Re-Manufacture Of The Compensating Centre - (August 2016)
The compensating centre was essentially complete, however, to ensure correctness was thoroughly checked over against the drawings. Three issues were identified, that needed correcting to ensure good operation of the finished engine. It was found that the two inner hubs were machined 0.1mm too narrow, i.e. the inner face of the two bevel gear were too close together. The result was that when assembled the axial thrust on the hub was taken up directly on the bevel gears meshing with a radial gears, and not on the effective bearing surface between the two inner hubs. In operation this would result in premature wearing of the gears as all the loading it taken on the meshing.
The second issue was that the width of the centre was marginally two small thus allowed the centre to flex. The first issue was corrected by turning 0.9mm off the bearing face of the inner hub section and then making a bronze washer 1mm thick to sit between on the rear axle – hence spacing the hubs a further 0.1mm apart. This corrected the meshing issue and allowed for a pleasing amount of backlash. However, increased the error on the centre thickness! Correcting this second issue was in principle far more complicated and risky as there was far more work investing in this part and thus any machining issue would be far more upsetting.
Thus it was decided that the beast way forward would be to make a washer to take up the slack. The washers ID and OD matched the centre and thickness was machine to 0.28mm. It was cut from brass and it did dish slightly when being parted off, however this was corrected one a surface plate with a soft mallet! The final issue, was that the small bevel gears did not have the oil hole drilled though them. This as a simple drilling jib on the milling machine, using a digital angle gauge to set the gears flat before drilling.
The result –the compensating centre now runs true and smooth, with all the loads taken on bearing surfaces – happy days!
The compensating centre was essentially complete, however, to ensure correctness was thoroughly checked over against the drawings. Three issues were identified, that needed correcting to ensure good operation of the finished engine. It was found that the two inner hubs were machined 0.1mm too narrow, i.e. the inner face of the two bevel gear were too close together. The result was that when assembled the axial thrust on the hub was taken up directly on the bevel gears meshing with a radial gears, and not on the effective bearing surface between the two inner hubs. In operation this would result in premature wearing of the gears as all the loading it taken on the meshing.
The second issue was that the width of the centre was marginally two small thus allowed the centre to flex. The first issue was corrected by turning 0.9mm off the bearing face of the inner hub section and then making a bronze washer 1mm thick to sit between on the rear axle – hence spacing the hubs a further 0.1mm apart. This corrected the meshing issue and allowed for a pleasing amount of backlash. However, increased the error on the centre thickness! Correcting this second issue was in principle far more complicated and risky as there was far more work investing in this part and thus any machining issue would be far more upsetting.
Thus it was decided that the beast way forward would be to make a washer to take up the slack. The washers ID and OD matched the centre and thickness was machine to 0.28mm. It was cut from brass and it did dish slightly when being parted off, however this was corrected one a surface plate with a soft mallet! The final issue, was that the small bevel gears did not have the oil hole drilled though them. This as a simple drilling jib on the milling machine, using a digital angle gauge to set the gears flat before drilling.
The result –the compensating centre now runs true and smooth, with all the loads taken on bearing surfaces – happy days!