"Jack Sprat" <[email hidden]> wrote in message
news:[email hidden]...
Quoted message said:I was riding my nearly new (less than 60 days old) Canaan Elite and it
exploded on me
I could have been KILLED!
I was riding down a steep hill and just at the bottom when all my weight
was forced onto the bicycle and it exploded. I obviously crashed and was
incredibly lucky not to be seriously injured. My helmet was also
destroyed saving my head from a similar fate.
I know that there is a warranty that could replace bike, but at this point
I'm scared that it could happen again with the new bike and I could break
my neck and DIE!
Do you bike experts think this is fluke or do you think it could happen
again?
http://www.cs.utexas.edu/~jss/canaan/broken1.jpg
http://www.cs.utexas.edu/~jss/canaan/broken2.jpg
http://www.cs.utexas.edu/~jss/canaan/broken3.jpg
http://www.cs.utexas.edu/~jss/canaan/broken4.jpg
http://www.cs.utexas.edu/~jss/canaan/broken5.jpg
Hope this isn't too personal. What do you weigh? If that happened to a
relatively slender person, I'm alarmed.
It looks like this disaster started at the bolt on the tube beneath the rear
shock. I think force from the front tire impacting a bump is going to put
that tube in tension along the bottom and compression where the weld is and
it's going to be most concentrated on the lowest spot of the outside of the
tube, right where they drilled a hole and put in that bolt. It's called a
stress riser. If there are any imperfections in that hole, the forces will
find them and work on them until that metal tears and once a lightweight
design like this starts to go, everything else will go rather explosively.
So why did they put the bolt hole in the worst possible spot? It should have
been to the side of the tube if possible.
My guess is it all happened very fast but in fact it started on that lowest
bolt hole and ended with the break on the top tube nearest the seat.
Isn't it aluminum that doesn't do well in repeated deformations? I think I
read that and that it's more brittle than steel. Brittleness will of course
cause more of a shattering type failure.
Another thing... the older style bike would have had the two tubes going up
to the seat from the rear axle. Those tubes would have prevented flexing at
the bolt hole. The rear tire puts leveraged force on the bolt again and
again. Most of it should be absorbed by the shock, but more of it will get
through than with the old style of diamond frame. Of course the whole lower
tube is also getting the force from both front and rear tires. It's just
that it's going to fail at the weakest point, which is that bolt hole. To
figure out the force on the bolt from the rear tire impacting, you take the
force and multiply by the length between the axle and the broken bolt hole.
