9mm drop-outs, 10mm hub motor flats - a query

[Bikes4two]

• As we all know the flats on many if not all hub motors are 10mm across the flats whilst drop-outs are 9mm and therefore the drop-outs need widening by filing
• So my latest project is to fit an Aikema 100sx (courtesy of a redundant Swytch bike kit) likely across more than one bike and therefore my query is, rather than file the drop-outs on multiple bikes, why not file the motor axle flats (and the anti-torque washers of course)?
• I'm mean, 0.5mm off each side of the axle can't be that bad for a 40Nm (max) motor can it?

Thanks in anticipation

 

[saneagle]

It's a lot safe to file the drop-outs. I've heard them filing motors on the Swytch forum. I know Swytch used different motors over the years. I'm not too sure which ones they're filing, but if yo have a normal AKM100 with a straight axle, I wouldn't recommend it. Don't forget that the axle is hollow on one side.

 

[Raboa]

To fit the motor axle you usually need to file the frame dropout sides and bottom.
If you file the axle it might fit in the frame but not fit properly in n the torque arm, if you file the frame it should fit properly in the frame and the torque arm
One of the disadvantages of filing the frame is that this makes the frame warranty invalid, this is one of the reasons people choose older bikes
Filling the motor axle might also damage the threads and weaken the structural integrity of the axle
The industry needs to go the way of Grin technologies (i believe one Chinese manufacturers is planning to copy this system) and have a system where you can fit motors without touching the frame dropouts.

 

[Bikes4two]

Thanks for both contributions - I'll stick to the tried and tested system of filing the dropouts as
(a) as @saneagle says, the axle thickness on the motor cable exit side as already quite thin on the flats and
(b) the practicalities of holding the wheel/axle in a suitable position for accurate filing, wouldn't be easy.

As an aside, in the many yt vids of Swytch bike installation, I've yet to come across anyone filing the dropouts - are some bike dropouts already 10mm then?

 

[saneagle]

Thanks for both contributions - I'll stick to the tried and tested system of filing the dropouts as
(a) as @saneagle says, the axle thickness on the motor cable exit side as already quite thin on the flats and
(b) the practicalities of holding the wheel/axle in a suitable position for accurate filing, wouldn't be easy.

As an aside, in the many yt vids of Swytch bike installation, I've yet to come across anyone filing the dropouts - are some bike dropouts already 10mm then?

The cheaper bikes tend to have 10mm drop-outs. 9mm is for Q/R wheels.

 

[eas2lv]

As an aside, in the many yt vids of Swytch bike installation, I've yet to come across anyone filing the dropouts - are some bike dropouts already 10mm then?

Swytch these days have an option to choose 10mm or 9mm axles (across the flats). That said, I have seen bikes with Q/R wheels that have dropout gap in between 9mm and 10mm -- like 9.6mm.

 

[Raboa]

Fit elastic spacers / packers behind the file, they are disposable items so it does not matter if they get damaged.
Put file in fork, pack spacers behind, take one sweep of file, repeat in the other side. The key is to take your time, you might need two files, one second cut flat file (I prefer the ones without the plastic handle so the weight is better distributed) and a 10mm half round file. A flat and half round combination file might do the job and it will save you money.
You might be able to find smaller pack sizes or if you know somebody with a 3d printer ask them to make you some

Plastic Packers

These plastic packers are a great toolbox standby. Each pack contains 100 pieces in assorted, colour-coded sizes. You can use them for any job - levelling, spacing or packing - where you need consistent placing. So whether you're laying out tiles, lining up decking or spacing bricks, these...

www.toolstation.com

 

[saneagle]

Fit elastic spacers / packers behind the file, they are disposable items so it does not matter if they get damaged.
Put file in fork, pack spacers behind, take one sweep of file, repeat in the other side. The key is to take your time, you might need two files, one second cut flat file (I prefer the ones without the plastic handle so the weight is better distributed) and a 10mm half round file. A flat and half round combination file might do the job and it will save you money.
You might be able to find smaller pack sizes or if you know somebody with a 3d printer ask them to make you some

Plastic Packers

These plastic packers are a great toolbox standby. Each pack contains 100 pieces in assorted, colour-coded sizes. You can use them for any job - levelling, spacing or packing - where you need consistent placing. So whether you're laying out tiles, lining up decking or spacing bricks, these...

www.toolstation.com

I use a Dremmel with a carbide cutter. You need to re-profile and deepen the bottom of the drop-out, which isn't easy by filing. These things fit in a normal drill too, which allows you to do the job more slowly and carefully. I get the cheap Chinese versions of these:

https://www.amazon.co.uk/Accessories-Heatigo-Tungsten-Engraving-Polishing/dp/B09YY4J5HJ?th=1

 

[Bikes4two]

The cheaper bikes tend to have 10mm drop-outs. 9mm is for Q/R wheels.

So if I file out my 9mm dropouts (which are indeed on a bike with Q/R wheels) to 10mm so I can fit the hub motor, but then subsequently want to use the motor else where and refit the Q/R wheel back into the filed out 10mm dropouts, is that going to be problematic in any way?

Thanks.

 

[saneagle]

So if I file out my 9mm dropouts (which are indeed on a bike with Q/R wheels) to 10mm so I can fit the hub motor, but then subsequently want to use the motor else where and refit the Q/R wheel back into the filed out 10mm dropouts, is that going to be problematic in any way?

Thanks.

No, I do it all thr time.

 

[matthewslack]

Sleeve the axle with 0.5mm thick aluminium rings.

Many mass produced cheap consumer items use aluminium tubes, always of minimum necessary thickness.