FEATHERBED RAKE ANGLE

Carbonfibre said:

As I suggested in an earlier post, when frames are being manufactured in any numbers using old fashioned production techniques, its highly unlikely the type of jigs which are today used for high end low volume aftermarket frames would have been used. Fixtures of some sort, to position the head stock and swinging arm pivot in the right place, would have been far more likely.

Reynolds today exists in name only, and markets a range of tubes which are produced in Germany and Taiwan...........the new generation German "Reynolds" tubes do seem ideally suited for use for making motorcycle frames though!

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Make up your mind, one minute its adjustable steering column angles on jigs, next its just fixtures no jigs. I think we are making assumptions here, without any knowledge of the subject whatsoever ?

Has Ken Sprayson or any of his associates written of this anywhere perhaps ?

The jigs for the old lugged frames that were hearth brazed were rather elaborate - and being done in-factory, were often photographed and shown in the press. Someones book showed such a view, anyone recall more precisely the details. Wartime magazines sometime showed inside factories, was it in WD 16h manufacture ? (tryng to stir memories here).

Has anyone been to see what exists of the old Reynolds factory - or even knows or explored where it is ? Who knows, the jigs might still all be out the back. The factory in Bracebridge St Aston Brook St is well commemorated, the Reynolds Factory was equally a part of featherbeds and no-one knows anything of it ?? (trying to stir memories here too).

Be interested to see any pics of the jigs used for building hearth brazed frames. They must have been pretty special pieces of kit to be able to resist the heat of the brazing hearth without distortion.

You are pulling our legs, right ?!!

Frames were pinned in the jig, removed, and into the brazing oven.

Seems that Ken Sprayson has written a book.
http://cache1.bookdepository.com/assets ... 497567.jpg

All our questions have been answered. (?)

Note that the publication date is given as March 2012.
Which I think means that he's probably still writing it...

Rohan said:

You are pulling our legs, right ?!!

Frames were pinned in the jig, removed, and into the brazing oven.

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If thats the case, then how on earth was distortion prevented, during and after the actual joining of the tubes? Bronze welded frames are commonly removed from the build jig, after initial tacking together of the main parts, then fully welded and sometimes forced back into the build jig, so that the swinging arm pivot can be fitted. Maybe the process was the same with the hearth brazed frames, but nails through the lugs used rather than tacking?

Sorry, slight confusion with words here - the FRAMES were pinned together, while in the jig. You use the word 'nails', same thing. Same meaning anyway, pinned is the word used though. And then removed from the jig and placed into the brazing hearths.

Yes, oven brazing sounds brutal - but lugged motorcycle (and bicycle frames) had been made in bulk like that for the best part of the previous century. On top of that, they were subsequently dipped in enamel and then cooked in the enamelling ovens. (Maybe this stress relieved them ??) Obviously they got good at putting them together so they didn't come out like a pretzel. How they were subsequently checked and any remedial straightening work done would be interesting to hear. Secrets of the trade, can't say I've seen that spelled out in detail anywhere - like many aspects of commercial motorcycle manufacture.

HTH.

( quote0 Make up your mind, one minute its adjustable steering column angles on jigs, next its just fixtures no jigs. I think we are making assumptions here, without any knowledge of the subject whatsoever ?
Has Ken Sprayson or any of his associates written of this anywhere perhaps ?
The jigs for the old lugged frames that were hearth brazed were rather elaborate - and being done in-factory, were often photographed and shown in the press. Someones book showed such a view, anyone recall more precisely the details. Wartime magazines sometime showed inside factories, was it in WD 16h manufacture ? (tryng to stir memories here).
quote]

Yes Roland it means exactly that!
Some of you have no idea of the modern practices carried out in frame manufacturing process.
Whilst I cannot speak for the original featherbed frame jigs, Rex McCandless was a very clever man and it would not surprise me if he could make more than one frame (Manx) on his first featherbed frame jig.
There seems to be some misunderstanding for you and others on how the frames were made.
Jigs & fixtures are time-consuming and expensive to make as any frame made on them will show up any shortcomings when made, and they will be put to the maximum use possible, as they are jigs and not fixtures, and are hence adaptable.
On the modern jigs that I have seen they can make a featherbed type frame either as normal and, with a slight modification, alter the frame jig to take a 500, 650 750 engine according to requirement. And if you grease the palm of the frame makers hand with the right amount of notes, he will make you a frame with a shallow angle headstock for quick steering for trail riding or make it with a steep angle rake for use on the drag strip! He will give you exactly what you want.

