FEATHERBED RAKE ANGLE

Strong tubular structures are made in one of 2 ways, the first being using heavy gauge tubes, the second being short light tubes in the style of recent Ducati frames.

A frame made using long unsupported runs of relatively thin cheap ms tube, is not that great structurally, and will mean that head stock and swinging arm pivot points will have considerably more flexure than frames which have not been designed with low cost as the primary objective.

Back in the day the Norton frame was certainly superior to the heavy hearth brazed rubbish that was being used by most other manufacturers, but today to suggest its still something that offers good handling is pretty ridiculous, if only for the fact that almost all original frames are likely to be bent, due to the design itself and use of the very cheapest materials.

I have read several references in this thread to the slimline frames being less desirable than the wideline frames. In what way? The narrowness at the top seems like it might be a good thing if they allow your knees to tuck in tighter. Are they structurally weaker?

Vintage Paul

hudson29 said:

I have read several references in this thread to the slimline frames being less desirable than the wideline frames. In what way? The narrowness at the top seems like it might be a good thing if they allow your knees to tuck in tighter. Are they structurally weaker?

Vintage Paul

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I think its only snob value ? . Norton (factory) race bikes only used wideline featherbeds, they didn't get around to making a slimline version of Manx before the race shop in Bracebridge street was closed. Slimline 650 bikes had done well in some of the long distance races, so its not like they were never raced or tried out in the heat of battle.

Correct me if I'm wrong - there were a number of Domiracer etc projects at the time, some of which have never seen the light of day, a slimline could be in there somewhere.

Cheers.

P.S. There is a school of thought that says motorcycle frame tubes have to be straight to be good engineering practice - and there is some merit to this line of thinking.
And the slimline's kinked in tubes at the front of the seat don't meet this goal as well as the wideline did. However, race results would suggest that this is not as detrimental as the theory would suggest.

Carbonfibre said:

"At the moment my headstock is at an angle of 67.5 degrees with respect to the frame bottom rails ie 22.5 to the vertical, so I will be pulling it by 5 degrees"

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As previously mentioned here, the diagram put up on the NOC website shows the slimline frame measurements. This seems to agree with pretty much everything written.

http://www.nortonownersclub.org/noc-cha ... IMLINE.jpg

If you've looked into this subject at all, Commando frames got more angle, for whatever reason. And the 850 yokes had the fork tubes pointing "backwards" with respect to the steering column - wonder how they came up with that ? !

If you put a featherbed and commando frame together, you can SEE that the featherbed has less angle. If you put bent and good frames together, you can SEE the differences (although not necessarily quantify them)- the human eye is a marvellous piece of work.

Carbonfibre said:

due to the design itself and use of the very cheapest materials.

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This is just nonsense. Manx featherbed frames were built from Reynolds 531 tubing, a leading hi-tensile tubing variety of the day. The inters were built of less exotica and the roadbikes a heavier tubing. Getting strength through being heavier doesn't make them inferior though, just a commercially sensible strategy.

Carbonfibre said:

" as your posts here seem to suggest you see yourself as an experienced frame builder, as well as having an in depth knowledge of the effect of tubing being bent well beyond its limits of elongation?

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You simply need to read Phil ivings writings on building and repairing frames. He writes extensively on this - older motorcycles going back into the dawn of time were structurally (how shall we put it) marginal sometimes - fork breakages and frame breakages were commonplace back then. The village blacksmith was often a common place to get such repairs done - that forge and anvil goes back into pre-roman times for working and shaping steel, this is not rocket science.

I've had some frames repaired, its not rocket science either. Brute force and heat can overcome most mishaps !! If it didn't, the infant industry of cars and motorcycles - and trains and steel ships - would have perished long ago...

Carbonfibre said:

" depth knowledge of the effect of tubing being bent well beyond its limits of elongation?

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P.S. Any tubing that has been visibly stretched or buckled will usually be cut out and replaced by a frame repairer - but it generally takes a severe impact to do this, most frame twisting or distorting is usually far more subtle than this....

Matt here with his slimline says he can't see any visible damage, bending or buckling, so its a good chance that a good frame repairer can make this right.

Actually, a good photo of the steering head area would probably allow a visual comparison with a good frame ...

P.S. I did a welding course, with the idea of going frame building - and being sure of being up-to-date with modern welding practice. But before even starting, I found there were 4 frame builders here within 50 miles, all doing versions of featherbeds ! And all scratching a living at it...

