Featherbed frame design went against all engineering princip

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Re: Featherbed frame design went against all engineering pri

Peter Williams on a Factory JPN Racer lapped the Isle of Man faster on a Commando
than a featherbed had EVER done, back in the 1970s,
so there can't be too many "handling errors", can there ?

Maybe owners should keep their isolastics shimmed up to factory specs,
and not become ole slopbuckets.....
 
Re: Featherbed frame design went against all engineering pri

No doubt some featherbed owner will now chime in,
and point out that his pride and joy laps faster with the head steady removed on their featherbed.

Or have we had that thread here already too ??
 
Re: Featherbed frame design went against all engineering pri

Stephen Hill said:
I am not sure if my question deserves a new thread, but so far this thread contains every tangent known to mankind, so here goes nothing.

I think one of the reason the Featherbed frame outhandles the Commando frame is it does not have the slop introduced by the isolastics. Everyone knows that the tighter you adjust the isolastics, the better the bike will handle. If the Commando has a better designed frame than the Featherbed, why didn't it just rubber mount the engine and not the swingarm, which introduces all the handling error??

Stephen Hill
Click to expand...

By rubber mounting the engine in a featherbed and retaining the frame mounted swinging arm, the required relatively stable relationship between the final drive sprocket and the rear wheel sprocket would be lost. The result would be unacceptably high rear chain wear, and a very low rear chain life. Even if a "Sort of Commando" style of isolastics were adopted the chain alignment shimming (side to side) would have to be separated from the engine vibration shimming, somehow. Bearing in mind the fear and wonder that standard Commando iso shimming seems to cause, this additional shimming requirement would cause unbearable angst in the Iso Featherbed community.
cheers
wakeup
 
Re: Featherbed frame design went against all engineering pri

As I see it, the featherbed was a good design in it's day. It used a large amount of metal to provide the characteristics deemed necessary, this made it relatively heavy by later standards, and because of all the bends it was expensive to manufacture.
So in the 60s, when everyone was saying that British twins vibrate, the Big Bananas at NV realised that to get an edge they had to make a motorcycle that didn't vibrate and handled roughly as well, if not better than, a featherbed. So some very smart blokes invented the Isolastic system. The rest is history.
It's called design evolution or something like that. It's very seldom that a perfect design is created at the first attempt, especially something as complex as a high performance motorcycle. A motorcycle designer would not be employed for very long if he tried to design a motorcycle without learning from what has gone before, what works and what doesn't.
After all is said and done I still loved my 650ss for it's high speed stability and excellent handling, old fashioned it may have been, but it did (and does!) work so well.
cheers
wakeup
 
Re: Featherbed frame design went against all engineering pri

Rohan said:
Peter Williams on a Factory JPN Racer lapped the Isle of Man faster on a Commando
than a featherbed had EVER done, back in the 1970s,
so there can't be too many "handling errors", can there ?
Click to expand...

doesn't this info speak volumes?

this is the type of info that gets my attention tho dunno if the commando here ran a higher horsepower engine in this situation, than a featherbed may have,

i'd think it would be known at this point which is a better handler based on race results with equal horsepower engines,

it doesn't seem like the question has been put to rest, if the commando is actually a faster frame, or even comparable to a featherbed, that would be quite an engineering achievement having tamed vibes at the same time,

then regardless of the above, folks went for and picked the commando vs featherbed option as far as a bottom line goes,

i think there was more to "Featherbed frame design went against all engineering principals" than just curved or rounded tubes, rather, an overall engineering approach to a frame, including real world driving comfort
 
Re: Featherbed frame design went against all engineering pri

well a 500cc manx as done the IOM at 106 mph lap. not bad for a one lunger! in a featherbed frame.
 
Re: Featherbed frame design went against all engineering pri

john robert bould said:
well a 500cc manx as done the IOM at 106 mph lap. not bad for a one lunger! in a featherbed frame.
Click to expand...

Modern tyres.
Imagine what Peter Williams could have done with those back then....
 
