The locknut on the bolt clamps the hitch adapter between the two towbar bushings. The torque on the hitch adapter isn't excessive (<100 in-lbs when the Xtracycle is loaded to its 50# rear weight limit), so with the locknut torqued down the adapter won't rotate around the horizontal bolt.

The adapter might need to be repositioned and the locknut re-tightened occasionally due to creep, but it shouldn't be necessary to do this frequently.

You ask a good question. I was concerned about this, too, when designing it, and was the main reason I wanted to test it before we shipped.

-Jim
Bikes At Work
www.bikesatwork.com

I really appreciate this thread!
its a good learning experience, and constructive.

Having a great time with it so far!(see two started threads)

PaPa, are you suggesting using an air hose fitting for the hitch coupler? Interesting idea. I wonder what the physical strength of those things is. I've never seen them used in an application where they get much stress.

The idea isn't original. Bike Friday uses and sells them.

https://www.bikefriday.com/thestore/...EFvJ0&cPath=51

Bike Friday suggests a 100 pound trailer gross. However, Bike Friday doesn't specify the 'weak link' that dictates the 100 pound limit - is it the hitch? - the rubber hose - the trailer frame or axle? - the wheels? - or some combination of all?

It doesn't matter what the air coupling was originally designed for. What matters is the anticipated, dynamic loads, and how best to safely exploit its structural limitations.