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Featherbed frame design went against all engineering princip
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Re: Featherbed frame design went against all engineering pri
Bauer felt that the featherbed frame was flawed due to the number of curved tubes used. I think the logic is each curve had the potential to act as a spring. Also using one large diameter thin wall top tube was in theory more efficient than using two small diameter heavy wall top tubes. The significant difference in weight was considered a measure of design efficiency.
The fact that the frames tended to break is a nice example of the triumph of theory over practice. Not to mention that most people who have ridden both will tell you that the featherbed frame handled better.
Stephen Hill
Bauer felt that the featherbed frame was flawed due to the number of curved tubes used. I think the logic is each curve had the potential to act as a spring. Also using one large diameter thin wall top tube was in theory more efficient than using two small diameter heavy wall top tubes. The significant difference in weight was considered a measure of design efficiency.
The fact that the frames tended to break is a nice example of the triumph of theory over practice. Not to mention that most people who have ridden both will tell you that the featherbed frame handled better.
Stephen Hill
Re: Featherbed frame design went against all engineering pri
Curved/bent tubes, at first glance, should not offer the rigidity and strength that you
would imagine that a motorcycle frame would require.
But the featherbed frame clearly worked.
So, as Joe Craig is once reported to have quipped
"If we ignore the theory, it will be quite good"
or similar words....
??
Don't be surprised if this topic is shifted over to 'other Nortons',
where it more correctly belongs.
And has been covered previously....
Curved/bent tubes, at first glance, should not offer the rigidity and strength that you
would imagine that a motorcycle frame would require.
But the featherbed frame clearly worked.
So, as Joe Craig is once reported to have quipped
"If we ignore the theory, it will be quite good"
or similar words....
??
Don't be surprised if this topic is shifted over to 'other Nortons',
where it more correctly belongs.
And has been covered previously....
Re: Featherbed frame design went against all engineering pri
We are not quite sure what that phrase actually means,
but modern vibration analysis, if applied to older type frames,
would suggest that some areas should have been reinforced or treated differently,
to avoid reasonant vibrations.
It is noticeable that the slimline blueprints that have appeared quite recently show reinforcement tubes
down inside the front downtubes - that were clearly intended to damp out one such problem.
AJS similarly found that having alloy engine/gearbox plates in some early 7R racers caused some tremendous vibrations
in the chassis, and a switch to steel ones almost completely eliminated this problem.
Thats one they didn't teach in engineering school..... ?
Stephen Hill said:
We are not quite sure what that phrase actually means,
but modern vibration analysis, if applied to older type frames,
would suggest that some areas should have been reinforced or treated differently,
to avoid reasonant vibrations.
It is noticeable that the slimline blueprints that have appeared quite recently show reinforcement tubes
down inside the front downtubes - that were clearly intended to damp out one such problem.
AJS similarly found that having alloy engine/gearbox plates in some early 7R racers caused some tremendous vibrations
in the chassis, and a switch to steel ones almost completely eliminated this problem.
Thats one they didn't teach in engineering school..... ?
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Re: Featherbed frame design went against all engineering pri
Can't beat large dia thin wall hollow triangulated steel for wt to strength but I salute Dr. Stefan Bauer and side kick Hopper for the ingenious Isolastic Commando spinal column and over lapped re-enforcement that driven my nutz to find its pecking order. Do keep in mind Norton bean counters likely stiffed its full development so un-tammed its too dangerous to test much for me. Sanely operated I love it most too.
Can't beat large dia thin wall hollow triangulated steel for wt to strength but I salute Dr. Stefan Bauer and side kick Hopper for the ingenious Isolastic Commando spinal column and over lapped re-enforcement that driven my nutz to find its pecking order. Do keep in mind Norton bean counters likely stiffed its full development so un-tammed its too dangerous to test much for me. Sanely operated I love it most too.
Re: Featherbed frame design went against all engineering pri
The featherbed was pretty good as an early 1950's design done in house by guys that were essentially welders. Sure it flexed a fair bit, particularly on bumpy corners, but it was predictable.
The Commando frame was an elegant piece of engineering, and if we'd had the kind of finite element structural analysis that came along a few years later, it would have been a lot better than it is. IMHO, the two biggest mistakes were 1) making the top tube so thin that it could buckle and 2) putting that monster stress raiser gusset between the headstock and the top tube. That almost guaranteed the cracking of the top tube.
