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Production of the P11 started in the spring of 1967. Surely the P11 had been tested by the Plumstead staff to exhausting in the early months of 1967. From footage taken at Mira it seems you got the follow-up version P11A for testing. Maybe this was part of the Commando frame development? Or simply concerns over fatigue issues.I agree with you - the thin-walled and very light frame vibrates like a leaf, which is to be expected. The frame really cries for a twin engine with a balance shaft.Maybe the "Jake" Commando prototype engine (a later development by Doug Hele) should have been married to the P11 frame .... as designed it was to be solidly mounted.I doubt the weaving is due to the engine's torque. My suspicion is weakness in the headstock/fork crown design. While good enough for a G85CS motocross bike, the bearing races are far from fixed in their seats and will allow the front wheel to move laterally back and forth under load. Furthermore, fork stanchins are slim for the weight of the Atlas lump. AMC had recognized this in 1963 during the development of the N15 Atlas Scrambler, and switched to much sturdier headstocks, stanchions and fork lugs for 1964. It wasn't just an act of rationalization. So why didn't the Plumstead engineers fit a stiffened headstock and fork lugs at least? The answer is probably lack of time and the desire to keep weight down. The Teledraulic fork served the purpose and some features worked better than Roadholder forks.-Knut
Production of the P11 started in the spring of 1967. Surely the P11 had been tested by the Plumstead staff to exhausting in the early months of 1967. From footage taken at Mira it seems you got the follow-up version P11A for testing. Maybe this was part of the Commando frame development? Or simply concerns over fatigue issues.
I agree with you - the thin-walled and very light frame vibrates like a leaf, which is to be expected. The frame really cries for a twin engine with a balance shaft.
Maybe the "Jake" Commando prototype engine (a later development by Doug Hele) should have been married to the P11 frame .... as designed it was to be solidly mounted.
I doubt the weaving is due to the engine's torque. My suspicion is weakness in the headstock/fork crown design. While good enough for a G85CS motocross bike, the bearing races are far from fixed in their seats and will allow the front wheel to move laterally back and forth under load. Furthermore, fork stanchins are slim for the weight of the Atlas lump. AMC had recognized this in 1963 during the development of the N15 Atlas Scrambler, and switched to much sturdier headstocks, stanchions and fork lugs for 1964. It wasn't just an act of rationalization. So why didn't the Plumstead engineers fit a stiffened headstock and fork lugs at least? The answer is probably lack of time and the desire to keep weight down. The Teledraulic fork served the purpose and some features worked better than Roadholder forks.
-Knut
