S*R swingarms are awesome

[DucHead]

I love this board.

Swingarms, sarcasm, symmetry, chemistry and engineering all in one thread.  

[aaronb]

The S*R swing arm is made up of two parts welded together, one of which is cast.

it's actually seven tubes and two castings.

(at least i think the hub carrier is a casting, i would have to go look.  it may be a machined extrusion.  hmmm)

[Capo]

The front is cast, the rear is an extrusion

[mitt]

Yes, with "equal material and equal weights" you limit the design quite a bit.  The SxR bikes' SSS uses a fully tubular design which is stronger than a box design (same reason modern tow hitches are tube and not box). 

If you had a tubular DSS, it would probably be stiffer, but the tube stuff is more expensive to work on.

Not entirely true...

For equal volume (weight) members, tubular may or may not be stiffer than a boxed frame.  If it is in bending, a box (rectangle actually) will win.  If it is in torsion, a tube will win.  If it is in compression, they are basically equal unless the member is long enough to buckle.  If it is for looks, then that is up to the beholder. 

Most stressed members are actually optimal in some odd custom shape that is perfect for the application.  But, for off the shelf selection and fabrication, a lot of parts come out as tubes or boxes even though a pear/conical/organic shape would be better.

mitt

[ducatiz]

Not entirely true...

For equal volume (weight) members, tubular may or may not be stiffer than a boxed frame.  If it is in bending, a box (rectangle actually) will win.  If it is in torsion, a tube will win.  If it is in compression, they are basically equal unless the member is long enough to buckle.  If it is for looks, then that is up to the beholder. 

Most stressed members are actually optimal in some odd custom shape that is perfect for the application.  But, for off the shelf selection and fabrication, a lot of parts come out as tubes or boxes even though a pear/conical/organic shape would be better.

mitt

good facts.

seems to me that torsion is a more relevant factor for swingarms than bending, no?

[CowboyBeebop]

The SSS are heavier, no? 

[localhero365]

Although I knew I wanted an S4R, this little gem of engineering was one of the reasons I really love this bike. I always draw admirers' attention to it, so much nicer than the usual swingarm.

[red baron]

The SSS are heavier, no? 

Depends which side you weigh.

[Rameses]

good facts.

seems to me that torsion is a more relevant factor for swingarms than bending, no?

That's a good question.

For a sss, maybe.

But for a dss, I'd say no.  Since both ends of the axle are supported, there's little to no torsional force on each side of the swingarm.

[ducatiz]

That's a good question.

For a sss, maybe.

But for a dss, I'd say no.  Since both ends of the axle are supported, there's little to no torsional force on each side of the swingarm.

i believe it is relevant -- even if you have a dss, the torsion is transferred to the frame. all bikes endure torsional forces when turning (leaning).

[SKOM]

My SSS got me out of a speeding ticket once. 

[peanut_man]

I love this board.

Swingarms, sarcasm, symmetry, chemistry and engineering all in one thread.  

I still didn't see any hot chic.  That's key!

[ducatiz]

I still didn't see any hot chic.  That's key!

here are 4

[Rameses]

i believe it is relevant -- even if you have a dss, the torsion is transferred to the frame. all bikes endure torsional forces when turning (leaning).

True.

But that's not a torsional force on the components of the swingarm itself.

That's bending one arm up and one arm down.

[ducatiz]

True.

But that's not a torsional force on the components of the swingarm itself.

That's bending one arm up and one arm down.

which would transfer to the swingarm pin in the engine case and torque the stressed engine case against the frame, no?