Juts to clarify, these early frames were bronze joined and later SIF bronze joined (Suffolk Iron Foundry).
They were done (in siu) in the jig with a welding torch, and not the hearth as some of you suggest, then after brazing the tubes are heated up to relive the stress on the metal and prevent it becoming brittle.
Those of you who have never seen a frame ‘jig’, you might want to look at;

http://www.dresda.co.uk/dresda.asp

For the Motoliner motorcycle frame straightening jig which has to be TWICE as strong and can accompany vitally ANY solo motorcycle frame ever made;

http://www.motoliner.com/
http://www.motoliner.com.au/

Frames built with lugs and hearth brazed, were indeed pinned together before the joints were brazed, and common or garden nails were used as pins. The lugs themselves were investment cast steel, and had the advantage of often being able to be used on more than one frame. Tubes were invariably thick wall ERW, and while the resulting frames didnt have many problems with cracking, they were very heavy. Main reason for this method of production, was it didnt require skilled workers, which meant it was quite a bit cheaper than most alternatives.

I would guess that lugged frames were pinned in some form of jig, but its doubtful if production workers would bother check very many after the brazing process, and in some cases distortion may well mean it would have been impossible to refit frame to the jig in any case.

Bernice, get folks names right.
We'd say thats a gross assumption on your part that the McCandless frame jig was adjustable - without seeing it, or knowing any details of it, 'we' are just making up stories.
No-one here suggested or said that featherbed frames were hearth brazed. The revolution in frame making was that they were welded, NOT hearth brazed lugged frames, after all.
This didn't just apply to featherbed frames either, of course, frame making generally across the motorcycle industry had been heading this way around WW2 and even before.
I have a little Villiers framed beastie with partly welded and mostly lugged frame, pre featherbed era.

Carbonfibre, where did you get the idea that the lugs were investment cast ??
That is a precision process that was quite expensive, and not used for something common like the old motorcycle frame lugs - which were easily sand cast. (In malleable iron, by the way). Its only fairly recently that investment casting, and cast steel even, has become a more mainstream production technique - and sand casting is still considerably cheaper for mass production. (And before more confusion reigns, welded frames did not use cast lugs - the tubes were just welded together).

P.S. Should mention that a lot of the bits and bobs on Nortons were forged.
Forging was way more common than cast steel, for many years.
(cast steel required a very sophisticated furnace, and was very expensive to run and operate, so quite rare until quite recently.).

hth

There is lots of love in this thread. Now this is from a commonsense take on the issues highlighted here, the hearth brazed frames would not have distorted much or even at all as every part of the frame undergoes the same heating and cooling cycle at the same time, distortion in welded steel structures is from the solid state phase transformation of the BCC lattice structure to FCC and back to BCC on cooling, depending on the alloy this occurs around 723 degC. A second way for distortion to be introduced is the stress relief of heavily cold worked areas, in this application it is not going to be a big issue due to the relatively low strength steels used.

Even in the chaotic mess the British manufacturing industry was reportedly in I very much doubt that the frame welding jigs/fixtures were non adjustable, now this is not to say they could be used to make any frame (ie completely different design) but they would have been able to be tuned to give a finished piece that is within the design tolerances.

I haven't read every answer in this thread, but why is it so important to know what the rake angle is on featherbed frames :?: :?: :?:

Jean

To dispell all the half-truths, assumptions and nonsense quoted along the way. ?
And to find why the officially quoted figures don't seem to agree with what is quoted elsewhere.

Reading the very first post may help... ?

Cheesy said:

the hearth brazed frames would not have distorted much or even at all as every part of the frame undergoes the same heating and cooling cycle at the same time <snip>

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Ever seen a steel framed building thats been in a fire - or anything with a complex shape for that matter. Curves tend to straighten, and straight bits tend to curl, especially with welded bits added to them in irregular patterns.

Having said that, the old lugged type frames had been oven-brazed for the best part of 100 years, so they probably knew what they were doing , and knew how to get them to work.
As was said previously, be interesting to see a good rundown of how it was done though - folks who can successfully rework the old lugged style frames (and forks) are a little thin on the ground these days.

As a perhaps an example, there are these replica girder forks coming out of India, for things like military M20s and 16H Nortons and 3HW Triumphs. Someone said the M20 version they received was about 1/2" out of square (why does my front wheel want to go sideways ?), and for such a simple shape that is a lot. Without seeing it, the reasons for that could be numerous, but not staying in shape while it was brazed up is certainly one of them, and sagging while hot is another.
It is probably quite important to support or hang the lugged frame in some way when it goes in for brazing, but knowing that method (without experimenting ?) is anyones guess ?
Obviously you want them all to come out with the wheelbases all the same, and the space for the engine/gearbox fitment all identical.

Cheers.