The Stormer had a similar frame design , except the top tube was welded at the opposite end of the headstock and the gusset was the opposite way up. It cracked on the opposite surface from the cracks on the Commando. Because of the very harsh workout the factory M-X machines got, the cracking problem showed up very quickly. Because its performance was right up there with the best, a quick resolution was needed.
I did some static load tests on a Stormer frame and it was quickly obvious that the gusset was the problem, since it caused a discontnuity in the stress distribution. I designed (back of an envelope sketch really) an alternate top tube configuration. I split the tube along the horizontal centerline, moved the two haves at the headstock end so that they were each welded very close to the ends of the headstock. At the seat end of the top tube, it remained in the original circular cross section. Long, skinny flat triangles were then welded in to join the top and bottom halves on both sides. It solved the cracking issue on the team bikes and I think it was the final production configuratiion.
The featherbed was pretty good as an early 1950's design done in house by guys that were essentially welders. Sure it flexed a fair bit, particularly on bumpy corners, but it was predictable.
The Commando frame was an elegant piece of engineering, and if we'd had the kind of finite element structural analysis that came along a few years later, it would have been a lot better than it is. IMHO, the two biggest mistakes were 1) making the top tube so thin that it could buckle and 2) putting that monster stress raiser gusset between the headstock and the top tube. That almost guaranteed the cracking of the top tube.
The Stormer had a similar frame design , except the top tube was welded at the opposite end of the headstock and the gusset was the opposite way up. It cracked on the opposite surface from the cracks on the Commando. Because of the very harsh workout the factory M-X machines got, the cracking problem showed up very quickly. Because its performance was right up there with the best, a quick resolution was needed.
I did some static load tests on a Stormer frame and it was quickly obvious that the gusset was the problem, since it caused a discontnuity in the stress distribution. I designed (back of an envelope sketch really) an alternate top tube configuration. I split the tube along the horizontal centerline, moved the two haves at the headstock end so that they were each welded very close to the ends of the headstock. At the seat end of the top tube, it remained in the original circular cross section. Long, skinny flat triangles were then welded in to join the top and bottom halves on both sides. It solved the cracking issue on the team bikes and I think it was the final production configuratiion.
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Re: Featherbed frame design went against all engineering pri
I think the Egli frame with the large diameter chrome-moly spine was superior to any Norton Frame. I really like the Seeley frame and I think the Seeley G50 was the best British single ever built. The featherbed was great for it's time, however I think a 1963 unit construction Bonneville 650 is better than any Triton ever was. The BSA A10 frame was really good if fitted with the 1963 Triumph fork yokes, however as standard was dangerous when fitted with a hot Triumph motor. There was also a mid-fifties Enfield frame which was not too bad with a Triumph motor in it. I watched one racing years ago which was pretty much unbeatable.
This is the mid 70s Egli Yamaha frame :
I think the Egli frame with the large diameter chrome-moly spine was superior to any Norton Frame. I really like the Seeley frame and I think the Seeley G50 was the best British single ever built. The featherbed was great for it's time, however I think a 1963 unit construction Bonneville 650 is better than any Triton ever was. The BSA A10 frame was really good if fitted with the 1963 Triumph fork yokes, however as standard was dangerous when fitted with a hot Triumph motor. There was also a mid-fifties Enfield frame which was not too bad with a Triumph motor in it. I watched one racing years ago which was pretty much unbeatable.
This is the mid 70s Egli Yamaha frame :
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Re: Featherbed frame design went against all engineering pri
This is the older style Egli frame (mid 60s) however it still has merit, the mid 70s frame was much better, and not difficult to make :
I think this is the frame that Patrick Godet uses for his Vincents, It was what Slaters of Bromich used in the mid 60s.
Patrick Godet :
http://www.godet-motorcycles.com/egli/egli.htm
This is the older style Egli frame (mid 60s) however it still has merit, the mid 70s frame was much better, and not difficult to make :
I think this is the frame that Patrick Godet uses for his Vincents, It was what Slaters of Bromich used in the mid 60s.
