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To the lighthouse diaries
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Jonathan Hare's diary about the challenge for the To the Lighthouse programme, from the BBC/OU series Rough Science 5
Our challenge is to make a lighthouse for an island off the coast of Zanzibar – Bawe Island. Ellen and Mike B will make the fuel and light source for the light, while I am making the mechanism to encode a signal onto the light. Kathy will make a system to drive it all.
We decide to build a moving structure that will block out the light in a regular manner so that the light will flash a signal showing where it is coming from. As the island is Bawe I decide to send a B in Morse Code. B is dash dot dot dot.
The basic idea is to make up a wooden curved structure or shade that will move around the central light in a circle. The shade has areas removed to let the light pass through and out into the surrounding area. By varying the amount removed and the speed of rotation we can set the Morse Code letter and speed. Half the shade is made completely of thin wood; the other half has areas of this wood removed to give a large gap followed by three smaller gaps. This then gives the correct light signal for a Morse Code B followed by a pause before repeating.
Although the mechanism was not heavy, it was quite large and so we needed some bearing to move upon so that it was as easy to move as possible. I used the golf balls we were given in the trunk to make up eight ball bearings for the apparatus to move upon. I also arranged for four vertical golf ball bearings to keep the system central. These worked really well. Each golf ball needs to be drilled centrally as best as possible as a wobble creates more friction and upsets the ease and ability for the thing to rotate freely.
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Content last updated: 26/01/2005
