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warriorracecars..thank you for the holiday wishes and i like that idea now that i understand it...seems to be the best way to hang left side weight and least hassle on camber build..
I am also curious about these "active rear suspension", here is a Port City asphalt car.Warriorracecars said:Thank you Mike. to be more specific, Left side weight being equal, other than camber gain/loss dependent on control arm length, can you think of any other reason to favor one style over the other? Moving inner pivot mounting points left would require a bigger split in LCA lengths left to right as compared to moving chassis centerline. Or in other words,, moving the tires to the right by mounting points moving right, which would allow for more equal length of the LCA. As far as droop, these cars are Using considerable amounts of rebound in the front shocks. The chassis stays down throughout once reaching bumpstops. On the rear end I have seen two chassis builders , (senneker and port city)utilizing a modified "birdcage" style of trailing arm configuration. still 3 link but the senneker style utilizes trailing arm mounts that "float" with attatchement point at the axle being centerline rather then from a dropped position under axle tube. same with port city, but the mount for them is solid mounted with a heim. they are calling this "active" rear suspension. Curious about your thoughts.
Rich
Thanks Ranger Mike. So to make sure I'm on the same page, top view looking down on the car, the angle that is there controls caster gain, positive or negative depending on if the wheel is in bump or droop ? I will review the previous info and research how this can benefit/not benefit my 86 chevy monte carlo street stock. By the way to determine roll center which mounting points do you use when in this situation the pivot points don't line up with each other? do you use a point that intersects the ball joint perpendicular arm pivot axis? Oh and by the way, real race cars have fenders! LOL. Thanks.Ranger Mike said:Welcome Loganc,
i am not a manufacturing or automotive engineer so the design reasons for this are not known since i was not in the design review. I can take a guess. Automotive companies need to compromise ride quality with safety considerations. The anti dive feature is the reason we have differing mount point angles. Rather than run very stiff front springs to resist the forces of inertia and mechanical resistance that the brakes create thru the front suspension,
we mount the upper and lower control ares at different angles from " level" as viewed front the side of the car. The Instant Centers thus created will cause the same effect as higher spring rates thru the braking force on the front suspension and the chassis will resist dive. This will handle the "weight" transfer to the front . and still enable soft springs for a pleasant ride.
On most chassis, the lower control arms are level front to back as viewed from the side. The uppers usually have about 2 degrees of angle front to back, higher in the front. This is called anti-dive. Now look at the vehicle centerline front to rear and the A-arm chassis mount points ( top view). No way are they parallel. The lower A-arm front mount is typically directly inside of the lower ball joint. ifin you drew a line between the lower ball joints (left and right), the front mount of the Lower A-arm fall almost on that line. The rear mount kinematically controls lower joint longitudinal movement during wheel travel. It contributes to caster gain and is also critical for comfort over bumps without using stiffer springs and harming the ride comfort. Compromise.
The same can be applied to the Upper A-arm. Draw your imaginary line between the upper ball joints and look for how the Upper A-arm relates. There are several thoughts on Upper A-arm mounting that ultimately control caster gain. You need find what adapts best for the 2D veiw of the suspension. It could be the front mount position or center of the A-arm.