- #1
kielbasa
- 21
- 9
- TL;DR Summary
- Forces applied on the bolts in the bike's hinge in the alluminium frame. Steel grade of the bolts is needed.
Hi,
I recently bought a folding bike and it turned out over time that its weak point is the main hinge where two bolts (vertically placed) are located.
I've had the lower bolt break twice during a ride, leaving a part of it stuck inside the hinge thread. It's clear that the forces applied were too much for the low-grade steel bolt to handle. Anyway - since I don't want to spend more money on service bolts which are obviously bad quality, I'd like to use ready-made ones but higher steel grade and modify them to my needs by a turner.
My main question is, how can I estimate the maximum forces applied during a ride, for instance when getting off a 10cm curb? I think in these circumstances the hinge is most vulerable to destruction (maybe there are some others?)
I primarily use this bike for city riding, not for off-road or mountain biking and I'm trying to figure out the appropriate steel grade for the bolts that will be sturdy enough for this purpose so I can use them instead. Good quality bolts are made of 10.9 graded steel, which means they can withstand around 1000mPa / approximately 100kg per mm2 of the screw section. This translates to a yield strength of around 1600kg for an M6 bolt. This seems like a lot, but I'm not sure if it's enough. I can't quite estimate the forces acting on the hinge. Any ideas on how to do it ? It looks like the forces are still significant enough to break the service bolts that are sold in shops, and I'm certain they're not made of plasticine...
My weight is around 105kg.
Any ideas? thanks!
I recently bought a folding bike and it turned out over time that its weak point is the main hinge where two bolts (vertically placed) are located.
I've had the lower bolt break twice during a ride, leaving a part of it stuck inside the hinge thread. It's clear that the forces applied were too much for the low-grade steel bolt to handle. Anyway - since I don't want to spend more money on service bolts which are obviously bad quality, I'd like to use ready-made ones but higher steel grade and modify them to my needs by a turner.
My main question is, how can I estimate the maximum forces applied during a ride, for instance when getting off a 10cm curb? I think in these circumstances the hinge is most vulerable to destruction (maybe there are some others?)
I primarily use this bike for city riding, not for off-road or mountain biking and I'm trying to figure out the appropriate steel grade for the bolts that will be sturdy enough for this purpose so I can use them instead. Good quality bolts are made of 10.9 graded steel, which means they can withstand around 1000mPa / approximately 100kg per mm2 of the screw section. This translates to a yield strength of around 1600kg for an M6 bolt. This seems like a lot, but I'm not sure if it's enough. I can't quite estimate the forces acting on the hinge. Any ideas on how to do it ? It looks like the forces are still significant enough to break the service bolts that are sold in shops, and I'm certain they're not made of plasticine...
My weight is around 105kg.
Any ideas? thanks!
Last edited by a moderator: