Rear Hub Motor - Correct Order for Washers?

portals

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Jul 15, 2022
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Its not that clear from your post whether your axle is 12 X 10 or 14 X 12. Anyhow I once fitted a Bafang geared hub with 12 X 10 axle to a similar 'semi horizontal' dropout type Apollo hybrid bike.
I removed the derailleur from the dropout and pushed the motor fitted with the anti rotation washers right back to the rear end of the dropout. I modified the derailleur hanger by discarding the screw fitting and semicircular nut thingy that normally takes up room in the dropout. I also ground flat the indent/rise that on the inside of the hanger and deepened the hanger slot.
The derailleur than is just held with its deepened slot in the axle and pinched between the bike frame and the nut. It wont turn. A washer between the nut and derailleur is desirable. You need to keep the derailleur hanger pushed home as you tighten the nut.
This works well but there is one drawback and that is that you have to be careful when you remove the wheel not to get the chain in a knot as the derailleur has nothing to support it (tends to turn from the springs) when the wheel is removed.
Thanks for the detailed response, the axle is 12x10 btw.

So if I'm understanding you what I should be doing is removing the derailleur and bolt and the cut nut on other side.

Then put in the hub/axle using the full dropout width (I like that idea!)

Finally put the derailleur on tight against frame, hold i place, then a washer then the axle nut. Forget about the bolt hole on the derailleur as the axle but will keep derailleur in place?

So this is how it is now and I 'lose' half the dropout width:
60252

And this is what you are suggesting?
60253
 

portals

Esteemed Pedelecer
Jul 15, 2022
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The derailleur has a slight dimple at back of drop out:
60257


The frame also isn't flush either where the derailleur would sit:
60256


I might be able to get derailleur to sit straight if I use a small washer between frame and derailleur, won't know until I try however what would you recommend in this instance?

Should I grind down the bump on the dropout and grind down the bump on the back of derailleur so they are both flat and can be butted up tightly?

I'm running out of tools to do a job like that, don't have anything suitable to grind steel down only a Dremmel that won't cut it I don't think..
 

Sturmey

Esteemed Pedelecer
Jan 26, 2018
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Should I grind down the bump on the dropout and grind down the bump on the back of derailleur so they are both flat and can be butted up tightly?
I just ground/filed the bump on the derailleur. The derailleur then was flat against the frame dropout. I did not have to do anything with the frame dropout other than widen it slightly by a rub of the file to remove some of the paint. A flat file should do the job. I got everything to fit together nice and cosy. I used no torque arms, just the two tabbed washers that came with the kit. If you want to mount the wheel slightly more forward, you can turn the tabbed washers by 180 degrees, so that the tabs go in first. Make sure that the cable is still facing downwards.
 

chris_n

Esteemed Pedelecer
Apr 29, 2016
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Niedeau, Austria
The derailleur has a slight dimple at back of drop out:
View attachment 60257


The frame also isn't flush either where the derailleur would sit:
View attachment 60256


I might be able to get derailleur to sit straight if I use a small washer between frame and derailleur, won't know until I try however what would you recommend in this instance?

Should I grind down the bump on the dropout and grind down the bump on the back of derailleur so they are both flat and can be butted up tightly?

I'm running out of tools to do a job like that, don't have anything suitable to grind steel down only a Dremmel that won't cut it I don't think..
Remove the bump on the derailleur hanger and remove material from the hanger if necessary to clear the raised area on the frame ( I don't think that is required as the area where the hanger sits appears to be raised anyway) . The hanger is usually aluminium so nothing more than a file is needed.
Looking at your new position pic it looks like the dropout has spread anyway so moving it further back is definitely a good idea.
 

portals

Esteemed Pedelecer
Jul 15, 2022
587
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Well I had a go at this tonight with just a bottle of red wine for company...funny how as the bottle drains you get more 'confident'...

The hub axle is now sat tight in the end of the dropouts, that has had a few minor side effects as the drive train is now probably 2cm longer and wheel sits 'higher'.

1. I've adjusted the brake pads down so they now hit rim and not tyre.
2. The chain seems a little tight so maybe needs an extra link or two
3. Not yet sanded down the bump on derailleur, when I tighten it all up the derailleur actually sits not too bad so sanding is not top of list but I will do it, tightish chain not helping though at moment.
4. non-drive side torque arm no longer fits in configuration used before, I think what's in pics below should work by changing orientation of one of the floating pieces as it's the bolt that holds the two pieces together that is fouling on frame as it sits higher.
5. looks like I may be able to get one of these torque arms on to drive side too as now there is now space (by a fraction), for the bolt that holds the two pieces together if I configure like in this pic.
6. will need to redo the derailleur Hi/Lo/B screws etc. to sort gear changes given it's now moved position

If this works out I will replace the torque arms with similar more heavier duty ones as long as additional width doesn't scupper anything - are there any better ways to add torque arms that the configurations I've used?

This is latest version of drive side (loose):
60259

Spacing is:
60260


This is latest version of non-drive side:
60258

Spacing is:
60261


Any comments on what I've done or should've done differently?

Again appreciate the replies so far.
 
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portals

Esteemed Pedelecer
Jul 15, 2022
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Here's another question, when you are riding the ebike and giving it some torque you might assume that both dropouts are under similar opposite forces with the axle trying to rotate it's way out?

I have read in few posts recently that a torque arm is more important on drive side but I'm wondering why that might be? I tend to keep rear hub in mid gear around 3/4 on rear cassette and flip between front 3 cogs to get some pedaling in when I want.
 
Last edited:

saneagle

Esteemed Pedelecer
Oct 10, 2010
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Telford
Here's another question, when you are riding the ebike and giving it some torque you might assume that both dropouts are under similar opposite forces with the axle trying to rotate it's way out?

I have read in few posts recently that a torque arm is more important on drive side but I'm wondering why that might be? I tend to keep rear hub in mid gear around 3/4 on rear cassette and flip between front 3 cogs to get some pedaling in when I want.
I think that's probably come from someone who doesn't have a clue about how motors work. There are only a very small number that have split axles. All the normal ones are either one piece or two pieces bolted together, so the whole axle transmits the torque. Rear motors nearly always have rotors that are offset to the left of the bike to make room for the gears. In that case there would be slightly more torque on the left side due to elasticity in the axle; however, the axle is often hollow on one side for the cable, which would weaken that side and make it more elastic.

It's academic anyway because whichever drop-out breaks first, all the torque is then transferred to the other one, which doubles the torque, then it normally goes too.
 
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portals

Esteemed Pedelecer
Jul 15, 2022
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I just ground/filed the bump on the derailleur. The derailleur then was flat against the frame dropout. I did not have to do anything with the frame dropout other than widen it slightly by a rub of the file to remove some of the paint. A flat file should do the job. I got everything to fit together nice and cosy.
Thanks!

Was looking at rasps/files online (ones I have are small cheapos used for 3d prints), I noticed an angle grinder online for £14 and nearly jumped but by time added some discs price went right up and for £14 it's gonna be crap grinder...

Splashed out £30 for one from Amazon that comes with some discs and it just arrived. Probably overkill but I've had a few jobs this year where I have had to resort to knock-off Dremmel to cut metal and sand it and it was not a lot of fun to do using a small cutting tool.

If I still have any fingers left :) I'll post back the final configuration of the rear axle spacers etc.