My astronomy project:
Building an Observatory
(or a playhouse for big boys and girls)

Content:

1. Frame
2. Roof
3. Roof mechanics
   1. Different designs of roof mechanisms
   2. Building the mechanism for the roof
   3. Hatch Hinges adjustment
   4. Roof Rail Mechanism
   5. Arm Rail Guiders and Stoppers
   6. Counter weight arm
   7. Counter weight
4. Floor

Note:
I take no responsibility or liability for what are written here, you use the information on your own risk!

Page III.6: Counter weight arm

The roof is not very heavy, but still needs a counterweight or a spring to be operated easily. One part of it will be a steel beam, it's heavy and also will be the anchor to the motor that in future will open and close the roof.

Here are two holes that I have drilled and threaded, in M8 dimension. It was not that easy because the steel beam's thickness is 6 mm.

The steel beam will be mounted here on downside of the arm that lift the roof. This wooden arm is weak and maybe have to be replaced with a steel arm in future. It was easier to work with wood now in the beginning when I test ideas.