KVA butted tubing-ride quality

[Mark Kelly]

The equation for deflection of a tubular beam does call out the materials Modulus of Elasticity, which is alloy specific.

Alistair.

Not really. All alloys of steel have the same modulus, 210 GPa, until you get to very high levels of alloying like 316 (which is only about 65% steel) and even then it only changes by 5%. If you assume 210 GPa for plain steel and 200 GPa for stainless you'll always be right within a percent or so.

[blasdelf]

Fred, I hear you and I'm pretty sure we're in agreement on your first point but just to be clear, what I was trying to say in my previous post is that I'm not married to any particular tubing diameter/wall thickness dimensions, be they Olde Worlde, OS, Double OS or otherwise. If the frame is able to provide the basis for the bicycle to have the ride qualities I want, then all is well as far as I am concerned.

I agree, and it's according to Richard's opinion too. In his case the PegoRichie OS tubing he uses now has thin enough walls to make the ride quality extremely similar by-the-numbers to the old world standard-diameter tubing he brazed by the bushel.

[Mike Mcdermid]

You know what the more I get into optics the more something dawned on me, you alter the air dampers you can shift resonances in or out of a specific range

You alter the air pressure the same must apply with a bike

[Curt Goodrich]

Some princess' can feel the pea. Some can not. Some like stiff. Others like flexible. Some like the newest trend. While others want what they cut their teeth on. It's all fine by me. I stopped worrying about the theoretical and just make bikes.

[Alistair]

Not really. All alloys of steel have the same modulus, 210 GPa, until you get to very high levels of alloying like 316 (which is only about 65% steel) and even then it only changes by 5%. If you assume 210 GPa for plain steel and 200 GPa for stainless you'll always be right within a percent or so.

Yep, I agree completely. When Fred said "the specific alloy content is irrelevant" I may have misunderstood and thought he was referring to metals outside the steel family (Aluminum, Ti etc.).

Within the range of steel alloys available for building steel/stainless steel bike frames, I've always considered the differences in Young's Modulus to be negligible, as you pointed out above.

Re-reading Freds post, I would agree that he was referring to alloy differences within the family of steel alloys, which for our purposes here are indeed essentially irrelevant. Sorry for the mis-understanding.

Alistair.

[suhacycles]

Doug

If it comes to pass, send me the dimensions of the 56 cm frame and I'll make carbon and wood/carbon/boron fibre frames to throw into the mix. I had been planning something similar for my own edification anyway. The wood/carbon/boron fibre frame's development was driven by acoustical theory, I've also got a ti frame with tube butts that were shaped according to vibrational nodes but it's 58.5cm with a long top tube. Maybe someone can do aluminium and ti as further reference points.

I can't promise to make it to the meet, your spring is my vintage.

Speaking of acoustic theory and wood/carbon combinations, this reminds me of one of my guitars, a Garrison. They're no longer made but at the time they had a neat concept of creating a composite internal skeletal structure made out of 4 pieces versus the traditional method of gluing dozens of pieces of wood. I think it sounds fine and it doesn't sound like it resonates any less than other guitars in its price range. However, when I looked up the company at one point I did come across complaints that the expansion/contraction rates of the composite and the surrounding wood possibly did not exactly match up so cracks developed. Anyway something to think about if you're planning on building a frame where it's likely to be exposed to even greater stress, temperature and humidity fluctuations than a guitar... well, at least my guitar... =)

[jclay]

Not really. All alloys of steel have the same modulus, 210 GPa, until you get to very high levels of alloying like 316 (which is only about 65% steel) and even then it only changes by 5%. If you assume 210 GPa for plain steel and 200 GPa for stainless you'll always be right within a percent or so.

Seven identical frames back in 1996: Magnificent 7

Too many bicycles, tubing differences too granular. It's why your optometrist has you select the best of two lenses at a time, exchanges the worst, repeats; its also imperfect. If I wanted to test the ability of human reviewers to differentiate otherwise identical bicycles (or test for planing) I'd start with two, one of straight gauge 1mm wall and one of 747, or some such large difference, and go from there. The results of a statistically sound analysis (many fit riders, same routes, etc., etc.) would speak for itself, in either direction.

If the discussion is about the broader question of what is most important to bicycle feel, performance and suitability to task then I agree that best placement of the contact points, good geometry, tires, etc. are far more important and noticeable to how a frame feels or performs than frame tube butting profiles.

[Mike Mcdermid]

Not really. All alloys of steel have the same modulus, 210 GPa, until you get to very high levels of alloying

https://mospace.umsystem.edu/xmlui/b...pdf?sequence=1

[e-RICHIE]

If the discussion is about the broader question of what is most important to bicycle feel, performance and suitability to task then I agree that best placement of the contact points, good geometry, tires, etc. are far more important and noticeable to how a frame feels or performs than frame tube butting profiles.

The takeaway is that if you want to make a better quality frame, or improve at any level as a commercial framebuilder, you have to make lots of frames for a long time (so you have some baseline to make references from - assuming your skills evolve atmo) or you have to find a material that is not part of the very narrow range of weights, diameters, gauges, and shapes that we all have tapped for many, many years.

Bicycles are lighter now than they were a long time ago. And the sizes of several pipes are different than they once were. And some steels dent less easily than others. But past that, the design parameters and manufacture of the frame, along with the components that are hung on it to make it into a bicycle - these are where the characteristics of the ride come from.

My guess is that it's much easier to talk about the what-ifs and the theory than it is to simply go to the bench and make lots of frames for a long time.