Too late on the patent..http://bikeforums.net/attachment.php...hmentid=293759

I'm not sure what the fatigue limit actually is - the notes from that lecture aren't somewhere I can get to them easily. Also, that was only talking about mild steel, not alloy steels, and I'm not sure if the fatigue limit of an alloy steel is dependant on its tensile strength directly, or if it's more complex. I suspect the latter.

I'm not even sure how I'd work out the force on a bike fork anyway - it's not just related to rider weight and road quality, obviously tyre pressure is a factor, but then there's the weight distribution of the rider to take into account, then there's extra force from braking and turning, and probably a lot else. It would probably be easier to start with a strain gauge on the fork and work back from there.

this steel frame is about the strongest and sturdiest bicycle frame I've ever ridden. I believe these are Tange frames, made by Miyata. its from late 1983. the wheels are really strong, too, the rear wheel was made with 0 dish, the axles are solid hardened steel. I did endless drops, curb hops, staircases, as well as all sorts of stupid forest tricks on this bike. that /is/ a replacement front wheel, the original got bent by a car.

http://www.hogranch.com/digi-2007/20...s/IMG_9137.JPG

my point is, not all steel is the same. neither is all aluminum. or anything, really.

My limited understanding was that fatigue limit is generally in the range, 30-60% of tensile strength, for whatever variety. I'd be surprised too if they were directly related. But anyway the alloys would take even longer to fail, no?

My musings on the fatigue failure of a steel fork were rough handling and a lot of time are necessary, not to say exhaustive. In other words, intuitively we don't ever reach the fatigue limit for steel in normal riding so fatigue failure, without something like crashes or stunts, is rare.

As you know, aluminum is a different story, not really having a fatigue limit. Who really knows with carbon fiber, so little data available and so much depending on how it's constructed. I've almost talked myself into replacing my cf fork here :eek:

It depends, if you double the tensile strength of your steel by going from mild steel to some super-steel alloy, but only multiply the fatigue limit by 1.6, then you'll be operating the material past the fatigue limit more of the time, assuming you lighten the structure by removing material to make use of the greater tensile strength. It all depends on exactly how the two properties are related.

Anyway, you're preaching to the choir here, so to speak. My initial post on the subject was in response to someone saying that all materials will eventually fatigue and break, which you agree isn't necessarily true.

Normally you'd alleviate that with larger diameter tubes. The problem is the "beer can effect" - you want wider or the same diameter tubes so that it doesn't get whippy, and so the walls get thinner if you reduce the amount of steel. Too thin and they crumple too easily. Thus you can't just lighten the structure in proportion to the tensile strength. But stronger alloys can be both lighter and stronger, just not in proportion.

I thought you were saying that steel forks would fail eventually but I think your clarification is probably correct. It's conceivable for steel forks to last indefinitely assuming normal use.

I was more than half serious about replacing my CF fork with steel. It has a small flaw near the right drop-out, a notch maybe a millimeter or two deep that I didn't notice when I got it new but saw shortly thereafter. I put about 6000 miles on it last year and it's really been bugging me that I have no way of checking whether the material has been weakened. Maybe I should post pics for opinions since this is a frame material thread.

Bold mine. Whose going to send out for popcorn.. then? :D Good idea IMO though... need a good clear pic I'd suggest.

Back when in this trail.. someone reminded about this actually being about FAILURE MODE. :thumb: Right on.

Possibly I missed remarks per aluminum's failure mode. In the end.. I'd think some bending.. advance warning per performance prior to winding up on your face [?].

I don't know.. are all al forks solid metal.. or some hollow tubed?

All are hollow tubed.

Is this the beginning of the end of the world as we now know it ?
 

Will the discussion on bike frame and fork materials bring on the zombie apocalypse ?:wtf:

I enjoy going into "the 41" and reading about frames breaking

Is it something in the water, or a contagion that has swept the forums ?............film at 11.

The news at 11...........ouch.
 

#!

IF your tolerance level for others is so low.. maybe you should take a vacation. ;)

Search function is mostly a non starter around here... mostly all salad which is the norm here. Like mining for gold.. tons and tons of dirt to get a day's wages. Someone who actually knows something might eventually respond. I know.. rare around these parts.

Define "knowing something" in this context... what are you actually looking for?

Right.. two--- shayyy.

Expert in how their fabricated... someone with long experience actually replacing them.

............if you want to search something, I get much more meaningful results with Google, using the subject and a limit to Bike Forums..

It almost always kicks up a number of threads that you can then access directly.

Not always was the case. Schwinn made many bikes with a solid fork blade. The Varisity stands out. Andy.

I meant to edit it to say virtually. But than I forgot. I should be pummeled.

ugh, those solid schwinn forks on the Varsity and Continental were such garbage. Heavy, AND wobbly, how did they manage such a combination?!?

How what are fabricated? Forks?

I think all my forks are stainless steel. I've never broken one. Bent some of the more flimsy spoons though.

most stainless steels are rather soft. more likely, good steel forks are a chrome moly, or something like 531, manganese moly or whatever steel. high grade forks on better road bikes were often fully chrome plated under the paint.

No, definitely stainless. I just checked. Says so right on the back.

Now that I think about it, how cool would it be to have a Reynolds 531 dinner fork? Would have to be chromed of course.

Oh dear....

ok, the yolk is on me.


http://www.nerdfitness.com/blog/wp-c...09/07/fork.jpg

Your most correct. Did that though.. did not find much meat.

Goggle searching.. invite you to run one. Possibly my titling of the search needs some refinement.. but I find most often nowdays the clutter of bullsh*t that comes back makes it not worth the effort. Hard info via the net is harder to find that hen's teeth.