Integrated seatposts in steel - wall thickness?

[cfrisia]

The ISP is 100% aesthetic in my case.
I didn't expect that the use is so controversial.
But this was not intended to be the point.
(btw.-who in this business is to criticise aesthetic decisions? Why not build all frames without ornamental elements and paint all white? ;) )

Garro, HAZ is in issue of course, but no need to remind me. There are excellent papers/investigations on this.
Same for your engineering criticism - we don't always need to learn by failure and doing things over and over again, this is where we differ from pre-scientific ages.

I just try to approach this with some hard facts, something that I sometimes miss when reading on frame building

Regards

[cfrisia]

This article sheds some light -
Bob Brown Cycles: analysis

scroll down a bit for the Rockwell hardness vs. distance from joint graphs.
A bit on metallurgy - Rockwell hardness and tensile strength are almost proportional in heat treatable steel (eg Chrome/Moly alloys, microalloys etc.).
That means, if the hardness drops to 82% (as in the ishiwata for example), tensile strength does too.
Keep in mind, this is the maximum drop. A positive prospect, isn't it?

back to my issue, the ISP would not bend, it would buckle. As also shown by Mark, the buckling resistance is not dependent on actual tensile strength.
It is determined by modulus of elasticity and radius vs. wall thickness.
Strictly spoken, even if the tensile strength would drop by 50%, the ISP is more likely to fail because of its dimensions rather than because of its strength.
(This is just a ballpark figure, maybe the heat required to drop the strength by 50% would totally destroy the brazing alloy or induce microscopic crystal structure faults etc)

Of course one needs to braze it properly, and I'm able to do so (please don't get me wrong in the post above - I'm not trying to say "there are investigations, no need to learn heat control" - this is not how all engineers think ).

regards

[steve garro]

I didn't expect that the use is so controversial.

Garro, HAZ is in issue of course, but no need to remind me. There are excellent papers/investigations on this.
Same for your engineering criticism - we don't always need to learn by failure and doing things over and over again, this is where we differ from pre-scientific ages.

I just try to approach this with some hard facts, something that I sometimes miss when reading on frame building

Regards

1st, I don't care how you build it, I do hope you do it safe.

2nd - dude, you've got it 100% backwards, and I fucking hate this about the internet and framebuilding - YOU ARE THE ONE ASKING HOW TO DO IT SAFELY AND WHEN CONFRONTED WITH AWNSERS YOU DON'T LIKE YOU GET ALL PISSY. i EXPECT THE WORD "HATER" TO BE THROWN OUT SOON.

3: IF YOU DON'T LEARN FROM THINGS FAILING OVER & OVER AGAIN, WHAT DO YOU LEARN FROM?

4: I HOLD THAT YOU HAVE ZERO HARD FACTS - YOU HAVE #'S

Man..........I'm starting to sound like Dazza.
I'm stoked on that.
I only jump in anymore to try to save people who I think are doing sketchy things, and that might make me sound like a curmudgeon, but if people seem to "have it down" then why chime in at all?



Good luck, really.
- Garro.

[Will Neide]

3: IF YOU DON'T LEARN FROM THINGS FAILING OVER & OVER AGAIN, WHAT DO YOU LEARN FROM?

I think he's just saying he wants to do this in a scientifically controlled way with numbers to support his assertions. My impression is that he's just kind of looking for real world buliders opinions to support what his math says. I don't think his goal is to fail at all, but start with a solidly safe, yet minimal, starting point. I'm sure if it does fail he will learn from it, but since he apparently has never built one, then he's hoping not to fail on his first attempt. IMO. Bricoleur vs Engineer?
:)

[steve garro]

I think he's just saying he wants to do this in a scientifically controlled way with numbers to support his assertions. My impression is that he's just kind of looking for real world buliders opinions to support what his math says. I don't think his goal is to fail at all, but start with a solidly safe, yet minimal, starting point. I'm sure if it does fail he will learn from it, but since he apparently has never built one, then he's hoping not to fail on his first attempt. IMO. Bricoleur vs Engineer?
:)

“An expert is a man who has made all the mistakes which can be made, in a narrow field.”
Niels Bohr

I'm not trying to piss in anyone's wheaties.
Just trying to keep someone from a forced 4130 anal probe.
What ever happened to building in a margin of safety & working backwards from there?
Nobody's goal is to fail, is it?
It's not like 1.125" x .035" is heavy..........!
- Garro.

[cfrisia]

woa woa Garro, I didn't mean it like that. English isn't my first language, it probably came out wrong.

I'm not pissy - there's been input from bellman/jake about using a 0.8 thickness instead of 0.6. after some input by Mark pointing out that my assumptions for dimension were faulty, I wrote that I'll take 0.8 because it compares well to aluminum posts in terms of buckling resistance.

I just tried to say that I am aware that proper brazing is important but not the vital issue for me.

Of course I want to do it safely, but I don't see why I should overdimension it. We had some calculations here, but the stresses in a seatpost are not completely tangible, so I sought for real life experiences. Otherwise I wouldn't have needed to discuss and could've taken a really thick gauge.

I learn from planning, investigating and doing. I make mistakes, but I can greatly reduce their number by emphasizing on the first two parts.

Please accept my apologies, I did not intend to make your angry. Please know that a lot of stuff you posted here and on the old framebuilding forum was a big help to me when I started.

[steve garro]

I did not intend to make your angry.

You haven't - frustrated, maybe.
I appreciate what you are trying to do.
Just maybe start off with a good margin of safety built in, yeah?

As we all know, ultimately all engineering disasters can be traced to a lack of redundancy, right?
Maybe bond in a CF or Al sleeve in the highest stress area?
- Garro.