Friday, March 13, 2009

19 Safety Moment : Downhill Cycling Accident Causes Death

Brace yourselves. Only this blog will be completely transparent to you and show you how an accident, human error or faulty design in cycling can hamper your health and put you in serious danger, sometimes even resulting in death.

This one culminated in a loss of life. Sadly. This story comes to you thanks to an email to me a couple of days back from a reader in Taiwan.

The victim was a 72 year old rider. He was riding with four of his friends on a local road in Taiwan on 2/28/2009. The section of that road was a gentle downhill, and not much wide with little traffic. The bike was a BMC road model ( I don't recognize it. An SL01 Racer?). So it seems no one really observed what happened. The rider in question may have strayed away from the group by dashing out in front, but from the fact that we know his age, I hinge on the assumption that he may have been left behind by the group.

Now, there was an impact. With what, how and why, no one knows for sure. Though the victim wore a helmet, his face hit the tarmac and his chest was struck by the stem. Later in hospital, he breathed his last.

Trusting that the information given to me is true, below is the scene of the crash. The blood on the road is likely to be the cyclist's.

And here is the observation of the transmission chain (Campagnolo) from the victim's bike :

Notice carefully that the chain appears to be jammed. On the front side, the chain appears to have slipped from the big chainring. On the rear, it is tangled onto the derailleur and the latter is also in a very atypical/extreme position.

What may have happened was the derailleur and chain jammed, stopping the rear wheel at once and throwing the rider off his bike. This comes from primary observations. Did something get stuck in his derailleur causing this? Was the chain too short such that when the chain was shifted onto the biggest sprocket in the rear (combined with big chainring in front), the derailleur ran out of travel and the entire setup jammed? Could it have been that in this situation, the rider went into panic mode and somehow made up his mind that gripping both brakes as hard as he can to stop the bike would be the solution and that eventually caused the crash? It is also not known whether there was an obstruction in the road, an animal that came in the way or the probability of a hit-and-run case from a reckless motorist.

Put on your thinking caps here and lets do a brainstorm. We will try and come to a reasonable conclusion about what exactly happened and also how it could be avoided. That this cyclist eventually died should ring some alarms in everyone's mind who comes across this story.

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  1. Anonymous11:59 AM

    While its very likely that this crash put some serious injuries to him, I would also be interested in knowing this man's medical history.

  2. Phil : Yes, he was pushing his 70's. But his previous medical condition doesn't interest me right now. I'm looking more at the series of events that led to the crash so it can be AVOIDED by someone reading the story.

  3. Anonymous2:01 PM

    I think that his age and his medical history would be pertinent to the crash.

  4. What happened I believe is that the outer limit on the front derailleur was improperly set and the chain jumped off the big ring just as he was pushing down on his right foot. The sudden lack of resistance resulted in a stem to the chest and a face plant in the concrete.

  5. For whatever it's worth, I had two Campagnolo rear derailleurs break catastrophically. The second one caused a chain jam up similar to what is pictured above. My rear wheel stopped rotating suddenly and completely, bending the drop out and throwing me off my bike. Fortunately, I was climbing and the speed was low.

  6. It appears that the upper hinge on the derailleur has become unpinned. That would certainly unship the chain, and possibly cause it to derail to the outside of the crank. (Although, that could have also happened during the impact with the road.)

  7. Jared : What does that have to do with the jammed chain in the rear derailler and the chain itself 'catching' into the right side pedal spindle?

  8. Anonymous5:59 PM

    We need the exact doctor's diagnosis on the cause of death.

  9. Ron: I think that once the chain popped off of the big ring there would likely be kind of a very quick loosening on the bottom portion of the chain. Mix this with the cassette that was likely still spinning with some force and I can imagine a chain getting sucked in all sorts of ways. As for the pedal/chain end spot this is a product of his foot likely keeping the chain on that spot. Being my own mechanic early in my racing and ridding days I have crashed or almost crashed in this way more times than I should admit. Thanks for the fun (and sad) question.

  10. I share the observation of an improper front derailleur limit screw adjustment, permitting overshift to the outside. The chain found the pedal spindle early in sequence, during the first pedal rotation of overshift. Sudden excess chain slack could cause the rear derailleur to snap back to 'home' position, with more length than it would ever have taken up. The snap can throw the chain slack, tangling it among pulleys and cogs. Nonetheless, I think the condition of the rear derailleur as we see it in this picture was NOT the cause of injury to the cyclist. Instead, sudden loss of drivetrain tension on the down stroke would have thrown the rider to the ground.