Patrick Godet :
http://www.godet-motorcycles.com/egli/egli.htm
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Re: Featherbed frame design went against all engineering pri
Well, if the featherbed "went against all engineering principles" then maybe he was applying the wrong principles to the situation of a racing chassis.
There were many assumptions made about what a chassis should do that by todays principles were simply wrong. Stiffness and strength are very different. Stiffness is useful up to a point but too much makes the bike unpredictable and hard to ride.
The very fact that the featherbed was so successful suggests that it was founded on sound engineering principles.
Well, if the featherbed "went against all engineering principles" then maybe he was applying the wrong principles to the situation of a racing chassis.
There were many assumptions made about what a chassis should do that by todays principles were simply wrong. Stiffness and strength are very different. Stiffness is useful up to a point but too much makes the bike unpredictable and hard to ride.
The very fact that the featherbed was so successful suggests that it was founded on sound engineering principles.
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Re: Featherbed frame design went against all engineering pri
A featherbed frame is really good if fitted with a single cylinder motor, well forward and down. Anything else always seems to feel vague in the front end when ridden hard. A 1962 500cc Manx was a brilliant motorcycle for it's time. I rode a very original one back in about 1973. It was extremely confidence inspiring and predictable, and I found out why the fast guys loved them so much. My 500cc Triton would have been 5 MPH faster down the straights however I would have been about 4 seconds a lap faster on a 3 KM circuit on the Manx.pommie john said:
Re: Featherbed frame design went against all engineering pri
Not necessarily ?
We have all heard that, in theory, bumblebees should not be able to fly....
There was also the later Manx T5 etc frame versions, with more straight tubes and less curved and bent tubes.
According to engineering lore, it was in theory a more 'correct' frame.
Too little too late to really know for sure.
And tubular framed motorcycles generally noticeably adopted more straight tubes,
with generally improved standards of ride and roadholding - particularly some of the oriental ones.
We have all heard the story that Jim Redman spirited a new Manx off to Japan,
for them to study the accumulation of frame tubes around the steering head (in particular),
which seems to have been the real strength of the Manx's featherbed frame.
Not to mention a swingarm pivot that was sufficiently braced to be able to stay in line, more or less, with the steering head.
Complicated business, this steering and roadholding.
So many factors, some of them competing against each other...
pommie john said:
Not necessarily ?
We have all heard that, in theory, bumblebees should not be able to fly....
There was also the later Manx T5 etc frame versions, with more straight tubes and less curved and bent tubes.
According to engineering lore, it was in theory a more 'correct' frame.
Too little too late to really know for sure.
And tubular framed motorcycles generally noticeably adopted more straight tubes,
with generally improved standards of ride and roadholding - particularly some of the oriental ones.
We have all heard the story that Jim Redman spirited a new Manx off to Japan,
for them to study the accumulation of frame tubes around the steering head (in particular),
which seems to have been the real strength of the Manx's featherbed frame.
Not to mention a swingarm pivot that was sufficiently braced to be able to stay in line, more or less, with the steering head.
Complicated business, this steering and roadholding.
So many factors, some of them competing against each other...
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Re: Featherbed frame design went against all engineering pri
Interesting analogy.
The idea that bumblebee couldn't fly "in theory" was put forward by a physicist who had no knowledge of bee anatomy so didn't know that a bee flies by flexing keratin and releasing it to make the wings rather than by pulling it's wings downwards with the muscles. That meant his calculations were meaningless.... he was applying the wrong principles to a subject he knew nothing about.
Rohan said:
Interesting analogy.
The idea that bumblebee couldn't fly "in theory" was put forward by a physicist who had no knowledge of bee anatomy so didn't know that a bee flies by flexing keratin and releasing it to make the wings rather than by pulling it's wings downwards with the muscles. That meant his calculations were meaningless.... he was applying the wrong principles to a subject he knew nothing about.
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Re: Featherbed frame design went against all engineering pri
I think we need to look at where the repairs are on well-used featherbed frames. It gives an indication of which parts are flexing. I was looking at my old Triton today, and there are repairs in about 4 places. Notably where the swing arm mounting plates finish on the main loops. The Mk3 Seeley has an almost straight tube running from close to the pivot to steering head. And the area around the pivot is really strong. The featherbed was good for it's time, however many later frames were better. I know that modern MotoGP frames are made with a controlled amount of flex to suit the tyres, however a good commando only has about 70 BHP to play with, and the tyres are skinny. It is the same game however a quantum leap slower.
