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- Forces balance out
- The LCA provides no restorative moment (worst-case, actual depends on attachment)
- The UCA only resists forces in the X-Z plane
- The UCA-upright node is free to move vertically (actually constrained to an arc)
- The moment of the upright about the Y-axis is handled by the steering system.
- The UCA-upright node does not travel more than 30mm in the Y from its clevis (currently about 25mm with a coilover compression of 40mm)
This means that for analysis purposes, we can treat it as exactly horizontal. This causes no more than 0.5% of error in this analysis.
Assuming no restorative moment, the moments at the LCA-upright node must cancel out. If we take a look at the upright, we can see that the contact patch is roughly 130mm from the LCA node, and the UCA node is roughly 450mm from the LCA node.this is a distance ratio of 1:3.46. We can safely approximate this as 1:3. We then have the system.
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This gives us the forces:
Worst Case Loading (N) Conditions | Fx at CP | Fx at UCA node | Fz at CP | Fz at UCA node |
---|---|---|---|---|
Braking & Cornering Inner (inside front wheel) | 1775 | 592 | 1672 | 558 |
Braking & Cornering Outer (outside front wheel) | -3550 | -1183 | 1672 | 558 |
We can use these forces to find the tensile/compressive forces in the arms of the UCA.
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Solving for the system of equations that arises, we get
Inner | Outer | ||
---|---|---|---|
FAB[compressive] | FAC[tensile] | FAB[tensile] | FAC[compressive] |
471.5N | 1075.5N | 1847.7N | 1243.7N |
To get the forces on the chassis bar through the clevises, we can resolve these forces into the X and Z directions.
Inner | Outer | ||||||
---|---|---|---|---|---|---|---|
FAB[compressive] | FAC[tensile] | FAB[tensile] | FAC[compressive] | ||||
x | z | x | z | x | z | x | z |
-180.4N | 435.6N | -411.6N | -993.6N | 707.1N | -1707.1N | 475.9N | 1149.0N |