RE: [CAD_CAM_EDM_DRO] Steel Channel flex ?

Dave I'll take a stab at this one...

OPEN sections (I beams, channel, angle, etc) are very soft in torsional
or twisting.

CLOSED sections (box, tubing, etc) are dramatically more resistant to
twist.

A classical experiment is with two thin walled pipes....one closed
and the other with a narrow longitudinal slit...like a "c" cross section.

Both will be stiff in bending, but the c cross section will be very
compliant
in torsion. You can try this by cutting a cardboard paper roll.

This begs the question as to why open sections are even used. Well,they have
some advantages:

1) they can easily be twisted to conform to another member without undue
stress
2) They are easier to fabricate
3) they can be joined without blind fasteners

In your case an offset load will create torsion in a single open member.
This will directly reduce the stiffness at the spindle. The lightest and
stiffest structure for this will be a closed section. In general open
sections
should not be used for torsional loading. The material will not be
efficiently used.

Does that help?

Les

Leslie M.Watts
L M Watts Furniture
Tiger Georgia
(706) 212-0242

Main page:
http://www.lmwatts.com
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>From: "turbulatordude" <dave_mucha@...>
>Reply-To: CAD_CAM_EDM_DRO@yahoogroups.com
>To: CAD_CAM_EDM_DRO@yahoogroups.com
>Subject: [CAD_CAM_EDM_DRO] Steel Channel flex ?
>Date: Thu, 06 Oct 2005 16:09:03 -0000
>
>I'm looking at a gantry with a pair of 3" (1/4" web )steel channels
>running about 36 inches.
>
>These are starting to get pretty heavy, and if the flex were not too
>great, it would be nice to be able to use only one.
>
>Anyone know how to determine what the flex would be on a channel if
>the cutter were mounted 6 inches off the face ?
>
>Any suggestions for a stronger frame ? I or box ?
>
>Dave
>
>
>
>
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OFF Topic POSTS: General Machining
If you wish to post on unlimited OT subjects goto:
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http://groups.yahoo.com/group/jobshophomeshop I consider this to be a
sister site to the CCED group, as many of the same members are there, for OT
subjects, that are not allowed on the CCED list.

NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM.
DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
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