Bike linkage system


I would like to ask you some help about bike linkage system. I am very new user of Kangaroo and kinetic functions.
My goal is to get numerical data or graph of the relation between the displacement of A point and the change of length of Point B,C(compressed). Please ignore the bike modeling and any pictures. Thery are only for understanding the system and only point and lines are important.
I know this system is not so complex. However, I don’t know how to apply displacement of Point A and how to get the change of length of point B,C.
Could you help me with this?

Thank you very much.


BIKE (15.2 KB)

I use this program it’s amazing.

Thank you for your reply. I have downloaded it but I’d like to do this with my own modeling and grasshopper.

Do you mean you want to know how the length of the red line BC changes as the triangle ABD rotates about D, while C stays fixed relative to D, like this?

I have a lot of similar stuff but are carried over via code. Anyway get a very simple one and let’s hope that some good Samaritan would provide a components based solution.

BTW: For real-life things and out of this word kinematics find a friend who knows what CATIA/Siemens NX are and ask a small demo.

SwingArm_Primitive_V1.3dm (33.6 KB) (125.0 KB)

A in the center how it will move ?
and how this part move when A and D are fixed? i just want understand

Yes, I’d like to know how the length of the red line BC changes as the Point A rotates about D. That is exactly what I want to know.

I don’t think you need Kangaroo, or even really Grasshopper for that - since you know B must also move on a circle, just rotate by the desired amount and measure the distance to C?

Thank you so much. I’m not good at coding but I realized that I need to study it through your files. Thank you again.

I’k like to know the numerical number of relation between Point A and length of BC, so I thought grasshopper could give me the solution. And after this, I have a plan to analysis little bit more complex linakage system. That’s why I want to use grasshopper.

When rear wheel steps on some obstacle like a stone, the ABD triangle turns on the point D. This triangle works like a suspension. That’s the idea.

1 Like

Well … given the opportunity:

  1. Google Honda ProLink and ProArm: The mother of modern swingarm suspension concepts started back in 81 (Honda XR) and carried over via the notorious RC211V and the CBR1000RR (aka Blade).
  2. What are these? These are linkage systems that allow a progressive compression. This plays a paramount role in the way that the shock delivers the goods and justifies the hi-low compression and rebound adjustments in any given shock (plus preload).
  3. Now … a top shock for a proper sports motorcycle is a 1.5K - 3K thingy (Ohlins TTX36, WP 4618, Showa Racing, Penske custom etc etc) … meaning that bicycles can’t affort them (say an Ohlins TTX22). Meaning that the more the suspension allows the shock to work properly the more a cheapo shock can deliver. That said Ducati did a BIG mistake in the Panigale V2 (using a direct linkage): the mass production big piston Showa used in my ProArm Blade (shock mounted in the swingarm) eats the whole Italian thingy for breakfast.
  4. All that were sci-fi for bicycles in the past. But these days … they start to catch up with progressive suspensions as well.


Screen%20Shot%20067 Screen%20Shot%20069

BTW: Added a ProLink system (“like a PL” in fact with regard the EXACT motion of linkage B … but GH is NOT CATIA you know).

SwingArm_Primitive_V1A.3dm (57.1 KB) (129.5 KB)

Study what’s happening and see why Honda is Honda (and the rest are just motorcycle makers).

1 Like

i create this assuming that this part is movable

1 Like


Your file is fatastic. Thank you very much.
I have two more questions about your file.
First, is there a componenet to check the length of displacement of Point A? Since the point A moves as an arc, I think I need something special component for check the length.
Of course, I can calculate it manually with the degree and radius(AD), but I’d like to know if there is a component for this.
Second, I think you drew the trace line(white line) of the moving point with interpolate component. Can you tell me how to remove the lines? I cannot select the lines.

you can use curve closest point and you find the distance
for your second question i used record data to create the paths and you can simply hide it



Added an exact ProLink motion mode (I was cheating in V1A - that was a shame for Honda): observe how compliant is the motion at start and how it becomes stiffer and stiffer at the end of the travel (BUT the shock compression rate is more or less the same). That’s the Honda brilliance.

SwingArm_Primitive_V1B.3dm (59.7 KB) (136.4 KB)

And this is a good progressive system (at a price) for a mountain bike:

Just for fun



amazing!! Thank you for showing me new world!!

1 Like