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11-23-2010, 05:06 PM
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Half-Ass Member
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Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 22,001
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Not Ranked
Lock Washers Are Useless!
I was perusing the NASA Fastener Design Manual today and came across an interesting statement about how split lock washers (that everyone on here uses), when fully torqued down, render themselves useless. Instead of sucker-baiting RodKnock, ERAChas, Lykins, or the like, I thought instead I'd just post it. I've pulled the quote from Page 9 and this is the link to the full NASA Fastener manual: http://gltrs.grc.nasa.gov/reports/1990/RP-1228.pdf
Last edited by patrickt; 10-25-2016 at 08:49 AM..
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11-23-2010, 05:09 PM
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CC Member
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The first time it loosens from full compression it then becomes a spring. On larger lock washers over 1/2" the majority of time one half will snag the parent material the other half the nut, so in reality not only do you have spring action, you have mechanical interference.
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11-23-2010, 05:13 PM
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Half-Ass Member
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Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 22,001
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Quote:
Originally Posted by madmaxx
The first time it loosens from full compression it then becomes a spring. On larger lock washers over 1/2" the majority of time one half will snag the parent material the other half the nut, so in reality not only do you have spring action, you have mechanical interference.
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Once it loosens you no longer have the proper torque.  And why didn't the NASA engineers see fit to mention that point if it is indeed correct? |
11-23-2010, 05:26 PM
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From Carroll Smith's "Engineer to Win", a bible of race car prep:
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11-23-2010, 05:31 PM
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Join Date: Oct 2003
Posts: 4,078
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Once again, thank you for yesterday's news today. Anyone who has not passed the Bar Exam (and some of those that have) already knew that. 
__________________
Chas.
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11-23-2010, 05:42 PM
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Half-Ass Member
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Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 22,001
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Quote:
Originally Posted by ERA Chas
Once again, thank you for yesterday's news today. Anyone who has not passed the Bar Exam (and some of those that have) already knew that. |
Apparently it was news to madmaxx, mechanical engineer par excellence. |
11-23-2010, 05:44 PM
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Senior Club Cobra Member
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Join Date: Feb 2007
Cobra Make, Engine: KMP 539, a Ton of Aluminum
Posts: 9,591
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What's a lock washer? 
Patrick must be bored. |
11-23-2010, 05:47 PM
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CC Member
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Join Date: Jul 2005
Location: Bartlett,
Ill
Cobra Make, Engine: Everett-Morrison LS1
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I'd like to add that in an application where the bolt is used in shear (not torque) even if it loosened up, then the washer would bite into the nut and bracket material and prevent it from falling out !!!!
Remember that these washers were designed before farm tractors had rubber tires---
And also in aviation and space things get safty wired---which also won't prevent the fastener from loosening---it just will still be with the junk at the crash site
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11-23-2010, 06:03 PM
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Quote:
Originally Posted by Jerry Clayton
And also in aviation and space things get safty wired---which also won't prevent the fastener from loosening---it just will still be with the junk at the crash site
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Jerry-you rock!
__________________
Chas.
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11-23-2010, 06:25 PM
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CC Member
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Join Date: Dec 2004
Location: Kansas City,
KS
Cobra Make, Engine: jbl
Posts: 2,291
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won't find'em on my cars, the parts i've fixed anyway!
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11-23-2010, 06:36 PM
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Senior Club Cobra Member
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Join Date: Dec 2000
Location: Chandler,
AZ
Cobra Make, Engine: 396W Kirkham KMPS036
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Having worked as a structural analysis for the past 40 years or so, I must say I have never seen anyone in the aerospace business use a split washer. For non rotational joints the FAA allows locking nuts (either the insert type or the ovalated varity) and these can only be reused three times max. For joints under rotation then the prefered method is a cotter pin. Safety wire is used more as an inspection aid, much like the safety wire on our wheel spinners.
Other specific methods of locking the joint have been developed and are allowed in specific instances. The NASA fastener manual is useful along with AC43.
