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Does anyone know the length of the rear shocks used on the original prototype, I cant find the detail anywhere
Cheers. Morts
Cheers. Morts
P11 prototype
- Thread starter simon.morton@sky
- Start date
As far as I know, N-V never saw a "prototype" P11. It was invented by one of the people at Berliner, the US importers of various AMC machines. They were heavily involved in long-distance desert racing in California and found the 500cc AJS/Matchless dirt racers they sold were under-powered. Someone there tried installing the Atlas 750 engine in a Matchless frame. It was very successful.
While I was at N-V (Wolverhampton) in late 1967/early '68, a brand new P11 showed up with instructions to break it in and get it ready for testing. I did most of the break-in riding. I disliked the high level of vibration and poor handling. At speed, it would start to weave, getting to a displacement of almost a full width of an M-6 traffic lane at about 60 mph. My impression was that the frame couldn't handle the torque of the 750 engine. My follow-up rider said the weaving stopped once you got above 85 mph! I was riding quite a lot after dark, and I was amazed how frequently I had to replace light bulbs, particularly the headlight, due to the vibration. I also carried a small tool-kit to re-tighten fasteners that came loose during my rides. The tail/brake light came off on almost every ride until I bought some anti-vibration nuts to hold it on.
We discovered, a short time later, that a rider in the US had been killed in a desert race when his P11 got into a high-speed "tank-slapper" and threw him off. We were told to get ready for a UK "cause of death" lawsuit. Before I even finished the break-in rides, the lawsuit was dropped. I got the impression that nobody at NV at the time wanted anything to do with the P11. I was surprised, quite a while after I'd emigrated to Boeing, that N-V were actually producing P11s and selling them in the UK.
I rode the US built P11 for quite a while as my commuter, during the time I was breaking it in. It was by far the most popular bike I'd ever shown to my church's youth club!
While I was at N-V (Wolverhampton) in late 1967/early '68, a brand new P11 showed up with instructions to break it in and get it ready for testing. I did most of the break-in riding. I disliked the high level of vibration and poor handling. At speed, it would start to weave, getting to a displacement of almost a full width of an M-6 traffic lane at about 60 mph. My impression was that the frame couldn't handle the torque of the 750 engine. My follow-up rider said the weaving stopped once you got above 85 mph! I was riding quite a lot after dark, and I was amazed how frequently I had to replace light bulbs, particularly the headlight, due to the vibration. I also carried a small tool-kit to re-tighten fasteners that came loose during my rides. The tail/brake light came off on almost every ride until I bought some anti-vibration nuts to hold it on.
We discovered, a short time later, that a rider in the US had been killed in a desert race when his P11 got into a high-speed "tank-slapper" and threw him off. We were told to get ready for a UK "cause of death" lawsuit. Before I even finished the break-in rides, the lawsuit was dropped. I got the impression that nobody at NV at the time wanted anything to do with the P11. I was surprised, quite a while after I'd emigrated to Boeing, that N-V were actually producing P11s and selling them in the UK.
I rode the US built P11 for quite a while as my commuter, during the time I was breaking it in. It was by far the most popular bike I'd ever shown to my church's youth club!
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
Knut:
The P-11 we got at Wolverhampton was shipped directly from Berliner and arrived about January of 1968, I think. I was only with N-V from about July of 1967 and left for Boeing in June '68. The bike only had about 20 miles on the odometer. I got the impression that it was the first anyone at N-V knew of the P-11's existence. I'm not even sure that's what Berliner called it. I was told the we were supposed to test it to provide evidence for a "cause of death" lawsuit by a California rider's family. With the shambles that was N-V at the time, nobody was really sure what was going on. Plumstead and Wolverhampton rarely talked to each other.
I'm amazed that Plumstead were already well into the design and manufacture of and Atlas Scrambler as early as 1963. I don't know when the "P11" designation was applied.
When I was doing the break-in rides, I kept the speed below 70 mph, and the weaving was very obvious from about 45 mph upwards. Of course, freeway cruising wasn't its natural habitat.
The P-11 we got at Wolverhampton was shipped directly from Berliner and arrived about January of 1968, I think. I was only with N-V from about July of 1967 and left for Boeing in June '68. The bike only had about 20 miles on the odometer. I got the impression that it was the first anyone at N-V knew of the P-11's existence. I'm not even sure that's what Berliner called it. I was told the we were supposed to test it to provide evidence for a "cause of death" lawsuit by a California rider's family. With the shambles that was N-V at the time, nobody was really sure what was going on. Plumstead and Wolverhampton rarely talked to each other.
I'm amazed that Plumstead were already well into the design and manufacture of and Atlas Scrambler as early as 1963. I don't know when the "P11" designation was applied.
When I was doing the break-in rides, I kept the speed below 70 mph, and the weaving was very obvious from about 45 mph upwards. Of course, freeway cruising wasn't its natural habitat.
