Hi Peter,
Uploading files to the documents page on this site is currently limited to the site administrators. This can only be done through the backside of the site, and is limited in file size and type. If you want to share a 3D file here, the easiest way I can think of is to upload it to a site like Grabcad.com or thingiverse.com. Then you can share the link to the file here on the forum.
It would be fun if sharing CAD files were possible here, perhaps if we get a new site in the future. Some years ago I have drawn a bunch of parts also. Some 2D drawings from those i have uploaded here on the site but the 3D files were not possible. Hopefully the site managers can incorporate that in the new site once work continues on that.
The Knurled knob from the Spartamatic AV I had also drawn I think, that knob is used on many types of Spartas. A few years ago we have in a club meeting we have spoken about having some parts replicated, that's not too expensive if it's done in Asia. But back then people were hesitant to invest club money in that. If people now do want to do that, I can still ask my contacts in China for the possibilities. Having parts like this knob or the yellow fendor plate moulded looks way better than 3D printing them.
Regards,
Geert