Golabandhas or Gola Yantras ( armillary spheres) are movable models of the solar system and other celestial bodies. They are referred to in the Surya Siddhantam, Aryabhattiyam and later texts like the Pancasiddhanthika of Varahamihira and Sisya-dhi-vrddhi-da of Lalla among other texts.
“The movable and immovable circles which form parts of the instrument are made out of thin bamboo strips. The earth and other celestial bodies are made out of wood and clay and the lines are connected by means of strings” . 
See Also : Astronomical Instruments in Ancient India
The entire design of the this instrument as given in the Surya Siddhantam is given below.
Ref 1. Encylopedia of Classical Sciences (Universities Press Ed Helaine Selin and Roddam Narasimha. Author: K.V. Sarma)
Ref 2. Goladipika by Parameswara Ed and Trans by K.V. Sarma
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