A question about the AP Link

[enduro250]

yes, there was an failure in my measurement,
will post tomorrow my new results

[elmo]

FYI- My swing arm length centers are 535mm, with stock chain and 15T front.

[Evill_Ed]

I just ordered mine from AP Motoarts.

[enduro250]

yesterday, remeasured,

swingarm pivot was wrong, new actual swingarm angel = 10.88 degree

I built an object with nail and wood for the simulation.
major problem , as we discussed, measurement is not exact enough,
in my case a slide  gauge and tape measure  (correct translation )  

the empirical investigation results:

stock link 80 mm:
for 130 mm wheel movement  results in 53 mm shock movement.
with very less differences a almost perfect linear run of the curve

swingarm angel = 10.88 degree

 

new link 73 mm:
for 130 mm wheel movement  -->  56 mm shock movement.
linear run of the curve as well
with the same shock length ride height increases for 25 mm
produces an swingarm angel of 13.5 grad

 

for my feelings, that's not exact enough , even if sound serious.
I will try to find a solution to calculate this  with Math.

[Mad]

Stock gearing? 

[enduro250]

sorry , which gearing ( no  English native speaker)

[enduro250]

and additional,
when I increase shock length for 10 mm ( 310 to 320)
ride height increases for 24 mm
 

means for me both changes has the quite same result
both have linear curves.
reducing link for 7mm results in 3mm more shock movement, I think this  negligible

[enduro250]

It will be nice if anyone can confirm my calculation / experiment
or discuss whit wrong in my thoughts.
I'm open for all ideas  

[enduro250]

stock gearing, yes, if you mean  chain sprockets
swing arm length in my calculation 530 mm (529.53 mm)

 

swingarm pivot to rear wheel axle

leveled length = 520 mm
heigth diff  = 100 mm
 

[blackout]

27 minutes ago, enduro250 said:

and additional,
when I increase shock length for 10 mm ( 310 to 320)
ride height increases for 24 mm
 

means for me both changes has the quite same result
both have linear curves.
reducing link for 7mm results in 3mm more shock movement, I think this  negligible

The more the shock moves relative to wheel travel, the better.  It makes sense that a shorter link, not longer shock, would do this.  The better motion ratio gives the shock an easier job at controlling wheel movement with it's valving.

[enduro250]

I have disassembled  my  rear end;

Looks like I had an additional measurement error:
length of stock LINK = 96 mm

as result of this , AP Link should be 89 mm
 

has anyone this part available and can provide the length?
THX

[enduro250]

during the last weeks have done a lot of calculation and simulation of my rear end.
sorry, the rear end of my MT (FZ)

to decrease the length of this link has the same effect as to increase the length of the shock

7 mm less on the link is almost the same as 10 mm more on the shock .

both results in app. 18 mm more ride height

and it doesn't influence the suspension behavior.

It is a strict linear relationship 1: 2.28

this  means for me, I will order a shock with length:   312 mm  -  322 mm
this gives me a great area for  the setup, and didn't need to change the link on the track.

[wmhjr]

On 11/5/2018 at 11:24 AM, enduro250 said:

during the last weeks have done a lot of calculation and simulation of my rear end.
sorry, the rear end of my MT (FZ)

to decrease the length of this link has the same effect as to increase the length of the shock

7 mm less on the link is almost the same as 10 mm more on the shock .

both results in app. 18 mm more ride height

and it doesn't influence the suspension behavior.

It is a strict linear relationship 1: 2.28

this  means for me, I will order a shock with length:   312 mm  -  322 mm
this gives me a great area for  the setup, and didn't need to change the link on the track.

I'm not sure I could agree with this.  "Almost" is not the same as "exact".  It's not just about ride height.  It's also about leverage.  I believe the rear suspension with the "ride height link" is still 22% progressive.  That being said, I'm probably moving to the full APMoto setup in the rear with KTech DDS Lite.  That complete setup reduces the progressive nature to 10%.  It is simply not correct to say that the setup is a strict linear relationship or that it doesn't influence the suspension behavior.

[enduro250]

sorry, I am not a English native speaker, so I am not sure, to follow you exact.

I have done measurement and simulation, a friend in a suspension company as well.
we got the same result.
if you draw a diagram with wheel movement on one axle and the shock movement on the other axle
the result is a straight line , this is what I mean , no progression, here
even ,if I use a shorter link , the line is moving parallel  does not influence this line itself

maybe I use the word progression in the wrong way.
As I use "no progression"  -> it is a straight line 

[wmhjr]

3 hours ago, enduro250 said:

sorry, I am not a English native speaker, so I am not sure, to follow you exact.

I have done measurement and simulation, a friend in a suspension company as well.
we got the same result.
if you draw a diagram with wheel movement on one axle and the shock movement on the other axle
the result is a straight line , this is what I mean , no progression, here
even ,if I use a shorter link , the line is moving parallel  does not influence this line itself

maybe I use the word progression in the wrong way.
As I use "no progression"  -> it is a straight line 

I don't think you understand the meaning of "progressive" in terms of suspension.  The wheel can only move along the axis of a single arc because it's mounted to a fixed position on the swingarm.  However, the leverage curve creates progresssion in terms of suspension performance.  The most subtle of changes in terms of lever length or position can have dramatic effects on actual performance and/or progressive responses especially as the system is dynamic, with different feedback as the system moves from maximum to minimum travel.  

