you shouldn't put ph_setgravity into an action, better in your main function etc...
then it would be good, if phent_settype and phent_setmass have the same hulltype.
I donno for what you are using it, but if you phent_Setdamping is 100 it don't move is not a force applied.

Make sure earthgravity is something as var earthgravity[3] = 0,0, -386;