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  1. #1
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    fork axle toosmall for new wheel

    I have an old miami sun tricycle with 24 inch wheels. ordered a front ewheel conversion kit. finally arrived on a slow boat from china. the axle slots on the old bike front fork are too small for the axle on the ebike wheel. any suggestions greatly appreciated.
    Last edited by davidswfla; 12-25-12 at 05:08 PM. Reason: mistake

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    Get out a file and open up the slots wide enough to accept the axle. Because don't want to change the wheel position file only from the front of each slot, being careful not to touch the top. That way the wheel will be located according to the unchanged back and top of the slot.

    You don'r want to go any wider than needed, so work slowly and check the width often. Stop when the axle just barely clears.
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  3. #3
    Andrew R Stewart Andrew R Stewart's Avatar
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    Or take the file to the axle. Two flats on each end, like a SA rear hub. Andy.
    .

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    Quote Originally Posted by Andrew R Stewart View Post
    Or take the file to the axle. Two flats on each end, like a SA rear hub. Andy.
    .
    I thought hub axles were generally harder than files?

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    None of the hub axles I've filed have been harder than my files. Perhaps if they were harder I wouldn't have to file them to repair the threads.

    - Joel

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    Quote Originally Posted by tomacropod View Post
    None of the hub axles I've filed have been harder than my files. Perhaps if they were harder I wouldn't have to file them to repair the threads.

    - Joel
    Ah, never mind. I've never filed one, I was once told that it wasn't possible. Clearly whoever said that was wrong.

    It would probably still be easier to file the fork ends than the axle.

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    Andrew R Stewart Andrew R Stewart's Avatar
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    It might be easier and in the long run the remanufactured (you are doing that BTW) fork will then accept other axles in it's future. But as a shop mechanic one of the policies that we should follow is to effect the easiest to replace part as a first choice. This is the axle, not the fork. Andy.

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    Quote Originally Posted by Airburst View Post
    I thought hub axles were generally harder than files?
    Not at all. Shortening an axle with a standard hacksaw blade, say to convert a 135 mm hub to 130 mm, is quite easy. Ever try to saw through a file?

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    Filing the axle or the fork are equally viable, but I prefer filing the fork for a few reasons.

    1- 5/16" axles are becoming rarer for all but 20" wheels, so this makes the bike more current for the future.
    2- filing the fork makes QR an option if desired in the future.
    3- it's slightly easier to mount round vs side flatted axles.
    4- I've seen too many people file axles with the flats at both ends not lined up, that means having to file more off that may be desirable.

    Filing the fork is very easy, and as long as the back and top of the slots are left untouched, the wheel position will stay correct.
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    None of the electric hub-motor axles I've worked with were hardened steel. Some could be a bit harder than others, but I'm going to guess that even then a file would still cut into it (engineers probably would rather have a "softer" axle bend, rather than risk having a "harder" axle snap or shear-off).

    Btw, I strongly suggest that you use a "torque arm" to keep the axle from spinning in the fork dropouts. This can, of course, damage the fork and/or the motor at best, and injure the rider at worst. Not sure if your kit came with one, but you can purchase one from various ebike retail outlets (such a ebikessf, ebikekit, and ebike.ca, etc) for about 10 USD.

  11. #11
    Senior Member Bill Kapaun's Avatar
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    Quote Originally Posted by Airburst View Post
    I thought hub axles were generally harder than files?
    That would sure make it fun to cut the threads!

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    Quote Originally Posted by Bill Kapaun View Post
    That would sure make it fun to cut the threads!

    Well, BB spindles have threads in/on them, and those definitely are hardened, so it must be possible. I can only assume they do it before they harden the metal.

    I've cut down axles with a hacksaw, but for some reason I thought HSS hacksaw blades were harder than files...

  13. #13
    coprolite fietsbob's Avatar
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    Many people screw up their files dragging them back and forth like it was sand paper
    and blunt the teeth, then they wont cut well.

