Featherbed frame design went against all engineering princip

Re: Featherbed frame design went against all engineering pri

L.A.B. said:

Jose Refit said:

As I implied, I've never seen any quotes from Dr Bauer regarding derogatory comments pertaining to the featherbed frame,

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Bob Trigg, the designer who worked under Dr. Stefan Bauer on the Commando frame (and whose name also appears on the patent) says the following on the Duke Norton video: http://www.dukevideo.com/prd1121/Best-o ... Norton-DVD

.....and Dr. Bauer, said OK, we need a completely new frame-because he didn't like featherbed frame, he looked at it not from the point of view of a motorcyclist but from the point of view of an engineer, and he always said: "Any frame with a bent tube is either unnecessarily weak or it's too heavy."

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Therefore I'm inclined to believe what he says is true.

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I agree with the above quote. Any bent tube will act like a spring in compression and tension and is inefficient regarding strength/weight and so it follows that a bent tube is too heavy which means it's an inefficient design. But my original point was beware of taking things for granted (especially) off the internet,

Jose.

Re: Featherbed frame design went against all engineering pri

Why is Captain Obvious (Alotment) posting under a fake ID ?

Re: Featherbed frame design went against all engineering pri

Jose Refit said:

L.A.B. said:

Jose Refit said:

As I implied, I've never seen any quotes from Dr Bauer regarding derogatory comments pertaining to the featherbed frame,

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Bob Trigg, the designer who worked under Dr. Stefan Bauer on the Commando frame (and whose name also appears on the patent) says the following on the Duke Norton video: http://www.dukevideo.com/prd1121/Best-o ... Norton-DVD

.....and Dr. Bauer, said OK, we need a completely new frame-because he didn't like featherbed frame, he looked at it not from the point of view of a motorcyclist but from the point of view of an engineer, and he always said: "Any frame with a bent tube is either unnecessarily weak or it's too heavy."

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Therefore I'm inclined to believe what he says is true.

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I agree with the above quote. Any bent tube will act like a spring in compression and tension and is inefficient regarding strength/weight and so it follows that a bent tube is too heavy which means it's an inefficient design. But my original point was beware of taking things for granted (especially) off the internet,

Jose.

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While coming at the issue as an engineer rather than a motorcyclist may be beneficial by bringing a fresh perspective and not sticking to convention for its own sake, ultimately your customers and development engineers are motorcyclists and it's unwise to dismiss previous designs osimply because they don't adhere to certain principles. The featherbed worked well but of course it could be improved on.

The issue of bent tubes acting as springs, quite right, they do, but the question you have to ask is whether that action is beneficial in the context of a motorcycle frame. It could well be that acting as a spring helps.

Re: Featherbed frame design went against all engineering pri

Anyone noticed how the Isolastic frame looks like a Duplex Triumph frame, and regards to Dr Steph not liking bent tubes ,why did he design a frame with "just" as many bends as a feather bed...Take away the featherbeds two bends on the top rail by the head ,because they are braced..forming bacily two straight tubes ..then the commando frame as just as many bends!
Thinner ,larger tubes would have done just as well...The "Doc" knew the big engine vibed and the simple and "cheaper" answer was a rubber mounted power plant, as the feather bed had wide spaced top tubes this made fixing the head to them unsuitable...did'nt take a Dr to replace the twin feather bed top tube's with one larger , and pronouce "wow ,look what i had done"
Norton knew they needed a fresh " LOOK" at an affordable price, emerging markets threatened sales , but it would'nt take much to keep exsisting Old Norton Boys happy ...all it took was 10 /- [ 50p] of rubber washers...simple .
norton had no money to address the real problem..that Vibration twin ,and if a few big rubber washer's could keep the boat a float a few more years ..

Over to you Jose, i will eat my hat if you dont respond :lol:

Re: Featherbed frame design went against all engineering pri

Some MotoGP frames are deliberately built with spring in them to suit the available tyres. That is at the extreme end of the sport however, and I doubt that spring in a featherbed frame is beneficial except that it might defer cracking a bit. As far as leaning a bike in corners is concerned, I don't consciously do it, nor do I deliberately reverse steer to induce the lean. The bike does it for me - it is very quick steering and wherever I put my mind, that is where it goes. If I get into deep shit, I sometimes climb off the side of the bike keeping it as vertical as possible and drag it around the corner trying not to run out of road. If I start to hit the dirt I stand it up and point it straight, and then try to gently turn it to stay away from the fence. (Never panic.) My childhood was spent racing on rock hard tyres with drum brakes. If the brakes fade or you go too fast in the wet you can easily find yourself doing the sort of antics I have described. If you are going to start racing, begin with a nice safe bike with good tyres and disc brakes. I'd choose a VFR400 Honda, you'd have to be really dumb to drop that.

