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In a generator that uses wood chips as the fuel a mechanism to move the hearth is needed. This can be constructed using a car windshield wiper motor. The motor can be controlled either by hand or automatically. The movement must not be continuous but the hearth must be moved now and then depending on the size of the wood chips. The movement removes ash and fine charcoal dust from the hearth and so the suction resistance is kept within acceptable limits. The motor can be mounted to a suitable place and connected to the hearth with levers.

Combustion chamber
The combustion chamber consists of a cylinder with a diameter of 500 mm and an air channel around it. The air channel is connected to the air channel of the outer mantle with a flange with diameter of 100 mm. From the air channel the air goes to the eight air nozzles placed evenly on the periphery of the combustion chamber. One of the nozzles must be aligned with the air channel (2) on the outer mantle to make it possible for the starting flame to directly touch the fuel in the combustion chamber thus making starting of the generator easier and quicker. The air nozzles are thread-mounted to be easily replaced if damaged or need to be replaced with differently sized ones. A bracket is welded below the air nozzles. On this bracket are mounted adjustment rings, bracket for the combustion chamber ring and the combustion chamber ring. The adjustment rings and the combustion chamber ring are separate parts to be easily replaced if the generator needs to be converted to use different kind of fuel or it is connected to an ICE with a different cylinder displacement. The round shaped hearth is mounted inside the lower part of the combustion chamber with four (part 4) brackets. Every other ring of the hearth is connected to the shaft (2) to be rotated slightly back and forth. This movement makes the charcoal layer move up and down that makes the fine ash and charcoal dust drop down through the hearth while the charcoal stays on the hearth.
The hearth can be made of 5 x 30 mm flat steel. The flat steel is bent to form rings which fit evenly inside each other. The rings are supported in the middle (2) and another shaft (3) is welded to the movable rings so that every other ring is movable and others are stationary. The gap between the rings is selected based on the type of the fuel, a typical value is 5 mm. The hearth is connected to the other parts with the flange in the upper end. In the final assembly the hearth is inside the lower part of the outer mantle. The flange joints are sealed with asbestos gaskets. The dimensions of the air nozzles, combustion chamber ring and the distance between the hearth and the combustion chamber ring is selected to match the properties of the ICE to be used. The distance between the combustion chamber ring and the air nozzles is adjusted to the right value with the adjustment rings. For proper operation of the gas generator the dimensions of the following parts and distances are critical:
If these are not properly dimensioned the generated gas will contain impurities, for example tar, or the amount of carbon monoxide produced is small.

Translated by Olli.