Constructing the AMSI-Cooker
The following pictures demonstrate the use of the wood model to make a parabolic cage out of reinforcement bars in the proper shape.
First of all the 4 rings have to be formed. They should be exactly round and flat. To check the shape of the rings draw circles with the right diameter on a level concrete floor or on a big peace of plate-wood. To check the rings place them on your drawing on the floor or the plate-wood. They have to cover the line an touch the level ground all over the circumference. If not, bend again and again and again ... because the quality of the cooker depends on it very much.
Then joint the two parts of the plate-wood model to form a cross as shown on the next picture and place all rings on it so that the rings are laying on the model at the positions marked with the small black arrows.
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Remarks:
- The little sun-like mark at the junktion of the two plate-wood pieces is the focal point of the parabola.
- To make the parabolic cage stronger the largest ring is doubled on this picture, where the hinges of the pot-holder will be placed. This is not needed if the cage is completely welded and not only fixed with wire.
Finally place the connecting sheet-metal piece (Part L in the construction plans) on the top of the wood-model so that the hole in the sheet-metal is exactly on the cross-point of the two model parts (see next picture)
After placing all the rings on the wood model bend the connection bars as described in the construction plans.
Measure the circumference of the biggest ring, divide the length by 6 and mark the six positions of the connection bars on the largest circle. Carefully hold the connection bars close to the final position and check that they just touch all the rings and the sheet metal plate on the top without displacing the positions of the rings on the wood model. If the shape is not absolutely perfect correct the shape again, and again, and again ... the quality of the cooker is depending on the exact shape of the paraboloid!
The next picture shows how the result should look like:
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Also you can see on the picture that finally all connection points are bended together by iron-wire pieces like people do to make reinforcement cages for concrete works on construction sites. If you did a good job with it the cage can be lifted of the wood model without any deformations.
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But better weld some or all connections point-wise together before removing it from the wood model. But avoid welding clos to the wood!
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Weld the sheet metal on the top to one or two bars with a welding point and remove from the cage the wood model
immediately not to burn the wood.
Now the most dificult part is done! The utmost degree of accuracy should be used to make this part of the cooker as it is important for the cooker quality. If the rings have a slightly different diameter or are not placed perfectly in the right position the fixation on the aluminium plates becomes difficult but the shape of the cooker is still perfect as long as all rings are touching the woofmodel at all possible points. This is the big advantage of using the model. (So: Accuracy becomes less important. But for the sake of quality: don't tell that to the metal workers.)
Now the Stand for the cooker is produced in the back you can see the finished pot-holder and the cage:
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And here are all may studends of the last solar cooker workshop showing prowdly their diploma.
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