On Tue, 07 Jun 2005 21:24:46 -0500, Jon Elson
wrote:
What's really driving me crazy is why this platen keeps cracking when
I'm cutting thin aluminum sheet. I am operating at half or less the
capacity the shear should be able to handle.
One "plan B" solution is to remove my patch and make a patch that runs
the full length of the platen, welding it in just to the side of the
two cracks. And, then jam in shims or weld on little blocks that
support the platen along the full length. That ought to work, and
should prevent any more cracking, but it will be a lot more work.
Silly wild-ass guess non-expert off the cuff analysis from a hundred
miles away comment... In other words, Feel free to ignore me, I'm
just thinking out loud here. ;-P
(Oh, and after a quick bit of research... From here to your address
in Kirkwood MO [
www.pico-systems.com - I'm not psychic] Mapquest says
it's 1838.67 miles, 27.5 hours. Seems my initial silly guess of 100
miles was a /bit/ low. But I digress...)
If this area is cast iron that gets shock-loaded in tension during
use, it won't take much to make it crack again. Since you tried a
fishplate on the bottom side, and it just cracked where the loads were
moved to one end of the fishplate, I'm thinking there may be an
inherent design weakness in the platen. (Bet you when they changed
over from "Peck Stowe and Wilcox" to "Pexto" they made it heavier...)
How about putting a tension rod through or under the platen, right
below the shear throat edge, thread the ends and use some fine thread
nuts to put some external compression on the platen? Maybe even a
V-block (or two on the webs) at the center like the tensioning rod on
your garage door, to counter any downward forces in the unsupported
center of the platen? THEN you remove the old fishplate, drill the
ends of the cracks, preheat and weld them up again.
You can check the finished side of the platen for bowing, and stop
tightening the tensioning nuts when it gets a very slight positive
arch from the preload.
Better than throwing it out.
-- Bruce --
--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545
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