Recent communications from Robert Watson on this Forum and from John Renwick in the May 2010 MPH, page 15, concern fitting two back to back taper roller bearings to the drive side main shaft. Robert was good enough to send me a copy of his hand drawn original note from which Dan Smith did the modifications and fitting. As this is likely to be of interest to others, as well as ‘Roy the Mechanic’, and with Robert’s permission I have made a drawing which will explain to those who have not seen Robert’s sketch just what is involved. Note that the Robert Watson/Dan Smith modification has the flange with the countersunk holes on the outside of the bearing housing, that is inside the primary drive chamber, while John Renwick has chosen to put the flange inside the crank case near to the flywheel. Both have fitted a housing to take an oil seal on the outer end of the main shaft and in Robert’s case this is housed in a screw in oil seal holder with a left hand thread. The outer spacer, which sits between the outer parts of the two taper roller bearings, is an integral part of the bearing housing and therefore the position of this is dictated by what bearings are used and their dimensions. The inner spacer has to be accurately machine/ground to give a four thou interference fit in Robert’s case or a two thou interference fit in the case of ‘passenger0-0’. As both have been successful modifications it seems that the exact figure is not critical.
Please note that I have deliberately not put dimensions on the sketch as these will depend upon what size main shaft you are using and which bearings. There is quite a choice when one looks through the bearing catalogues. For either beefing up an engine or for recovering a worn set of castings this seems to be a useful piece of information which might help any of us in the future.
Please note that I have deliberately not put dimensions on the sketch as these will depend upon what size main shaft you are using and which bearings. There is quite a choice when one looks through the bearing catalogues. For either beefing up an engine or for recovering a worn set of castings this seems to be a useful piece of information which might help any of us in the future.