SAND BLAST ThSTS ni NKW SmT 1 . 1 \VAI.)> TIM15KRS. 621 



is contained in the reservoir y. from which it trickles down 

 through the opening /' and nozzle j on to the tray e. The 

 jet of steam rushing with velocity through c causes a 

 partial vacuum, so that the sand which has fallen on e enters 

 through the small aperture k, and is caught up by the jet 

 of steam which carries it upwards and projects it against 

 the specimen /. After impact with i the heavier portions 

 of the sand fall downwards into h y from which it may be 

 removed from time to time. The exhaust jet c already 

 mentioned, produces a partial vacuum, and in the manner 

 indicated by the arrows, causes the exhaust steam and dust 

 in chamber m to rush down through n into o and q, from 

 which it escapes to the atmosphere at c. By means of r 

 we can shut off the jet of steam and sand from the specimen. 

 The flow of sand through the pipe i is regulated by perforated 

 ring j partially rotated by means of a lever s, so that the 

 orifices at j may be opened or closed as desired. The 

 specimen I is held in place by a screw u which presses the 

 plate t against it. The specimen is rotated about its own 

 axis and by means of an epicyclic wheel train w the axis 

 itself rotates along the circumference of a circle. 



We thus see that every part of the exposed surface of the 

 specimen is subjected to the action of the jet, thus assuring 

 a uniform rate of abrasion over the exposed part of the 

 specimen. # is a pressure gauge marked in kilogrammes 

 per square millimetre. At the back of the apparatus we 

 have a door z which is opened for cleaning the machine, y 

 is a rubber ring to make a tight joint. A constant pressure 

 of 3 dgm. per sq. mm. which is equivalent to VI'G lbs. per 

 square inch was used throughout the tests. 



In order that each particle of sand may strike the speci- 

 men once only and not be used again, two feeding devices 

 « * have been arranged to allow the fresh sand to flow 

 through i and j on to the tray e. The used sand accumulated 



