Update, June 2001... The first two pictures are of a quickly made pail sprayer, ( for a "5 gallon" or "20 litre" pail). The first picture shows the lid of the pail to which a hose, a valve, a funnel and brackets have been fastened.
The next picture shows the underside of the lid, revealing the simplicity of screw gun fasteners and the simple 90 degree elbow pipe fitting which directs the spray air. The lid is held on to the pail using a simple rubber strap. Moderate slump cement effectively can be sprayed by balancing the filled pail rig on one's knee and opening valve while "pouring" the cement.
A summary of experiments will be reported here eventually. Pictures below are of an earlier, smaller sprayer used for more delicate cement spraying.
Below is a close up looking down the "barrel". The 3/4" (2cm), I.D. copper tube has been cut at center with an oval hole to allow cement to fall into barrel. At the far end the small orifice has been forced into the 3/4" tube, itself wrapped with odd bits of tubing and tape to secure in place. Although i never got around to it, i was going to place a small "air-bladder" (balloon) to check the cement when air is not triggered into use. An elegant way would have been to connect the air -bladder through small orifice to the same air line. Then, when the trigger is pulled, the air bladder deflates, allowing cement to fall onto airstream. (In the picture below, the rubber tube needs securing away from nozzle, this is a quickly written/ photographed page).
Comments are invited. Consultancy or constructive cooperation is offered.