Another fastener question: why thru axles are used without nuts and washers?

[MikeD]

All of this assumes that the bolted joint is correctly designed to carry the required loading from external forces.

The way that a bolted joint works is by placing the bolt under a tensile load (the bolt is stretched) when tightened to specification. This is preload on the bolt and it prevents the threads from unwinding while the preload is present. The torque spec is derived from operational external loads the joint is expected to see in service. The torque specification is a convienient way to ensure the correct preload is applied to the fastener.

Washers are typically used to distribute the compressive force under the head of the fastener thereby reducing the stress in the clamped material under the washer. If you are not plastically deforming the clamped material under compression by the head of the fastener then the washer will not increase the load capacity of the bolted joint.

If you are not familiar with the theory behind bolted joint design, the basics are addressed here.
https://www.boltscience.com/pages/basics1.htm

That works if you can torque the bolt up to like 90% of proof strength, but for NDS spokes, a thread lock should be used like low to medium strength Loctite. I can imagine there are lots of fasteners on a bike that can’t be done up that tight (stems, water bottle cages, etc.).

[kode54]

Righty tighty, lefty loosey.

Like threaded bottom brackets and pedals...threads tighter as you roll forward. All my disc thru axles are threaded regular right tight (forward).
No nut required.

[tjvirden]

Some pics of the drop out design https://photos.app.goo.gl/Qn87EUFFgkPkeiFu7

Photos are ideal - they explain everything. I really can't believe that this has made it to market - as you've discovered, it can't work properly! You've every right to feel furious.

Yes, that's almost exactly the same as the ones I saw before. It's almost a perfect example of what not to do.

This sums it up well.

You'd need to remove paint, prep the surface and provide some sort of wrap to support the join.
Just gluing a block of aluminium to a carbon structure won't last.

As does this.

Are any other frames using this dropout design?!!