Frank,
The marketing department at Plumstead had intended the name Matchless Cheetah 45, in line with the previous model names Matchless Apache, Trailblazer, Westerner, etc. However, at some time it was decided to sell the model as a Norton as well. Norton Cheetah didn't match other Norton model names, so the Cheetah name was silently droppped and the development number (prototype 11 or P-11) used instead, which catched on in the american market. Yes, the Berliners called the model P-11 and advertised it as such. (Btw, the predecessor was P-10 - the nameless 800cc DOHC prototype at Plumstead that was carried on in Volverhampton as project Z26 before being axed in favour of the old Atlas lump - go figure!).
-Knut
The marketing department at Plumstead had intended the name Matchless Cheetah 45, in line with the previous model names Matchless Apache, Trailblazer, Westerner, etc. However, at some time it was decided to sell the model as a Norton as well. Norton Cheetah didn't match other Norton model names, so the Cheetah name was silently droppped and the development number (prototype 11 or P-11) used instead, which catched on in the american market. Yes, the Berliners called the model P-11 and advertised it as such. (Btw, the predecessor was P-10 - the nameless 800cc DOHC prototype at Plumstead that was carried on in Volverhampton as project Z26 before being axed in favour of the old Atlas lump - go figure!).
-Knut
Knut:
There was a near-unbreachable wall between Wolverhampton and Plumstead at the time I joined N-V (autumn of 1966). Plumstead gave the impression they'd rather have gone bust than being "rescued". The way they"bodged up" the Commando after they took over the production role really got the design and development teams at Marston Road angry. This communication issue was one of the main reasons I bailed out at Easter of' '68 to emigrate to join Boeing. The second big reason was that the funding for the job for which I'd been hired (Test Instrumentation) had been frittered away on the "Green Blob" publicity fiasco in which all markings on the Commando which carried the Norton name were removed. I never found out how much reworking of casting moulds, etc., to remove the name had cost.
I have some recollections of the P-10 engine. To save development time and funds, the cam drive stayed in the crankcase, with a camshaft chain that ran around from there, up though the old push-rod tunnels to and from the head. It was fairly light-duty chain and about 3 feet long and was nowhere near rugged enough for the job. I think it stretched fast enough to require adjustment every few hours of running the engine.
There was a near-unbreachable wall between Wolverhampton and Plumstead at the time I joined N-V (autumn of 1966). Plumstead gave the impression they'd rather have gone bust than being "rescued". The way they"bodged up" the Commando after they took over the production role really got the design and development teams at Marston Road angry. This communication issue was one of the main reasons I bailed out at Easter of' '68 to emigrate to join Boeing. The second big reason was that the funding for the job for which I'd been hired (Test Instrumentation) had been frittered away on the "Green Blob" publicity fiasco in which all markings on the Commando which carried the Norton name were removed. I never found out how much reworking of casting moulds, etc., to remove the name had cost.
I have some recollections of the P-10 engine. To save development time and funds, the cam drive stayed in the crankcase, with a camshaft chain that ran around from there, up though the old push-rod tunnels to and from the head. It was fairly light-duty chain and about 3 feet long and was nowhere near rugged enough for the job. I think it stretched fast enough to require adjustment every few hours of running the engine.
Frank,
I don't want to drift too far apart from the topic of this thread, suffice to say that the Plumstead staff were proud of working for AMC / Matchless. "Who are you to tell us how to design motorcycles? We have been doing so since the 50's!"
You get the point? Maybe Dennis Poore was a bit arrogant as well. The axing of most of AMC's models certainly didn't go down well. It seems the succeeding P10 / Z26 assessment and re-development was half-hearthed at best, much like the later P86 Cosworth engine project. Maybe the man's gold-digging nature shone through?
Anyway, the P10 engine's major problem was not the chain camshaft drive (although badmouthed by the press - providing a rugged chain and an hydraulig tensioner wouldn't have been difficult) - it was heat transfer, vibration and mechanical noise. Each of these problems could have been solved by assigning the right men on the job. Mr. Poore failed to do so, as he failed in his management role on the P86.
As for Commando production at Plumstead, I haven't noticed any problems mentioned in the literature. Do you have examples? All drafting and tooling work for manufacture was planned and exercised at Plumstead, and I know part of the development (esp. the transmission) took place there as well, assisted by NV staff of course. Plumstead had an excellent manufacturing environment with skilled staff and relatively modern machine tools. There will always be some teething problems after a take-over, especially when two companies are to merge. Having a development team separate to manufacturing is not beneficial.
-Knut
Having had the same top-tube fatigue issues on the pre-Stormer motocross machines as later appeared on the Commando (though the opposite way up because of the headstock to top tube alignment) I thought Wolverhampton had made a much tidier re-design, splitting the tube and inserting a long triangular filler. It would have been a big job to retrofit the Commandos already in the field with a similar set-up, but introducing it into production wouldn't have been a big deal.
I agree with your comments regarding Dennis Poore, but without his rescue of Norton and merging it with Villiers (which he already owned), the Commando would never have been born and Plumstead would have closed. He had some "interesting" choices of personnel also. The way the two branches of the company were run was one of the reasons for me bailng out over the US after less than 2 years at N-V. We're still there, living in the seaside town of Anacortes. I'm now into my 20th year of retirement, after 3 years at NASA, 28 years at Boeing and 2 years post retirement as a transit coach driver.
