Featherbed frame design went against all engineering princip

acotrel · Nov 6, 2014

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...

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

I think Rohan was referring to the pre-war Sunbeam singles which were serious racing bikes. The inline twin was post war and bloody horrible.

acotrel · Nov 6, 2014

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.

I ran into a friend of mine in the mid-70s whom I had not seen for a while. He'd been racing on the IOM on a manx. He was certainly no chicken, however he told me that when he first went there his best lap was 84 MPH. However he said that if you keep going there you get faster. When I was about 19 years of age, I failed a few exams at night school and my idiot mate suggested I join him at the company he worked for and we could both be transferred to London and go racing. I decided to stay here and have a family. I know now that the way I used to ride, I'd probably have come home in an urn. That I did not do that racing is now one of my greatest regrets. Those videos of Dave Roper on the G50 on the IOM are scary. It's is not the speed down the straights, it's the speed they hold in corners with those solid objects all around.

baz · Nov 6, 2014

Re: Featherbed frame design went against all engineering pri

LUCKY DAVE said:
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.

The one I rode must of had something wrong with it because every time you changed gear it felt like it had a hinge in the middle and the handling appalling my mate owned the bike and said it was normal !! As I say this is my opinion and I believe there was something wrong ..the only bike I've ridden worse than that was a plunger A10 with SM tires .....baz

74ok · Nov 6, 2014

Re: Featherbed frame design went against all engineering pri

https://www.google.ca/search?q=harley+d ... 8QeakYCgDQ

http://books.google.ca/books?id=XgSgJnl ... em&f=false

Featherbed frame design went against all engineering princip

http://books.google.ca/books?id=XpCM0o_ ... em&f=false

Jagbruno · Nov 6, 2014

Re: Featherbed frame design went against all engineering pri

ludwig said:
Jagbruno said:

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

Click to expand...

Fine .
Now , If you where to put some decent brakes on that 'thing' ..

Yep.
Plan for the winter. AP racing calipers and proper master cylinder.
I am not rich, and I had to rebuild the thing and make it run first. It does, and very well. The brakes are on the weak side, obviously, but not too bad during the running in period. Now that is over... :mrgreen:

texasSlick · Nov 6, 2014

Re: Featherbed frame design went against all engineering pri

"Fine .
Now , If you where to put some decent brakes on that 'thing' .."

Ludwig

"I build my vehicles to go, not stop!"

Ettore Bugatti (when questioned why his cars had bad brakes)

Jagbruno · Nov 6, 2014

Re: Featherbed frame design went against all engineering pri

texasSlick said:
"Fine .
Now , If you where to put some decent brakes on that 'thing' .."

Ludwig

"I build my vehicles to go, not stop!"

Ettore Bugatti (when questioned why his cars had bad brakes)

What's not to love with Ettore Bugatti, I ask you?

:lol:
:mrgreen:

worntorn · Nov 6, 2014

Re: Featherbed frame design went against all engineering pri

In the same vein , Enzo Ferrari once said " aerodynamics are for people who don't know how to build engines"

Glen

acotrel · Nov 6, 2014

Re: Featherbed frame design went against all engineering pri

Good brakes are every bit as necessary as a good motor if you want to go quick. I once won a race with a drum braked Suzuki Cobra, which ran out of brakes on the first lap. I simply took a very wide line going into corners and sort of went into a glide around them trying not to do anything sudden. At one stage there was guy on a BSA Gold Star ahead of me as I lined the corner up, and he was on my line. I was going far too quick, totally committed and I couldn't stop. Somehow I managed to get underneath him without knocking him off his bike. The fellas in the pits could smell my brakes burning as I passed them during the race. Also when I started racing the Seeley, I had a single Suzuki disc with a Lockheed caliper, and the standard wide ratio gearbox - the bike was hopeless, almost impossible to ride fast. I now use two discs with the old style asbestos pads in two calipers, and a very close ratio box, and methanol fuel to get it going. It is a very good thing to ride, I kid you not. I never imagined it would be so good with such a relatively unmodified motor, before I actually raced it.

