I remember Fluff Brown very well, as I spent a lot of time with him and Malcolm Davis doing test work on the Stormer. I believe Fluff passed away a couple of years ago and his son is now running the business.
The Stormer's frame was definitely an N-V design and owed nothing to James, Francis-Barnett or anyone else. It was derived from the Commando, and featured the same large-diameter top tube. The major difference was that it was attached to the headstock near the bottom rather than the top, as the Commando was configured.
In competition we suffered three top-tube fatigue failures, which look exactly the same, but upside down, as those referred to as "widow-maker" failures on the Commando. I did a quickie analysis of the structure and showed that the gusset between the top of the headstock and the top tube made a stress concentrator of about 6-times magnitude, which was causing "oil-can" deformation of the top tube and failure in the top half. The same problem affected the Commando, with fatigue cracking in the lower half of the tube, just aft of the gusset.
Late production models had a top tube that was made up of two semi-circular tubes with a triangular filler between them. The two semi-circular pieces were welded close to the top and bottom of the headstock, and came together at the back of the seat pan as a circular tube. The triangular piece was welded in to make a complete tapered ovoid structural item. i wanted to do a logarithmic curved piece, to match the stress concentrations, but was shot down on costs.
I wish the Commando folks had taken that design instead of the extra tube installation. At least it would have looked more professional!
ex-Norton Villiers - Marston Road
Develpment & Competition Department