Dirt Late Model Vehicle Dynamics - Part 4

[chop6259]

Here is the next installment in our series on DLM vehicle dynamics. Let me know what you think so far.http://forum.bartlettmotorsportengineering.com/index.php?board=4.0

[hotshoe65s]

So far you are correct, but I feel like you'll be on part 200 before you get enough equations to fully define the system. Or, you will have to take a simplistic approach to it making a lot of assumptions about the geometry of the suspension.
I am working on what you are trying to describe in your blogs, and things become drastically more complicated as you get into it. If you want to correctly model everything, you will either have to make it in a CAD program and let the CAD do the work for the equations, or you better have some serious coding skills and be able to model multibody dynamics.
Either way, your blogs are a good explanation for most people of the acting forces. Keep it up, looking forward to part 5.

[chop6259]

So far you are correct, but I feel like you'll be on part 200 before you get enough equations to fully define the system. Or, you will have to take a simplistic approach to it making a lot of assumptions about the geometry of the suspension. I am working on what you are trying to describe in your blogs, and things become drastically more complicated as you get into it. If you want to correctly model everything, you will either have to make it in a CAD program and let the CAD do the work for the equations, or you better have some serious coding skills and be able to model multibody dynamics.Either way, your blogs are a good explanation for most people of the acting forces. Keep it up, looking forward to part 5.Hey hotshoe65s,yes, yes, and yes...There are four more equations to come that will define the dynamics of the system. The kinematics are another story all together. I have a completely separate kinematics model that defines the entire suspension system in three dimensions. It is heavily dependent on multibody systems techniques, and yes it is entirely done in the Python programming language. No pencil and paper work here. The kinematic model for the rear end alone is a system of over 50 nonlinear equations. The front and rear modules are written so that the entire geometry of the system can be defined using the heim-to-heim distances of the front, rear, and fifth-arm shocks. The geometry model is updated every iteration of the dynamics numerical solution method to provide the three dimensional points needed in the dynamic equations described in the blogs. If you have the money, a CAD package is definitely the way to go. Sometimes us poor folks have to do things the hard way. Thanks for the insights. I often wonder if all the work I've done on this stuff is just a waste of time.Joe

[hotshoe65s]

Hey hotshoe65s,yes, yes, and yes...There are four more equations to come that will define the dynamics of the system. The kinematics are another story all together. I have a completely separate kinematics model that defines the entire suspension system in three dimensions. It is heavily dependent on multibody systems techniques, and yes it is entirely done in the Python programming language. No pencil and paper work here. The kinematic model for the rear end alone is a system of over 50 nonlinear equations. The front and rear modules are written so that the entire geometry of the system can be defined using the heim-to-heim distances of the front, rear, and fifth-arm shocks. The geometry model is updated every iteration of the dynamics numerical solution method to provide the three dimensional points needed in the dynamic equations described in the blogs. If you have the money, a CAD package is definitely the way to go. Sometimes us poor folks have to do things the hard way. Thanks for the insights. I often wonder if all the work I've done on this stuff is just a waste of time.Joe

Haha, I think the same thing all the time. I'm building one in Python right now as well. Using the sympy and pydy packages really helps with the kinematics.

[chop6259]

Haha, I think the same thing all the time. I'm building one in Python right now as well. Using the sympy and pydy packages really helps with the kinematics.That's awesome! We should collaborate. It's rare to find other people, especially in the dirt racing world, that enjoy doing this kind of stuff. It would be nice to have a partner in crime to bounce ideas off of. I am also using the sympy package. I don't think pydy was around when I developed my kinematics model, but I'll have to take a closer look at it and see if it is a better application. I am sure it is more efficient than the tool I built.

[fastford]

hey guys, im to old to understand a lot of this computer tech stuff, but my son is a computer guru and im going to show this to him so he can help me, who knows, this may spark some, or more interest in racing for him being as how this is right up his alley, thanks for you guy,s work......