FEATHERBED RAKE ANGLE

Both frames are cheaply made, but welded ones do costs ore to make than brazed, as the tubes need to fit together relatively accurately, and the welding cannot be done by a semi skilled worker as is the case with hearth brazed. Nothing at all wrong with welded frames, but up until relatively recently the only way to weld high tensile tube was either bronze or TIG, so mild steel mostly ERW is the most commonly used material.

Nothing wrong with the Norton steering when compared to bikes around at the time, but they are effectively a race frame, and certainly not ideally suited for road use, but the main thing which would detract from handling today, would be the fact that as in the case of the OP a good number are likely to be badly bent, and I am not completely sure any bike would handle properly with a head angle distorted 5 degrees? Easy to check this by measuring the wheelbase though.

Triumph and BSA single frames up to about 67 were both hearth brazed, as were all of the BSA and Triumph triples.............how these manufacturers felt they could compete against the Japanese using production methods that were even at that time antiquated is hard to understand?

Larger diameter tubes of thinner gauge will provide a far stronger frame than smaller diameter using thicker gauge, so there is every possibility of building a frame which is both lighter and stronger, and other than tooling costs (which would have had to be met in relation to the crude rehash of the wideline frame anyway) these would not have cost a great deal more to make.
 
Carbonfibre said:
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.
Click to expand...

So, you have finally realised what most here realised all along. !
Look back at all the rubbish you have written along the way.

Thanks for the advice on framebuilding - not.
I'm with tritonthrasher, your words are unreliable.
 
Both frames are cheaply made, but welded ones do costs ore to make than brazed, as the tubes need to fit together relatively accurately, and the welding cannot be done by a semi skilled worker as is the case with hearth brazed. Nothing at all wrong with welded frames, but up until relatively recently the only way to weld high tensile tube was either bronze or TIG, so mild steel mostly ERW is the most commonly used material.
Click to expand...




I'm sure the economics are more complicated. Brazing required a continously fired furnace and a supply of cast and machined lugs. It was obvious at the time that the Japs were managing with semi-skilled welders, which must have saved a bit of money.

Anyway, I think Matt's bike will steer fine with any angle that isn't so far out that it looks like a chopper, or so far in that the wheel hits the frame. Featherbed frames are pretty forgiving.
 
Triton Thrasher said:
I'm sure the economics are more complicated. Brazing required a continously fired furnace and a supply of cast and machined lugs. It was obvious at the time that the Japs were managing with semi-skilled welders, which must have saved a bit of money.
Click to expand...

This is actually similar in some respects with what happened with ship building around the WW2 era.

The old system of building with plates hot rivetted together - millions of rivets for a big ocean liner - was replaced by the american system of welding ships together.
This reduced the time for building a big liner (like the Titanic - poor example !) from years to a far shorter time. In WW2, a liberty ship could be welded up in just weeks. (With several crews working on several components at the same time, and then all fitted and welded together.)

With advances in metallurgy, and welding - so the weld or surrounds wouldn't crack when stressed - this obviously transformed how things were built. And motorcycle building eventually became part of this production 'revolution' - took a while though.

Smaller Brit bikes (and others) were welded far earlier than bigger bikes though - small Villiers powered bikes were welded (no lugs) way before the featherbed appeared....
 
Carbonfibre said:
Both frames are cheaply made, but welded ones do costs ore to make than brazed,.
Click to expand...

Tritonthrasher has partly answered this, but you need to reconsider this statement.

There are about 30 lugs large and small in a Norton lugged frame - to cast each of these, bore them all, cut all the tubes, hand fit each of them, get brazing paste in each of them, pin tham all together, braze them in a furnace, cool it off and check and correct for distorton and clean up the brazing residue was an enormous task for one frame.

Welded frames just need the tubes cut to length, bent to shape, the ends profiled (which is a bit of work ) and held in place while being welded in a jig. Then cleaned, checked and corrected for distortion. And off to the enamelling shop. Fraction of the work.
IF the featherbed frames were built of straight tubes, not impossible, then even less work.

Hi-tensile tubing is harder to bend, and needs better welding, but these were race frames built in limited quantities.
 
Carbonfibre said:
Both frames are cheaply made, but welded ones do costs ore to make than brazed,.
Click to expand...

I think you need to explain how a frame could have been made otherwise back then, cheaply or expensive or not ?

Cast aluminium frames mostly only appeared in the 1980s (with some exceptions) they were VERY expensive to make at the time. And when they first appeared, aluminium alloys were in their infancy, and very prone to cracking...

Carbon fibre has only appeared in frames quite recently, and Ducati appear to be still grappling with how to make it perform. Ask Casey Stoner or Valentino Rossi, they just can't stop that front end chattering...
 
Carbonfibre said:
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.
Click to expand...

Would I be right in taking from this that you are saying the production MS frames were not as stiff as the race versions?
Would I also be right in assuming that the MS frames were the same diameter but with a thicker wall?
 
Rohan said:
I think you need to explain how a frame could have been made otherwise back then, cheaply or expensive or not ?
Click to expand...

P.S. Triumph tried a monocoque frame (steel sheets together), it killed the rider while out on test. Others were trying this idea also, but then lost a lot of enthusiasm...

Velo with the LE and Vincent tried other ideas, but while successful don't seem to have caught on.
 
