Final FEA simulation results. Axle and two nuts weighs approx 1.65 pounds. Stainless axle included with arm weighs 1.95 pounds. I can live with it.

Thread pull test. 1000 pound load..5x safety factor
https://cimg7.ibsrv.net/gimg/www.hdf...730e069043.jpg

axle displacement (simulation included the rest of the hard parts but are invisible here) - .0012" max displacement with 1000 pound load from belt/chain AND 500 pound load from rider&bike.https://cimg4.ibsrv.net/gimg/www.hdf...3cbfd51b47.jpg

Safety factor using above loads - minimum 2:1 which is less than I want but it's all compressive at the edge of the nut so I'm OK with it. The rest is at least 5:1
https://cimg5.ibsrv.net/gimg/www.hdf...ebb39a8c0c.jpg

detail of the high stress area of the nut.
https://cimg6.ibsrv.net/gimg/www.hdf...14b12242e3.jpg

Got the weight down to 1.47 lbs without hurting strength but it will increase cost. Probably have it quoted both ways. Oh, also reduced the stress on that edge of the nut. Safety factor now 2.5:1 in that area. The rest is still 5+.

What's the OD of the nut? Same on both ends?

The entire assembly is perfectly symmetrical. Both nuts are identical.

Quick section view with dims... (This design will not work with the stock swinger)

https://cimg8.ibsrv.net/gimg/www.hdf...ae66ec7b03.jpg

Gathering parts for some new LED tail lights. They may or may not make it onto the bike. Still mulling over ideas. The Ghozt card is a programmable sequencer so I can make the lights dance. The Pickit is the interface to talk to a PC.

I want to try and make some switchback signals with motion (dual color, red brake/run and amber turn under same lens) . Both for show and safety. Motion catches the eye and so does the color change.

https://cimg8.ibsrv.net/gimg/www.hdf...a4749ef695.jpg
https://cimg9.ibsrv.net/gimg/www.hdf...5591b60494.jpg
https://cimg0.ibsrv.net/gimg/www.hdf...a2e1a14a22.jpg

What IDE are you using for the code development?

Good ol' Microchip PIC stuff.

Ghozt has their own software. I'm no coder!

Originally wanted 3mm diodes but couldn't find any bright enough so I settled on 5mm. That was eating at me so I decided to order some PLCC2 surface mount diodes to see if I could work with them. They are as bright or brighter than the 5mm but small as the 3mm. Might have to learn PCB design and have so e boards made but that's OK.

The PLCCs also have a 120 degree viewing angle versus the 35 degree of the 5mm so hopefully they illuminate more evenly.

L to R: 5mm, 3mm, PLCC2
https://cimg1.ibsrv.net/gimg/www.hdf...0ab58171e0.jpg

Surface mounted are brighter because they use a heat sink other wise they will overheat.