Auto site declares lock washers as useless?

D

deardancer3

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Here is the site;
http://www.eng-tips.com/viewthread.cfm?qid=114051&page=1

part of the discussion:

btrueblood (Mechanical) 4 Feb 05 11:50
"The root cause failure mode is that the split washer is specified or installed by somebody who presumes it is an adequate thread locking or anti-rotation device. In its intended use, the split washer cannot prevent nut rotation when the joint is torqued down tight, since the cutting edge is acting parallel to the nut surface. Only after the nut has loosened (which is considered by most good engineers as a failure of the joint) can the edge of the washer "dig in" to the nut and the parent body."


second quotes:
http://www.eng-tips.com/faqs.cfm?fid=1257

Quote:
NASA Fastener Design Manual RP-1228:

"The lockwasher serves as a spring while the bolt is being tightened. However, the washer is normally flat by the time the bolt is fully torqued. At this time it is equivalent to a solid flat washer, and its locking ability is nonexistent. In summary, a lockwasher of this type is useless for locking."

Or the US Navy.

Quote:
Naval Ships' Technical Manual, Chapter 75:
"Although lockwashers may be encountered, using the flat washers with selflocking nuts, self-locking fasteners, self-locking inserts, or thread sealants such as MIL-S-22473 anaerobic compounds is preferable.

If loosening has been a problem, however, replace the lockwashers with self-locking fasteners.

The helical spring lockwasher (Figure 075-5-11) is flattened when the bolt is torqued down. Once compressed, it acts as a flat washer, contributing normal friction between the nut or bolt and the bearing surface during tightening."


any opinions fromthe M.E./ Scientist folks ?

I have some bolts that keep loosening up in a dirty environment down by the chain, (chainring to clutch attachment on cyclone crankset, 5 threaded holes in freewheel). Am wondering the best technique to stop this from happening, considering locktite, fingernail polish, lock washers and/or longer screws and boltign on the outside.

I am thinking that the bolts and mating freewhel threads have gotten munged from loosening, maybe get new longer bolts, clean everything up, and use threadlock AND nut on the back side, then use torque wrench to tighten to spec.

but what about usefullness of lock washers?

Thanks

D
 
Lock washers are useless in many situations. You will never find a split-washer on a Honda anywhere.

Places they are useless?

Anything on an engine.
Anything that gets hot (like at least 400f)
Hardened surfaces.
High vibration or shock environments.
Situations where maximum faster strength and rigidity is critical (because they just stand the head away from the material and increase the external shank length).


For soft metals, a star washer works decently, as does nylock (if you have the space, and the part never gets hot) or simply dimpling the face of the nut with a center punch in a few places near the threads after installing.

If you're willing to pay for it, this is the best I've found is nord-lock. They are the only thing that keeps a giant turbo-charger on a crappy thin-flanged turbo manifold. Immune to heat, vibration, shear load, and just totally rock except for the price.

This video will give you the straight-scoop:
[youtube]mgwmuZuJ02I[/youtube]
 
Jack Rickard has been advocating the use of Nord-Lock washers for Thundersky cell connections. I am NOT convinced that they will work for that application.
Against the manufactures specs Jack installed a flat washer under the Nord-Lock. This makes the bolt no more effective than using a flat washer alone.

My biggest concern is thermal cycling and material "creep" or deformation. That is what caused the problems with aluminum house wirings back in the sixties. If you heat up and cool aluminum under pressure eventually the aluminum will change shape and just move away from the bolt. Once this starts it is just a spiral of more resistance more heat and more movement.

Does anyone have a proven fastener for large format cell connections?

Thanks,
Brad
 
Nord-lock and a washer under it... LOL Only that old windbag would come up with something so silly. All of the cost of nord-lock, with none of the advantages. ;)

For large cell format connections, what about avoiding the forces that loosen the fasteners? Like soft braided straps?
Or, it also seems like an excellent application for a chemical fastener locker.
 
The US Federal Aviation Administration outlines fastener best practices for aircraft in USDOT/FAA AC43.13.1A Acceptable Methods, Techniques, and Practices.

