29th September 2013: Making the gas tank Retrospectively adding some information about making the gas tank backpack following a request from another member:
The main tank is made from a thick cardboard poster tube with the top part from a lemonade bottle glued at each end. I glued these to the plastic end caps of the poster tube but only glued the bottom end cap into the tube as this allowed me to remove the top cap so that I could store my drink bottle in the tank (I also lined the tank with some foam to stop things rattling around). It is painted up with Plasticote Acrylic spray paint, apart from the yellow part, which I masked off and then painted with yellow enamel paint after sanding down the lemonade bottles.
The smaller gas tank is made from a piece of plastic pipe with half of a ping-pong ball glued to each end. Before I glued the ends on I drilled two holes in the side of the pipe and the main gas tank so that I could bolt the two together. This was also painted with acrylic paints. The valve on the small tank is made from a red plastic milk bottle top with triangular sections cut out of it to leave spokes. I then attached it with a long brass screw that went through one of the ping-pong balls and into a cork on the other side to hold it in place.
The backpack itself is the remains of an old rucksack- it is just he straps and the back piece with some extra webbing sewed on to attach the tanks to the backpack. To make the join more secure I added bands of sticky Velcro to the main tank and sewed the other side of the Velcro to the webbing. Note that it is very hard work sewing sticky Velcro onto webbing and if I did this costume again I would probably try using pop-rivets to hold the tank directly to the back piece of the rucksack and then just glue two bands of webbing on for show.