What's become of the humble spring washer?

[PeterAllen]

It’s more than three decades since I ‘played’ with cars or did any real hands-on engineering and now that I’m starting the final assembly of my kit car I’ve become aware that all the components I salvaged from the donor car (’05 GM product) were secured without spring washers. All appear to have flat washers integrated with the bolt head or nut – which I assume expedites assembly but I’m wondering what’s happened to the humble spring washer and what in the design of current fasteners compensates for their function.

[HealeyRick]

This is going to seem like heresy to most of us non mechanical-engineering types, but here it is:

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."

[bobcowan]

That is correct. Although the spring lock washer does have it's place, it really only works once the bolt has come loose.

The purpose of a flat washer to to spread the load around the base material, and prevent galling. It gives the head of the fastener something to work against besides the base material.

Fasteners like the one in your picture are kind of a compromise. They have no real locking feature at all. They do spread the torque out on the base material. But they also work against the base material. They are cheap, and easy to use at the factory.

[Paul F]

Yes, I saw a video where star washers and split washers were tested under vibration. They did nothing. This isn't the video, but it is similar
Video of a Helical Spring Washer subjected to a Junker vibration loosening test

[Modena]

On important fasteners (eg brakes and suspension) you should check with the OEM (Holden in this case) for the specs of the fastener. I have bought quite a few new fasteners from Holden during my build. You will find that many of the type of fastener you have pictured are in fact designed as single use items. This is not marketing to get you to buy a new one, rather when you have a new one you can see why - the nut will thread on by hand only about half way before stopping. Torquing with tools then stretches/gives in the bolt and the nut and it torques up tight to spec, but will not fasten the same a second time. Someitmes it is just the nut which is single use, and sometimes the bolt and nut. Check the workshop manual to be sure.

Otherwise, I replace with grade 8+ bolt, washers and nylocs.

[Zedn]

Bolts are expensive from Holden. I had to replace one of the long skinny bolts at the back of the sump and it was hugely expensive. The crush nuts you refer to are available from bolts shops. I got the torque to yield bolts from Holden, but that was just crank bolt.

The other thing I have wondered about is the dissimilar metals when using alloy parts. The bolts from Holden have that silver frosting coating on them. Anyone know what that is? I wouldn't think it would be gal because zinc in alloy is not a good idea. I used Holden bolts or stainless on the alloy motor.

I don't believe the stuff about spring washers not working Bobcowan is right, it might be flat when tightened, but in doing so it is squeezed open, so hence trying to return back which splits it up. This means that when undoing there is a constant pressure as opposed to sudden release. Obviously the more it is used the less it works though.

[PeterAllen]

(edit) Oops - Info posted earlier

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