I think we need to look at where the repairs are on well-used featherbed frames. It gives an indication of which parts are flexing. I was looking at my old Triton today, and there are repairs in about 4 places. Notably where the swing arm mounting plates finish on the main loops. The Mk3 Seeley has an almost straight tube running from close to the pivot to steering head. And the area around the pivot is really strong. The featherbed was good for it's time, however many later frames were better. I know that modern MotoGP frames are made with a controlled amount of flex to suit the tyres, however a good commando only has about 70 BHP to play with, and the tyres are skinny. It is the same game however a quantum leap slower.
ashman
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Re: Featherbed frame design went against all engineering pri
I don't care about any priciablies all I know since owning my Norton Commando from new and replacing the frame to 57 Wideline frame in 1980 was the best move I ever done, less vibrations, yes less, better handling, never suffered flecks at all and to this day I still love riding it, I have ridden early Triumphs, owned 80s Triumphs and a new Triumph Thruxton, I still rather ride my 850 Norton Featherbed, it handles so much better than the rest, so knock them if you wish I have rode them all, I know how well my Featherbed handles and the harder I ride it through the corners the better it rides.
Ashley
I don't care about any priciablies all I know since owning my Norton Commando from new and replacing the frame to 57 Wideline frame in 1980 was the best move I ever done, less vibrations, yes less, better handling, never suffered flecks at all and to this day I still love riding it, I have ridden early Triumphs, owned 80s Triumphs and a new Triumph Thruxton, I still rather ride my 850 Norton Featherbed, it handles so much better than the rest, so knock them if you wish I have rode them all, I know how well my Featherbed handles and the harder I ride it through the corners the better it rides.
Ashley
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Re: Featherbed frame design went against all engineering pri
just about everything i've read or info i''ve come across regarding the featherbed indicate or point to a superlative achievement, including comments that it is better handling than a commando so..
seems a bit weird to say "against all'' engineering principles
the round tube was used as a spar in the v1 buzz bomb as well as in some planes, jim bede was a major player in that
pommie john said:
just about everything i've read or info i''ve come across regarding the featherbed indicate or point to a superlative achievement, including comments that it is better handling than a commando so..
seems a bit weird to say "against all'' engineering principles
the round tube was used as a spar in the v1 buzz bomb as well as in some planes, jim bede was a major player in that
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Re: Featherbed frame design went against all engineering pri
May money is on the Isolastic wonder, once its springy-ness is tamed so takes up sideways tire vector conflicts by twisting stem to rear patch But Does Not Spring Back Nor Rebound but to neutral centered again, so nothing else can put down hook up more power planting so harshly in full control than a tri-linked Commando with some compliance in the headsteady and front breast support. Hope to hear more from comnoz now tri-linked with a different front link positioned helper, don't think is in the best place there.
May money is on the Isolastic wonder, once its springy-ness is tamed so takes up sideways tire vector conflicts by twisting stem to rear patch But Does Not Spring Back Nor Rebound but to neutral centered again, so nothing else can put down hook up more power planting so harshly in full control than a tri-linked Commando with some compliance in the headsteady and front breast support. Hope to hear more from comnoz now tri-linked with a different front link positioned helper, don't think is in the best place there.
