Wideline featherbed frame tube
- Thread starter Bernhard
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Mine's inch and a quarter.
A clip-on sidestand won't hold, if that helps.
A clip-on sidestand won't hold, if that helps.
johnm
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The road frames were made of 14 guage. Which is basically 2 mm wall thickness.
The Manx frames were 16 guage which is a little over 1.5 mm wall thickness.
This means for a given tube diameter the Manx frames were less stiff but lighter than a road frame.
The Manx frames were 16 guage which is a little over 1.5 mm wall thickness.
This means for a given tube diameter the Manx frames were less stiff but lighter than a road frame.
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Webby03 said:
Unless you can verify this information, I will have to assume you are wrong on this count, unless they were to special order, however, if you were talking about single cylinder 350/500 Manx frames only, which were always made from 531 tubing.
Miles of tubing were ordered to make the roaster frames, the Reynolds factory were, as far as I know, the sole supplier for the Norton featherbed frames
http://en.wikipedia.org/wiki/Reynolds_Cycle_Technology
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Interesting about what Johnm said about the Manx 16 gauge frames being less stiff than 14 gauge. A 16 Gauge straight tube length for length would be less stiff than it's 14 gauge counterpart.
The motorcycle chassis is so much more complicated than a straight tube though.
The main path on a featherbed frame from the swingarm up to the steering head has as much or more to do with the engine/gearbox unit and their engine plates as the frame itself, and figures into overall stiffness just as much also. Then there is the variation in the bends between a manx, road and slimline featherbed frames.
The Manx frame had a bit shorter tubes running on the top from the swingarm gusset up to the steering head, which would change it's stiffness over the road frame. Also the Manx frame being made of high tensile steel, though not changing the modulus of elasticity some harp about endlessly, would certainly change some handling quality just as a spring made of the two different materials would act differently?
The Manx had alloy engine plates, which may in fact have hurt it's stiffness over the steel ones used by the road bike, again hard to say because the plates were different shapes to fit different engines, but aluminum is much less stiff than aluminum size for size, and although the Manx plates were thicker than the road plates they were probably not enough thicker to be of any advantage in stiffness or weight, and coupled with their expansion which could push the chassis out of alignment and screw with primary chain adjustment they may have been more of a concession to style and trends than any advantage.
The slimline frame with it's longer-yet top tubes with extra bends connecting the swing-arm gussets to the steering head may indeed have been the least stiff of all if tested as a bare item devoid of all other components.
The Manx engine being taller and with a different head steady, along with it's standard metal swingarm mounts, was a motorcycle different enough in design to have a noticeable difference in handling.
In fact for mortals using the bikes as they are most commonly used, there will be no difference at all. And since top-tier Gp riders even back in the day never switched between the different types of featherbeds daily, weekly or even yearly, and since no engineer has ever completely computer-modeled the different featherbed bikes and frames, my opinions and anyone else's are just opinions.
True, some opinions may be from those who are more sane and better educated on the subject than others, but since all will make the claim that theirs is best and/or will choose the one which suits only their ideals, the only wise men here are those who know they are only here for specific information or entertainment......
The motorcycle chassis is so much more complicated than a straight tube though.
The main path on a featherbed frame from the swingarm up to the steering head has as much or more to do with the engine/gearbox unit and their engine plates as the frame itself, and figures into overall stiffness just as much also. Then there is the variation in the bends between a manx, road and slimline featherbed frames.
The Manx frame had a bit shorter tubes running on the top from the swingarm gusset up to the steering head, which would change it's stiffness over the road frame. Also the Manx frame being made of high tensile steel, though not changing the modulus of elasticity some harp about endlessly, would certainly change some handling quality just as a spring made of the two different materials would act differently?
The Manx had alloy engine plates, which may in fact have hurt it's stiffness over the steel ones used by the road bike, again hard to say because the plates were different shapes to fit different engines, but aluminum is much less stiff than aluminum size for size, and although the Manx plates were thicker than the road plates they were probably not enough thicker to be of any advantage in stiffness or weight, and coupled with their expansion which could push the chassis out of alignment and screw with primary chain adjustment they may have been more of a concession to style and trends than any advantage.
The slimline frame with it's longer-yet top tubes with extra bends connecting the swing-arm gussets to the steering head may indeed have been the least stiff of all if tested as a bare item devoid of all other components.
The Manx engine being taller and with a different head steady, along with it's standard metal swingarm mounts, was a motorcycle different enough in design to have a noticeable difference in handling.
In fact for mortals using the bikes as they are most commonly used, there will be no difference at all. And since top-tier Gp riders even back in the day never switched between the different types of featherbeds daily, weekly or even yearly, and since no engineer has ever completely computer-modeled the different featherbed bikes and frames, my opinions and anyone else's are just opinions.
True, some opinions may be from those who are more sane and better educated on the subject than others, but since all will make the claim that theirs is best and/or will choose the one which suits only their ideals, the only wise men here are those who know they are only here for specific information or entertainment......
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Tell us something we didn't know, Ben ? !!
2 observations to follow your comments though - its curious that the manx frames never had the steering head gussetted, like the roadbike frames did. This would imply that the flexi nature of the manx frame had something to do with its good steering, and bracing the steering head lost something of this ??
And I've seen it said that some frames were bent up and welded with a smaller diam tube fitted inside the main tubes - this would stiffen up the frames somewhat. The only way to see this would be to cut the frames open - or weigh them ?? Fact, or fiction ???