Re: Featherbed frame design went against all engineering pri

Put a JPN motor in a Featherbed frame and set it up right with good brakes and moden tyres, I wonder how fast it would be then around the IsMan and Peter Willams on board, now that would have been a great test, my 850 Featherbed is no race bike but It will do well over the ton and more if pushed, it is very stable at that speed and grips the road like glue, in my younger days of riding my Featherbed, the only speed to sit on was over the ton, but now I am more muture I still take it to the ton every so often but now mostly sit between 70 to 90 when on the outback roads, it will sit on these speeds all day with out any problems.

Lets see how long running a Featherbed without a strong head stay will be on the road for, not very long me thinks and in 34 years of riding my Featherbed I have never had any cracks, broken welds or nothing, no things falling off and I still have every nut and bolt that went on the bike 34 years ago, except for the top gearbox nut (forgot to tighten it up) and one nut off a muffler mount, so not bad for a bike that is surpose to vibrate as much as everyone reconds they should.

I am no engineer and only had limit schooling but what ever I done when i built my 850 Featherbed it has worked great for me and my riding style and it blows a lot of my mates out that I have been riding with for over 40 years and scares the shit out of any new riders that come out to play with us or try to play with us.

Ashley
 
Re: Featherbed frame design went against all engineering pri

Norton had race 650ss and 750cc Atlas before the JPN era, in featherbeds.
And the Dunstall and Gus Kuhn race teams when Doug Hele left,
and the Norton AMC empire started crumbling....

To AVERAGE a 100+ mph lap of the Isle of Man,
the bikes are pulling 130 or even 140 ? mph on some of the straighter bits.
Even the fully faired 500cc Manx and 500cc domiracer in the early 1960s...

Anything that is in that league is a fairly capable bike !!
 
Re: Featherbed frame design went against all engineering pri

ashman said:
It will do well over the ton and more if pushed, it is very stable at that speed and grips the road like glue.

Ashley
Click to expand...

My own very basic Wideline special is noticeably steady at over 100.
 
Re: Featherbed frame design went against all engineering pri

Triton Thrasher said:
ashman said:
It will do well over the ton and more if pushed, it is very stable at that speed and grips the road like glue.

Ashley
Click to expand...
Click to expand...

My own very basic Wideline special is noticeably steady at over 100.[/quote

I'll third that with my 63 Atlas!

Slick
 
Re: Featherbed frame design went against all engineering pri

On the broad topic of engineering principles, I asked why the swingarm on the Commando was rubber mounted, which compromises the handling of the bike? Wakeup responded as as below.

Other bikes have rubber mounted engines, such as Harley Davidsons, Sunbeams, etc. Why could they do it but not Norton?

Stephen Hill


"By rubber mounting the engine in a featherbed and retaining the frame mounted swinging arm, the required relatively stable relationship between the final drive sprocket and the rear wheel sprocket would be lost. The result would be unacceptably high rear chain wear, and a very low rear chain life. Even if a "Sort of Commando" style of isolastics were adopted the chain alignment shimming (side to side) would have to be separated from the engine vibration shimming, somehow. Bearing in mind the fear and wonder that standard Commando iso shimming seems to cause, this additional shimming requirement would cause unbearable angst in the Iso Featherbed community.
cheers"
wakeup
 
Re: Featherbed frame design went against all engineering pri

Stephen Hill said:
Other bikes have rubber mounted engines, such as Harley Davidsons, Sunbeams, etc. Why could they do it but not Norton?
Stephen Hill
Click to expand...

Good question. Sunbeams were shaft drive, and were designed with similar engine mountings to a car. So the rear wheel could be effectively isolated from the wobbling engine/gearbo lump. I would hesistate to suggest that HD have ever had anything to do with good design, but that might light a few fires, so I won't say it. However I did hear that Bob Trigg, one of the recognised three designers of the Isolastic system, was recruited by HD, when NV went under. If it's true then maybe he was involved in any HD attempt to smooth out those HD vibes. Assuming that a few HD owners also get on here, maybe one of them could describe the HD rubber mounting system, is it anything like the Iso system?

