The importance of frame stiffness.

[jclay]

I think those links both go to the same paper. I thought the paper was confusing as it claimed to compare different tube sets from different manufacturers but it did not specify which tubes were used. They say" Clearly for the out of plane load case, the dominant tube is the down tube whereby the lateral displacement can vary by up to 71% simply by changing the down tube from Reynolds 853 (lowest stiffness) to Columbus Life (highest stiffness), while in the vertical load case the seat stays can have a significant effect on the vertical compliance of the frame with only a relatively small change in sectional profile compared with other tubes. " There are several possible Reynolds 853 and Columbus Life tubes which could be used as downtubes. If you stick to 31.75 alone, Reynolds produce 11 different 853 tubes with wall thicknesses varying from .65/.45/.65 to .9/.6/.9 and variations in the length of the butts. Similarly there is a range of possibilities in the Columbus Life series.

I scanned it quickly and they seem to have used the tube name instead of identifying the tubes by dimension.

[Paul Jacobs]

I scanned it quickly and they seem to have used the tube name instead of identifying the tubes by dimension.

That is exactly how I read it.
" A range of existing frame geometries were subject to various in plane and out of plane loading conditions to examine the influence of tube profiles (as published by the Reynolds, Columbus and Tange manufacturers) on the lateral stiffness and vertical compliance of steel frames."
" Beam element sectional properties for top tube, down tube, seat tube, seat stays, and chain stays were taken from the tube profiles published by the manufacturers Reynolds (953, 853, 725, 631, 525 tubes), Columbus (XCR, Spirit, Life, Zona tubes) and Tange (Superlight, Ultra Strong, Infinity tubes). "
"The FE model was firstly used to analyse the influence of the 12 different tube profiles" - presumably this means the 12 different tube types, 5 Reynolds, 4 Columbus and 3 Tange listed above.
This would only be meaningful if the manufacturers made tubesets so that there was only one possible 953 tubeset and one possible XCR tubeset and so on. This is not the case. It is not very helpful to the framebuilder to say Reynolds 953 makes the best top tube and Reynolds 853 makes the least stiff downtube without specifying which one of the many possible 953 top tubes and which one the many possible 853 downtubes were chosen.

[Mark Kelly]

You're not seeing the wood for the trees.

The important information in that paper is largely in the graphs I posted (that being why I posted them). This information is independent of the identity of the tubes used to construct it.

If you are really focussed on a particular tube it's a simple matter to work out where it lies on the relevant line. You just have to calculate its moment of inertia, easily derived from the manufacturing specs.

[Paul Jacobs]

You're not seeing the wood for the trees.

The important information in that paper is largely in the graphs I posted (that being why I posted them). This information is independent of the identity of the tubes used to construct it.

If you are really focussed on a particular tube it's a simple matter to work out where it lies on the relevant line. You just have to calculate its moment of inertia, easily derived from the manufacturing specs.

I understood that the graphs were independent of the tubes and I am grateful to you for posting them. I just could not understand why the bulk of the paper looks at "the 12 different tube profiles" when they are really talking about 12 names or types of steel and when they then go on to compare (in figure 3) 12 different "tube sets" when such a thing as a defined tube set no longer exists for most of the materials mentioned (Reynolds don't list any 853 seatstays for example).

[steve garro]

IMG_0745.JPG


People with more mass get tubes with more mass.

And if you want to stiffen it from there, bump up the tube size

- Garro.

[progetto]

Show me on the graph Steve, it can't be that simple.

IMG_0745.JPG


People with more mass get tubes with more mass.

And if you want to stiffen it from there, bump up the tube size

- Garro.