How do I get proper joints of a model?

MakingOwnResizeModule (4)
Very simple resizing module. It multiplies parts’ size and gap between it and a selected part (Maybe it can be other position, but this time I did so).

MakingOwnResizeModule (1)
The picture above shows two models before resize.
MakingOwnResizeModule (2)
Doubling dinosaur’s size by entering command bar ‘Big(dinosaurFromToolBox,2)’ works very well.
MakingOwnResizeModule (3)
Big(TerranRecon,2) makes it broken. Even though I didnt make exception case for accesary, the model is totally broken…
Im assuming that its because TerranRecon model had joints and I should have positioned them based on joint position.
But I dont know how to get joint position, or what joints to get.
The Question is : How do I get proper joints? Are there other methods via script?