if the replacement bearings have a similar level of play (measured by a C number ranging 1-5 I believe). It's hard to guarantee equal play because the OD tolerance being off by a little will impact the internal play when the bearing is pressed into and compressed by the bearing seat in the motor cover.

We don't have "axle" nuts.. Axle is welded in middle > followed by motor covers(which hold the bearings) > then pedals "L" brackets.

[Funky]

For reference how it looks inside:

Edited November 1, 2023 by Funky

[alcatraz]

Just now, Funky said:

We don't have "axle" nuts.. Axle is welded in middle > followed by motor covers(which hold the bearings) > then pedals "L" brackets.

Ok. I'm not familiar with that design so I probably should stay quiet.

Just saying that shims are usually used to take play out of the assembly and adjust the bearing preload to acceptable level. 

If you have too much play in the system you might hear noises when the motor is loaded sideways like in turns.

[Funky]

Just now, alcatraz said:

Ok. I'm not familiar with that design so I probably should stay quiet.

Just saying that shims are usually used to take play out of the assembly and adjust the bearing preload to acceptable level. 

If you have too much play in the system you might hear noises when the motor is loaded sideways like in turns.

What i was trying to say.. That gold "shim" doesn't even touch the bearing. - Because motor covers that hold the bearings are little bit away from where the gold "shim" would sit. So i can't really see that 1mm "shim" doing much.. By tightening motor covers "tighter", you could move the bearings closer to axle. Or if you have done bearing change - how deeply you have pressed the NEW bearings in the motor cover groove.

I have been 3 times inside my motor also done bearings changes.. That "shim" really doesn't do anything. And i have been riding 3 years whiteout problems.

Edited November 1, 2023 by Funky

[Funky]

If my memory serves right.. I think it was at sensor wire side. Not motor wire.

Found my motor images.. I was right. You can even see one has flat surface. Other side has more narrow rounded "step". So i simply put it on sensor side, as it "sit" perfect there.

[alcatraz]

In the picture on the left there is still a ridge on the axle, albeit smaller. 

What indicates to me that a shim probably was used is the axle wear mark. There is a space from that ridge to the beginning of the wear mark.

But hey, if you're not experiencing play, axially or radially then frankly I do not know what it's for. 

What you don't want is the stator inside to touch the rotor housing. Also you don't want the bearings to bind, or the rotor to move sideways.

[rumpel]

I put my on the power side cause it was not flat but shaped to fit this one. I also do not understand what it is for. I do not feel any difference in riding quality beside now bearing are completely quiet. Altough I’m thinking  about reopen the engine cause I did not put a lot o grease into the bearings housing.

Edited November 1, 2023 by rumpel

[Funky]

5 hours ago, alcatraz said:

What you don't want is the stator inside to touch the rotor housing. Also you don't want the bearings to bind, or the rotor to move sideways.

Stator has quit plenty of spacing left till motor covers. (Not every single motor is equally "spun" around the stator (Or what ever it's called where the copper is spun around. Some place sit higher some lower..) 

Bearings can't really bind. As outside of bearings wall doesn't move at all.. Only middle part spins around. Middle part of bearing doesn't sit/press against anything. (Well it has some big "long" barrel like o-rings that sit behind pedal hangers. Right against bearing middle.)

As for rotor. Can't say much.. But if axle is welded and only part that "centers" the rotor itself right into middle is motor covers - themselves. (Yes the covers center the rotor.. When you screw the motor cover close - you can hear it gets centered. At one point it makes "chung" noise as it sit's into center/place.)

 

Off topic: I even had broken axle weld that i re-welded.. The original 2 dot welds are to weak!!!. I welded all around axle. Still no rubbing and such. Wheel moved freely around without any noise that would make me think it's "catching/rubbing" against something. (I could tell that welds where broken because i had play while changing riding directions, or braking. Whole euc case move about 0.5Cm (5mm) one way or other. Thank GOD for axle having "key groove". Otherwise i would have tear of the wires and had faceplant.)

Edited November 1, 2023 by Funky

[alcatraz]

You can always try to pull and push on the axle after assembling everything. It should feel solid. When your body weight is on it any residual play left in the system should become noticeable.

[Funky]

5 hours ago, alcatraz said:

You can always try to pull and push on the axle after assembling everything. It should feel solid. When your body weight is on it any residual play left in the system should become noticeable.

Emm... Tell me how should i push the axle.   No really, i wanna know. All weight goes downwards onto pedals. Not side to side. We should look for side to side play..

As rotor is welded to axle. Only play would be the little gap between magnets and rotor itself. Only thing that makes the rotor sit right in middle, not scrapping outside magnets, or have any play are motor covers. As they center the axle/rotor. And the axle itself sits quit snugly into the bearings, which sits in motor covers.

The magnets are quit strong. So i really doubt you could "push" with hand.. As you said only with body weight. But the real question would be: Would you feel the 1-2mm play with body while riding? - I think not?

Better options would be to ride and listen if nothing is scraping or making @Funky noises. 

Edited November 2, 2023 by Funky