 

What I'm pretty comfortable in saying is that people making some of these changes and comparisons who are putting bikes on the podium on professional racing and who are experienced engineers and designers probably have a little better understanding than you're trying to duplicate with simple lines.  JMHO.  You might be able to get "kind of close"  - or not.  

 

I can tell you for sure that changing link length absolutely changes the relative angles of the swingarm compared to the shock position at least on my bike!

[twf]

5 minutes ago, wmhjr said:

I don't think you understand the meaning of "progressive" in terms of suspension.  The wheel can only move along the axis of a single arc because it's mounted to a fixed position on the swingarm.  However, the leverage curve creates progresssion in terms of suspension performance.  The most subtle of changes in terms of lever length or position can have dramatic effects on actual performance and/or progressive responses especially as the system is dynamic, with different feedback as the system moves from maximum to minimum travel.  

 

What I'm pretty comfortable in saying is that people making some of these changes and comparisons who are putting bikes on the podium on professional racing and who are experienced engineers and designers probably have a little better understanding than you're trying to duplicate with simple lines.  JMHO.  You might be able to get "kind of close"  - or not.  

 

I can tell you for sure that changing link length absolutely changes the relative angles of the swingarm compared to the shock position at least on my bike!

He is correct. Wheel to shock travel is what makes it linear, progressive or digressive. If for every mm of wheel travel you get same amount of travel at shock than linkage is linear. 

I have measured it as well. 

[wmhjr]

3 minutes ago, twf said:

He is correct. Wheel to shock travel is what makes it linear, progressive or digressive. If for every mm of wheel travel you get same amount of travel at shock than linkage is linear. 

I have measured it as well. 

 

I'd  love to see exactly how you're measuring this, as it flies in the face of what others have said - plus it seems to me to defy physics as if you change the length of the lever that would be impossible.

 

[twf]

I posted pic long time ago. Rod going from rear axle straight up and shock mounted without spring. Than measure movement at rod and shock. 

I measured stock bike. Found no need to change links. I did modify link to get ride height I wanted. 

[mossrider]

It's linear.

 

The ratio of axle travel to shock piston travel is the same at the top of the stroke as it it at the bottom of the stroke. I could check my notes but it was basically 2-1 or something (actual numbers are irrelevant) as the ratio never changed.  

 

If it was 2-1 at start of travel and 3-1 at end of travel for instance it would not be linear.

 

.02

[wmhjr]

I'm going to have to mock this up.  From an engineering perspective I'm finding it difficult to understand how shortening or lengthening the lever would not result in a different ratio.  The lever is not perpendicular to travel.

[blackout]

50 minutes ago, twf said:

He is correct. Wheel to shock travel is what makes it linear, progressive or digressive. If for every mm of wheel travel you get same amount of travel at shock than linkage is linear. 

I have measured it as well. 

100% Yup!  

[mossrider]

Just now, wmhjr said:

I'm going to have to mock this up.  From an engineering perspective I'm finding it difficult to understand how shortening or lengthening the lever would not result in a different ratio.  The lever is not perpendicular to travel.

Have at it, that's what I did.

 

Don't forget there's a lot of fulcrums, bell cranks, levers, angles and dangles that figure in. I am still fascinated to play with it, makes my fat head hurt. And this one is relatively simple w/o any scissor type levers in it.  I'm sitting here right now with a small bungee in place of the shock messing with it.

[blackout]

24 minutes ago, mossrider said:

It's linear.

 

The ratio of axle travel to shock piston travel is the same at the top of the stroke as it it at the bottom of the stroke. I could check my notes but it was basically 2-1 or something (actual numbers are irrelevant) as the ratio never changed.  

 

If it was 2-1 at start of travel and 3-1 at end of travel for instance it would not be linear.

 

.02

Yup, 2-1 would be the motion ratio, but still linear.  

 

Our bikes need a heavier rear spring than a S1000RR.  lol  The BMW has a better motion ratio.

 

[twf]

5 minutes ago, mossrider said:

Have at it, that's what I did.

 

Don't forget there's a lot of fulcrums, bell cranks, levers, angles and dangles that figure in. I am still fascinated to play with it, makes my fat head hurt. And this one is relatively simple w/o any scissor type levers in it.  I'm sitting here right now with a small bungee in place of the shock messing with it.

And you can add thousand more or change half of them but on the end all it matters is wheel to shock travel

[wmhjr]

Have any of you played with the newer rear suspension links from Andy that allow you to mount the DDS Lite for example?  

 

The  STX46 still doesn't give me what I'm looking for when pushed past 85%   For track days or street it's a great solution, but I think that it's been limiting in racing this year.