Powertrain Mount Reaction Forces

[Robo25]

Good Afternoon All,
I am new to the site and new to the world of engineering (more of a math go-er). I am working on calculating the reaction forces of a 3 or 4 powertrain mount system. If I apply a load on the CG in the x,y,z direction how is it possible to calculate the reaction forces (x,y,z) for the different mounts? I know the mass of the system, the stiffness, orientations (euler angles) and positions of the mounts and have already worked on calculating the natural frequencies and kinetic energy of the system but I am hung up on how to do the reaction forces and it seems so simple to do. I know the equation is Mx..+Kx=f(x) where M is the mass matrix (I have a 6x6 matrix) x.. is acceleration, K is the global stiffness (also have a 6x6) and f(x) is the reaction force.
Any theory or advice on where to go would be greatly appreciated.
Thanks so much.

 

[GregLocock]

3 mounts is easy, if you ignore stiffnesses and other such side issues. First year statics.

4 mounts less so, as there is one redundancy in the vertical direction. This means you need to consider the various stiffnesses of the mounts.

If you actually want to do the job properly then you need to be very sure of the location of the engine mounts if there are 4 of them.

Roll restrictors and the like usually don't matter but they could add further constraints.



Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[inline6]

i would get a basic FEA package to do this. unless you are wanting to do it by hand as an academic exercise