SAE Extreme Pressure Lubricant Testing Machine

Since  investigators  often  refer  to wear  tests using  the SAE EP Lubricants  Tester, this  apparatus  deserves  mention at  this point. The machine  was  constructed  under  the  sponsorship  of SAE  by  the  Bureau  of Standards. The  action  is  presumed  to  imitate  the  rubbing  of  gear  teeth  by  rotating  two  Tim ken  test  cups (T-48651)  in line  contact  with  each  other  and  in  opposite  directions, under  controlled  speed, slipping  velocity,  temperature  and operating  pressure.

The  conditions selected by  Calish  for wear  tests  on an SAE  machine  were: 500 rpm; 3:4:1  roll ratio; 180 lb  load; 225 degree F; 500 ml /min  flow  rate; and  4  hours  test  duration. This author makes the following comment relative to this test:

“ Experience  in the  laboratory  and  from  service  indicates  that  it  is  desirable  to  hold  the wear to less  than  30 mg  in the  test  consistent  with  other  desired  oil  properties.”     

The Timken test cups can be weighed before and after a run and thus the weight loss in mg determined. For  wear tests on an  SAE    EP Tester  the  conditions  should  be  modified over  those  used  to  determine EP values. Such conditions are speed, rubbing ratio,     pressure and perhaps temperature.                              

Hydraulic Transmission Fluid, Type C-1

In 1995 Allison  Division  of  GMC  provided a  specification  for a  fluid  for  use  in  heavy  duty  truck, bus  and  earth  moving  vehicle  hydraulic  transmission, which  they  manufactured. In  these  application, Type  A  and Type A, Suffix A,  ATF  products,  described  later, showed  exceptionally  satisfactory   performance. However, the service in question did not demand all of the characteristics   of ATF. Therefore, by reducing the requirements of the fluid, less costly ingredients could be used.

The Allison specification was designated Hydraulic Transmission Fluid, Type C. Many heavy duty motor oils in the SAE 10W, SAE 20, and 20W viscosity classes in addition to some special fluids, adequately met the specification. Subsequent service showed that fluids in the SAE 10W class were most desirable. Consequently the specification was modified and updated as of 1997. A designation Hydraulic Fluid Type C-1 was   assigned to the new product. It  will  be  found  that other  manufacturers also  recommend  fluids of this type  for their  heavy  duty  torque  converters.