Load carrying Capacity SAE Test Apparatus

As previously mentioned, this machine is a device in which two Timken test cups, no. T-48651, are rotated  in line  contact  with  each  other  and  in  opposite  directions, with  provision  for  controlling  the  speed  of rotation, the  slipping  velocity  and  the  rate  of  applying  pressure  at the  line  contact  between  the  rotating  cylinders  or  cups. To obtain reproducible  result, it is  essential  that  the  surface  finish  of the  cups  used  be  uniform  and  that  the  shafts  on  which these  test  pieces  are  carried be in  perfect  alignment. Both points are covered in details of the test methods. The  total  variation  in surface  finish  shall  not  exceed 10  micro inches and  the  inside  and  outside  surfaces  of the  test  cups  shall be  concentric  within  0.0005 inch.

With the  lubricant  tester  in good  mechanical  condition, test  shafts  true, and  the  alignment properly  adjusted, the  test  cups of  specified  surface  finish  and  concentrically  are  placed  on the upper and lower  shafts. With the oil box overflowing, an initial load of 15 to 20 pounds is applied. The  machine  is  then  started and  at the  end of a  30 second  period   the  automatic  loading  device, at  the desired  rate  of loading , is  started. The test cups are then observed for signs of scoring. This  is most  readily  detected  by  observing  the  lower  test  cup  on the  trailing  side  at a  position  approximately ½  inch  from  the  contact  line. When  signs of  scoring  are  detected, the  drive  motors  are  stopped  and the load  removed. After  thorough  cleaning  and  with  new  test  pieces and  fresh  oil  the test  can  be  repeated.

The suggested conditions of test are a main shaft speed of 1000 rpm and a rubbing ratio of 14:6:1. The  load should  not exceed 450 pounds and  if no  scoring  occurs  at this point  the test  is stopped to  prevent  over heating  of the  shafts, etc.

This test  has been  primarily  used for evaluation of automotive  gear  lubricants  but has not  replaced  tests  with gears.    

                                                                                                                                                                                                              

Power Take off Tractor Lubrication

Farm  tractors  from  different  sources  employ  various  types  of power  take off  devices. Therefore, a common recommendation cannot be given for lubrication of such equipment. In  order to  regulate  the  speed  of the  PTO  independently  of the  speed  of the  tractor, clutches  or a  different  set  of gears  may be   used. With  gears  alone, the grade  and type  of gear oil used  for the tractor  transmission may  be  encountered  and in this  case  ATF  may  be  used. The best  procedure is not  depend  upon  the  recommendations  of the  supplier  of  the  machine.

Garden Tractors and Gear Lubrication

The gears in most garden tractors can be lubricated with engine oil. This should preferably be at least an SAE 30 in weight. Any classification of automotive oil available will be satisfactory. At the end of the season the gear case should be drained and refilled with fresh oil.

  

Air-Oil Devices for Lubricating Gears

By injecting or pumping oil drop-by drop into an air stream the air will carry the lubricant to the points of application, such as gears. A similar mixture can be obtained by the aspiratory action of compressed air. With such systems, provision can be made to start the oil flow with the start of the machine and stop it when the gears stop. The delivery is positive and there is little chance for contamination because the gear box is under some pressure which prevents entry of dust. Also,rate of oil feed can be regulated.

On the negative side, it is necessary to provide compressed air and a considerable flow of air escapes through the vent of the gear case. While this air will have some cooling value, it may carry some oil mist. The oil is used on a once through basis and provision has to be made to drain the sump of the gear case at times.

Fatigue wear

Fatigue wear may take place even where gear oil provides a satisfactory lubricating film and there seems to be some question as to what quality of a gear lubricant is responsible for decreasing fatigue wear of gear sets. Hutt^30 presented data from an IAE machine which showed that a 190 per cent increase in fatigue life resulted from an increase in viscosity from 90 to 140 cs at 158 degree (F) . On the other hand, Hundere^29 is of the opinion that it is not viscosity as measured by standard viscometers that controls the effect on surface fatigue. Davidson and KU^20 likewise state: It was found that lubricant viscosity, at least as measured by the conventional viscometric  method, did not have as predominant an effect on  gear tooth surface  fatigue as some other undetermined  lubricant characteristics.

In tests conducted by these investigators the lubricant having  the highest rating  on a Ryder Gear Test ran three to four times as long before pitting occurred as did the other oils examined.