Boxerworks.com

richard t wrote:damm! a airhead bobber, I seen a airhead chopper once, but never seen a bobber before now

Apparently he forgot about the front fender.

And please, Richard...







etc.

that last one is.....chunky! wonder how it would handle a dirt flat track?

twist wrote:that last one is.....chunky! wonder how it would handle a dirt flat track?

Bit heavy I would think. Maybe that just means you need a heavier shoe?

twist wrote:that last one is.....chunky! wonder how it would handle a dirt flat track?

Without a fork brace?! Poorly, I'd think.

twist wrote:that last one is.....chunky! wonder how it would handle a dirt flat track?

It's a speedway bike. No front brake.

Chuey

At that angle, I think the shock is more decorative than useful.
I measured the top shock locations on both my SWB and /7. A stock LWB swingarm and a STOCK SWB subframe would not give that angle. The subframe's been messed with, and probably a longer shock, too
So, we are back to: WHY?

Native /5 wrote:Seems to me that a shock spring's geometry is neutral (vs progressive) when the length from the SA pivot to the lower shock mount equals the length from the SA pivot to upper shock mount (isosceles triangle.) Moving the upper shock mount laterally either forward or aft changes the geometry to progressive (vs neutral) with the spring rate (due to geometry) decreasing with further compression.

VR=Lw:Ls
Where VR is the Velocity Rate or Velocity Ratio
Lw - the horizontal distance between the wheel axle and the swing-arm pivot.
Ls - the distance between the shock's upper axis and the swing arm pivot


Lw varies little, so Ls largely determines any rate variation.

Jean wrote: ... So, we are back to: WHY?

In the absence of actual dimensions to calculate specific Velocity Rate
and therefor understand how these changes might actually affect suspension performance ...
or the occasion to ask the builder what his intentions might have been ...
we are left with one of two possible scenarios:
1.) The changes are intended to modify VR in a prescribed manner, or
2.) the changes were haphazardly implemented.

Without further evidence,
"WHY?"
might best be satisfied with the words, "Because that is what the builder wanted".


Check out the angle on these babies !
1979 Sparton framed Suzuki RG500 based race-bike:


Decorative ? I will think not !

vanzen@rockerboxer.com wrote:

Native /5 wrote:Seems to me that a shock spring's geometry is neutral (vs progressive) when the length from the SA pivot to the lower shock mount equals the length from the SA pivot to upper shock mount (isosceles triangle.) Moving the upper shock mount laterally either forward or aft changes the geometry to progressive (vs neutral) with the spring rate (due to geometry) decreasing with further compression.

VR=Lw:Ls
Where VR is the Velocity Rate or Velocity Ratio
Lw - the horizontal distance between the wheel axle and the swing-arm pivot.
Ls - the distance between the shock's upper axis and the swing arm pivot


Lw varies little, so Ls largely determines any rate variation.

That's what I said.

Native /5 wrote:...when the length from the SA pivot to the lower shock mount equals the length from the SA pivot to upper shock mount (isosceles triangle.) Moving the upper shock mount laterally either forward or aft changes the geometry to progressive (vs neutral) with the spring rate (due to geometry) decreasing with further compression.

VR=Lw:Ls
Where VR is the Velocity Rate or Velocity Ratio
Lw - the horizontal distance between the wheel axle and the swing-arm pivot.
Ls - the distance between the shock's upper axis and the swing arm pivot



Given this motorcycle:


Notice that the "length from the SA pivot to the lower shock mount"
as Native has chosen to define the term "Lw"
and "the horizontal distance between the wheel axle and the swing-arm pivot"
as the term will be properly defined
results in 2 very different distances / lengths.
In fact, "the distance between the wheel axle and the swing-arm pivot" will not be precise, either,
because if the swing-arm is angled and not horizontal (picture a dirt-bike),
the value of Lw would be changed.