This is a very interactive model tried by visitors of all ages. A timer device stops after 1 Min.
Ball Chain of 4.5mm dia. is used. Two bicycle wheels are welded together to form pulley for drive and chain. The chain slips on the pulley for safety.The speed of the wheel 40 rpm. The chain falls on a coir Matt.
The drawing board of size 8'x4' mounted on a steel frame. The structure is of 50mmx50mm Sq. steel frame with truncated joints which are held in place with bolt and nut so that the whole assembly can be dismantled and transported. The pen table can be moved along the rail for different positions. We have used steel rope with plastic covering to hang the table. Standard 10Kg weights are provided to make the table heavy.
We were having difficulty in getting a glass bell jar. Finally we decided to use a SS container with a 5mm acrylic dome with compact PVC gasket held in place with C clamps. For all threaded joints we used shellac. The entire cycle of switching of vacuum pump on / off and air release are done through three cam switches driven by a 1 rpm motor .Recently we have added a Solenoid valve after the pump so that oil vapors do not enter the jar when the pump is in off position. For bell we have used one from old type telephone ringer with gongs which we used to supply to ITI.
This is an exhibit which involves the visitor manually. Ball bearings were used to make the freely oscillating pendulum and table . To start the motion ropes are pulled instead of pushing by hand ,this avoids wobbling of the pendulum. An acrylic cover was added to avoid visitor contact. First we used fine grained sand on the table but the markings were not very visible . So finally we settled on white fine stone powder (Rangolipowder)