

A lubricant is valuable in proportion to its durability and its freedom from tendency to gum, and in proportion 

 as it exhibits a low measure of friction. In making comparisons, always test the standard, as well as the competing 

 oils, on the same journal, and under precisely the same conditions. An approximate value, by which to compare 

 the oils, can be calculated, based on the assumption that they will have a money-value proportionate to their 

 durability and to the inverse ratio of the value of the co-efficient of friction. Thus : suppose two oils to run, 

 the one 10 minutes and the other 5, under a pressure of 100 Ibs. per square inch, and both at the same speed, and 

 suppose them to give on test for friction the co-efficients o.io and 0.06 respectively. Their relative values might 

 be taken at ^{ = I and = .833. If the first is worth say 100 pence, the second should be worth 83} pence. In 

 many cases, however, about the same quantity would be applied by the oiler whatever oil might be used, and their 

 values to the consumer would be in the inverse proportion of the values of their co-efficients of friction, i.e., as 

 6 in the above case is to 10, thus showing that it would be cheaper to use the latter if its cost is anything less than 

 its relative value. 



N.B. Be Exceedingly Careful of the Testing Journal : a scratch will modify the result. Scientific accuracy 

 can only be attained by extreme care and cleanliness, and nicety ot measurement. See that all the drops used are 

 of uniform size. Strain the oil through a muslin cloth before testing. Keep on hand a standard oil of known 

 purity for comparison, weighing on a chemist's balance for fine work and using an apothecary's " dropper " for 

 ordinary tests. A good way, also, of securing uniformity, is to draw a No. 8 wire, a few inches long, to a fine 

 point ; dip it in the oil and allow it to drip half a minute, the succeeding drops will then be of very uniform size. Always 

 relieve the spring from pressure when the machine is not in use. See that the compressing-screw is always well oiled. 



Whenever, by an}' carelessness or inadvertence, the journal loses its surface in the slightest degree, keep it 

 running under light pressure until it is made right again. Move the bearing backward and forward two or three 

 times on its journal, just before taking each reading to redistribute the oil. Hang a tackle or deferential pulley 

 over the pendulum of the large machine, by which to lift it. 



5046 



5046 s Thurston's Patent Recording Oil Tester, " Railroad and Steamship Pattern," with 

 Mr. W. Worsdell's Improved Reciprocating Bearing, and facilities for testing bearings 

 of different alloys 



5047 s Thurston's Patent Oil Tester, the Bathgate Standard Pattern, as first built for the 

 Pennsylvania Railroad Co. Full size car axle, 7 by sf in., pressure as high as five tons ; 

 also supplied to Messrs. Young's Mineral Oil Works, and many railway and other com- 

 panies, without recording arrangement. This pattern is a small model of Fig. 5046 





90 



53 



CROSS STREET HATTCXN GARDETST, E-C 