In any event, it's not just the rubber mounting that makes the Iso system so good, it's the way that the rubber mounted bits (engine/gearbox/cradle/swinging arm etc) are accurately aligned, so that they can only move in a vertical direction, not sideways. I still maintain that having an Iso system mounting the engine and gearbox in a featherbed, with a frame mounted swinging arm would result in at best, very very rapid chain wear. What do the people who build Iso Featherbeds do? Do they have frame mounted swinging arms or is the swinging arm mounted to a engine/gearbox cradle, like a Commando?

Also, neither Sunbeam or HD have been aimed at the high quality handling/steering end of motorcycing. Although I believe that the Sunbeam S8 (so called "Sports" model) was a competent handler, it could hardly be considered as a high performance machine.

Another thing to consider, and another (minor) reason for the superceding of the featherbed, was the fact that it was heavy. From memory I seem to remember that a f'bed was 8 or 9 ibs heavier than a Commando frame.
cheers
wakeup
 
Re: Featherbed frame design went against all engineering pri

I wonder if that frame weight difference includes the Commando Isos. For some reason the Featherbed Atlas or 650SS is about fifteen or twenty pounds lighter than the 750 Commando, according to most info. Seems the Featherbed frame can't be all that heavy, even though the road going version is relatively thick walled mild steel.

Glen
 
Re: Featherbed frame design went against all engineering pri

wakeup said:
Stephen Hill said:
Other bikes have rubber mounted engines, such as Harley Davidsons, Sunbeams, etc. Why could they do it but not Norton?
Stephen Hill
Click to expand...
In any event, it's not just the rubber mounting that makes the Iso system so good, it's the way that the rubber mounted bits (engine/gearbox/cradle/swinging arm etc) are accurately aligned, so that they can only move in a vertical direction, not sideways. I still maintain that having an Iso system mounting the engine and gearbox in a featherbed, with a frame mounted swinging arm would result in at best, very very rapid chain wear. What do the people who build Iso Featherbeds do? Do they have frame mounted swinging arms or is the swinging arm mounted to a engine/gearbox cradle, like a Commando?
wakeup
Click to expand...

The featherlastics use the normal frame mounted swinging arm, with plastic guides, upper and lower, attached to the swinging arm, for the chain. The system seems to work quite well, and they don't have particularly rapid chain wear.

If you search featherlastic bob cox, you should find some pictures. Bob wrote up the build process, including some great pictures.

Ken
 
Re: Featherbed frame design went against all engineering pri

I would hesistate to suggest that HD have ever had anything to do with good design, but that might light a few fires, so I won't say it. However I did hear that Bob Trigg, one of the recognised three designers of the Isolastic system, was recruited by HD, when NV went under. If it's true then maybe he was involved in any HD attempt to smooth out those HD vibes. Assuming that a few HD owners also get on here, maybe one of them could describe the HD rubber mounting system, is it anything like the Iso system
Click to expand...
HD uses an improved version of isolastics, with cross rods/spherical joints -similar to the aftermarket head steadys some of us use- at three points, front, back, and cylinder head to eliminate any side play and make for smoother running as there is no isolastic bushing friction or fiddly adjusting. Ever.
Ride one, it works very well.
Exactly like the Commando design, the HD swingarm/engine is one assembly with the swingarm mounted rigidly to the engine, the frame/forks/rider another assembly.
HD's system was designed by Erik Buell.
 
Re: Featherbed frame design went against all engineering pri

The Sunbeam didn't have a chain or a swing arm, if that helps the debate.
 
Re: Featherbed frame design went against all engineering pri

texasSlick said:
Triton Thrasher said:
ashman said:
It will do well over the ton and more if pushed, it is very stable at that speed and grips the road like glue.

Ashley
Click to expand...
Click to expand...

My own very basic Wideline special is noticeably steady at over 100.[/quote

I'll third that with my 63 Atlas!

Slick
Click to expand...

I'll fourth that with my Slimline racer, 850 engine with PW3 camshaft, box section swingarm, special crankshaft, prepared head, Dunstall exhaust and fairing.

That 'thing', at any speed, is as stable on the tarmac as an anvil bolted to the ground. Not a hint of wobble. Ever.

Featherbed frame design went against all engineering princip
 
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