Jagbruno · Nov 6, 2014

Re: Featherbed frame design went against all engineering pri

worntorn said:
In the same vein , Enzo Ferrari once said " aerodynamics are for people who don't know how to build engines"

Glen

The same also said that the E-type Jag was the most beautiful car ever made and that he wished Ferrari would have designed it...I can only concurr...Besides my vintage bike I drive mine as often as I can... 8)

acotrel · Nov 6, 2014

Re: Featherbed frame design went against all engineering pri

Jagbruno said:
worntorn said:

In the same vein , Enzo Ferrari once said " aerodynamics are for people who don't know how to build engines"

Glen

Click to expand...

The same also said that the E-type Jag was the most beautiful car ever made and that he wished Ferrari would have designed it...I can only concurr...Besides my vintage bike I drive mine as often as I can... 8)

A friend had a E-type Jag, it was like riding on a wooden cart drawn by a horse. Another had a 911S Porsche, it felt better than a Z900 Kawasaki. The same guy had a 300SL Mercedes and a Cord. I wouldn't get into the 300 SL with him, he was very rich and could afford the fines. The other thing he had was a 750cc MV4, he paid $4000 for it and it came with every possible spare part. (In those days that was the price of a new Ford Falcon). He'd been a fairly respectable B Grade racer on Manxes in the 50s.

Jagbruno · Nov 6, 2014

Re: Featherbed frame design went against all engineering pri

Your friend's E-type must have been seriously wrong somewhere, mine is extremely comfy, I have logged very long trips (over 1000km in a day) on it without any problem...a vintage 911 is spartan by comparison...at best...

If you are ever in Brussels, I'll prove to you... 8)

ashman · Nov 6, 2014

Re: Featherbed frame design went against all engineering pri

As for chain wear on my Featherbed, I get very long life out of my chains, my last chain has done well over 30,000 miles, it been on the bike that long I can't even remember when I brought it, it is still good for many more miles but decided to replace it with one of Andy's chains, I will hang the old one on the wall if I need a spare.
As for good brakes, I do have good brakes on my Featherbed, but when riding fast or slow I don't use my brakes much, but I know they are there when needed, I slow down before major corners using my motor and once in the corners use the power of the motor to push the bike through the corners, pushes the bike down and makes it grip even better, my 850 Featherbed is a way lot lighter than a Commando and steers a lot quicker than a Commando without any effort on the rider, I built my Featherbed so nothing scraps, exhaust tucked in close to the frame, foot pegs sit high and now with better tyres than the old K81s I push it even harder, most of the weight is down low, so not much weigth up top except for the fat bugger that rides it, only a few of my trusted friends have ridden my Norton and it blows them out how it handles, how light it feels, how smooth it is for a hard mounted engine and how quick it is.

All I can say is I love my hot rod 850 Featherbed and would't change a thing, it works so well.

Ashley

wakeup · Nov 7, 2014

Re: Featherbed frame design went against all engineering pri

That Bob Cox "Featherlastic" is pretty speccy. I still reckon that it would suffer from high chain wear. Anyway, a beautifully built motorcycle.
Were the pre war Sunbeam singles rubber mounted??
Which leaves the question "why didn't NV do it?"

Some speculative reasons why....
1/ Needed to be seen to be different from traditional f'bed, and therefore making progress (in management speak "new" = "better")
2/ In engineering terms having a chain drive with both centres moving is normally considered a bad thing
3/ With all due respect to the featherlastic, the motor seems to be further back than standard. This will have an effect on handling

cheers
wakeup

74ok · Nov 7, 2014

Re:

wakeup said:
Which leaves the question "why didn't NV do it?"

