Query regarding Jounce and Rebound Bumper modeling definitions in MotionView

PedroNeto

Hi,

I am setting up a shock absorber assembly in MotionView and I am having some difficulties understanding how to properly map my physical bumper specifications into the software properties, specifically regarding the bumper free lengths (longueur à vide) and the dataset clearances.

Here is the data and context of my model:

1. Hardpoints / Attachment Points (Coordinates as per attached image 1):

• UT: jounce bumper attachment point on shock rod (point d'attache de butée d'attaque sur tige amortisseur)
• ST: jounce bumper interface with shock body (interface butée d'attaque avec corps amortisseur)
• UD: rebound bumper attachment point on shock rod (point d'attache de butée de détente sur tige amortisseur)
• SD: rebound bumper interface with shock body (interface butée de détente avec corps amortisseur)

2. Physical Bumper Specifications:

• Jounce Bumper Free Length (Longueur à vide): 94 mm (Curve shown in Image 2)
• Rebound Bumper Free Length (Longueur à vide): 7 mm (Curve shown in Image 3)

My questions are:

1. Bumper Free Length Input: Where exactly in the MotionView entity/property panel should I input the free length (longueur à vide) for both the jounce bumper (94 mm) and the rebound bumper (7 mm)? Does the software calculate the contact based solely on the curve's X-axis offset, or is there a dedicated parameter for the bumper's uncompressed height?
2. Dataset Parameters (Image 4): In the Entity Editor for the ds_reb_bmp (Rebound bumper lengths) dataset, could you clarify the physical meaning of the following parameters and how they relate to my hardpoints/curves?
   • Tube lower to bumper tip (mm)
   • Tip to contact dist. (mm) - clearance to be set manually in the curve x offset
   • Shock length (mm)

Any guidance on how to correctly align my hardpoints, physical bumper lengths, and these dataset parameters to ensure accurate contact simulation would be highly appreciated.

Thank you for your time and assistance.

Best regards

,

Christopher_Fadanelli

Hello @PedroNeto

Please refer to the image below for guidance on how the dataset parameters should be interpreted for the both internal jounce and rebound bumpers.

For the jounce and rebound bumper curves, I recommend adding an entry at x = -1 with a corresponding y value of 0. This precaution ensures that no unrealistic force is generated by the stops when they are not yet in compression.

The distance between the UT and ST represents the length before initial contact and should be assigned to the “Tip-to-Contact” input (and similarly for the rebound bumper). The free length of the bumpers should be used for the remaining associated input.

To validate whether the bumpers are engaging at the correct shock displacement, I suggest running a KNC event with the shock moving through full jounce and rebound. In the KNC report, verify that both the jounce and rebound bumpers engage appropriately. If they engage too early or not at all, adjust the Tip-to-Contact distance until the results appear reasonable.

Best,

Christopher Fadanelli