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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)

Image Added


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