One might presume that the thimbles supplied by guy grip makers will not
deform loaded to the rated strength of the grip. They are definitely
heavy duty. I've never seen a hardware/big box store with such
thimbles, but no doubt they are used. Then the risk is the thimble
bends to less than the minimum specified bend radius of the EHS and its
strength is compromised. And/or the thimble "U" flattens and the EHS
comes out.
The stress in the thimble in the contact area with another radius is
known as Hertzian stress, a pretty complicated topic beyond my pay
grade, but the bottom line is the larger the contacting radii, the lower
the stress levels for both deformation and fatigue failures.
https://en.wikipedia.org/wiki/Contact_mechanics\
Understanding the gross deformation of a thimble under load probably
requires finite element analysis or destructive testing.
Grant KZ1W
On 5/24/2018 4:01 AM, john@kk9a.com wrote:
Unless the cylinder has the same radius as the thimble it will still only
hit or connect in a very small area. At what tension will the heavy duty
thimble crush? I doubt most hams will see this much guy wire stress.
John KK9A
Steve Maki K8LX
I'm not convinced that a preform/thimble combo MUST be mated to a
straight cylinder, even though the examples shown don't include anything
but. I've seen BIG preforms installed through a closed link for example,
that seem to satisfy any concerns. As long as the curved link is smooth
(to avoid abrasion), it might offer an advantage over a straight pin.
At any rate, in ham applications it's mostly all academic.
-Steve K8LX
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