On my vehicles all instances of "lock washers" have been replaced with suitable locking nuts. Also make sure you are not running any threads in shear when put joints together. The shear strength through the threads is very poor.
__________________
Bob McLinden
ERA FIA 2080 SOLD
Kirkham KMPS036
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11-23-2010, 06:54 PM
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CC Member
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Mostly on large bolts and studs the sharp ends of the lockwasher actually penetrate/dig into the base metal when the nut is tightened. When loosening I have seen both mating surfaces on either side of the lock washer severly gouged.
As far as auto manufacturers using them, wouldn't gm and ford have to know this after the billions of cars they have sold between them.
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11-23-2010, 06:56 PM
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CC Member
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Join Date: Sep 2009
Location: Camarillo,
CA
Cobra Make, Engine: SPF #2608, Roush 427SR T-W
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OK, I'm not a gear head. What's a locking nut? Something with a wire through it?
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11-23-2010, 06:57 PM
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I may have an engineering degree but I am no engineer. That would be way to hard and they dont make any money!!!!! Brother has 6 patents, poor bastard doesnt even have a cobra yet
Quote:
Originally Posted by patrickt
Apparently it was news to madmaxx, mechanical engineer par excellence. |
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11-23-2010, 07:02 PM
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Found this on the web
"I've thought about this and discussed the matter with engineering colleagues, and confess I don't understand why a split-ring lockwasher is useless when flat. As far as I know, a spring's resistance is greatest when fully compressed. It's possible the manuals mean that, once a split-ring lockwasher is flat, its cut ends no longer dig into the surfaces being fastened together and thus don't prevent the nut or bolt from turning, as the star washes discussed later in this report do. But the manuals don't explicitly say that.
I think the Nasa guys are wrong, they had a little mishap with an o-ring calculation back in 1986 you may remember.
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11-23-2010, 07:11 PM
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CC Member
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Join Date: Jul 2008
Location: Driftwood,
TX
Cobra Make, Engine: Contemporary Cobra, 427 side oiler
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So be honest, you woke up this morning, walked into the water closet, squattted down and thought, "Should I read the McNabb contract again, or the NASA Fastener Design Manual?" |
11-23-2010, 07:14 PM
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Half-Ass Member
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Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 22,001
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Quote:
Originally Posted by WardL
OK, I'm not a gear head. What's a locking nut?
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I use these Locking Nuts: http://www.nylocknut.com/
Quote:
Originally Posted by elmariachi
So be honest, you woke up this morning, walked into the water closet, squattted down and thought, "Should I read the McNabb contract again, or the NASA Fastener Design Manual?" |
Uhh, yep. |
11-23-2010, 07:57 PM
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CC Member
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Join Date: Sep 2010
Location: starke,
fl
Cobra Make, Engine: Contemporary Classic Car Co. replica of 1966 Cobra made in 1988 with big block bowtie (600 hp 454), Bought about 4 months ago
Posts: 80
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lock washers are what they use to put on Mercury automobiles to differentiate them from Fords
scaffold
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11-23-2010, 08:05 PM
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Senior Club Cobra Member
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Join Date: May 2006
Location: Manteca,
Ca.
Cobra Make, Engine: None, sold it
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Quote:
Originally Posted by WardL
OK, I'm not a gear head. What's a locking nut? Something with a wire through it?
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Look here,
http://www.mcmaster.com/#hex-locknuts/=9unh7r
__________________
Terry
"I may be paranoid, but that doesn't mean they are not watching me"
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11-24-2010, 08:46 AM
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Senior ClubCobra Member
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Join Date: Feb 2006
Location: Northern,
Ca
Cobra Make, Engine: LA Exotics
Posts: 1,037
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Quote:
Originally Posted by ERA Chas
Once again, thank you for yesterday's news today. Anyone who has not passed the Bar Exam (and some of those that have) already knew that. |
For those of you that are as old as dirt, this may be old news. But not everyone is an old. That's why magazines run the same engine builds over and over. There are new people coming along learning every day.
Grumpy old men..... |
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