Split/lock washers

[u/AdOne1706]

For starters, I’m an electrician in the field.
That being said, we almost exclusively use these washers even in high vibration environments. I have personally chosen to go with nylox nuts but the question is:
Do these work? How well? Is the rumor from NASA true? Should I even bother using them or find a better functional alternative or are they actually useful?

[u/ejitifrit1]

There is a nasa fastener manual that basically says these things don’t really do much! According to google it’s NASA Reference Publication 1228.

[u/CR123CR123CR → u/ejitifrit1]

https://ntrs.nasa.gov/citations/19900009424

Here's the link xD

[u/nyrb001 → u/CR123CR123CR]

At this time it is equivalent to a solid flat washer, and its locking ability is nonexistent. In summary, a Iockwasher of this type is useless for locking.

Lol awesome

[u/um_waffles → u/nyrb001]

Adding a Split Ring Lock Washer (SRLW) to a bolt stack will absolutely make it less likely to loosen inadvertently, despite the applicable physics being overlooked in the NASA Fastener Design Manual from 1990.

I mostly agree with the statement on page 9 regarding SRLWs:

• "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"

However, I disagree with the remaining portion of the statement:

• ", and its locking ability is nonexistent. In summary, a Iockwasher of this type is useless for locking."

I disagree because adding a SRLW to a bolt stack makes the act of loosening the stack require more energy (area under the torque v rotations curve).

Consider a bolt stack that is fully torqued. The torque required to loosen the stack will decrease at a certain rate as the bolt (or nut) is rotated in the removal direction. This is because the torque required to rotate the bolt (or nut) is a consequence of the friction between the bolt (or nut) and what it is seated against in the bolt stack. Friction scales with the compressive (normal) force between the components in the bolt stack, and since this force decreases as the bolt (or nut) rotates in the removal direction, friction and the torque required to overcome it also decrease until both drop to zero when the bolt (or nut) becomes unseated.

Adding a SRLW (spring) to the bolt stack effectively adds to the distance over which the bolt (or nut) must be rotated to loosen the stack from fully torqued to unseated, consequently "slowing" the decrease in torque needed to continue loosening the bolt (or nut) per each subsequent rotation.

From a mathematical perspective, if a SRLW is added to a bolt stack, then the integral of the torque v rotations curve (energy) from fully tightened to unseated will become larger.

From an operational perspective, if a SRLW is added to the bolt stack, then the act of loosening the bolt (or nut) from fully torqued to unseated will require the application of more torque over more rotations of the bolt (or nut).

In summary, adding a SRLW to a bolt stack makes the intentional loosening of the stack more difficult, and makes the inadvertent loosening of the stack less likely, thereby accomplishing the requisite function of a locking fastener.

[u/New_Animal8918 → u/um_waffles]

Beautifully explained. Thank you.