Roll stiffness: Difference between revisions
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Rolls stiffness is a measurement of a vehicle's resistance to chassis roll. Total roll stiffness for an axle is calculated by adding up the roll stiffness of all elastic suspension components. On a typical vehicle, that may include the springs and the anti-roll bars. However, as of 2025, we do not use anti-bars, so our total roll stiffness is equivalent to our spring roll stiffness. | Rolls stiffness is a measurement of a vehicle or axle's resistance to chassis roll. Total roll stiffness for an axle is calculated by adding up the roll stiffness of all elastic suspension components. On a typical vehicle, that may include the springs and the anti-roll bars. However, as of 2025, we do not use anti-bars, so our total roll stiffness is equivalent to our spring roll stiffness. Each axle has its own roll stiffness. The vehicle has a total roll stiffness as well which is found by adding the roll stiffnesses of each axle. | ||
== Spring Roll Stiffness == | == Corner Spring Roll Stiffness == | ||
Spring roll? Yum! | Spring roll? Yum! Corner spring roll stiffness on a given axle is determined using the following: | ||
<math>k_\theta_c_s = 1/2 \times k \times MR^2 \times t^2</math> | <math>k_\theta_c_s = 1/2 \times k \times MR^2 \times t^2</math> | ||
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* k<sub>theta cs</sub> is the contribution to overall roll stiffness by the corner springs | * k<sub>theta cs</sub> is the contribution to overall roll stiffness by the corner springs | ||
* k is the linear spring stiffness | * k is the linear spring stiffness | ||
* MR is the motion ratio | * MR is the motion ratio between the corner spring and the displacement of the wheel center | ||
* t is the tract width of the axle | * t is the tract width of the axle | ||
== Anti-roll Bar Roll Stiffness == | |||
The estimated torsional stiffness of an antiroll bar on a given axel can be calculated using: | |||
<math>k_a_r_b = \frac{\pi D^4 G}{32l}</math> | |||
* k<sub>arb</sub> is the torsional stiffness of the anti-roll bar | |||
* D is the diameter of the anti-roll bar | |||
* G is the anti-roll bar's material's shear modulus | |||
* l is the anti-roll bar's effective length | |||
The ARB roll stiffness is determined using: | |||
<math>k_\theta_a_r_b = k_a_r_b \times MR^2 \times t^2</math> | |||
* k<sub>theta arb</sub> is the contribution to overall roll stiffness by the anti-roll bar | |||
* MR is the motion ratio between the twist angle of the anti-roll bar and the wheel center displacement | |||
== Sources == | |||
[https://kktse.github.io/jekyll/update/2021/05/12/simplied-lateral-load-transfer-analysis.html Simplified steady-state lateral load transfer analysis for spring rate and anti-roll bar selection | Kelvin Tse] | |||
Revision as of 15:48, 31 July 2025
Rolls stiffness is a measurement of a vehicle or axle's resistance to chassis roll. Total roll stiffness for an axle is calculated by adding up the roll stiffness of all elastic suspension components. On a typical vehicle, that may include the springs and the anti-roll bars. However, as of 2025, we do not use anti-bars, so our total roll stiffness is equivalent to our spring roll stiffness. Each axle has its own roll stiffness. The vehicle has a total roll stiffness as well which is found by adding the roll stiffnesses of each axle.
Corner Spring Roll Stiffness
Spring roll? Yum! Corner spring roll stiffness on a given axle is determined using the following:
- ktheta cs is the contribution to overall roll stiffness by the corner springs
- k is the linear spring stiffness
- MR is the motion ratio between the corner spring and the displacement of the wheel center
- t is the tract width of the axle
Anti-roll Bar Roll Stiffness
The estimated torsional stiffness of an antiroll bar on a given axel can be calculated using:
- karb is the torsional stiffness of the anti-roll bar
- D is the diameter of the anti-roll bar
- G is the anti-roll bar's material's shear modulus
- l is the anti-roll bar's effective length
The ARB roll stiffness is determined using:
- ktheta arb is the contribution to overall roll stiffness by the anti-roll bar
- MR is the motion ratio between the twist angle of the anti-roll bar and the wheel center displacement
