My van hates me wrote:https://www.ebay.co.uk/itm/225901734355?var=0&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338749392&toolid=20006&_ul=GB&customid=GB_131090_225901734355.142394001106~1872072053958-g_CjwKCAjw_e2wBhAEEiwAyFFFozTcRIXHOLRqEyVIm4m0PgKYtV916iHdEswaoMGfeiiyl-2ut4sRtRoCz6IQAvD_BwE&gbraid=0AAAAADihhqVAlArIsiS66EQ2cPpxin81o&gclid=CjwKCAjw_e2wBhAEEiwAyFFFozTcRIXHOLRqEyVIm4m0PgKYtV916iHdEswaoMGfeiiyl-2ut4sRtRoCz6IQAvD_BwE
Thanks for the links. The cogs in those photos have the bayonets disengaged. When they are engaged the end of the spring in the thin cog is pushed towards the centre and then turned anti clockwise. Like this.
https://flic.kr/p/2pK9tEq
You can see a hole is revealed when the cog is moved around. Is this for a locking pin?