2 observations to follow your comments though - its curious that the manx frames never had the steering head gussetted, like the roadbike frames did. This would imply that the flexi nature of the manx frame had something to do with its good steering, and bracing the steering head lost something of this ??
And I've seen it said that some frames were bent up and welded with a smaller diam tube fitted inside the main tubes - this would stiffen up the frames somewhat. The only way to see this would be to cut the frames open - or weigh them ?? Fact, or fiction ???
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Rohan said:
That's something of a conjecture. I would conjecture that the road frame was modified to prevent, or delay front end collapse of a heavily laden tourer, over thousands of bumpy miles. Look at the modifications done to the Les Archer Manx scrambler, for similar reasons.
It's well worth checking for cracks where the trouser plate attaches to the downtubes though.
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Early F'bed (below ) bolt on pre 54 subframe .
88
and the later welded subframe ( line stright through ) Dominator frame . and Pipi Longstocking .
MANX , disceraable by the low seat / main tube intersection ( Though theres three or more series of 30M 500 Manx swing arm )
Slimline. ( Thanks G.P. )
Curved
Obvious ' at a glane ' Identifier is Top rear shock mounts and supports ( subframe curved / brackets aft ). particularly in a side on view .
notta the bad one , eh . http://www.pbase.com/jeandr/cafe_racer
The factory ' lowboy ' twin race frame .
Dunstall Version .
Just in case anyone was wondering or hadnt gotten round to figureing it out .
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Just I.D. , theres Featherbeds and Featherbeds . The Strut Brace to head on the Domiracer types pertanant to your ' investigation ' .
The Old Top Tubes on my cobbled up 1 in Dia loop Triton would get ' Excited ' in the manner put forth . At speed / loading , Such As
Lauching and landing , also had chatter once understeering F oversteering R forceing around R.H. sweeper after apex , ceased on Cnr Exit .
Commando would do this too .
Both at shallow angle of lean , comparitively .
Though the Triton was the only machine I road that would shift right one lane in the same distance forward ( i.e. a 45 degree Zag, effectively )
and youd fall Onto It , if youd hung on . Overdriveing can illuminate behavioural characteristics .
The Strees distribution in the various frames pictured varies, Obviously. Theyre not all ' The Same ' .
The Old Top Tubes on my cobbled up 1 in Dia loop Triton would get ' Excited ' in the manner put forth . At speed / loading , Such As
Lauching and landing , also had chatter once understeering F oversteering R forceing around R.H. sweeper after apex , ceased on Cnr Exit .
Commando would do this too .
Both at shallow angle of lean , comparitively .
Though the Triton was the only machine I road that would shift right one lane in the same distance forward ( i.e. a 45 degree Zag, effectively )
and youd fall Onto It , if youd hung on . Overdriveing can illuminate behavioural characteristics .
The Strees distribution in the various frames pictured varies, Obviously. Theyre not all ' The Same ' .
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Rohan said:
I don't know. A racer is lighter, made from more expensive stuff stuff and isn't required to last as long as a tourer.
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It is an old bit of information that can be found in many books on the subject of Nortons that the gusset was stuck under the steering head of roadster featherbeds to strengthen it fore and aft. Supposedly the roadster frames were found to be flexing at this point when bumping up against a curb hard.
Back in the 50s a lot of roads were like motocross tracks once you got out of the cities, not to mention pot-holes. Braking and jumping on a road race course would surely stress the frame, but not as much as braking while going in and out of a large pothole, or running the front of the bike into a curb, especially if as Thrasher points out, the bike was a heavy roadster with a big-fat rider, and maybe even a big fat wife on pillion. Poor thing. Most top-level road-racers were like little horse jockeys.
Someone needs to ask Ken Sprayson about the gusset for the street bikes, as Rohan says, it may even be cleared up in the new book out about Sprayson's life.
One sure thing the gusset did in a production environment, is it added a cheap place to bolt a steering stop to. It would have cost Norton a lot more to have to put all the Manx stop/damper bits onto every roadster. The roadster steering damper kit was an extra-cost option that you never see on old bikes that are lying around, the featherbed really did not need it.
Later on AMC- made bikes took it a step further by eliminating the bolt-on stop and just welding onto the gusset a little piece of metal to do the job, super-cheap to do.
Back in the 50s a lot of roads were like motocross tracks once you got out of the cities, not to mention pot-holes. Braking and jumping on a road race course would surely stress the frame, but not as much as braking while going in and out of a large pothole, or running the front of the bike into a curb, especially if as Thrasher points out, the bike was a heavy roadster with a big-fat rider, and maybe even a big fat wife on pillion. Poor thing. Most top-level road-racers were like little horse jockeys.
Someone needs to ask Ken Sprayson about the gusset for the street bikes, as Rohan says, it may even be cleared up in the new book out about Sprayson's life.
One sure thing the gusset did in a production environment, is it added a cheap place to bolt a steering stop to. It would have cost Norton a lot more to have to put all the Manx stop/damper bits onto every roadster. The roadster steering damper kit was an extra-cost option that you never see on old bikes that are lying around, the featherbed really did not need it.
Later on AMC- made bikes took it a step further by eliminating the bolt-on stop and just welding onto the gusset a little piece of metal to do the job, super-cheap to do.