checking a bike after big crash

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checking a bike after big crash

Postby ennsu » Wed Feb 06, 2013 10:03 pm

hi friends! i don't post very much but i lurk here quite a bit. well, not so much since i had a scary crash about a year and a half ago which did this:

Image

digressing context (optional): it was about 4:30am, almost sunrise (i was out all night but was pretty much sober by then) and i was riding down george st (sydney), down the gradual slope which goes from town hall to chinatown (before the road slopes up again to central). it was a saturday night (sunday morning?), the road was pretty empty and i was being a naive kid sprinting down the hill probably going the fastest i've ever gone, hands resting on the top of the handles nowhere near the drop-handle brakes like some sort of cool cucumber, when a guy in a car speeds up next to me and cuts me off without indicating, pushing me into the parked car lane with a row of parked cars ahead of me. it took what seemed like 5 years for me to reach down to one of the brakes but it was too late and i made a split second decision to try and split off the road and go on the pedestrian path but i was going way too fast and my front wheel folded in half, i flew and slid across the ground about 10 meters (no joke). i wasn't even mounting the curb, was going up a driveway ramp but i guess it was too fast. lay on the ground for about 2 minutes or something trying to figure out what happend. got up and saw i lost most of the skin off both of my elbows, flesh exposed and blood pouring out down my arms, fingers making puddles on the pavement. went back to my bike, front forks are completely splayed, front tyres and rims are folded in half halfway down the street. sat against some building while some kid on the 10th floor or something on his balcony and his girlfriend are laughing at me (assume they were drunk after a kick-on) while i'm completely dazed and confused, blood dripping down my arms. luckily some friends of mine who i was with before i got on the bike drove past when i had just crashed and saw me lying on the path with my bike in pieces, they swung back around and took the bike and me back to theirs (i left the rim, tyres, front hub and bits of the front brake on the path. sorry for littering, i didn't know what else to do at the time) and i had a beer with them while they kicked on (pretty funny / weird).

anyway, that was my first major crash after riding for 2 years (only had two bikes. both japanese racers) and after i got my bike home later that week, i hung it up in the garage and haven't since touched it or any other bike. not so much that i'm afraid of riding. I want to replace the damaged front fork, get new rims and tyres for the front, fix everything up etc. but people keep telling me that after a big crash, there are microfractures all over the frame and i shouldn't ride it again. i really loved this bike so i do want to ride it again, but i won't be able to ride properly (fast) if i can't trust in it, so how do i go about checking it's okay to just replace parts and keep going? assuming it does have microfractures all over it, why does this matter? is the bike going to just fall apart mid-ride, or is there more of a danger that if i get into another accident then injuries will be more sustained?

further info:
the bike was a chromoly apollo racer from the 80's or 90s. kuwahara frame, nitto headset, nitto & bars, weighed about 9 kilos. dont remember what the hubs were (i can look at the back one, but i dont want to revisit it in the garage just yet) but they were crazy good ball-bearings which would spin forever.

piccy:
Image

sorry for the really long post, i got a bit carried away reminiscing about it. hopefully i get a bit of guidance, but i don't expect to get plenty of help since i hardly contribute here, but it's mainly because i stopped riding after the crash.
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ennsu
 
Posts: 7
Joined: Mon Feb 14, 2011 12:23 pm
Location: Sydney, Australia

by BNA » Thu Feb 07, 2013 8:29 am

BNA
 

Re: checking a bike after big crash

Postby Wal42 » Thu Feb 07, 2013 8:29 am

The advantage of a steel frame up against other materials is that steel will normally fail slowly.

If you've fitted a new fork, the only other place it is likely to fail from your crash is around the headtube lugs, you should see the paint start to split around the lugs before the frame fails in anyway dangerously. The odds of it failing safely are in your favour, it's probably about 99% that if it did fail you'd see it way before you were in any serious trouble, in other words you've have plenty of time to stop if it did.


You could get the frame tested, the first way would be a visual inspection, you'd have to strip the paint off to visually inspect the frame properly, then this is not a lot better than just keeping your eye out for any cracks now, the second would be a chemical inspection (any boilermakering business should have a chemical test kit or could easily get one to do the test), again to do it correctly, you'd have to remove the paint, again there is still a small possibility that the frame could still fail after that.

You could get the frame x-ray tested by an industrial radiographer, this would be quite expensive, your paint wouldn't be damaged & it SHOULD (remember there can be no 100% concrete guarantees with stuff like this) show up any cracks or weakness' in the metal, there still could be stress points that won't show up, so you'd be back to watching the lugs around the bike to catch any impending issues.

Last way is a destructive test, it would find any weakness' in the frame, problem with that is, they need to destroy the frame & a similar non-damaged frame to ensure it was strong enough, this testing is normally used to certify a design or welding process on most jobs that if they failed it could be hazardous to the public. This really isn't suitable for what you are trying to discover.

By the description of the accident, I feel that the wheel & fork acted like an impact absorption zone (like a crumple zone in a modern car), most of the forces would have been absorbed by the wheel & fork collapsing therefore saving the frame.

I've had a steel frame fail on me, it doesn't happen very fast, the steel slowly tears as it weakens, you have more than enough time to stop because the process is so slow, the only time this is fast is if it is subjected to a very violent impact/s, I looked at a mate's early steel mtb that was tearing around the steering head, he was still riding the thing, dropping of jumps etc. his reasoning was that is was only getting worse very slowly. My one was my own fault, I was young didn't have the training in boilermaking that I now do, I decided to modify a steel race frame & weld it up, when I welded it, I weakened the surrounding parent material (rookie error) & it failed mid race, the tear was slow, I actually rode for another 10 minutes before it got that bad that I felt I was no longer happy riding the bike.

Now what do you do?

It depends on how comfortable you feel about the frame, check around the lugs (that will be the first place it will crack), if you can't see anything then it is probably ok (I'm assuming you've fitted a new fork), just have a look around the lugs after you ride it, if you can't see any signs of cracking then it's probably ok to ride the next time (yes I'm using probably quite a bit, these days you can't say definite as some numpty will seek legal action because you gave some advice. Advice is that, it's an opinion, hopefully based on experience or training but still an opinion).

If you aren't comfortable with just a visual check, then ring around a few boilermakers, ask them if they can perform a liquid penetrative or chemical test, they can possibly do this without removing the paint (it will be up to the individual boilermakers discretion to whether he's happy to do it without removing the paint), that should show you if there's any cracking around the lugs.


It shouldn't be the actual tubes that you worry about, if they aren't dented or deformed then they're probably ok, it will be the bonding where the tubes go into the lugs (that could be a welded, brazed or chemical bonded process), if it's going to fail then that's where it's likely to happen, that is the spot you need to be aware of.

If it was me, I'd have a close look around the frame, lugs, etc. if I couldn't see anything amiss then I'd go back to riding it (acceptable risk), I'd be checking the bike everytime I cleaned or serviced it (I do that now on all my bikes), if it is going to fail I'm happy enough will my knowledge of steel frames that I'll spot any issues way before it was in any way dangerous.

I hope this helps you out a little.
Wal42
 
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Joined: Thu Jul 21, 2011 7:09 pm


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