Certainly a frame made out of thin gauge steel tube would distort to the extent it would not be usable if built using the hearth brazing process. However as the ERW tubes used are approximately double the wall thickness of a welded frame, problems with distortion are easily avoided.

The ancient Triumph movie with them building T100s around 1955 shows a Brazed lug frame being built . Is on a Video & C.D .

Carbonfibre said:

Certainly a frame made out of thin gauge steel tube would distort to the extent it would not be usable if built using the hearth brazing process. However as the ERW tubes used are approximately double the wall thickness of a welded frame, problems with distortion are easily avoided.

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You just keep making these pronouncements that are just plain not true.

I've had an early Model 7 Norton twin dommie frame (lugged, with plunger rear suspension) that was made in thin wall tubing. If you flick the tubing with your finger, it went 'ting' - not the thunk of plain old pipe. How or why this may have been used for I can't imagine, but it had to be factory, no-one would go to all that trouble to totally retube it ?.

It was said that Manx plunger frames had hi-tensile tubing, anyone confirm ?
Renowned for cracking/breaking and needing constant repairs for the privateers, the featherbed couldn't come soon enough....

Not sure whether or not you have ever done any work on an old lugged British frame? I suspect not, as if you had then the heavy gauge tubes used would be pretty familiar to you!

Going back to basics, discounting the problems related to tubes distorting if thin high tensile tube was used in a lugged frame (as you suggest), there would certainly be problems with cracking as the HAZ affecting the tube adjacent to the rather substantial investment cast frame lugs, would mean problems with cracking were almost inevitable. This being another very good reason for heavy gauge ERW being used, rather than the chrom moly (?) tubes you claim.

If you would like to confirm any of the above contact any professional frame builder, and I am sure they will agree than other than on push bikes, very thin high tensile tubes are simply not used to build lug type hearth brazed frames!

Carbonfibre, I have plenty of Norton / lugged frames, some (most !) of them have needed work.

http://i1113.photobucket.com/albums/k50 ... CN0890.jpg
This is a plain 1950 Model 7 frame (500cc dommie twin), freshly blasted and phosphated prior to painting. Nortons painted some frames, in colours, in the early 1950s, so its being painted not enamelled. If you look VERY closely, you can see where the rear suspension towers have been (professionally) welded, in nickel bronze. Common fault in old Norton frames if they had a hard life...

The Model 7 frame in hi-tensile tubing seems to be pretty special stuff, but have yet to find out why. Obviously it can be done....

Rohan said:

Cheesy said:

the hearth brazed frames would not have distorted much or even at all as every part of the frame undergoes the same heating and cooling cycle at the same time <snip>

Click to expand...

Ever seen a steel framed building thats been in a fire - or anything with a complex shape for that matter. Curves tend to straighten, and straight bits tend to curl, especially with welded bits added to them in irregular patterns.

Having said that, the old lugged type frames had been oven-brazed for the best part of 100 years, so they probably knew what they were doing , and knew how to get them to work.
As was said previously, be interesting to see a good rundown of how it was done though - folks who can successfully rework the old lugged style frames (and forks) are a little thin on the ground these days.

As a perhaps an example, there are these replica girder forks coming out of India, for things like military M20s and 16H Nortons and 3HW Triumphs. Someone said the M20 version they received was about 1/2" out of square (why does my front wheel want to go sideways ?), and for such a simple shape that is a lot. Without seeing it, the reasons for that could be numerous, but not staying in shape while it was brazed up is certainly one of them, and sagging while hot is another.
It is probably quite important to support or hang the lugged frame in some way when it goes in for brazing, but knowing that method (without experimenting ?) is anyones guess ?
Obviously you want them all to come out with the wheelbases all the same, and the space for the engine/gearbox fitment all identical.

Cheers.

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Yes I have but the steel in the building has significant external loads on it, the bike frame only has to support its own weight, Im not saying it wont 'move' it will but it will not be very significant (again due to the uniform heating and cooling).

Carbon, can you please explain to me why a hearth brazed frame could not be made with thin wall tubing and also where the heat affected zones are and what causes them?

The main reason for hearth brazed frames was to reduce production costs, as its something that could be carried out by semi skilled workers. The process necessarily involves uneven heating, as the lugs themselves have to be hot enough for the braze to flow into the joints properly, while other parts of the structure dont get anywhere near as hot.

Heavy investment cast lugs used by makers such as BSA and Triumph, dictated the use of thick wall ERW tubes, but the light looking lugs on the frame in Rohans pic would work very well with high tensile tube, as the levels of heat would be far lower and HT tubes would not be adversely affected. The lugged frame seems to have originated from cycle manufacturers, and the production process was over the years altered to reduce costs, which resulted in heavy but reliable frames, with handling and feel which often wasnt that great.