Hello! By now you should have gone through the statics tutorial series, and be ready to tackle a 3D statics problem on your own. Always feel free to reach out for help if you get stuck. This is a trial run of the curriculum, so any feedback you have on any aspect of it is also much appreciated!
The image below shows the front suspension of MSXIV with transparent parts. The lines you see inside these parts make up the 3D sketch that defines the geometry of the suspension. You’ll notice things don’t fit very well. This is because our CAD is a mess. So we’ll be providing you with a simplified geometry sketch for the project.
Part of the early design process of the suspension is defining the maximum loading conditions on the contact patch between the tyre and the road. These will be given to you, and are out of the scope of this introductory curriculum. We can use the geometry of the 3D sketch, along with knowledge of how the components fit together, to calculate the forces exerted on various components in the suspension.
These are the loading conditions you should use (applied simultaneously at the contact patch):
Direction | Force (N) |
|---|---|
X | 3500 |
Y | 5000 |
Z | -1800 |
The image below is of the simplified suspension geometry. The following table describes the sequence of joints. You should be able to infer what the lines in the sketch represent based on which joints they attach to.
Code | Type of Joint | Description |
|---|---|---|
SB1 | Spherical Bearing | Connects the Upright to the Lower Control Arm (LCA) |
SB2 | Spherical Bearing | Connects the Pushrod to the LCA |
SB3 | Spherical Bearing | Connects the Upright to the Upper Control Arm (UCA) |
SB4 | Spherical Bearing | Connects the Pushrod to the rocker (don’t worry about this) |
Cl1 | Clevis | Connects the LCA to the Chassis |
CL2 | Clevis | Connects the LCA to the Chassis |
Your task is to find the forces at CL1 and CL2. You can break this into two parts:
1. Find the load at SB1
This is the start of the LCA, and you want to translate the forces from the contact patch to here. You’ll need to consider the reaction forces at SB1 and SB3. Some notes:
The UCA cannot apply any force in Y (No reaction force in Y from SB3)
Do not consider moments about Y. These are taken care of by steering, which is not included in this project
2. Find the load at CL1 and CL2
You’ll need to consider the forces you calculated at SB1, as well as reaction forces from SB2, CL1, and CL2. Some notes:
This is a statically indeterminate problem. What assumptions can be made for a “worst-case” loading condition on CL1 and CL2?
The pushrod has a spherical bearing on both ends. What does this imply about the force it exerts on the LCA?
You can use the CAD to find the dimensions you need, or refer to the images below.
Image 1: Side view in Y-Z planes, Z+ to the right X+ into the page
Image 2: Front View in Y-X plane, X+ to the right, Z+ out of the page
