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Rear suspension geometry

Started by PiBoSo, February 03, 2020, 04:44:49 PM

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PiBoSo

February 03, 2020, 04:44:49 PM Last Edit: May 31, 2020, 10:35:14 AM by PiBoSo
GP Bikes supports 6 types of rear suspension geometry.

There are 3 main categories:
1) "Classic". The shock is linked to the chassis and swingarm directly.
Examples: Ducati Monster, KTM 450 EXC, vintage bikes.

2) Linkage suspension. There are two additional elements, rocker and rod.
Example:

The rocker is blue, the rod red.

2a) "Linkage Rocker Chassis". The shock is linked to the chassis and the rocker to the chassis.
Examples: Ducati Panigale V2, Kawasaki Uni-Trak, stock M2 bike.

2b) "Linkage Rod Chassis". The shock is linked to the chassis and the rod to the chassis.
Example: Honda Pro-Link.

2c) "Linkage Rocker Swingarm". The shock is linked to the swingarm and the rocker to the chassis.
Examples: Ducati Desmosedici, Suzuki Full Floater.

2d) "Linkage Rod Swingarm". The shock is linked to the swingarm and the rod to the chassis.
Example: Honda Unit Pro-Link.

3) "Hardtail". There is no suspension and the rear wheel is connected directly to the chassis.
Example: speedway bike.
"Obviously your ambition outweighs your talent".

matty0l215


Manu

It's Easier to Fool People Than It Is to Convince Them That They Have Been Fooled.

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Myst1cPrun3

I have some questions about the rear suspension simulation, and BikeED....

1) on the picture above you've got the rod as the blue triangle, and the rocker as a red, erm, rod.
Is this right? I would assume that the red, rod, is, well the rod, and the rocker is the blue triangle arrangement, that 'rocks' with the suspension movement? (This is also backed up with a quick ebay search, that the parts are actually the other way around)

2)
The second, is that it appears that the parts are not going to where I would like them. Taking the labels from the diagram above, my red linkage, which is the rocker here (but Really the connecting rod) does not attach to the swinging arm as it should, whenever I get it in the right postion, it pings to a different location and the graph of suspension travel goes all over the place. (The linkage (which is the rocker here)  can be attached to either the chassis or swinging arm, in real life and this doesn't seem to be possible here)

Motorcycle Dynamics Second Edition by Vittore Cossalter seems to show this on page 149. fig 5-6. The labelled parts on this fig are the ones that directly connect to the chassis, showing that the rocker and rod can connect to either, in a lot of different orientations, so I cannot see why this would not be possible?

2.5)
One extra little thing relating to the above point, is the suspension I'm working on is a variation of fig 5, the rocker-chassis (also the way it connects, rocker to chassis, not rod) however, the rear suspension (Shock and spring) joins the rocker (triangle piece) at the bottom. When this is introduced BikeED doesn't seem to like it. This may be something I'm doing wrong however.

Any advice would be useful thanks.

Discord is a good place to reach me for more detail or screenshots

As usual Keep up the good work :)

PiBoSo

February 16, 2020, 09:21:02 PM #6 Last Edit: February 17, 2020, 01:03:59 PM by PiBoSo
Quote from: Myst1cPrun3 on February 13, 2020, 10:47:46 PMI have some questions about the rear suspension simulation, and BikeED....

1) on the picture above you've got the rod as the blue triangle, and the rocker as a red, erm, rod.
Is this right? I would assume that the red, rod, is, well the rod, and the rocker is the blue triangle arrangement, that 'rocks' with the suspension movement? (This is also backed up with a quick ebay search, that the parts are actually the other way around)

2)
The second, is that it appears that the parts are not going to where I would like them. Taking the labels from the diagram above, my red linkage, which is the rocker here (but Really the connecting rod) does not attach to the swinging arm as it should, whenever I get it in the right postion, it pings to a different location and the graph of suspension travel goes all over the place. (The linkage (which is the rocker here)  can be attached to either the chassis or swinging arm, in real life and this doesn't seem to be possible here)

Motorcycle Dynamics Second Edition by Vittore Cossalter seems to show this on page 149. fig 5-6. The labelled parts on this fig are the ones that directly connect to the chassis, showing that the rocker and rod can connect to either, in a lot of different orientations, so I cannot see why this would not be possible?

2.5)
One extra little thing relating to the above point, is the suspension I'm working on is a variation of fig 5, the rocker-chassis (also the way it connects, rocker to chassis, not rod) however, the rear suspension (Shock and spring) joins the rocker (triangle piece) at the bottom. When this is introduced BikeED doesn't seem to like it. This may be something I'm doing wrong however.

Any advice would be useful thanks.

Discord is a good place to reach me for more detail or screenshots

As usual Keep up the good work :)


1) This error has already been reported. Unfortunately I did a nomenclature mistake. At the moment in GP Bikes and BikeEd the element connected to the chassis is always called "rocker", and the element connected to the swingarm "rod". In real life the rocker is the element with 3 links, and the connecting rod the element with 2 links.
This issue will be fixed as soon as possible.

2) Please try changing the "Ref. Angle" in BikeEd, that sets the reference angle to help the simulation calculate the direction of the link between the rocker link ( either chassis or swingarm ) and the shock link.
"Obviously your ambition outweighs your talent".

Myst1cPrun3

Cheers pib will look into that Tonight

PiBoSo


First post updated with the correct nomenclature, used in GP Bikes beta18.
"Obviously your ambition outweighs your talent".