They require a locking nut in all applications (all metal, nylock, or castellated with cotter pin). Spring washers are used in many joints but are only used with locking nuts - never alone with a regular nut. Bolts are normally used with a flat and a spring washer, but the bolt heads are drilled and safety wired as well.

One factor for our battery terminals is torque. I really like nylocks for PSI studded terminals, but they have to be broken in first to keep the torque within specs for the aluminum stud. We have the same concern for the large format cells with aluminum terminals.

It's even more of a factor with lubricated terminals - like using anti-corrosion products. We have to drop the torque ~30% for lubricated joints.

That being said, I used stainless 1/4 inch flat and spring washers on my 21S TS pack's 6mm bolts, and torqued to 106 in-lb dry (75 in-lb lubricated). There were no lose connections after ~18 months and ~1900 miles.

Andy
 
This is a great thread and should be archived "somewhere." The Nord Lock video is the best I have seen on how fasteners loosen under vibration. Great info gents!
 
WOW!

When I posted this question, it was not my anticipation that the title would ring true in "Failure is not an Option" uses.

We all have these location on our e-bikes and cerainly e-motorcycles, and e-cars. Certainly makes one wonder about accepting common engineering practices. (BTW-the one plug in Prius conversion that caught fire happened because an electrical high power bolt/nut connection loosened)

So what is going on with all the Hub motor sellers? For want of two $2 parts?

In small quantities, these are quite expensive, yet mailing/shipping rather cheap; an opportunity for quality dealers?

And yes great video.

Still wonder about the permanent locktite.

As the Moose said, this should be saved/propigated.
 
Yup as per usaual luke teaches me a very valuable lesson! :mrgreen:
 
re split washers, from the man himself (those guys shoulda just read their carrol smith)

http://books.google.com/books?id=A81HmmRCN7YC&pg=PA116&lpg=PA116&dq=lock+washers+carrol+smith&source=bl&ots=ZvqLEGzAQs&sig=YcuHA0c3pNFI9ZyubJLcKWtyvFQ&hl=en&ei=lqHSTN6TKIX2tgORlYzqCg&sa=X&oi=book_result&ct=result&resnum=1&ved=0CCIQ6AEwAA#v=onepage&q&f=false
 
NorCalTuna said:
re split washers, from the man himself (those guys shoulda just read their carrol smith)

http://books.google.com/books?id=A81HmmRCN7YC&pg=PA116&lpg=PA116&dq=lock+washers+carrol+smith&source=bl&ots=ZvqLEGzAQs&sig=YcuHA0c3pNFI9ZyubJLcKWtyvFQ&hl=en&ei=lqHSTN6TKIX2tgORlYzqCg&sa=X&oi=book_result&ct=result&resnum=1&ved=0CCIQ6AEwAA#v=onepage&q&f=false
Click to expand...


Wow, another great read on fasteners. Thanks
 
Carroll Shelby would have LOVED the nord-lock washers.
 
I am in your debt. I learned a lot, and I am amazed at the tech hidden in those two little solid pieces of steel. I never would have guessed.

Katou
 
I was skeptical, and I only watched the video just now (saw it when it was first posted) because I was bored and I figured "why not? LFP usually has a good reason when he likes something"...

I am impressed. $20 + tax & shipping for 25 sets of 3/8"/10mm, so...roughly a dollar a set, $2 per E-bike axle to guarantee you avoid an axle nut coming loose?

http://www.clipsandfasteners.com/Nord_Lock_s/210.htm
 
that opened my eyes.after 30 plus years of nut and bolt unsureness,my answer is in nordlock.thanks alot.
thanks for the laugh today lfp,old windbag :lol: .
what size are 9c bolts?
 
Thanks for the kind words guys.


For the folks who might not be seeing what sets this apart from other "locking" devices, it's the ability to accommodate the inevitable motion that WILL happen to a fastener under dynamic loads (unlike most all other lockers that pretend it wont have motion), yet to always have the motion always be increasing tension at a rate steeper than the thread pitch, so the threaded parts stay right in place through anything you throw at it. It's a sneaky-clever design, almost like tricking the fastener into staying put while the otherwise dangerous loosening motion occurs between the upper and lower washer ramp faces.
 
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