I have a question regarding the structural integrity of my aluminum frame after its having... incurred damage;

Question

Apologies if this has been covered previously, but I didn't see it if it had been, and at this point I'm at a loss.

For context, the bike in question is this year's Haro Double Peak Sport 29 https://harobikes.com/products/double-peak-29-sport-2021 I have recently completed(?) a conversion to electric power utilizing a rear hub motor kit purchased from a domestic retailer. A couple of days ago while on a ride it became necessary to stop to investigate the source of a sudden and clamorous racket, and... well, I was taken aback when I discovered this:

Where once there were braze ons, now

there are just gaping holes in my seat stays(?!)

Now... I think its relevant to point out that the only weight on said rack was the weight of the UPP hailong battery (less than 9 pounds). Clearly, any rack being marketed is rated to be capable of bearing a considerable amount beyond that (the Topeak UNI SUPER TOURIST DX (DISC) being no exception to this rule, itself (per Topeak website) boasting "MAX WEIGHT CAPACITY26 kg / 57 lb," So... I guess this raises quite a few questions-- was it... erm... the additional stress caused by vibrations(?)-- that doesn't make much sense to me. Was it simply absurdly sloppy welds? I'd like to think that's not the case either, but... am I correct in assuming that these Gaping maws

In my seat stays will continue to degrade if I endeavor to engage in the very activities one might be motivated to purchase an MTB for? Does there exist some product on the market that can correct or reinforce this unlikely circumstance? I've been unable to find it if it has, and this same line of inquiry gleans as many and varied responses as the number of local industry professionals I present it to...

Weld it again?? Is a hole weldable? It certainly doesn't predispose me to await whatever other potential hoodwinks

I'm sorely vexed to scrap it (having invested no small measure of time, effort and the extent of the meager resources I had at my disposal) and replacing it is quite beyond my means. And as if to add insult to my admittedly-merely-euphemistic (at this juncture) injury, I can't petition Haro for warranty as I purchased this contraption from a private seller subsequent to she having determined after its maiden voyage that it's frame was just too large for hers.

I've quickly come to rely on cycling as legitimately the only activity that restores me to some semblance of sanity in an otherwise antagonistic and hostile personal life circumstance, so... I guess I'm hoping to hear that I'm overstating the problem(?) 'it's really not something that constitutes a catastrophic failure; just slap some X____ in there and get back to it...'

Right?

Answer 1

Unfortunately the frame is now scrap. I would not ride it. The jagged edges of the hole will not help, it will induce a stress riser and the frame will crack. The question when, not if.

You will almost certainly be unsuccessful with a warranty claim on the frame (although you have nothing to loose trying), the reason the braze ons failed is they were subjected to a rotational stress from the spacer and extra wide bracket. The rack should have been attached to the frame with no spacers. The spacer created rotational forces the braze on was not designed to handle.

You may have a claim against the rack manufacturer if it has been installed according to mounting instructions.

As far as 'the only weight'. The 9 pounds were mounted on a spacer that looks like at least 1 inch, the torque on the mounting point would have been 20 times compared to if there were no spacer mounted and the rack was bolted directly to the braze-on. Roughly equivalent to putting 90 pounds on the rack, without considering the dynamic loadings.

Answer 2

You've bought it this year! In that case it is surely still covered by warranty, even though you've bought it from a third person. Contact the dealer and let them have a look before undertaking any attempt on repair.

Answer 3

It is weldable, but it will probably be expensive because not too many companies are experienced in welding Aluminum. Another option would be to place something strong around the damaged part, like the cast for a broken limb. I would just keep riding it if I couldn't fix it.

The issue is almost certainly caused by vibrations. The rack was certified for a higher weight, but it was not the rack that broke. Two things that make the situation much worse in your case are that there is a little cantilever arm there, which increases the stress, and shock loads from the battery pack. It looks like you have already bought a new rack, I would also try to mount the batteries on shock-absorbers. A simple rubber ring of 1 to 2 cm high will do just fine.

The reasons why I think this is not very dangerous:

1. The damage is at the rear wheel. Failure would probably not cause you to fall.
2. The stress level should not be very high in this part, there is little bending.
3. The hole is at a favorable location on the tube, stresses are highest at the top and bottom.
4. This part has compressive stress, little cracks at the ragged edge will not open and grow.
5. Fatigue cracks in aluminum grow very slowly. Sudden breaking is unlikely, if you are worried you can inspect it weekly or monthly.

Answer 4

This might be repairable, if a technique used on airplanes works on bikes.

To begin with, I just want to emphasize that I don't have any particular experience with bicycle repair, so I might be wrong. However, I do have some training in aircraft maintenance and repair - and in aircraft, if there is a significant dent, crack, or hole in the airplane's aluminum skin, there was often a procedure used to repair it that involved cutting a hole around the crack or dent, and then welding or riveting a patch over the hole and extending a certain distance past its edges in all directions. For instance (making up numbers), if you have a 1cm hole, you might be able to weld a patch that's 5cm across such that the patch extends 2cm past the edges of the hole.

Here's a Wikihow article demonstrating this repair procedure, though obviously any real aircraft maintenance should be conducted in accordance with the Aircraft Maintenance Manual for that variety of aircraft rather than a random wiki page: https://www.wikihow.com/Repair-Minor-Aircraft-Skin-Damage

It seems plausible to me that a similar repair might be possible on a bicycle.