One of them was ex-Harley Davidson factory trained on frame repairs - his frame jig was a big cube of steel girders, ~1/2 ton of it, with bolt-in sections to do everything imaginable to a frame. This gave great leverage to be able to push, pull and tug in every direction. A true perfectionist. He does a lot of vintage and veteran frames, as well as forks. His Norvin has a featherbed frame that a whole Vinnie motor just bolts into - no frame cutting or engine cutting required. Twin dunstall disks too, so it stops as well.

Carbonfibre said:

Strong tubular structures are made in one of 2 ways, the first being using heavy gauge tubes, the second being short light tubes in the style of recent Ducati frames.

A frame made using long unsupported runs of relatively thin cheap ms tube, is not that great structurally, and will mean that head stock and swinging arm pivot points will have considerably more flexure than frames which have not been designed with low cost as the primary objective.

Back in the day the Norton frame was certainly superior to the heavy hearth brazed rubbish that was being used by most other manufacturers, but today to suggest its still something that offers good handling is pretty ridiculous, if only for the fact that almost all original frames are likely to be bent, due to the design itself and use of the very cheapest materials.

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Stop your tendentious pontificating and tell us about the Dominator handling problems you've endured.

Its been a long time since I have owned a Featherbed framed bike, but from what I can remember the handling was probably better than most other 1960's Brit bikes I had, but not comparable in any way to more recent machinery which was also considerably more powerful. The bike was also very high and uncomfortable to ride, feeling much like sitting on a plank of wood.

Frames on most of the old Brit bikes could have been improved enormously if the cheapest possible production costs had not meant that things like hearth brazed ERW tubes were the accepted norm, and the performance of frames like the Featherbed, originally designed for racing, being compromised by use of mild steel tubing, which was of too thin a gauge to perform anywhere near as well as the 531 race versions.

Rohan said:

Carbonfibre said:

" depth knowledge of the effect of tubing being bent well beyond its limits of elongation?

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P.S. Any tubing that has been visibly stretched or buckled will usually be cut out and replaced by a frame repairer - but it generally takes a severe impact to do this, most frame twisting or distorting is usually far more subtle than this....

Matt here with his slimline says he can't see any visible damage, bending or buckling, so its a good chance that a good frame repairer can make this right.

Actually, a good photo of the steering head area would probably allow a visual comparison with a good frame ...

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As you seem to be something of an expert on working with bike frames, I wonder if you can advise all those following this thread where exactly would the tubes likely to be bent on a Featherbed frame whose head angle differed 5 degrees from the factory figures?

Rohan said:

P.S. I did a welding course, with the idea of going frame building - and being sure of being up-to-date with modern welding practice. But before even starting, I found there were 4 frame builders here within 50 miles, all doing versions of featherbeds ! And all scratching a living at it...

One of them was ex-Harley Davidson factory trained on frame repairs - his frame jig was a big cube of steel girders, ~1/2 ton of it, with bolt-in sections to do everything imaginable to a frame. This gave great leverage to be able to push, pull and tug in every direction. A true perfectionist. He does a lot of vintage and veteran frames, as well as forks. His Norvin has a featherbed frame that a whole Vinnie motor just bolts into - no frame cutting or engine cutting required. Twin dunstall disks too, so it stops as well.

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Firstly professional frame building entails rather more effort than attending a welding course or watching things like "American Chopper" on TV! It takes many years of experience to be able to make high quality road or race frames, that are anywhere near as good as current production frames, so the main interest here relates to older bikes.

However in the US particularly there seems to be quite a reasonable living to be had by semi skilled people with a bit of money to invest, who are able to join a few crudely bent tubes together with a MIG welder. This being the custom/chopper market, which seems to have become even more popular on the back of various TV shows!

If you want to make money at frame building its pointless making things that no one wants, and it the US it seems that custom/chopper frames are the way to go, and here in the UK frames for Tri/BSA triples and various classic competition applications have always been popular, with frame builders here often having a very long waiting list .