  11. Hello, all: I was the person who sent the photos. After knowing the event and sending out the photos, I got to know more about this cyclist. He was a regular cyclist around this region and could easily ride around 400 km during a week. Therefore, I don't think he was a novice in this case. But still, unfortunate things happen sometimes.

    It's not clear whether the rear wheel was jammed or not. It could be also due to the hard brake that caused his fall. In any case, the derailleurs seemed to be the initial cause, whether due to the improper setting or handling. I think we all should be careful about our bike before going for a ride. When something goes wrong, don't be panic. The last thing is the difficult part.

  12. Anonymous2:24 AM

    Nbob sez :

    If the chain slipped off the front ring wouldn't that release the tension on the freewheel and you'd just coast?

    My uneducated guess:

    1. spring inside rear derailleur malfunctions ( snaps? comes loose?) tension on freewheel lost and he begins to coast

    2. As fellow continues to peddle tension pulls upper pully up and back

    3. As he still peddles chain loops out between upper and lower pully ( as seen in picture) and there is no more tension on the chain

    4. Poor fellow wonders what's going on back there - leans a little forward to look back and down under his arm -thus putting chest closer to stem

    5. As he does so the feed from the lower pully back to the cogs gets jammed (between the dropout and outermost cog?)

    6. Suddenly there is alot of tension on the upper length of the chain as he continues to peddle which causes the chain to slip off the front ring.

    7. Just as sudden there is no tension on the crank arm - it induces a tripping like motion. The inertia propels him forward so chest hits the stem and he falls off.

  13. Anonymous3:27 AM

    Nbob sez:

    Upon closer look it seems the lower pulley seems to have rotated clockwise so that it is the one behind the deraileur.

    The chain that feeds into the lower pulley crosses below the return feed from the upper pully and looks to be seated in the cogs so as he peddled those cogs would continue to feed the lower pulley ( now the rear pulley)

    Since there is no longer any tension on the upper pulley the chain becomes slack and loops off but the attitude of the upper pulley feeds the chain to an outer cog whereas it is being pulled back to the crank on one of the larger inner cogs.

    The rpm of the smaller outer cog is faster than the rpm of the larger inner cog so the chain buckles and gets jammed.

    I still think it starts with a malfunction of the spring and ends with inertia throwing him on the stem and then to the ground.

  14. Anonymous12:10 AM

    It looks to me that the chain has broken. That could cause a crash.
    I had a similar crash 30 years ago, I hit a bump and my chain bounced off the freewheel and into the spokes, instantly locking my rear wheel. Fortunately I was not going fast. It also wreched my derailleur by pulling it right back.

  15. I'd go with the chain somehow jumping off the big ring, losing tension, then somehow jamming the rear.

    Possible with a violent enough crash - bike flipping over and over - have chain come off like this? If that was the case, the bike would show other damage as well - which I guess is not the case.

    Either way - freak deal. Too bad for the rider, not a pleasant outcome for all involved.

  16. Thank you folks. Very nice indeed.

    So a number of you have been hinting at the fact that due to the chain slipping off from the front big chainring (due to improper limit setting in the front derailleur), the rider had a sudden loss of tension while pedaling and the momentum caused him to dive forward. The stem hit him on the chest before he lost balance and crashed. The events leading to the jamming of the chain in the rear derailleur seem a little murkier at this point.

    David I thought the chain was broken. And Anon at 2:24 thought the spring in the rear derailleur malfunctioned. Anon has also described what he feels may have been the series of incidents in the rear at the site of the pulleys that may have led to the chain jamming.

    All were interesting points.

    Anyone else?

  17. Anonymous12:40 PM

    72 years and still riding is nothing short of commendable. I wish the friends and family of this man my sincere condolences.

  18. Anonymous9:28 AM

    Without an eye witness account and/or more evidence, e.g., photos of any skid marks on the road, flat spotting on the rear tire, etc.. it's impossible to know what happened and whether or not the drive train ended up looking the way it does before or as a result of the crash.

  19. I'm with Atlanta Mark -- there's no way to tell if the chain ended up that way after the crash.

    Condolences to the cyclist's family and friends -- I hope to still be on bike at 72 years old.


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