Can someone help me examine how badly is my frame damaged?

stratohunter

10 mW
Joined
Apr 12, 2022
Messages
34
Today when I was doing a recreational riding, my TSDZ2-equipped gravel bike started to make loud squeaking noises halfway. I disregarded it for half an hour, until it developed to loud enough to force me to stop for an inspection. I then found my TSDZ2 had broken the securing and swung up, chiseling a small dent on the aluminum downtube with one of the extruding screw nuts (see pictures below).

To explain, I did not use the securing block and the bridge-plate provided by the manufacture since my chainstay was too thick. Instead, I used aluminum cables to tie the big securing bolt of the motor onto the chainstay. This worked for several months before today's failure.

The dent is about 3cm from the spindle radially. So considering the 90Nm torque of the TSDZ2, the force making the dent was close to 300 kg. The frame looks fine apart from the dent, but considering the motor had been "biting" the downtube with varying forces up to 300 kg (as proved by the squeaking sounds) for half an hour, could my frame be weakened already due to fatigue? Is the frame still safe to ride at 40+ km/h on very bumpy roads for commuting after me finding a better way to secure the motor? Thanks!
 

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I then found my TSDZ2 had broken the securing and swung up, chiseling a small dent on the aluminum downtube with one of the extruding screw nuts (see pictures below).

Its not a durable motor, some have luck babying it, I guess.



To explain, I did not use the securing block and the bridge-plate provided by the manufacture since my chainstay was too thick. Instead, I used aluminum cables to tie the big securing bolt of the motor onto the chainstay. This worked for several months before today's failure.

Let me guess, you bought those aluminum cable zip ties off ebay and not a real store, heck even Auckland would have had good ones of known quality. Some like to gamble, and throw the dice.


The dent is about 3cm from the spindle radially. So considering the 90Nm torque of the TSDZ2, the force making the dent was close to 300 kg. The frame looks fine apart from the dent, but considering the motor had been "biting" the downtube with varying forces up to 300 kg (as proved by the squeaking sounds) for half an hour, could my frame be weakened already due to fatigue? Is the frame still safe to ride at 40+ km/h on very bumpy roads for commuting after me finding a better way to secure the motor? Thanks!

Who's to say how much the force was. I've ridden frames in worse condition.
 
Your frame is fine; the damage is superficial. That's the benefit of using metal instead of plastic-- it had to be smashed and squished into shape to begin with, so a tiny bit more cold work doesn't make much difference.

Don't improvise when it comes to mounting your motor. That TSDZ2 may be a hokey piece of junk, but it's still both your bike's power unit and the thing that holds your weight when you stand on the pedals. It needs to be attached for real, not lashed on with whatnot.

P.S. -
It's probably not a good idea to stand on the pedals very much, considering how inadequate the TSDZ2's bottom bracket spindle is compared with any other bottom bracket.
 
Chalo said:
It's probably not a good idea to stand on the pedals very much, considering how inadequate the TSDZ2's bottom bracket spindle is compared with any other bottom bracket.
One example:
https://endless-sphere.com/forums/viewtopic.php?f=49&t=115972&p=1714021&hilit=tsdz2+crack%2A#p1714021
 

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calab said:
Let me guess, you bought those aluminum cable zip ties off ebay and not a real store, heck even Auckland would have had good ones of known quality. Some like to gamble, and throw the dice.

I didn't state it clearly in my post, it's actually 16 AWG aluminum electric wire, I wound it 8 turns around the bolt and my chainstay. It's actually the threads on the bolt cutting apart the aluminum wires, making it to break. I covered the exposing bolt threads up with aluminum sheets and epoxy to make it smooth, then wound the wire back. I will keep watching on it for any sign of another failure.
 
Thanks for the replies! I put the motor back and will keep riding as before. But I will keep an eye on any cracks developing near the dent on the downtube, as well as signs of failing among the securing of the motor. I don't ride aggressively a lot, and I'm within 75kg with my backpack, so I'm expecting the torque sensor and the spindle to last me a while. I can just throttle back if they happened to break :)
 
If it cracks, it will be at the margin of the weld, not at that wee dent. And it won't be related to the mid drive going rogue.
 
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