    Push and lift, push and lift !

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    Quote Originally Posted by Airburst View Post
    Well, BB spindles have threads in/on them, and those definitely are hardened, so it must be possible. I can only assume they do it before they harden the metal.

    I've cut down axles with a hacksaw, but for some reason I thought HSS hacksaw blades were harder than files...
    Yes, it's standard practice to hea treat after all machining operations except for grinding. However many things are in what could be described as a "half hard" condition where threads can still be rolled in, yet hard (and tough) enough to do the job. Spokes fall into this category, as do many "B" quality axles.

    Files are among the hardest of finished metal products. As a rule they're not annealed from the quench hardness, so they're about as hard as the material allows. A Bi-metal hacksaw's teeth, since they're usually HSS, or another higher alloy. A conventional (not bimetal) hacksaw blade won't be as hard as a file since at that hardness it would be prone to shattering.

    Machinists often use a file to test material before machining and use the term "file hard" for those which cannot be filed, and therefore cannot be machined (conventionally).
    FB
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    Thank you for your advice. It took about a half hour to get the wheel mounted. I didn't put the tire and tube on until I was sure it worked. Hooked it all up and road tested it this evening. Just a 24 volt 250 watt system with a battery pack I made from two 12volt 18ah batteries. Used a wood frame and believe it or not I used return air hvac louvers for the sides. lots of air flow. Thanks again.

  16. #16
    Senior Member Bill Kapaun's Avatar
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    Quote Originally Posted by FBinNY View Post
    Yes, it's standard practice to hea treat after all machining operations except for grinding. However many things are in what could be described as a "half hard" condition where threads can still be rolled in, yet hard (and tough) enough to do the job. Spokes fall into this category, as do many "B" quality axles......
    Wouldn't stainless spokes get their hardness from the drawing operation, rather then heat treatment?

  17. #17
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    Quote Originally Posted by Bill Kapaun View Post
    Wouldn't stainless spokes get their hardness from the drawing operation, rather then heat treatment?
    Yes, I was pointing out that the final hardness was such that they could be threaded in the final condition, rather than heat treated after threading.
    Another example is threaded fork steerers.
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  18. #18
    coprolite fietsbob's Avatar
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    Just hope there is sufficient fork tip left after filing enough to make it fit..

    Given it transmitting drive torque .. I wonder what else is there to take the Power, an E-wheel puts out.
    a strut further up the fork leg?

  19. #19
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    Quote Originally Posted by fietsbob View Post
    Just hope there is sufficient fork tip left after filing enough to make it fit..

    Given it transmitting drive torque .. I wonder what else is there to take the Power, an E-wheel puts out.
    a strut further up the fork leg?
    What you've described is called a "torque arm." These are used to keep the axle from spinning in the dropouts.

    Properly designed and installed torque arms are a very important component on most hub-motor conversions.

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    Quote Originally Posted by Andrew R Stewart View Post
    It might be easier and in the long run the remanufactured (you are doing that BTW) fork will then accept other axles in it's future. But as a shop mechanic one of the policies that we should follow is to effect the easiest to replace part as a first choice. This is the axle, not the fork. Andy.
    +10 to Andrew; When doing a one off fix or mod, always try to fix or mod the cheapest part or the one most available just in case it goes badly. Having the ability to go back without major cost is vital. Kind of like that poster who thought his seatpost was a smooge too tight for this new CF frame build up so instead of trying a different seatpost or applying some emery cloth to the alloy seat post, he ran a ST reamer down the neck of the ST, killing the frame if I remember correctly. Umh $600 frame vs a $20 seat post..ok lets think; Now if this goes badly which will be the easier to fix?

  21. #21
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    This being an electric hubmotor could make finding a replacement axle (let alone installing it) a difficult, if not impossible, proposition imo.

    This, and the shipping via "a slow boat from China" could possibly end up costing more time and/or money than it would be to replace the fork.

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