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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
http://www.clubcobra.com/photopost/d...kwasher001.jpg |
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 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.;)
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What's a lock washer? :LOL:
Patrick must be bored. :rolleyes: |
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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won't find'em on my cars, the parts i've fixed anyway!
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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. |
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. |
OK, I'm not a gear head. What's a locking nut? Something with a wire through it?
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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:LOL:
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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. |
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?":LOL:
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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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http://www.mcmaster.com/#hex-locknuts/=9unh7r |
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Grumpy old men..... |
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