FEATHERBED RAKE ANGLE

Rohan · Sep 6, 2011

mattyboy said:
Ken in his own words 'positively confirms' that the headstock angle for all featherbed frames should be 64 degrees with respect to the bottom frame rails; in the manufacture of the frames this was never altered.

On the face of it, this is a very odd statement.
Firstly, its an odd way to quote angles - sitting on and relative to the road is what counts.
So what does that give as a working steering angle ?

And Manx frames were quoted as different steering angles to the roadbikes, and slimlines as different to widelines.
Maybe the angle of the bottom frame rails varies then ??

Triton Thrasher · Sep 8, 2011

Rohan said:
mattyboy said:

- sitting on and relative to the road is what counts.
So what does that give as a working steering angle ?

Click to expand...

Ken Sprayson didn't chose the forks, springs, shocks, wheels or tyres.

Bernhard · Sep 12, 2011

grandpaul said:
"no two alike"

I wonder what the factory's QC allowable margin of error was?

Lets be quite clear on this matter, NO featherbed frames were ever built in house at the factory-none!
They were all built after Rex and Commie Candless designed and build the first few in 16- Gauge Reynolds 531 tube for the Manx only. Later, at the Reynold tube factory by Ken Sprayton and his team in class B tubing for the road going Norton’s, 88,99, 650 & Atlas.
From the information I have heard over the years when owners obtained frames for specials, a large number of frames needed straightening e.t.c - ask Dave Degens of Desda Autos.
Any old featherbed frame could have been involved in at least one accident, could have been done on at least two jigs which were supposed to be identical, but with slight differences.

beng · Oct 21, 2011

mattyboy said:
Ken in his own words 'positively confirms' that the headstock angle for all featherbed frames should be 64 degrees with respect to the bottom frame rails
This query has been now truly put to bed! I can now take my frame to my MOTOLINER man and provide him with the correct info to work with.Matt

I have a letter from Ken Sprayson and a drawing he made of the 1960 Manx frame, and it backs up the info that "mattyboy" has got from Mr. Sprayson. It is drawn with one line coming off the bottom of the frame intersecting another that is the centerline of the steering head. Maybe Mr. Sprayson sends out a form letter and drawing to all who make the same inquiry?

The material I have a friend of mine got directly from Sprayson, it is a 1/4 scale drawing which I have gone over with an architect's scale. I have found two mistakes on the drawing, one on a dimension where it looks like he held his ruler on "1" instead of "0", and another where he maybe got confused and wrote the wrong figure in, but anyone with any training in drafting can see what he was trying to do.

Says Manx frame was 1 1/4" O.D., .064 wall 531 tubing.

Mr. Sprayson says in the letter that all featherbed frames have basically the same dimension whether Manx or road bike. I sort of confirmed this at one point, I did take the complete powertrain from a Featherbed Dominator and bolt it right into a Manx chassis engine plates and all.

Matt Spencer · Oct 22, 2011

Is the narrow bit on the slimline , from where the riders knees were knocking , then .

Ive seen drivle in the past quoteing ( I think ) Wideline 27 , slimline 26 , Manx 28.5 . Naa na naa na naaa. Actually , id assume the variation correct .Hitting a brick wall is apt to shorten the wheelbase .
Wouldve been in 1970s or earlier English ' period ' magazines . IF Id kept HALF of them .

.

Carbonfibre · Oct 22, 2011

Whats the caster angle on the fork yokes fitted to these bikes, and what is the fork stanchion angle with the bike standing on a dead flat level surface, which is being used as fixed datum?

Bernhard · Oct 22, 2011

Just to throw another wobble into the mix, how about asking your question to a frame repairer like those who have a Motoliner Jig or similar?

beng · Oct 22, 2011

mattyboy said:
This query has been now truly put to bed! I can now take my frame to my MOTOLINER man and provide him with the correct info to work with.Matt

Wishful thinking on any internet forum. Despite having facts staring them in the face there is always the group that is incapable of understanding the questions, seeing what matters, seeing the fact, or will simply not believe it.

Rohan · Oct 22, 2011

Yes, and then you get published details like -

Roy Bacon Appendix 13 quotes frame head angles.

Manx 26
Wideline 26
Slimline 24
750 Commando 27
850 Commando 28

Bacons published data is always taken from official sources, so it would be interesting to see why the variation in details here.

Various manufacturrers have recently been quoting "made from Norton blueprints" in respect of some of the reproduction featherbed frames kicking around.
Be interesting to sight those blueprints ?

Rohan · Oct 22, 2011

There is also an interesting story in one of the many published memoirs from AMC days, (Bill Cakebeads was it ?) wherein it is mentioned that featherbed blueprints and production were discovered to vary by 2 degrees. This would have been slimline era.
Did anyone get to the bottom of what that was about ? And how long that had been occurring ?
I gather that Bill was not directly involved, And after 50+ years whispers, rumours and memories are not infallible...

Bernhard · Oct 24, 2011

Rohan said:
There is also an interesting story in one of the many published memoirs from AMC days, (Bill Cakebeads was it ?) This would have been slimline era.
Did anyone get to the bottom of what that was about ? And how long that had been occurring ?
I gather that Bill was not directly involved, And after 50+ years whispers, rumours and memories are not infallible...

