Featherbed frame design went against all engineering princip

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Re: Featherbed frame design went against all engineering pri

Tell me this = how does an engineer interpret the place a riders brain has to be when he is riding a race bike at high speed around a circuit
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Alan states the most vital characteristic of a good frame how ever that is arrived at, it takes the load off the pilot effort and error. Every cycle I've pressed harsher got harder and harder to control till I or it just couldn't take it, not Ms Peel > easier and strangely more calm to point she literally invited me into new ways to take even decreasing turns accelerating to leave me refreshed not over adrenalized-weakened. Those who can understand - will take this as meant = like a tripped out hippy pointing out a great new way to get high, not the laid back hippy. Dr. Bauer is my hero then the riders who tired various stabilizing links.


Featherbed frame design went against all engineering princip
 
Re: Featherbed frame design went against all engineering pri

The 0.1 % proof stress is the point of intercept of the line drawn parallel to the stress-strain curve at a load of 0.1 % of the UTS. It give the elastic limit of materials in terms of load Air craft materials are stressed to within about 5% of the limit past which they experience plastic deformation. Fatigue effects are a different aspect. Manx frames break in a certain way which is not due to excessive load. Because they have a certain amount of flex they last longer. The Seeley frame has a lot of strength built into it, and the loads are directed to where they do less harm. If you have a look at what is around the pivot, they make a commando frame look very flimsy.
 
Re: Featherbed frame design went against all engineering pri

acotrel said:
The 0.1 % proof stress is the point of intercept of the line drawn parallel to the stress-strain curve at a load of 0.1 % of the UTS. It give the elastic limit of materials in terms of load Air craft materials are stressed to within about 5% of the limit past which they experience plastic deformation. Fatigue effects are a different aspect. Manx frames break in a certain way which is not due to excessive load. Because they have a certain amount of flex they last longer. The Seeley frame has a lot of strength built into it, and the loads are directed to where they do less harm. If you have a look at what is around the pivot, they make a commando frame look very flimsy.
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Ah ok, the "Aircraft" bit is a red herring. 0.1% or 0.2% proof stress is used when the material does not have a well defined yield point (some steel alloys do have this yield point), it is noting to do with safety factors.... And yes as the offset is into the nonlinear plastic region so using a value of 90%-95% of the proof stress could be a good idea to prevent plastic deformation, although this can vary greatly depending on the actual stress strain curve.

No aircraft component will be loaded to 90% of its proof stress, the closest you will get is bolts being torqued to 70% yield. Also it is not 0.1% of UTS, it is 0.1% strain
 
Re: Featherbed frame design went against all engineering pri

If we are talking about MotoGP or F1 car components, aren't they in the realm of aircraft technology ? So where are we going with our old dungas ? You can end up just as dead if you get it wrong.
 
Re: Featherbed frame design went against all engineering pri

acotrel said:
So where are we going with our old dungas ? You can end up just as dead if you get it wrong.
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Since they were designed and put together 40 or 50 years ago now, at least,
most of the glitches have been ironed out. !!

Which is more than you can say of these new fangled space-tourist transports.....
 
Re: Featherbed frame design went against all engineering pri

looks like saying "the featherbed frame design went against all engineering principals" was at the very least, if actually even said, a poor choice of words,

just doesn't add up that something that works so well could be described that way, at all
 
Re: Featherbed frame design went against all engineering pri

Not necessarily.

We quoted earlier that BumbleBee,
which at first glance is scientifically unable to fly.
But does so anyway, in spite of all the theory....

Featherbed frames have something similar in their makeup ??
(And, do emit a loud BUUUUZZZZIIINNGGG noise in action....).
 
Re: Featherbed frame design went against all engineering pri

84ok said:
looks like saying "the featherbed frame design went against all engineering principals" was at the very least, if actually even said, a poor choice of words,

just doesn't add up that something that works so well could be described that way, at all
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Has there been a picture of a bare 1950 frame posted.
What were the engineering principles it went against, having a swinging arm or no top tube ?
Improved design become the principle.
 
Re: Featherbed frame design went against all engineering pri

Do keep up Les - there are 24 pages of discussion of bent tubes ......
 
Re: Featherbed frame design went against all engineering pri

BTB, the McCandless Bros and Artie Bells original featherbed concept had a semi-monocoque rear frame part,
which Nortons didn't implement....
 