Frank
I agree with your comments regarding Dennis Poore, but without his rescue of Norton and merging it with Villiers (which he already owned), the Commando would never have been born and Plumstead would have closed. He had some "interesting" choices of personnel also. The way the two branches of the company were run was one of the reasons for me bailng out over the US after less than 2 years at N-V. We're still there, living in the seaside town of Anacortes. I'm now into my 20th year of retirement, after 3 years at NASA, 28 years at Boeing and 2 years post retirement as a transit coach driver.
Frank
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frankdamp, you mention "bodging up" the commando, please explain.
IMO, the second. lower "top" tube is a "bodge". I think the AJS Stormer frame redesign, which put a long triangular component, welded between the top and bottom halves of the top tube, was a much cleaner design. That wouldn't have been feasible as an in-the-field retrofit for the Commando, but the additional upper tube was. It still looks like a "bodge" to me, since production bikes from long after the additional tube first appeared still use it.
Frank, I have a vague recollection the frame "bodge" was conceived by Ken Sprayson at Reynolds Technology. As for the AJS Stormer frame, the top tube appears to be a large elliptical tube tapering to the rear. I don't see any "long, triangular component" there.
A picture of an AJS Stormer frame is provided in the book "AJS and Matchless Post-War singles and twins: The complete Story" by M. Vale.
The particular picture can be seen in the pre-view of the book at
https://books.google.co.uk
-Knut
A picture of an AJS Stormer frame is provided in the book "AJS and Matchless Post-War singles and twins: The complete Story" by M. Vale.
The particular picture can be seen in the pre-view of the book at
https://books.google.co.uk
-Knut
Last edited:
Junglebiker
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I think frankdamp may be referring to the taper in the top tube as the "triangular component".
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So no idea on length then !!!!!!!
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Maybe you find out from the pics in that story:
https://www.motorcycleclassics.com/classic-british-motorcycles/norton-p11-prototype-replica
Maybe it was the same as in the G85.
Maybe Anthony Curzon the socalled P11 Guru knows.
There is a famous restaurer in the US. Don H...... I have to look for the complete name, forgot it.
Best
Peter
https://www.motorcycleclassics.com/classic-british-motorcycles/norton-p11-prototype-replica
Maybe it was the same as in the G85.
Maybe Anthony Curzon the socalled P11 Guru knows.
There is a famous restaurer in the US. Don H...... I have to look for the complete name, forgot it.
Best
Peter
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Don Harrell, Visalia, California- British motorcycle works
Simon, you should be able to find out his adress. I don`t know if this genius is still in business.
Peter
Simon, you should be able to find out his adress. I don`t know if this genius is still in business.
Peter
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13 1/4 inch rings a bell, I will do a bit of home work. my p11 is built as the prototype so will measure them as well
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Interesting
I have never experienced a 60 mph wobble or head shake riding my P11, but it isn't the original US prototype either. It's a late '67 according to the serial number data base I was able to track down on the interweb. Mine didn't start to do much of anything unusual in a straight line until around 108mph on the Smiths. Not sure what that equates in the real world. I have not ridden it that fast since around 1993. It did feel like a wet noodle pushed hard into turns though. I never rode the P11 with the as delivered forks, which probably has a lot to do with the improved stability. I have always had a set of slightly modified Betor forks on it.
My guess is the front end geometry on the original prototype was set up for off road racing with off road spring and valving rates, which would not be the same set up as how one would set up a road racing motorcycle. Racing a Norton P11 off road would require a lot of upper body strength. Could have been a lot of reasons for someone getting killed racing in the desert. None of them having much to do with the motorcycle other than it being a serious hand full for off road. I wouldn't ride one off road, cuz I'm just not that crazy, but they do throw one heck of an impressive rooster tail of dry loose dirt with a Dunlop K70 on the back.
My P11 has 13 inch Koni shocks on it. No problems. That 1/4" will make approximately no difference with the right spring rate.
I have never experienced a 60 mph wobble or head shake riding my P11, but it isn't the original US prototype either. It's a late '67 according to the serial number data base I was able to track down on the interweb. Mine didn't start to do much of anything unusual in a straight line until around 108mph on the Smiths. Not sure what that equates in the real world. I have not ridden it that fast since around 1993. It did feel like a wet noodle pushed hard into turns though. I never rode the P11 with the as delivered forks, which probably has a lot to do with the improved stability. I have always had a set of slightly modified Betor forks on it.
My guess is the front end geometry on the original prototype was set up for off road racing with off road spring and valving rates, which would not be the same set up as how one would set up a road racing motorcycle. Racing a Norton P11 off road would require a lot of upper body strength. Could have been a lot of reasons for someone getting killed racing in the desert. None of them having much to do with the motorcycle other than it being a serious hand full for off road. I wouldn't ride one off road, cuz I'm just not that crazy, but they do throw one heck of an impressive rooster tail of dry loose dirt with a Dunlop K70 on the back.
My P11 has 13 inch Koni shocks on it. No problems. That 1/4" will make approximately no difference with the right spring rate.
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