# How to properly set up physics with door hinge?

I am a newbie with blender trying to create a simple animation where a safe falls on the floor, making its door open when it lands. I tried to set this up by making the cube and the door active rigid and the small rectangle that should serve as a hinge, passive. Then i connected the "hinge" with the "door" and gave a Hinge type body constraint to the rectangle. When i play the animation the objects will not fall, only move away from each other as seen on the picture. What did i do wrong? (i also changed their shapes to "mesh") Thank you all for your answers!

• please provide your blend file. so we can help you quickly. else we have to redo all your things you did...and even then ...could be, we do it in another way than you did. blend-exchange.com – Chris May 20 at 15:40
• Hinge type constraints are meant to work with emptys. IDK why you’re putting the passive body there, but you shouldn’t. Would have to play with this a bit to be sure, but try deleting that passive, putting an empty in its place and parenting to the safe, making the empty into a hinge constraint (make sure the axis is right!), and either set the safe to mesh collision instead of convex hull collision, or change the hinge settings to disable collision between the two altogether. – TheLabCat May 20 at 16:09
• Thank you very much for your help! :) – Matthew May 21 at 8:39

How to do it:

1. add an empty where you want the hinge to be. Important is the z direction. This has to be right, else the hinge won't work.

1. enter the parameters for the Rigid body constraint for the empty from 1:

object 1: safe object 2: door

you can limit the z-angle, if you want to.

1. give the safe and the door a rigid body

i gave my safe a weight of 4000 kg because it has such a treasure in it - should be safe enough for suzanne.

Shape: mesh

Friction should be high - you don't want the safe to slip on the floor, right? Bounciness should be very low - else the safe jumps around. Would look weird.

1. give the door a lower mass.

2. add a plane, give it rigid body passive.

3. move the safe up in the air, rotate it a bit, and start the animation and enjoy the fun you will have! ;)

Here is the blend file:

Here is the result:

https://youtu.be/s-ZfOSBvxZM

• Thank you very much for your help and the detailed instructions! Nice touch with the golden monkey head :) – Matthew May 21 at 8:38
• You are welcome. Can you please check the checkmark left of my answer if the answer is ok for you? – Chris May 21 at 8:49