Some speculative reasons why....
1/ Needed to be seen to be different from traditional f'bed, and therefore making progress (in management speak "new" = "better")

after saying, that is if it was actually ever even said, but prob good bet some slam dunk thoughts along the lines of "Featherbed frame design went against all engineering principles" were made

dude then had to come up with something ("new" = "better") big time, otherwise his legacy would have that of an idiot

this is how it played out
http://www.nortonownersclub.org/models/commando

With the appearance of the revolutionary Commando in 1967, the Atlas became somewhat redundant and was deleted together with the 650SS from the range in 1968.

Fast Eddie · Nov 7, 2014

Re: Featherbed frame design went against all engineering pri

When I stripped my Commando, I was very surprised how light the frame felt.

Is it just because I'm getting stronger... Or is it lighter than, say, a featherbed?

Anyone know how they compare?

acotrel · Nov 7, 2014

Re: Featherbed frame design went against all engineering pri

You would need to weigh the engine plates and isolastics with the commando frame, and the aluminium engine plates with the featherbed frame. I can see value in the isolastics if the ends of the pivot are fastened as in the normal featherbed construction. It would force the engine/gearbox assembly to rotate around the pivot when vibrating, and the torque reaction would be directed that way too. You could do it to a normal commando if you redesigned the Z plates and used a longer pivot shaft. That way the handle bars and your backside and your brain would remain in communication with the rear tyre contact patch.

Fast Eddie · Nov 7, 2014

Re: Featherbed frame design went against all engineering pri

acotrel said:
You would need to weigh the engine plates and isolastics with the commando frame, and the aluminium engine plates with the featherbed frame. I can see value in the isolastics if the ends of the pivot are fastened as in the normal featherbed construction. It would force the engine/gearbox assembly to rotate around the pivot when vibrating, and the torque reaction would be directed that way too. You could do it to a normal commando if you redesigned the Z plates and used a longer pivot shaft. That way the handle bars and your backside and your brain would remain in communication with the rear tyre contact patch.

You've mentioned that Z plate / swinging arm pivot before... But you seem to ignore the fact the clutch is a tad in the way...

Rohan · Nov 7, 2014

Re: Featherbed frame design went against all engineering pri

wakeup said:
Were the pre war Sunbeam singles rubber mounted??

No.
A different Company owned them postwar (BSA).

And prewar they were fast sporting singles.
The Model 90 among them, which refers to 90 mph, was exceedingly fast for its era,
I doubt Nortons even produced anything stock in road models that was guaranteed that quick.

Postwar, BSA acquired Sunbeam, and produced 'gentlemen's tourers' - the ohc inline twin mit shaft drive.
It perhaps should be pointed out that gazillions of cars, trucks, buses etc have had rubber mounted engines and drivetrains,
it was very rapidly established that this gave a smooooooth ride compared to metal-to-metal engine mounts.
Going back a century or more.... ?

wakeup · Nov 7, 2014

Re: Featherbed frame design went against all engineering pri

Rohan said:
wakeup said:

Were the pre war Sunbeam singles rubber mounted??

Click to expand...

No.
A different Company owned them postwar (BSA).

And prewar they were fast sporting singles.
The Model 90 among them, which refers to 90 mph, was exceedingly fast for its era,
I doubt Nortons even produced anything stock in road models that was guaranteed that quick.

Postwar, BSA acquired Sunbeam, and produced 'gentlemen's tourers' - the ohc inline twin mit shaft drive.
It perhaps should be pointed out that gazillions of cars, trucks, buses etc have had rubber mounted engines and drivetrains,
it was very rapidly established that this gave a smooooooth ride compared to metal-to-metal engine mounts.
Going back a century or more.... ?

That was pretty much my understanding. The S7 was pretty grim, big balloon tyres, handling pretty awful, and gutless, but the S8 ("sports" version) was a fairly good touring bike, albeit so powerful that rice puddings needn't quiver in fear........ Apparently the S8 handled a bit better as well, although no featherbed.
cheers
wakeup