Good with geometry and physics?

[GeeP]

Ahh, I see...

That makes me feel a little better.  That stock swingarm doesn't have any meat in it. 

Keep in mind that rapid stiffness changes will result in flexural fatigue cracking, especially with near reversing loads.  Flexural fatigue cracking is what happens when you take a thin sheet of aluminum, or a copper wire and flex it back and forth in your hands until it cracks.

The same thing will happen if the stiffness of a beam section changes rapidly.  The change in section acts as a focal point for stresses to concentrate.  One end fixed, load at the other and cantilever beam sections are usually the most prone to flexural fatigue failure near the fixed attchment.  This is due to the freedom of motion at the end of the beam section and the fixed nature of the attachment.

Have fun, think it though.   

[makenzie71]

I'm not pioneering anything.  The bracing on the new swingarm will be modeled after bikes like the TL1000R and late 90's/early millennium GSXR750's and such.  Just adding a hair of stiffness to it...ran the same swingarm on my FZ600 and hated that I could actually feel the rear flexing under hard turns.  I won't be riding that hard anymore, though, so it'll be more for cool factor hah.

I would really like to build a custom tuber swingarm, though, based on the stocker but made with heavier steel (mmmmm stainless maybe) and some intricate bracing and such...but my hydraulic tubing bender has gone AWOL...damn hoodlums keep swiping my tools.

[wladziu]

Ran some numbers for you, man.  Doesn't look like it's gonna work well enough.  I think it's just a no-go on the shocks. 

I used 45 centimeters from the axis point to where the shock meets the swing arm.  Supposed about 100 N of shock force (completely arbitrary), and it's at maybe 60 degrees. 
At "Torque = Force times Lever Arm" to find your "baseline" of one angled shock:
sin60 = lever arm/0.45 meters                             
     lever arm = 0.3897 meters

T = 100N x 0.3897m
T = 38.97 Nm     


Using the same shock force, of course, but putting the shock at 90 degrees to the swing arm:
(and this is moving the top of the shock rearward)
T = 100N x 0.45m
   = 45 Nm

So, a 6 Nm gain per side... it's a gain, and you'd notice it, for sure.  But it's not gonna give you enough, I don't think. 
Those are arbitrary numbers of course, but your ribs will break between 75 and 100 Newtons.  I figure... 100 N on both sides...  sounds realistic to dampen a bike.  Maybe.   
Course, if the shocks have more force, it'll be more than a single Newton per centimeter of change... 
I'm guessing those shocks - not so much. 



If you move the bottom of the shock toward the front of the bike, instead of the top of the shock toward the rear, it'll have the same effect.  Probably the same numbers.  I'm too lazy to find out.  But, you're also shortening the shock.  It'll put out the same force, but it'll have less range of motion.  Less travel.  That means you'll have a little more dampening, but less travel in which to do it. 
Sorry, bro.  Would have looked sweet.  Could have had a long bracket with different positions, TIG welded on by a good welder, braced/gusseted nice and pretty.  Would have looked sexy under that seat, maybe stainless steel or lacquered machined steel.   

[makenzie71]

Until I get my new swingarm in, I'm going to be running a different adapter.  I'm going to have a buddy of mine build me one at work.  It'll be stainless, which may damage the base plate on the shock, but, in the end, I'll make a new baseplate for the shocks from stainless too.

I updated my project...I'm actually pretty confident my latest experiment will get me good results.

Thanks for all the math maestro!