''wherein it is mentioned that featherbed blueprints and production were discovered to vary by 2 degrees.''

Nothing unusual in this Plus or Minus tolerance, just because the frame was done in a jig, there would or could have been a certain amount of ‘spring’ when frame was removed from the jig.

grandpaul · Oct 24, 2011

beng said:
I have a letter from Ken Sprayson and a drawing he made of the 1960 Manx frame, and it backs up the info that "mattyboy" has got from Mr. Sprayson. It is drawn with one line coming off the bottom of the frame intersecting another that is the centerline of the steering head.

All that is needed is to absolutely confirm the validity of this drawing and this entire discussion will be settled for eternity.

A basic 2-D drawing with one relative angle measurement. It doesn't get any better than that.

Rohan · Oct 24, 2011

Yes, but the discussion is whether Slimline frames were 24 or 26 degrees. ?
Manx frames ARE KNOWN to be 26 degrees.

Someone local made some replica Atlas frames, using a made up frame jig. (Atlas frames are getting tough to find, good ones anyway). I saw this in action, he used 24 degrees, since thats what the Atlas frames measured out out. Maybe they'd all been in accidents, to all arive at that number ?

And Roy Bacons book quotes 24 degrees for a slimline - all data is taken from official Norton sources in his books, so something is wrong here somewhere...

Rohan · Oct 24, 2011

Bernhard said:
Nothing unusual in this Plus or Minus tolerance, just because the frame was done in a jig, there would or could have been a certain amount of ‘spring’ when frame was removed from the jig.

Where did you work Bernhard, 2 degrees is a fair bit to be out by on bikes sitting in the showroom ? You should even be able to see that for 2 bikes sitting side-by-side.
And you'd imagine that frames coming out of a jig would be subject to remedial work, it would not go unnoticed if springing / warping that much .

It has also been mentioned elsewhere that Nortons manufacturing transfer to AMC / Plumstead brought to light that blueprints had not always been updated in some cases, the operators simply knew what was required. This is mentioned in some of the published memoirs from AMC days. Did Bert Hopwood mention this too ?

Carbonfibre · Oct 25, 2011

The actual fork angle can easily vary by 2 degrees due to different caster angle on the yokes, and I would imagine this is why 2 figures are quoted in regard to a chassis which probably has the same head angle. The effect of differing caster angle tends to be more noticeable than the same change on the head itself, with increased caster tending to provide lighter steering.

Bernhard · Oct 25, 2011

[quote="Rohan"

Where did you work Bernhard, 2 degrees is a fair bit to be out by on bikes sitting in the showroom ? You should even be able to see that for 2 bikes sitting side-by-side.
And you'd imagine that frames coming out of a jig would be subject to remedial work, it would not go unnoticed if springing / warping that much .

quote]
I think you are quoting me out of context there, as unless the frames were manufactured as precision engineered, then even a tolance of + or – 1decree would be acceptable on the production line.
Why the surprise, even the camshafts were not always 100% accurate, don’t ask me how I know!

Carbonfibre · Oct 25, 2011

I doubt very much that these frames were made on proper jigs as such, more likely to have been relatively crude fixtures which denoted the position of the headstock to the swinging arm pivot. As such I would think a 2 degree difference certainly wouldnt have been unheard of, although probably not that common.

Amusingly on aftermarket frames which are made using the bronze welding (brazing) process, its common to remove them from the jig to help with brazing all the joints, and sometimes to need considerable force to get them back into the jig, to complete the final operation, which is fixing the swing arm pivot.

Bernhard · Oct 27, 2011

Carbonfibre said:
I doubt very much that these frames were made on proper jigs as such, more likely to have been relatively crude fixtures which denoted the position of the headstock to the swinging arm pivot. As such I would think a 2 degree difference certainly wouldnt have been unheard of, although probably not that common.

Amusingly on aftermarket frames which are made using the bronze welding (brazing) process, its common to remove them from the jig to help with brazing all the joints, and sometimes to need considerable force to get them back into the jig, to complete the final operation, which is fixing the swing arm pivot.

Also from some of the frame jigs that I have seen, the headstock angle is adjustable for making different types of frames, so that may be another explanation......Although I would like to make it clear that these jigs were not the Norton featherbed frame jigs.

Rohan · Oct 27, 2011

If Reynolds were turning out ~200 frames per week, all about the same, an adjustable jig is rather unlikely. ?
In fact, to turn out 40 frames a day, how many jigs would be required ?
How big would the team be that could do that week in week out.

Given that Reynolds were doing this for the best part of 20 years, did any of the motorcycle mags visit and do a write-up, with pics. Be interesting to see ?
Anyone ever seen a featherbed jig ? Or was it a series of smaller jigs ?

Reynolds still exist, though in different hands these days, what is their take on this ?
Are the old jigs still sitting out the back ?
Blueprints still pinned to the wall. ??

Be very interesting to see those blueprints, answer a lot of the questions crashing around here...

P.S. For many years it was said that those blueprints weren't available, or didn't exist.
How is it that suddenly a number of concerns are saying they have them, or access to them ?

Carbonfibre · Oct 28, 2011

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!

FEATHERBED RAKE ANGLE

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