Carbonfibre said:

Its been a long time since I have owned a Featherbed framed bike,

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I'm almost surprised you've ridden one at all.

but from what I can remember the handling was probably better than most other 1960's Brit bikes I had,

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No handling problems stick in your memory then.

but not comparable in any way to more recent machinery

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That doesn't really have a meaning. You can compare anything to anything else, especially with licence to compare "in any way". If you mean modern bikes are more comfortable over bumps, then yes, a lot of them are. If you mean many modern bikes can be hustled round a corner by an expert, faster than he could get round on a Dominator then yes, that's true too. I'd say though, that if you habitually corner faster, on public roads, than you could on a Dominator, you will not reign long. Oh look- I'm comparing the incomparable!

The bike was also very high and uncomfortable to ride, feeling much like sitting on a plank of wood.

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I like that- it's a valid opinion, based on experience. I like the Manx style single seat, even though it's not soft. I bought a new Wideline dualseat once and it did feel high and strange. I attacked the foam filling with a hole saw, so that it sank down to near the frame tubes when sat on and now it's pretty comfortable for rider and pillion. My long-didsatnce experience on modern bikes is limited to a Honda CB500 twin of the recent type and a Guzzi Targa. Both were torture to sit on after an hour or so.

Frames on most of the old Brit bikes could have been improved enormously if the cheapest possible production costs had not meant that things like hearth brazed ERW tubes were the accepted norm,

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That sort of brazing was the industry standard until welding improved. Brit factories were slow to leave it behind because that's what equipment was in the factories and those were the frame designs aleady in use. Norton and BSA went to mostly arc welding reasonably early, I'd say. Your wisdom is rather compromised by the fact that many big Jap frames were fully welded and handled worse.

and the performance of frames like the Featherbed, originally designed for racing, being compromised by use of mild steel tubing, which was of too thin a gauge to perform anywhere near as well as the 531 race versions.

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Exaggerated to the point of being nonsense. Mild steel makes it slightly heavier because thicker walled tube is used to maintain strength. The thinner walled 531 frames would be lighter, but probably not much stronger. People won races on road Featherbed frames. As another old guy you know that already.

Have you produced the mild steel strength data Rohan asked for yet?

Carbonfibre said:

Firstly professional frame building entails rather more effort than attending a welding course or watching things like "American Chopper" on TV! It takes many years of experience to be able to make high quality road or race frames, that are anywhere near as good as current production frames, so the main interest here relates to older bikes.

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Not at all. You just have to award yourself a silly name and argue on the internet.

Carbonfibre said:

What datum is the 24 degrees being measured from I wonder?

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Hi Carbon,
24° measured from the vertical, just as the diagram with the frame lower tubes sitting horizontal, or at 90° from the vertical if you like. Personally, if I was the chap with the bent frame I'd try contacting Dresda for some info, they also straighten and true featherbed frames.

Webby

Webby03 said:

Carbonfibre said:

What datum is the 24 degrees being measured from I wonder?

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Hi Carbon,
24° measured from the vertical, just as the diagram with the frame lower tubes sitting horizontal, or at 90° from the vertical if you like. Personally, if I was the chap with the bent frame I'd try contacting Dresda for some info, they also straighten and true featherbed frames.

Webby

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It seems as though the OP may have been provided the wrong information on what the correct angle should be then, unless the frames were built with several differing angles?

That sounds a very good idea..........and perhaps the ideal man for the job.

In comparison to a modern motorcycle frame, which has been properly designed and made out of appropriate materials, something like a Featherbed isnt even on the same planet, but thats to be expected of just about anything that was first designed and made in the 1940s!

In nostalgic terms the old Norton frame stacks up pretty well when its up against the rubbish that was being made by other manufacturers around at the time, but its design was still compromised to some extent by having been originally conceived as a race frame built by the original designer using 531 tubes, which was then translated into a road frame but without increasing the tube diameters, so the mild steel material used could provide somewhere near the same strength as the 531 original design.

The main reason crude heavy hearth brazed frames continued to be used by Brit motorcycle manufacturers up until the late 1960s was to do with cost, with ERW tube secured into cheap investment cast lugs with nails, and then brazed together by a semi skilled workers.

Its quite correct that early Japanese machines did not handle that well, but it has to born in mind that some were considerably more powerful and heavier than Brit machines. However the final complete collapse of the British motorcycle industry in the late 70s seems to strongly suggest that an awful lot of people were prepared to suffer slightly less than perfect handling, in exchange bikes which offered far superior performance, reliability , and build quality, rather than carry on buying Brit machines some of which used power units whose original design dated back to the 1930s!

