J
Jobst Brandt
Guest
Ken Harper writes:
> So, the real question is, from my point of view, has your engineering knowledge been applied in a
> methodical way to reach the 5,000 mile number, or was that a dislike of the design coupled with a
> guess? Which is fine, too; I've certainly got my guesses on things as well.
> But a statement like "5000 mile life duration" is going to suggest to me, and the OP, at least,
> that this is not a particularly good bike to ride, at least not often.
> Is the following a valid conclusion from your statement: if I have a frame with at least 5,000
> miles on it, and if it has such a crown, then I've already exceeded the crown's life duration, and
> I just might reasonably expect a failure at any point now?
I think you are reading your own scenario into my response of 5000 miles. That is how long the two
forks with the Cinelli crown that failed lasted. I had others that lasted longer but I have no way
of estimating how much because in those days we had no Cyclometers and I don't remember how long I
kept the bicycles. I had a number of Cinellis before getting frames from local builders.
The 5000 mile figure applies to the two failures. As I said, I don't have statistics to say more
about durability but the two design flaws, weight and stress concentration are hard facts.
Jobst Brandt [email protected] Palo Alto CA
> So, the real question is, from my point of view, has your engineering knowledge been applied in a
> methodical way to reach the 5,000 mile number, or was that a dislike of the design coupled with a
> guess? Which is fine, too; I've certainly got my guesses on things as well.
> But a statement like "5000 mile life duration" is going to suggest to me, and the OP, at least,
> that this is not a particularly good bike to ride, at least not often.
> Is the following a valid conclusion from your statement: if I have a frame with at least 5,000
> miles on it, and if it has such a crown, then I've already exceeded the crown's life duration, and
> I just might reasonably expect a failure at any point now?
I think you are reading your own scenario into my response of 5000 miles. That is how long the two
forks with the Cinelli crown that failed lasted. I had others that lasted longer but I have no way
of estimating how much because in those days we had no Cyclometers and I don't remember how long I
kept the bicycles. I had a number of Cinellis before getting frames from local builders.
The 5000 mile figure applies to the two failures. As I said, I don't have statistics to say more
about durability but the two design flaws, weight and stress concentration are hard facts.
Jobst Brandt [email protected] Palo Alto CA