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Re: Contact loads from moving loads

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Thanks Scott and Steve,

I've gotten that far with this and with other problems of a similar nature.
I was just hoping that from that last guard rail type problem someone has
joined the list with a great "snap your fingers" easy way to go about it.
Guess I'm back to armwave the movement to get an answer.

Thanks
Joe
----- Original Message ----- 
From: "Scott Maxwell" <smaxwell(--nospam--at)engin.umich.edu>
To: <seaint(--nospam--at)seaint.org>
Sent: Tuesday, October 07, 2003 10:35 PM
Subject: Re: Contact loads from moving loads


> Joseph,
>
> The problem is easy, but not really.  <grin>
>
> If you know how quickly the log stops from 200 ft/s to zero and over what
> distance, then the problem is relatively simple.  You would be able to
> determine the decleration and multiply that by the mass of the log to get
> your force.
>
> But, the problem is that determining how quickly it stops and over what
> distance is not easy.  Thus, the problem becomes difficult.  As Michael
> pointed out, it will be come a function of the stiffness of the stop (i.e.
> is it really stiff such that it does not compress much and stops the log
> rather quickly or somewhat soft so that the log takes a little longer to
> stop over a longer distance).
>
> Beyond the above, I am not much help.  I could only suggest that you take
> a "reasonable" guess.  If you take a guess as to the distance that it
> takes to stop (i.e. how much the stop compresses), you should be able to
> get an approximate decleration value.  But, to really be accurate, you are
> talking about dealing with the mechanics and dynamics of non-rigid
> bodies...stuff that make my head hurt (and not because my non-rigid head
> would rather be bounced on the more rigid desk than think of such things).
>
> HTH,
>
> Scott
> Ypsilanti, MI
>
>
> On Tue, 7 Oct 2003, Joseph Grill wrote:
>
> > 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.
> >
> > Thanks,
> > Joseph R. Grill
>
>
>
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