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Mike Leahy's Diary

Day 11: Automated Panning

Typically the Gold is in the ‘wrong place'
It was another fine day, meaning we were to be very cold at first. As I wander around the sawmill trying to get my limbs to move properly and my brain in gear the view is amazing. There is a thick frost everywhere and the cobwebs are decorated with ice making them look like delicate lace.

Mike, Kate and JonathanTime is a real problem with this challenge. We haven't only got the cradle to finish but we have to connect it to the water wheel and construct a water pump. I start work on the water pump and at first try using half a tennis ball as a valve. The ‘pump' consists simply of a drainpipe which will be immersed in the water. A broomstick with half a tennis ball can then be slipped inside it and when moved up and down should pump water. The half-ball, because of its shape, acts like a one-way valve, very similar to the valves in your heart. When I push down, it should collapse and less water pass it to fill the drainpipe above, but when I pull back up, the half-ball should return to its original shape and bring the water up the pipe to the top. The first tests are promising, but when I try a longer pipe the valve isn't efficient enough. It's time for a re-think. A new valve is made up of a disc of wood which fits snugly in the drainpipe. There are holes drilled in it to allow water through when I push the broomstick down, but when I pull the stick back up a flap of rubber closes over the holes as water tries to flow through them. This seals the wooden disc, allowing me to draw water up the drainpipe. It works very well.

Mike explains the cradle to KateLinking the cradle to the water wheel is easy and involves the use of another broomstick. The water pump is powered in a very similar way to the cradle. We go through a dry run for the camera and are then set to go to the river. This is not easy because our ‘inventions' were huge.

When we reach the river we are immediately downheartened. It appears that the task of making an automated gold panner is impossible if only because of one fact. Fine gold is carried by water and is believed to be moved during floods. Like any particle suspended in water, it is most likely to ‘fall out' when the water slows. This tends to happen on the inside of river bends and behind boulders. In the first programme we chose to work on the inside of a bend and managed to get over half a gram in very little time. This is all very well, but the water wheel needs a strong current. These tend to be found on the outside of river bends. As the Whataroa River is quite wide at the location where we are working, our task looked hopeless. There is no way that we can find water fast enough to turn the waterwheel anywhere near the gold. Bummer! We wander around the side of the river near the gold for ages trying to find a decent current and finally plumped for a place sixty or seventy metres away from the area that we planned to dig. The tail is now wagging the dog - sort of. Our automated gold panning device is going to be more labour intensive to use than the simple sluice.

Nice grub.

I'm beginning to feel more comfortable with the evening filming now. I don't swear and I am trying not to wind Pippa up (the assistant producer who is filming us).

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Photo: Mike Leahy
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