About 1967, Phil Vincent published a piece in the weekly mag (Motor Cycle, I think) claiming wondrous properties for his trangulated rear swing-arm and single damper. Other manufacturers have done a good job with the concept in more recent times.
He reckoned that the twisting moment on a swing arm could get up to the equivalent of hanging a London bus off a 2-ft moment arm throught the rear wheel spindle. He'd calculated something on the order of 50g acceleration (1500 ft/sec/sec)
My boss at N-V said "see if you can shoot this down". When I looked into it, it turned out that Phil had assumed an infinitely stiff tyre, and infinfitely stiff spoked wheel and infinite mass of the bike against which the forces were being reacted.
I took a more reasonable premise, assuming a very low spring rate for the tire, a realistic spring rate for the wheel and a reasonable pitch moment of intertia, based on the Commando. I got an acceleration of about 4 g, a good bit of which went into pitching the bike tail-up, if the force was only on the rear wheel. If you assumed the front wheel had hit the same bump shortly earlier, the overall pitch variation was quite reasonable.
The Stormer , whose frame was based on the Commando, had a pretty wild ride in bumpy conditions, with very violent pitch-up at the rear. Malcolm Davis was very critical of the characteristic, saying he was often winded when the seat hit him in the backside.
We did some high-speed filming, trying to find out why. One segment I filmed at a race meeting up in Cumberland showed some very vicious pitch activity, going from fully extended off a jump, with about 20 degrees nose-up, to hitting the rider in the backside, 10 degrees nose down, in less than 2 frames, at 64 frames/second.
Because the frame was so stiff in the pitch axis, a lot of the small displacement rear suspension motions that were absorbed in frame deflections on other bikes had to be absorbed by the shocks. It wasn't unusual to see the paint blistered off the rear shocks and they were often too hot to touch an hour after the race.
I remember on post-race discussion where Dave Bickers was invited to take the AJS 250 for some laps. He reported "very good handling" and expressed interest in a works ride. When we got back to the factory, we found that the top tube on the bike Dave had ridden was broken clean through. just at the point where the gusset that stiffened the joint with the headstock was attached.
I later determined that there was a major stress concentration at that point and suggested a redesign where the top tube started out as two semi-circular sections with a filler plate welded between, tapering off to a circular section at the seat tube. I believe this was adopted and was part of the design sold to Bombardier.
I tried to get some decent test instrumentation to try and sort the problems out, but the decline of the company in early 1968 dried up the funds.