Vincent, Many thanks. My VH was 7 1/2 inches between the inner faces of the rear forks ( 8" between the centers of the forks as shown in blue on your diagram). My WNG was too narrow to get the rear wheel in without splaying the fork ends apart so I have 'adjusted' them with a scissor jack to match my VH (I found that the lower gearbox bolt needed to be in place or the jack just splayed the tubes outwards and then they sprung back). It did not take much force to get the extra bit needed.
Reference the Rigid 4" on the drawing I managed to find the same diagram on the internet and it is labeled 'Rigid Ariel Single and Twin 1947-53. The 4" measurement apparently relates to the rigid frame. There are also other measurements labeled for the twin and single on this drawing:
Hi Lee, through my ad in the Cheval I now have a girder fork, but thanks for thinking of me ! But what I am still after is a Terry or Lycett saddle, a prewar Amal 89 carb, a 1" handlebar and a BTH KD1 magneto
I don't know what else he has. He has the one ariel which is a 38 nh. With a 50 vh engine and 49 forks on it, it's a complete bitsa to be honest. I know for a fact he has girders. Unfortunately I have none of the above. But I know someone else who may!
Hi Vincent, I ordered a nice saddle for my pre war Ariel some weeks ago from a person in the czech republic. Its of very good quality, all the dimensions to fit to the frame are correct so it should bolt on directly. It has rubber springs instead of metal springs. If you like I can forward some piccies and the contact adress. Best Klaus