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Re: Load Indicating Washers.

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Here is a lengthy summary of the Belleville washer and similar concept
washers that you might find interesting:

http://www.fastener-world.com.tw/new/Manag_contents_e/fw_colum/e_sc_fw69_03.htm

Of course, I've never used this site before, so take it for what it is
worth.  It sounds like stacking two *might* give you something like twice
the resistance if everything worked exactly right, like stacking two beams
without connecting them to one another, but there also seems to be a lot
that could go wrong.  If they bind and try to act compositely, you could end
up with too much load.  If they don't overlap exactly, you could start to
bend them one after the other, each would fail one after the other at the
same load, kind of like the CMU block analogy.  I might try this if I was
putting up something in my garage, and I don't really need the intended
load, but I wouldn't stake anything important on it.  Might be a good time
to find the right tool for the job, instead.  Good luck.

Regis


From: "Conrad Guymon" <conrad(--nospam--at)karren.com>
Reply-To: <seaint(--nospam--at)seaint.org>
To: <seaint(--nospam--at)seaint.org>
Subject: Re: Load Indicating Washers.
Date: Tue, 22 Jan 2002 15:19:31 -0700

I don't know what a Belleville washer is, so maybe I'm exposing my
ignorance.  It seems that if you stacked these washers, it could be
compared to stacking blocks.  Say one of them fails at  1699 lbs, the other
1701 lbs.  You would load the stack to 1699 lbs, and one block fails.  You
add two more lbs, and the other block fails.  If you stack them, it seems
that you are only getting an indication of the weaker of the two, not the
sum of both.

Am I thinking this through right, or did I just expose my ignorance?

Would a Simpson PLI washer give you the values you need?  I can't find
values listed in the catalog I have, just pretty pictures.

Conrad Guymon, P.E.
  ----- Original Message -----
  From: vicpeng
  To: SEAINT
  Sent: Tuesday, January 22, 2002 2:08 PM
  Subject: Load Indicating Washers.


  I'm sure this topic was discussed in the past, however, a search of the
archives didn't find the answer.  I'll keep looking, it's possible that my
search query on "washers" & "DTI washers" is wrong.

  I need to clamp a bracket (to be used for a friction grip), and I need a
washer/other that will indicate when I have reached the clamping force.

  I have access to beveled (Belleville) washers that give a clamp force of
2373 lb (max P = 3078 lb).  I need 3400 lb.  Would  putting 2 washers of
1700 lb on one side give me the load I need.

  Methinks that it doesn't add that simply?

  Thor A Tandy P.Eng
  Victoria BC
  Canada
  e-mail: vicpeng(--nospam--at)sprint.ca


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