Ixif iltroxnetex* Cozi.stx*\xctioxi a.xxd Operation 



In the following discussion, the numbers enclosed by brackets refer to the nimbers 

 in figure 4. The water supply [1], a 5-gallon polyethylene bottle with a 1/2-inch 

 tubulature, rests on a 4-inch-high styrofoam block [2] placed on top of the water 

 chamber [3]. A 16- inch-long, 1/8-inch i.d. acrylic tube [4] passes through the bottle 

 cap and allows air to enter at a point about 1 inch above the bottom of the bottle, 

 thus maintaining a relatively constant head. A Manostat (Cat. No. 36-541-30) flow 

 meter [5] is used to measure flow. The 3/8-inch i.d. plastic tubing [6] is connected 

 to the water chamber by a polyethylene quick-disconnect coupler. Flow rate is 

 controlled by an ordinary screw-type tubing clamp [7]. The 6-inch-long 1/8-inch i.d. 

 acrylic tube [8], connected to the water chamber by a polyethylene quick-disconnect, 

 serves three functions: it allows air to escape the water chamber during filling, it 

 indicates water pressure within the chamber, and it facilitates draining. 



The water chamber (fig. 5) is similar to the one described by Chow and Harbaugh 

 (1965), but has been modified for field use. It is constructed of plexiglas bolted to 

 angle aluminum. The numbers in parentheses in the figure indicate the number of pieces 

 needed. For added strength, four plexiglas spacers are placed as shown. All joints 

 are sealed with caulking compound. Each dot on the bottom view represents a 3/4-inch- 

 long 23-gage stainless steel tube.^ These 517 raindrop-producing tubes project 1/8 inch 

 above and 3/8 inch belcw the lower plexiglas sheet and are held in place with a small 

 amount of epoxy cement. Holes for the tubes were drilled with a No. 71 wire gage drill. 

 Holes for the 5-40 bolts were drilled oversize to 5/32 inch to avoid stress on the 

 plexiglas and to facilitate assembly. 



^0. 025-inch o.d., 0.00625- inch wall thickness, obtained from Vita Needle Co., 

 Needham, Mass. 02192. 



17 



