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Re: Contact loads from moving loads

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The answer involves very complex and random guesswork to get values for a
simple equation.  The equation is F = m*a.  You have the mass and the force
is what you want.  The acceleration is a function of the stiffness of the
stop, the stiffness of what the stop is attached to (if it's on an elevated
platform, the log hitting the stop could cause the entire platform to sway
several inches - I've seen this), and even the stiffness of the LOG (the
front end of a long log will stop and compress because the back end of the
log is still moving).

Unless you want to do some VERY detailed and time-consuming theoretical
calculations (which will probably wind up being wrong), you should just
guess based on a factor of the weight.

Or you could do what my dad would do in his sawmill.  Look at it, scratch
your head, then weld something that looks strong.  If it breaks, weld it
back stronger and add a gusset.

Also, keep this in mind:  How many thousands of dollars will a breakdown
cost this place?  Think about that if you're trying to save a on
labor/materials with this stop.

Jason Kilgore
Leigh & O'Kane, L.L.C.
816-444-9655 (FAX)
----- Original Message ----- 
From: Joseph Grill
To: seaint(--nospam--at)
Sent: Tuesday, October 07, 2003 10:06 PM
Subject: Contact loads from moving loads
Gentlemen and ladies of this fine list,
I know I am taking you California engineers away from the election this
evening, but I need to ask a question that I am not too familiar with.  I
have a situation where a 6200# log is moving along a support driven by
chains.  The log will contact a stop mechanism which is supposed to stop the
log.  The log will be moving at 200 ft/min.  I need to calculate the force
on the stop.  Can you give me any help or send me to a reference that I hope
I have that may explain what I need to do.  I have been looking at a 25 year
old dynamics book from college, but to be honest it isn't helping me very
much.  It is a little late this evening, but I need to get going on it in
the morning.  I can scratch out some numbers which I think will be pretty
conservative, but would like some other input if I can get it.  The stop
mechanism needs to be designed after the force is determined.
Joseph R. Grill

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