On Tuesday, August 27, 2019 at 5:02:10 PM UTC-4, Tom Kunich wrote:
On Monday, August 26, 2019 at 2:04:35 PM UTC-7, Radey Shouman wrote:
Tom Kunich writes:

Frank, stop showing your engineering inability. Did I not talk about
the Octalink BB? Is that the same diameter? And since you seem to
think that mild steel and Chrome Moly have the same torsional strength
why do they make drive shafts on high performance cars out of chrome
moly instead of mild steal since the cost difference is 200%? They do
no increase the diameters.

It would help if you quoted the stuff you're objecting to. Frank's
point, if I understood it correctly, was that strength != stiffness.
Chalo commented on a lack of stiffness in some obsolete bottom bracket
format or another, not a lack of strength.

I believe Frank would say that CrMo and mild steel have approximately
the same stiffness, and also that he would be right.

While it is easy to say that the Young's modulus of ferrous materials is "about the same" it isn't the same and the higher grade materials are indeed stiffer if not by much.

Now that you've googled "modulus of elasticity," why not give values for two
alloys we were talking about? And why not give the percent difference? Quantify!

I ask because in reality, the differences are tiny.

But these higher grade materials allowed for large improvements in power transfer.

Explain. If you take a bottom bracket axle made of steel with yield strength
100,000 psi and replace it with an identical part made of steel with yield
strength 120,000 psi, will it transfer more power from the same rider?

- Frank Krygowski