Re: Featherbed frame design went against all engineering pri

here's what they ended up against
here's what the buying public had to say,
wiki production numbers 69-75
CB750K0 53,400
CB750K1 77,000
CB750K2 63,500
CB750K3 38,000
CB750K4 60,000
CB750K5 35,000
CB750K6 42,000

not bad considering or despite the norton assessment

wakeup said:

84ok said:

looks like at this point norton went against reality

"what are we up against?"[/size][/b]
Almost the ONLY area that the Honda was considered to be better was braking in the dry[/size][/b],

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Which particular bit of reality did the accumulated experts go against??

The Honda was better at braking in the dry, it was not better at braking in the wet. The first generation of Japanese disc brakes were next to lethal in the wet. The Commando WAS faster, handled and steered better, the first 750/4 handled like a sockfull of diarrhoea, the Commando accelerated better and was more economical. Full stop.
The point was, that whilst the Commando was considered to be less reliable than the Commando, at the time there was little that could practically be done.
cheers
wakeup

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Re: Featherbed frame design went against all engineering pri

You guys sure about that :roll:




It would appear that a '68 commando vs a '69 honda is a bit of a bad comparison.... basically the same price, does a 1/4 mile quicker, does the 1/8 quicker as well, higher top speed (if you're an enthusiast). These figures went up for the commando and down for the honda, but you get the point. This is also stock for stock, when modified it becomes quite the thing to compare. I'd still ride the norton...but there is quite a reason why people bought 750's...even if in stock shape they drove like appliances.... I will also point out that arguing over minor performance quibbles on stock bikes is largely irrelevant today, considering how cheap performance is and how often people change things on these bikes.

Also as for the curved tube comment...it's still a rather valid point that the featherbed frame leaves something to be desired, which is why you don't see motogp racers after the 70's sticking to the exact same design. One can hardly argue that a double cradle frame is not an effective frame to use...but there are many weakpoints that were refined over the years. One of the main developments in frame design from the 80's onwards was bracing the neck torsionally, increasing bending stiffness of the frame, and strengthening and reinforcing the swingarm to keep it from flexing. Hence bellcranks on shocks, hence monoshocks, hence spar/beam frames with stressed member engines.

Re: Featherbed frame design went against all engineering pri

to get easy more, playing with cams on the 4 is childs play and chump change, not mention electric start

a quick google of honda cb 750/4 - honda 750 four speaks volumes

http://world.honda.com/history/challenge/1969cb750four/

By introducing the CB750 FOUR, the company planned to become the world's top manufacturer in terms of quality as well as volume.

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http://world.honda.com/history/challeng ... age02.html

To facilitate the collaborative process among design engineers and production personnel, common engineering targets were established for product development. These included the following:

[1] Ensure stability during high-speed cruising (between 140 and 160 km/h) on highways, yet retain an ample margin of output for effective maneuvering in traffic.
[2] Provide a braking system that is reliable and resis tant to high loads by anticipating frequent rapid decelerations from high speeds.
[3] Minimize vibration and noise in order to reduce rider fatigue during long-range cruising. Provide an ideal riding position for comfort and the proper operation of controls based on human-engineering principles, and design the mechanisms so that the rider can easily learn how to operate them.
[4] Ensure that various ancillary devices, such as lights and instruments, are large and reliable. They must be designed to help the rider make sound judgments and ensure sufficient visibility for surrounding vehicles.
[5] Extend the service life for each device and ensure that it provides for easy maintenance and servicing.
[6] Create original designs that also are easy to mass produce by utilizing newer, better materials and production technologies. This applies particularly to cutting-edge surface-treatment technologies.

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Re: Featherbed frame design went against all engineering pri

Rohan said:

Just for the record, CB450 pistons can't fit a CB750/4.
Thats a 7mm bore increase per cylinder !

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X-file said:

The pistons from the CB 350 twin were used to overbore a CB 750 Honda. That gave 830 cc.

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No they weren't - CB350 std pistons are only 1mm larger than CB750/4 pistons,
so wouldn't take it anywhere near over 800cc.

Yoshimura and Kingston etc big bore kits for the CB750/4 all used custom made pistons,
Onda didn't supply anything in stock sizes that could be used for this....

Re: Featherbed frame design went against all engineering pri

X-file said:

The pistons from the CB 350 twin were used to overbore a CB 750 Honda. That gave 830 cc.

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That is correct, the 836 cc kits used modified oversize CB350 pistons, the standard CB350 piston was already 3mm oversize compared to the 750's 61mm bore.

Re: Featherbed frame design went against all engineering pri

Re Honda fans;

Cycle Magazine, March 1970 Superbike Seven- the Norton Commando blitzed the field. A search here will bring up lots of discussion. Serious Commando lovers generally own a copy or two.