Re: Featherbed frame design went against all engineering pri

84ok said:
looks like saying "the featherbed frame design went against all engineering principals" was at the very least, if actually even said, a poor choice of words,

just doesn't add up that something that works so well could be described that way, at all
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It's not a bad statement in itself however it demonstrates the black and white thinking of many engineers. Motorcycle frame problems are not the same as the problems encountered in building construction. If that comment had been made by an aircraft engineer, I would be inclined to listen to the rest of the explanation. With motorcycles frames, as far as feel goes, for myself - the more rigid the frame is the better. However I only ride old motorcycles with very limited power. If you consider MotoGP bikes, the relationship between the tyre adhesion and frame rigidity is important. It is obviously a different world when you get to those speeds and power characteristics. To me they look like speedway bikes in there handling characteristics - there is certainly no nimble tip-toeing around corners.
With an old bike with limited power the quickest way around is often to have the bike tighten it's line using skinny tyres, and with a torquey motor get the power on very early - you don't need extreme grip tyres for that. If the motor is nasty and the bike tends to run wide, the whole thing tends to become 'point and squirt' with the frame trying to tie itself up in knots. You end up out on the ripple strip coming out of corners, point the bike and give it everything down the next straight.

https://www.youtube.com/watch?v=kY9VPjF46Gc

https://www.youtube.com/watch?v=aOlDGxTN9vI
 
Re: Featherbed frame design went against all engineering pri

I suggest that the claim that the featherbed frame goes against all engineering principles is incorrect. The frame obviously flexes because a common cause of failure is cracking of the tubes at the front and rear engine mounting points. You could also claim that the Ducati frames which rely on the swing arm pivot mounted in the aluminium casting at the back of the gearbox also goes against all engineering principles. It is a matter of what is lightest and still works reliably. To my mind the commando isolastics should have the ends of the pivot shaft fastened to the footrest plates, so the motor is forced to rotate in only one plane - around the pivot shaft. And the head steady should be constructed to stop sideways motion of the top of the motor - perhaps an extra rubber mount.
You could make an isolastic featherbed by making a close tolerance rotating mount for the rear of the engine plates directly in front of the pivot, or actually have it as a centre part of the pivot. I don't know how you would fit the head steady, it is an essential part of the featherbed frame - you might need an extra cross member between the top tubes to tension the steering head.
 
Re: Featherbed frame design went against all engineering pri

acotrel said:
You could also claim that the Ducati frames which rely on the swing arm pivot mounted in the aluminium casting at the back of the gearbox also goes against all engineering principles.
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Actually, having the swingarm pivot as close as possible to the sprocket is a GOOD idea.
Which cornflakes packet did you get your engineering training from ?

When the alloy castings break, it probably seems like a bad idea though.
Quite a few bikes have used this scheme over the years, as long as its strong enough its good...
 
Re: Featherbed frame design went against all engineering pri

UGH - Swing arm pivot mounted close to or in line with the drive sprocket only works well in stationary - cruiser applications and ignores the critical effects of applying strong power through chain or drive shaft to rear does to bike handling reactions - especially in leans. This is main reason you don't see this feature in elites, conflicts of mass and mechanical drive sprocket placement with suspension drive action. Can get up to speed on this here...
https://www.google.com/?gws_rd=ssl#q=mo ... %20effects
 
Re: Featherbed frame design went against all engineering pri

Stretching the chain with suspension action would have more effect than some of described there ??

Can recall a superbike race where a Suzook was black flagged for evil handling,
and it was found the chain was simply a bit tight.

And haven't we previously seen Allan advocating swingarm pivots outboard of the sprocket...
??
 
Re: Featherbed frame design went against all engineering pri

hobot said:
UGH - Swing arm pivot mounted close to or in line with the drive sprocket only works well
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Quote from one of the first articles your search pops up.

"The cases in which this is possible are rare, however, as during the design phase the chassis builder will usually strive to have the swingarm pivot mounted as closely as possible to the main drive sprocket."

Paragraph 2
http://www.eniracing.com/en/2012/06/27/ ... ro-catena/
 
Re: Featherbed frame design went against all engineering pri

Rohan we can all pull out scriptures or engineering references to support our favorite concepts but in the end takes trial and error for each type cycle as the only way to know for sure in that particular cycle and pilot. Peel's geometry is 2" lower rear axle to pivot point which references says should help forward thrust some but may find out different.
 
Re: Featherbed frame design went against all engineering pri

There is no substitute for basic engineering.
 
Re: Featherbed frame design went against all engineering pri

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
 
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