Chuck Schmidt wrote:
> Thing I always wondered was why the milled flutes in the late SR crank's
> spider weren't eliminated at the same time as the milled flutes in the
> crank arms and the seat post?!
>
> Reminds me of something I once heard a machinist say, "If you can drill
> or mill a part to make it lighter and it doesn't break in use then the
> part was designed too heavy to begin with." He did like the look of
> drilled and milled vintage parts though.
>
I think Campy was following a form-follows-function approach when they eliminated only the arm's flutes. The flutes in the spider would help make the section lighter while maintaining width in the directions of loading, while the flutes in the arms are more troublesome in terms of that section resisting the torsional loads fed into them by the pedals.
The machining of holes or flutes into a forged part might make more sense as the part is downsized or has relatively thin sections. Smaller holes and flutes can be harder to hold as net-shape features in a forging, especially when the flutes are shallow with respect to a to-be-machined surface. Maybe the best argument for post-forge relieving is the ability to fine-tune the net shape as test data from lab and field accumulate, and the same forging can also be used for a lower-level product line, with the relieving eliminated to save cost.
David Snyder
Auburn, CA