Versuche an Schiffsgetrieben

Summary

In the work carried out at Pametrada Research Station full size marine gears were tested in a back to back rig. This was to enable the maximum data of the losses, tooth strength (both breaking, pitting and scuffing), oil flow, etc. to be obtained under carefully controlled conditions. A method was developed for applying known circulating torques during running and a torque meter was used to measure the total driving power.

The results show, on analysis, that the bearings account for about 80% of the total losses. The tooth friction is relatively small. Measured values for the average coefficient of friction were 0.03 for hardened and ground gears, and 0.047 for soft steel hobbed gears.

The tooth losses were obtained by running the gears at constant speed and oil temperature and altering the load rapidly. The measured change in driving torque was therefore due only to alteration in the losses of the teeth. The coefficient of friction can be calculated from this change.

The bearing losses, obtained by subtracting the tooth losses from the total driving force, were compared with the simple Petroff formula. The agreement is reasonable.

Oil flow, as a function of pressure and speed, were also measured and analysed.

A simple quantitative method of measuring pitting was developed. This consisted of counting the number of pits per unit lenght of tooth (1/2 inch). The variation along the tooth was recorded as well as the increase in the number of pits with load. The pitting was found to be a maximum just below — not on — the pitch line.

It will be seen that apart from the measurement of tooth friction and the pitting, which can be determined in service, all the other quantities can be measured in a single gear box test. All that is necessary is to put a driving torque meter and oil flow meters on to the gear box, during the normal light running test which is usual after manufacture.