Constraints Added for a transformed body

[bindumol]

Hi,
I am using bullet and irrlicht to develop some applications. In this each body part is an .obj file and i am making rigidbody from the mesh. I have some doubts in adding the constraints.
Firstly my bodies are having linear, up/down and angular motions. I am using hinge constraint for an angular motion . But after that i want to do some up/down motion. At that time i added fixed constraints with other body and the least body's linear velocity increases. In that situation i lost my angular motion and all body parts are moved to original position.
1.Is there any mistake in the sequence i have done in my application?
2.Can you give me any suggestions about my problem?
3.(or) Is there any other solution to solve this problem?



Thanks& Regards,
Bindumol