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      02-15-2008, 04:01 AM   #104
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Drives: E30 M3; Expedition
Join Date: Apr 2007
Location: USA

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Originally Posted by malter2.0 View Post
Springs do not support constant mass. Technically, they do support constant mass, but not constant weight. Weight=force. People often use weight and mass interchangeably, which is ok, but in physics there is a clear delineation because weight takes into account gravity. Nit picking...anway. If you assume frictionless, even road, then yes. Real world ...definitely not. If you are in a curve do you think your springs are experiencing the same force as on the straight?
Huh? So the mass of the overall spring mass damper system for the car changes over time? The only way that's going to happen is if the number of passengers or the cargo mass changes. Well, fuel is being burned, so mass does decrease at a very negligible rate. Apart from that the mass is constant. You are mixing up spring force (and damper force for that matter) with the mass of the system. Again, the vehicle can be modeled as a spring mass damper system for many intents and purposes. You can write the system equation for it and solve for displacement, velocity, acceleration of different point of the chassis of the car for given inputs. Force is simply a variable in that consideration. Force can also be one of the inputs to that model depending on how complex your model is, such as air resistance related down force.

Originally Posted by malter2.0 View Post
Damping and springs are two separate things. I believe vette on one of the packages (and caddy as well) have MR fluid suspension which can vary damping and rebound.
Of course they are different variables. The solution for the displacement of the two ends of a spring/damper (suspension) assembly over time is a function of k, c, and m. One can control for that displacement by varying k, c, or both.

Anyway, a highly non-linear spring might be useful in a truck where the vehicle mass can change drastically, but that is clearly not what you are talking about. I am not sure how non-linear progressive springs are for a car exactly, but they can't be that non-linear. In the case of the Corvette, assuming the leaf spring is fairly linear, what exactly is the problem? Knowing your vehicle mass will not change, you can still control for a significant part of the transient response with the dampers.

Last edited by lucid; 02-15-2008 at 05:14 AM.