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Re: Featherbed frame design went against all engineering pri
Tri-linked in my Ms Peels case means 3 radius rod end helm's joint links at rump, head and breast areas. Only 3 isolastic Commando so far tr-linked, one Doug McRae on Herb Becker racer that is about solidly fixed by close fitting robust-ridgid swash plates, so gives up nothing in handling against world class famous solid Seeley frames, & Jim Commstock very recently this month finally added 3rd 'rump' rod plus his prior robust front link close to and below front isolastic along with the universal type robust ie: non compliant rod headsteady. Reading and seeing what Doug describes, still seems too rigid as only matching rigid frame races instead of out handling them in secure delight. Jim has not had time to work up canyon chicane testing but says he is sorry he didn't put on rump rod decades ago and liked the way it steadied cross winds in Texas panhandle turn pike semi truck blasts speeds this week. ONLY Ms Peel has Robust non compliant rump rod and two weaker compliant head and breast links, which still allow full flex of frame/stem but absolutely prevent any rebounds but back to pure neutral on let off, which in Peels case is used to get saving high sides out of the snatch down by power leans low sides to spring up in line by just letting go of bars, to point will lift one or both tires off surface, like releasing a sling shot not a stiff diving board. I've not yet seen any one ride a cycle like Ms Peel invited me into, expect for some racers loosing it in low sides then saving it almost by accident but not trying to do this on purpose like I did on Peel. Unbelievable so don't expect belief from anyone till Peel power enough to prove it but wonderful side effect besides extra safety reserves was how extra smooth a sense of huge massive inertial dampening like an over loaded Goldwing >> that does not transmit even the valve train buzz like they do. I tested Peel in way worse tighter faster rougher dangerous narrow wagon trail Mt side switch backs than racers encounter, packing all up at semi sharp turns to start race all over again, pashaw, so not speculating but hoping to tempt others, if stupid enough to press cycles like crazy.
Tri-linked in my Ms Peels case means 3 radius rod end helm's joint links at rump, head and breast areas. Only 3 isolastic Commando so far tr-linked, one Doug McRae on Herb Becker racer that is about solidly fixed by close fitting robust-ridgid swash plates, so gives up nothing in handling against world class famous solid Seeley frames, & Jim Commstock very recently this month finally added 3rd 'rump' rod plus his prior robust front link close to and below front isolastic along with the universal type robust ie: non compliant rod headsteady. Reading and seeing what Doug describes, still seems too rigid as only matching rigid frame races instead of out handling them in secure delight. Jim has not had time to work up canyon chicane testing but says he is sorry he didn't put on rump rod decades ago and liked the way it steadied cross winds in Texas panhandle turn pike semi truck blasts speeds this week. ONLY Ms Peel has Robust non compliant rump rod and two weaker compliant head and breast links, which still allow full flex of frame/stem but absolutely prevent any rebounds but back to pure neutral on let off, which in Peels case is used to get saving high sides out of the snatch down by power leans low sides to spring up in line by just letting go of bars, to point will lift one or both tires off surface, like releasing a sling shot not a stiff diving board. I've not yet seen any one ride a cycle like Ms Peel invited me into, expect for some racers loosing it in low sides then saving it almost by accident but not trying to do this on purpose like I did on Peel. Unbelievable so don't expect belief from anyone till Peel power enough to prove it but wonderful side effect besides extra safety reserves was how extra smooth a sense of huge massive inertial dampening like an over loaded Goldwing >> that does not transmit even the valve train buzz like they do. I tested Peel in way worse tighter faster rougher dangerous narrow wagon trail Mt side switch backs than racers encounter, packing all up at semi sharp turns to start race all over again, pashaw, so not speculating but hoping to tempt others, if stupid enough to press cycles like crazy.
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Re: Featherbed frame design went against all engineering pri
The featherbed frame came out of an era when tyres did not have much grip. If you ride the bike hard for a long time and climb off it regularly to get around corners, even with the old low grip tyres the frame will often crack because of the flexing caused by the cross loads from the swing arm, even though the manx frame was made out of chrome-moly tube. A Seeley frame is a much better option. Also the geometry and motor position are often better with the Seeley. The one thing that interests me is the crack which sometimes appears just below the front engine mount on the featherbed frame. I believe that many of us underestimate the forces involved when the bike is used in anger. There are plenty of replica featherbed frames around which have been made out of mild steel.
The featherbed frame came out of an era when tyres did not have much grip. If you ride the bike hard for a long time and climb off it regularly to get around corners, even with the old low grip tyres the frame will often crack because of the flexing caused by the cross loads from the swing arm, even though the manx frame was made out of chrome-moly tube. A Seeley frame is a much better option. Also the geometry and motor position are often better with the Seeley. The one thing that interests me is the crack which sometimes appears just below the front engine mount on the featherbed frame. I believe that many of us underestimate the forces involved when the bike is used in anger. There are plenty of replica featherbed frames around which have been made out of mild steel.
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