There is also a forum for lovers of CB750 s out there somewhere, might be CB750.com
. You might be able to hook up with a dude named JAW and another named Carbonfibre there. :idea:

Glen

Re: Featherbed frame design went against all engineering pri

Anyone seen Great British Bikes Video?, Bob Trigg talking about the Commando design, interesting. The first rubbers incured Vibes at 6000, cut in half 4000.then cut in half again 2300, guess the engine was about to jump out of the frame at this point?

Re: Featherbed frame design went against all engineering pri

You seem to be confusing your imagination with your memory, are you related to Rohan. :lol:
At least Jose Alotment seems to have vanished.

Most folk know a frame can be made to rigid, most are about feedback or controlled deflection and that seems to be a high point of the Featherbed.
Great design, the rest is history.

worntorn said:

Cycle Magazine, March 1970 Superbike Seven- the Norton Commando blitzed the field. A search here will bring up lots of discussion. One eyed Commando lovers generally own a copy or two.

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Re: Featherbed frame design went against all engineering pri

maan, what a story! and a lesson in history, i doubt there are many here who had a taste (few years) of norton back in the late 70s, as a first bike for me, didn't know anything or much about the history other than in many ways it was all gloom and doom coming to an end for brit bikes,

then ~ 40 years goes by and i finally end up stumbling on this forum, and am completely blown away,

i never could or would have imagined what norton commando from back in the day would become today

Re: Featherbed frame design went against all engineering pri

'i never could or would have imagined what norton commando from back in the day would become today'

Just because we never believed in commandos back then, it does not mean they weren't any good. I watched Jeff Curley ride a near standard one to a few wins against 750cc Japanese fours in the early 70s.

Re: Featherbed frame design went against all engineering pri

84ok said:

maan, what a story! and a lesson in history, i doubt there are many here who had a taste (few years) of norton back in the late 70s, as a first bike for me, didn't know anything or much about the history other than in many ways it was all gloom and doom coming to an end for brit bikes,

then ~ 40 years goes by and i finally end up stumbling on this forum, and am completely blown away,

i never could or would have imagined what norton commando from back in the day would become today

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I'm not sure exactly what you mean, but having bought a 75 Commando 850MKIII new back in the day, I recall that it was pretty quick and a smooth ride. I was coming from a 66 BSA 650, so the smoothness and lack of vibration of the Commando compared to the BSA was obvious. I actually remember marveling at the Commando back then. I raced a few CB750's and could take most of them if there were curves involved. Buddies Harley was no match except for straights over a couple of miles long because his top end speed was better. But then my recollection is probably horrible after all these years.

Re: Featherbed frame design went against all engineering pri

Time Warp said:

You seem to be confusing your imagination with your memory, are you related to Rohan. :lol:

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No imagination needed here:




Nor here:

'Next, the Norton, easily the easiest of the seven to ride"

"(Commando) Handling is extremely light and precise for a big machine. All the controls are in the right place and they work as they should......Drifting the machine through sweepers was easy and non frightening."

and, of course
"There is no bothersome vibration that can be felt by the rider during hard riding. Indeed, the only vibration that is noticeable on the Commando is the narrow period that comes right at 2000 rpm, when the throttle is tweaked off idle."

Glen

Re: Featherbed frame design went against all engineering pri

Time Warp said:

That is correct, the 836 cc kits used modified oversize CB350 pistons, the standard CB350 piston was already 3mm oversize compared to the 750's 61mm bore.

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Perhaps it should be pointed out though most big bore kits that went into CB750 fours were the 810cc kits,
using the Yoshimura (expensive) or Bert Kingston kits = custom pistons.
These required the steel sleeves to be pressed out, the alloy bored out, and new larger steel sleeves pressed in.

Onda genuine parts were durned expensive.
And the 836 sleeves were getting a bit thin, and getting awful close to the cylinder studs ?

I still have some loose Kingston pistons, if Les/timewarp wants to see em.
Were available for a range of Ondas, including trailies.
They were good, although needed to be bored to tighter clearances than recommended, or they rattled a bit...

Re: Featherbed frame design went against all engineering pri

worntorn said:

Time Warp said:

You seem to be confusing your imagination with your memory, are you related to Rohan. :lol:

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No imagination needed here:

Glen

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May need to link the rest of that :wink: The commando was a wonderful machine on paper and a wonderful machine in person, if you were a bike enthusiast. When the honda's came along, it was a dying effort for most part as far as production bikes go, because there is simple chart that sums up "company management" and "average rider desires".

Re: Featherbed frame design went against all engineering pri

When the CB750s became 836cc they were fast enough. These days in Australian historic racing they are much bigger. I've raced against them on two occasions. On the second, I turned under them with the Seeley on turn two at Winton, and was beside the leader before my bike had a minor problem which stopped it. Getting a decent start with the high first gear of the 4 speed CR box was difficult, and I can see how main shafts can get bent.