Carbonfibre said:

In comparison to a modern motorcycle frame, which has been properly designed and made out of appropriate materials, something like a Featherbed isnt even on the same planet, but thats to be expected of just about anything that was first designed and made in the 1940s!

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More meaningless metaphors. What planet? OK the seat was too high for your low-down bum, but you seem to be unable to specify the handling problems of this awful weak, cheap frame, even after all the repetitive posting you've done here.

In nostalgic terms the old Norton frame stacks up pretty well when its up against the rubbish that was being made by other manufacturers around at the time, but its design was still compromised to some extent by having been originally conceived as a race frame built by the original designer using 531 tubes, which was then translated into a road frame but without increasing the tube diameters, so the mild steel material used could provide somewhere near the same strength as the 531 original design.

The main reason crude heavy hearth brazed frames continued to be used by Brit motorcycle manufacturers up until the late 1960s was to do with cost, with ERW tube secured into cheap investment cast lugs with nails, and then brazed together by a semi skilled workers.

Its quite correct that early Japanese machines did not handle that well, but it has to born in mind that some were considerably more powerful and heavier than Brit machines. However the final complete collapse of the British motorcycle industry in the late 70s seems to strongly suggest that an awful lot of people were prepared to suffer slightly less than perfect handling, in exchange bikes which offered far superior performance, reliability , and build quality, rather than carry on buying Brit machines some of which used power units whose original design dated back to the 1930s!

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You sound like a page of Classic Bike or some derivative coffee table book about old bikes.

Even Norton and Renolds had enough production engineering sense to use mild steel. You know as well as I do that lugged frames were rare by the mid sixties.

You are nothing more or less than a pub bore. Your non-argument has veered and repeated between metal fatigue, annealing, steel quality, cost, skill, and God knows what else and now it's about engines. Your "advice" to the OP is rubbish and some people would take some convincing that anything you say from now on is dependable. If I ask for help here, I'll be circumspect about trusting any replies from you.

The Norton frame was good back in the day in comparison to others which were even more cheaply made, so handling of the Norton was appreciably better in comparison. However long unsuppported runs of cheap ms tube make for a relatively flexible chassis which distorts quite easily during normal use, and far more so if accident damage is sustained.

Anyone who has ridden a good modern machine and something fitted with a 1940s designed frame, will recognise the fact that the 2 cannot really be compared. Trying to do this is a bit like saying should one of the participants in a gun fight be armed with a knife, then both would have an equal chance of winning...............its simply not the case!

Triumph and BSA were both using hearth brazed ERW frames right up to about 67/68, and would probably have continued to do so had they not been obliged to change to the even worse Umberslade Hall oil in frame design. Sadly one of the many reasons the Brit motorcycle industry went down the tubes was to do with penny pinching, which led to poor design being the rule rather than the exception, with this ultimately opening up the whole world motorcycle market to non British manufacturers.

In respect of poor design, if a race frame using high tensile tubing is to work well in road applications, then the best way to gain the required additional strength if mild steel tubes are to be used is to increase the tube diameter, rather than simply increase gauge size and keep diameter the same.

Personally I find the current "Classicbike" to be a very good read, and it now seems to be going from strength to strength with well re-searched and accurate articles covering bikes from many different countries, and not entertaining the type of thing which seems to place more faith in well worn myths, than simple and easily verifiable engineering truths.

You're a bit inconsistent about which is the cheap one- Featherbed or brazed lug.



You don't seem to know what the word "compare" means. No-one is saying the Norton frame is as "good" as or better than the best modern frames. Someone might come along and say such a thing (Norton forum after all), but they haven't yet. But you are still unable to tell us what is wrong with Norton steering, caused by your "weakness which moves all over the frame"

(TT checks Google) Yes, the Triumph Unit frame has a steering head lug and an unfortunate looking swingarm lug along with numerous welds, so you're right it has been through a hearth for brazing.

Something else no-one denies is that larger diameter tubes can be a good route to stiffness. You're arguing with yourself. But Norton did not take that route and ended up with an easily built frame that works well. Could Renolds bend bigger tubes so easily in production? How thick would the walls have to be to prevent crumpling? And if the walls were thicker what would it all weigh?

I read Classic Bike because they still send it long after I stopped paying subs. They print rather a lot of mistakes. So do I, I know, but I don't charge money.