Axle does not fit into dropouts perfectly

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transposon   10 W

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Axle does not fit into dropouts perfectly

Post by transposon » Nov 15 2019 4:20pm

dropout1.png
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Hi know this question has been asked here many times, but this is my first build and I wanted to see if filing down my dropouts was a good idea. It seems like I may not have a whole lot of material in the drop out. There is about 1-1.5mm of distance between the bottom of the dropout and the motor axle.

This is an aluminum Trek 4500 with a 1000W ebay hub motor. I am using a grin v4 torq arm on the other side of the motor. I wanted to use two torque arms, but my second v4 wont fit over the disk brake housing bolt.

Thanks.
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E-HP   100 kW

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Re: Axle does not fit into dropouts perfectly

Post by E-HP » Nov 15 2019 8:51pm

If you file them by about 2mm, then the center of your axle will rest in a the similar position as a normal bicycle axle would fit. You'd have more purchase for your axle nuts, and the rotor and caliper would line up as they were designed.

Balmorhea   100 W

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Re: Axle does not fit into dropouts perfectly

Post by Balmorhea » Nov 15 2019 9:07pm

E-HP wrote:
Nov 15 2019 8:51pm
If you file them by about 2mm, then the center of your axle will rest in a the similar position as a normal bicycle axle would fit. You'd have more purchase for your axle nuts, and the rotor and caliper would line up as they were designed.
Careful not to leave sharp inside corners on the axle slot. Those constitute stress risers that invite the dropout to crack and snap off at that point.

Best, I think, is to leave the dropouts alone and make a left side torque arm that screws to the eyelets. Carefully done, this takes all the prying forces off the dropout while leaving the dropouts with the structural integrity they were made to have.

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MadRhino   100 GW

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Re: Axle does not fit into dropouts perfectly

Post by MadRhino » Nov 16 2019 2:37am

Torque plates, each side, 1/4 steel. Ideally 2 screws each to hold em on the actual dropouts, but one screw and glue is OK.
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dogman dan   100 GW

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Re: Axle does not fit into dropouts perfectly

Post by dogman dan » Nov 16 2019 7:59am

Well, at the very least, one good torque arm is needed for sure. Try to modify the other grin arm so it can fit. Play with different ways to put it together, or grind a notch in it to go around that bolt.

I would file the drop out deeper, till the center of your motor axle matches where the center of your old axle was. This makes sure the disc lines up good with your calipers. But not too deep, too deep makes the nut fit better, but it then makes your caliper grind on the disc.

transposon   10 W

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Re: Axle does not fit into dropouts perfectly

Post by transposon » Nov 16 2019 10:06pm

I posted pics of the torque arm on the other side in this thread:
viewtopic.php?f=3&t=103295

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wturber   10 MW

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Re: Axle does not fit into dropouts perfectly

Post by wturber » Nov 19 2019 1:15am

I made these for my bike with the same (and very typical) issue that you have. It looks to me like this approach might work for you on the one side. This kind of thing is fairly easy to make.
viewtopic.php?t=26444&start=175#p1315521

Not filing the dropouts does keep the brake disc from sitting high enough for the brake pads to fully engage. That isn't a huge deal since it is only short by a millimeter or so. But you won't get the full wear out of your disc pads. I eventually switched to a 180mm rear disc and filed the 180mm adapter down by a millimeter or so to compensate. That resolved the disc pad/rotor depth issue.

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Re: Axle does not fit into dropouts perfectly

Post by kcuf » Nov 19 2019 9:27am

avoid regen
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