DEHYDRATION OF VEGETABLES 11 



In the construction of the forced air unit an ordinary household fan with a 

 blade diameter of 8 or 10 inches can be used. This is removed from its base and 

 the motor screwed to the framework on the false top by means of the guard braces 

 as illustrated (Fig. 4a). The fan is mounted with the blades facing upward so 

 that a space of approximately 2 inches remains between the blades and the top. 

 The air is blown against the top and is evenly distributed down the channel be- 

 tween the back and the false back. In this manner a maximum area of the heat 

 spreader is covered by the air blast. If the fan has been properly set, the»air blast 

 coming over the bottom should be sufficient to blow small pieces of paper placed 

 on the bottom out of the open door. The outlet for the fan wire is a small hole 

 directly below the false top brace, and may be bored on either side of the cabinet. 



When an electric heating element is used in this unit, the metal heat spreader 

 can be eliminated and the bottom of the cabinet made from the same material 

 as the rest of the dehydrator. A porcelain socket is screwed to the bottom over 

 sheet asbestos or some similar fireproof material to prevent scorching of the 

 wood by the radiant heat. Likewise, a canopy of similar material — or a cover 

 from a tin can will serve — must be placed over the top of the element to prevent 

 scorching of the product on the lower tray. Since no thermostat is used in this 

 unit, control of the temperature is achieved by an increase or a decrease of the 

 incoming air by varying the number of fresh air apertures. 



The following is a list of the material required. The cost as figured is the max- 

 imum. In many instances the cost of the items will not approach the listed cost, 

 and considerable saving can be effected by the use of crate lumber and other 

 materials usually available. 



32 square feet plywood (1 piece 4' X 8') for walls, top, $1.75 



chimney, etc. 

 56 feet 7/8" X 7/8" strips for supports, braces, tray 



frames, etc. 

 18 feet 3/8" X 3/8" strips for tray slides 

 32 feet 7/8" X 1/4" strips for screen strips 



All of these pieces can be cut from a 12-foot 2X4. 0.50 



H lb. 3-penny nails 0.10 



M Id. %-inch brads 0.10 



2 2-inch hinges with ^-inch screws 0.30 



5 feet 14-mesh galvanized screen, 30-inch width, for trays 0.50 

 1 piece, 18" X 1734", 24 gauge galvanized sheet, for 



heat spreader 0.50 



Total $3.75 



Additional material required for forced air unit with 



electric heating element: 



1 250-watt heating unit and socket 0.75 



1 sheet IS" X 1734" asbestos (or^other fireproof material) 0.50 



10 feet household electric wire 0.30 



$1.55 

 Less $0.50 for heat spreader 0.50 



$1.05 

 3.75 



Total $4.80 



