310 



ILLINOIS STATE ACADEMY OF SCIENCE 



to make the speed tests since a pump was sorely needed as 

 a fore pump in the junior electrical measurements work, 

 and later also in research. The pump was put to work at 

 once and has been in almost continuous use three days per 

 week ever since. 



Just recently (in April) it was arranged to try it out 

 quantitatively. To this end the pump was connected 

 directly through a short large diameter tube to a 12 liter 

 flask which had attached to it a 500 cc. McLeod gauge for 

 measuring the pressure, making with the connecting tubes 

 13 liters as the total volume to be exhausted. The connec- 

 tions and dimensions of the various parts are shown in 

 Fig. 1. In a test like this it is necessary that all connecting 

 joints be absolutely tight. The only two in this set-up, the 

 one connecting to the pump, and the other to the McLeod 

 gauge, were protected by heavy oil seals. The test consisted 

 in noting the time and reading the corresponding pressure. 



TABLE I. 

 Cenco-Hyvac Oil Pump No. A112 



13 liter volume 



RPM Equals 225 



Time in Pressure in 



minutes mm. mercury 



30 00786 



1.3 liter volume 



RPM Equals 225 



Time in Pressure in 



minutes mm. mercury 



4 01152 



6 00234 



8 00133 



10 00105 



12 00103 



17 00092 



27 00090 