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!
Click to expand...

So you are saying that the Featherbed was IMPROPERLY DESIGNED, and made out of INAPPROPRIATE MATERIALS?

That's pretty amazing. For rubbish, they STILL fetch more than almost any other factory-built frame you could mention; perhaps ANY other!

Carbonfibre said:
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.
Click to expand...

Which has nought to do with the original question.

Carbonfibre said:
Its quite correct that early Japanese machines did not handle that well, but it has to born(e) 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!
Click to expand...

And yet the steady queue of Featherbed frame buyers lines up every morning, like clockwork, even in a bad eceonomy. Furthermore, you don't see very many custom cafe racers using any OTHER frames as a basis for thier projects...
 
When you look back at all that that particular poster has replied to, in other threads too,many other posts are in a similar vein....
 
makes me wonder why the op asked this question on here in the first place,when he had no intention of beleiving any replies with published data on the subject,including factory specs,with all due respect to ken sprayson,if the factory wanted frames building with a 26 deg rake angle i think thats what reynolds would have done or they would,nt have been making featherbeds very long
 
chris plant said:
makes me wonder
Click to expand...

The trouble is, when you don't know the answer, and every tom dick and harry offers up their own opinion, all different, you don't know what to think.
Especially if you convince yourself the frame is not what you thought it was....

Then, the answer is to try it and see.
And ignore all the doomsayers, who don't know anyway...
 
Rohan said:
When you look back at all that that particular poster has replied to, in other threads too,many other posts are in a similar vein....
Click to expand...


He thinks it makes him stand out as a free thinker when he says "It's weak" or whatever. When pressed, he doesn't even know what weak means; just witters on about frames on different planets.

Hey Carbonfibber- Norton Mercury was just a name. It didn't actually come from Mercury.
 
Triton Thrasher said:
Norton Mercury was just a name. It didn't actually come from Mercury.
Click to expand...

Are you sure it wasn't brazed using mercury? If so, that would explain the "inappropriate materials" comment...
 
grandpaul said:
Triton Thrasher said:
Norton Mercury was just a name. It didn't actually come from Mercury.
Click to expand...

Are you sure it wasn't brazed using mercury? If so, that would explain the "inappropriate materials" comment...
Click to expand...

Why not?

It worked on my teeth, for a while.
 
Cheesy said:
Would I be right in taking from this that you are saying the production MS frames were not as stiff as the race versions?
Would I also be right in assuming that the MS frames were the same diameter but with a thicker wall?
Click to expand...

Since the youngs modulus of elasticity for mild steel and 531 is (about) the same, on the frames with same size tubing the tubing stiffness is for all intents the same. The higher tensile strength of the 531 is roughly matched by the thicker wall thickness of the mild steel frames, so the tubing strength is about the same too. The race frames would be a few pounds lighter though, all other things being equal.

Note that this is for the tubing, the actual layout of the frame tubing design considerably affects overall frame stiffness and strength, and the manx and road frames differ in a lot of minor ways here.

Also, the heavy bracing around the steering head means the road frames are considerably stronger here than the manx race frames, and also around the seat area - they had to be, to carry rider +pillion + luggage..

Enough for now ?
 
Rohan said:
Cheesy said:
Would I be right in taking from this that you are saying the production MS frames were not as stiff as the race versions?
Would I also be right in assuming that the MS frames were the same diameter but with a thicker wall?
Click to expand...

Since the youngs modulus of elasticity for mild steel and 531 is (about) the same, on the frames with same size tubing the tubing stiffness is for all intents the same. The higher tensile strength of the 531 is roughly matched by the thicker wall thickness of the mild steel frames, so the tubing strength is about the same too. The race frames would be a few pounds lighter though, all other things being equal.

Note that this is for the tubing, the actual layout of the frame tubing design considerably affects overall frame stiffness and strength, and the manx and road frames differ in a lot of minor ways here.

Also, the heavy bracing around the steering head means the road frames are considerably stronger here than the manx race frames, and also around the seat area - they had to be, to carry rider +pillion + luggage..

Enough for now ?
Click to expand...

Plenty, I was just string a little bit... On a more serious note though, are the top and bottom frame rails parallel on a featherbed?
 
Thought U waz a-stirrin.
But thought someone should post something before some nonsense appeared, folks seem to take more note of the first thung they seeez....

The top and bottom tubes are parallel to each other, sort of.
http://www.nortonownersclub.org/noc-cha ... IMLINE.jpg

Can't vouch for other frames, although the layout is similar, there were about 20 varieties of (factory) featherbeds and probably more...
 
Rohan said:
Thought U waz a-stirrin.
But thought someone should post something before some nonsense appeared, folks seem to take more note of the first thung they seeez....

The top and bottom tubes are parallel to each other, sort of.
http://www.nortonownersclub.org/noc-cha ... IMLINE.jpg

Can't vouch for other frames, although the layout is similar, there were about 20 varieties of (factory) featherbeds and probably more...
Click to expand...

I had a hell of a time trying to convince an old boss (at an engineering company) that a springs stiffness (K value) didn't have anything (well almost nothing 208-210GPa) to do with the steel or its heat treatment but was dependent on its geometry... It doesnt seem to be common knowledge that strength and stiffness are not interchangeable terms
 
You must log in or register to reply here.
Back
Top