Envelope

The physical implementation of the robot uses a lighter than air vehicle (LTAV) in the form of a helium filled balloon (blimp). The blimp consists of a two-panel metalised nylon envelope 130cm in diameter (un-inflated), which once filled has the shape of a squashed sphere 1m in diameter. The envelope has a small non-return valve to facilitate inflation with the desired lifting gas; this valve can be opened using a tube to allow the envelope to be deflated for storage or replenishment of the gas. If the envelope is split or damaged it can be easily repaired using cellophane tape or ‘Sellotape’. The volume of the envelope is approximately 203 litres giving a net lifting capacity of 210g when filled with pure Helium (He) gas.

As the diameter of the envelope is greater than the maximum width of the material each envelope is made from four strips. Two strips are joined along their length to give a wide sheet with a central join which make one half of the envelope. Two of these wide sheets are then placed insides together on a flat compliant surface such as linoleum covered in thick paper (paper stops linoleum melting), the sealing jig is then placed on top and the heated rolled carefully moved round the edge of the envelope. It is important to get the right temperature and pressure settings for the joint to be successful; temperature of the roller is adjusted with a control dial whilst pressure is adjusted by adding weight to the jockey wheel bracket. The best way to get the correct settings is through trial and error.

Heat Sealing Jig

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