BadAtThis

so I got a new hub after upgrade to 1000W and it twisted the motor itself when I rode the cable was still fine but the dropouts on the frame are all gone and it got loose because the axle isn't gripped anymore. I wanted to weld something on to extend backwards so that it doesn't stress the swingarm. Turns out there is no space and aluminium can't be weld in that way so far. Please help me salvage this I was working on this for months now with this going out over and over, just the screws from the brake don't even clear if I attach another point there and the cable is so far twisted i'm afraid it'll snap as well if I drop the motor again

looking into taking this to a fabrication shop to get the frame sorted out anyone know what to else to do?

Smaug1

Looks like you have a nice parts bike to start your next project.

Moe Zhoost

I'm not sure what's going on here, but it's obvious that you've reached the engineering limits of your modifications. A bit more specific info from you may result in some good recommendations. Otherwise, current price for Al scrap is $0.75.lb.

CliffordK

Ok, so it looks like you've torn off the back half of the left dropout. Did you also file a V-groove into the dropout?

It isn't that aluminum can't be welded. It was welded 2" in front of the break. However, you will lose some heat treating, making it more pliable.

Talk to a shop about getting it welded and built back up to profile.

Now, any electric motor will need some kind of a reaction arm attached to the frame so that the motor doesn't wind itself off of the frame. And likely it should have a fairly rigid bolt to the frame.

Now, considering an electric motor from the left side of the bike. To give forward motive force, it will try to turn the tire counter clockwise and the motor clockwise.

So, if your reaction arm is forward of the motor, it will attempt to rip the motor out of the dropout.



I'm not quite sure what the solution is. Do any rear wheel electric motors come with "Thru-Axles"?

Your idea of hanging a triangle out back for the reaction arm might work, if it doesn't interfere with the brake. Perhaps more welding and machining than you would be comfortable with.

BadAtThis

Exactly what I was thinking if I weld a triangle to this swingarm from blow it could extend the frame a little back to where the hub is narrower and then I can attach it to the motor axle without it catching on the brake disc screws. They have like 1mm of tolerance as it is and I'm worried even if I get new torque arms it will shred the frame again. Been hating that this stuff falls apart anyway i don't need more of that lol....

Need to get into aluminum welding or find someone who can attach a new point to that arm, as well as the other side (it's not apart yet but it cracks and the axle can freely twist again. no drive with this as I thought)

unterhausen

I'm pretty sure you aren't going to get good enough at welding aluminum from scratch to be able to fix this yourself. Hopefully there are welding shops nearby. Depending on the aluminum, it might be okay without heat treat. It's not a spot that I think of as being subject to cyclic forces.

merlinextraligh

Assuming you’re not going to scrap the frame and start over, I’d find a custom builder,who works,in aluminum and talk to them.

2old

Since aluminum loses strength when it's welded, IMO you would need to heat treat it after fabricating a new part. There are individuals that extend the chassis of aluminum frames with reinforced parts (look at barncat's bikes on endless sphere). I think a less expensive, more feasible option would be a new frame, possibly steel, unless you have some special affinity for aluminum.

CliffordK

Ok, so 6061 is supposed to be weldable. But, I'm seeing notes that the post weld strength is down by 50% to 80%. That is a little more than I anticipated.

So weld or modify it if you wish, but it should be a fun project. The expense of hiring a shop to do work that may be more than you would want for a weakened frame.

That appears to be a FAT bike. I've seen a few electrified FAT bikes on the road, and I think they are made. Perhaps that would be the way to go, with something that someone is already doing rather than retrofitting.

m@Robertson

Unfortunately you are far from the first person to have this happen. Typically when this occurs the frame is a write-off. The costs and the risks associated with fixing it will exceed the costs of starting fresh with a frame that is not compromised. Even on steel frames where the dropouts just spread... they're never the same afterward.

Its a bitter pill to swallow but there it is. Before the next one gets built, research torque arms and find a way to use two of them on a big motor. Its by no means an issue to build a bike with a powerful hub motor but a strong torque arm solution is part of the cost of admission.

Also... it looks like you filed the dropouts to get a better axle fit. I can see the edges front and top of what is left are squared off. Its not an uncommon move especially for 14mm axles that are way taller than the dropout depth. But that introduces a classic weak spot on a frame that - over and above the torque arm issue - can cause exactly what we see here. In fact it looks like what you suffered was not a spinout but an outright snap since the front of the dropout is pretty well intact - no gouge where one half of the axle dug in like you usually see. Seems like the back half just broke off before a gouge could occur.

If you are going to go big on power, in addition to torque arms... consider a steel frame with steel dropouts.

portals

Good advice above, bin the frame and thank your lucky stars that you weren't riding at speed when it happened.

You should also as said have two torque arms, get the 4mm for non-drive side and depending on what you drive side is like another on that side too.

crn3371

You’re trying to shove a ten pound motor into a five pound frame.