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Beneath the waves diaries
Swim with the fishes
Ready for some deep sea diving, but no oxygen tanks? No problem, if you understand pumps and pressures.
Jonathan Hare's diary about the challenge for the Beneath the Waves programme, part of the fifth BBC/OU TV series Rough Science, based in Zanzibar
Day 2
Today I had a lot of fun plumbing-in all the copper pipe work and using an oxy-acetylene blow torch. This torch was far more powerful than I needed and nearly melted holes in the copper tubing, so I had to be careful. Tony, the cameraman, gave me loads of tips on how to use the pipe fittings.
I make up one-way valves from mouse balls (computer mouse balls!) These are slightly rubberised and make a really good seal with the copper fittings. Copper adaptors and fittings were used to make a vertical cylindrical container that was about twice the diameter of the copper tubing. Within this construction the ball rested in a funnel like section at the bottom. When air was pumped through the device, the ball would be blown up slightly to allow the air to pass. When there was no pumping (on the return stroke of the pump) the positive pressure above the ball kept it forced-in this funnel, blocking the tube and acting as a one way valve.
Two of these were made up and one fitted to each pump. The tubing following the one way valves were then joined up to form the output of the pumping system. The two pump plungers were then attached to a single wooden arm so that a see-saw action by the operators (Ellen and I) pushed one pump while the other pump refilled with air. Constantly see-sawing the arm constantly pumped air through the system. We had a lot of fun blowing up balloons and plastic gloves to unfeasible sizes before they exploded!
End the day with the sun going down and a little test of all the kit in the water tank.
Day 3
Today we all go out to film the diving gear working. We spend most of the morning travelling to a lovely location where we are to film. It’s near a private island where the rich and famous go!
The sea water is starting to corrode the outside of all the equipment but the insides all seem to be working OK. Kathy does a test of the air meter and we set up for Kate to start the test. It all works! Ellen and I pump away to get enough air to the tank as possible and Kate seems to be able to stay down and breathe for as long as she wants.
At the end of the day I also get a chance to re-use the hydrophone. I have fitted a new crystal and made up a better amplifier, after re-sealing I manage to get a much better recording of fish at this location. Two successes in one great day!
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Content last updated: 26/01/2005
