Brian,
Well done indeed; finally a practical home test for hardness.
Regards, Gilbert"much wiser now" Anderson
In a message dated 11/2/01 5:52:41 PM, rocklube@adnc.com writes:
<< Gilbert,
I think the Rockwell test goes something like this. It requires two genuine Rockwell paintings of the same size (generally 16" x 24") and of equal huge value, placed 2 feet in front of a concrete wall. Next a mechanical arm that can sling a crankarm at equal force is required.
The proceedure goes like this. The mechanical arm is set to sling the arms at 50 feet per second from a distance of 10 feet from the face of the canvas (12 feet from the wall). Each arm is slung through each painting and slams into the concrete wall. The technician then measures the tear in each canvas and multiplies that measurement buy the length of the mushroomed part of the crankarm where it impacted the concrete wall. The softer material will naturally deform more than the harder material. The lower number will be the harder material. Since the factor of the tear almost always cancel each other out; one could forgo the paintings, but then you couldn't call it a "Rockwell" test. So I guess you kinda need the paintings to do it right. Oh, and you ask why it's called the "Rockwell C Scale"? The answer is simple, the parts are hitting Concrete. Duh! Hope that answers your technical questions, Gilbert.
Brian Baylis
Institute of Technical Bufoonery
Advanced Metals Testing Department
La Mesa, CA
>
> In a message dated 11/2/01 2:42:18 PM, rocklube@adnc.com writes:
>
> << You could be correct about that. Maybe there is also a heat treating
> sequence that they leave out of the BMX version of the cranks in
> addition to the lesser finish. Something has to account for the drastic
> difference in the price of the arms when new. I suspect you may be
> correct that they are softer. A Rockwell test would tell the story.
>
> Brian Baylis
> La Mesa, CA >>
>
> Brian,
>
> What test did Norman Rockwell perform and what paint and brush did he use to
> test the hardness of metals? Is it perhaps possible that the Campy BMX
> cranks were anodized rather than painted colors?
>
> Inquiring minds want to know.
>
> Gilbert Anderson
> in Raleigh NC >>