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October 16, 2019, 06:39:08 pm

Swing arm pivot

Started by Toomes1, October 02, 2013, 04:00:01 pm

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Toomes1

Is the swing arm pivot actually usable in the setup options

HornetMaX

Last comment from Piboso I remember said that you can change it but it doesn't actually affect anything.
Just there for future use.

MaX.

neoraptor

Exactly. If you check the geometry file, there are 2 parameters called chassis_rsusp_min and chassis_rsusp_max.

They have actually the same position set, so if you move the pivot, you will move it between the same position  ;D ;D
Our greatest glory is not in never falling, but in rising every time we fall. Confucius
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Stout Johnson

Quote from: neoraptor on January 14, 2014, 10:15:44 am
Exactly. If you check the geometry file, there are 2 parameters called chassis_rsusp_min and chassis_rsusp_max.

They have actually the same position set, so if you move the pivot, you will move it between the same position  ;D ;D


thank you neoraptor for the indisputable evidence that it doesn't affect the bike's setup as of yet - very helpful information.
    -----------   WarStout Kawasaki Team   -----------

HornetMaX

But the question now is: if we alter the geom file, is this taken into account by GPB ?

MaX.

neoraptor

January 14, 2014, 01:46:01 pm #5 Last Edit: January 14, 2014, 02:08:36 pm by neoraptor
I will give it a try ;).
I don't know if PiBoSo already has implemented it.

Theoretically, the pivot position affect grip when going out of the corner.
If I move the pivot higher, I will have a higher chain pull angle and the suspension will extend more, so better traction (more range).
If it is move too far, it can results in high side as the rear suspension is then fully released.
Am I right?


Edit: some useful links to understand the effect of the pivot point :
http://www.eniracing.com/en/2012/06/27/tecnica-limportanza-del-tiro-catena/
http://bienvillestudios.com/index.php/chassis-dynamics/
http://www.sportrider.com/tech/146_0404_motorcycle_traction_geometry/
Our greatest glory is not in never falling, but in rising every time we fall. Confucius
>> Wiki to help modders <<

HornetMaX

Quote from: neoraptor on January 14, 2014, 01:46:01 pm
Theoretically, the pivot position affect grip when going out of the corner.
If I move the pivot higher, I will have a higher chain pull angle and the suspension will extend more, so better traction (more range).
If it is move too far, it can results in high side as the rear suspension is then fully released.
Am I right?

It depends. Too far in which direction ?

For a bike with a "simple" chain transmission The reasoning is: you take the upper chain branch direction and intersect it with the direction of the swingarm (that of course depends on the swingarm attach point), you obtain a point A. The line between the rear contact point and A is the squat line.

Then you compare this point with the "load transfer line" (line from the rear contact point with same angle as the sum of transfer load on rear wheel + driving force).


  • If point A is on the transfer line, accelerating will not change the suspension load, no change compared to the static (i.e. no acceleration) situation.

  • If point A is below the transfer line, accelerating will compress the rear (bike will squat).

  • If point A is on the transfer line, accelerating will extend the rear.



Things are slightly different for special cases: transmission shaft instead of chain, transmission shaft + 4 bar suspension instead of chain, bilever or tracklever systems, other exotic designs.
For GPB we may care only about chain transmission.

MaX.