Anti-squat when car is on an incline

[rcx194]

What do people think happens to a cars anti-squat percentage when the car is on an upwards incline, i.e. climbing a hill?

I'm designing the anti-squat for a 4x4 which needs to be optimised when it's climbing up hill. Ie I want 100% anti-squat when I'm on a 20 degree incline and not on a flat road. I have some ideas on how anti-squat is affected but I would like to see what others think before I lead them along my ideas which could be wrong.

 

[rcx194]

Oh lets ignore that the suspension compresses/droops on incline and focus purely on how the geometry changes.

 

[BrianPetersen]

Why would you think it's meaningfully different? The forces involved when going uphill are akin to the forces involved when accelerating on the level.

 

[rcx194]

I don't know if it is different. I'm trying to figure that out. I've done some diagrams. And going to try to model it but I'm no specialist at these things.

 

[BUGGAR]

It's the same thing that happens under acceleration or deceleration. Your torque about the axle and the link geometry is the same. Look at the diagram and just tilt the page.

 

[rcx194]

I've gone over the diagrams a bit more now, and assuming my assumptions are correct, it turns out there is no difference whether the car is on a flat road or on a climb.

My assumption is that the "100% antisquat line" represents like a neutral axis caused by a forward force from the contact patch of the rear tyre and the reaction of the vehicles mass acting at the height of the centre of gravity at the front wheel.

Therefore if the instant centre of the axle links is on the antisquat line then there is no moment on the axle so no squatting.

If this is all correct then incline makes no difference (aside from the weightshift compressing the suspension which does alter the antisquat but that's easily calculated)

 

[NormPeterson]

What's different might be the maximum acceleration possible before a wheelstand becomes the result. That's a limit rather than part of the definition of anti-squat, but's probably worth considering.


Norm

 

[MrKennedy777]

Why would you want 100% anti squat?

 

[GregLocock]

Good point. I prefer to let my springs do the ground reaction bit rather than locking the suspension up.

Cheers

Greg Locock


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