Please note, there is no absolute necessity to convert the assembly to run on ball race bearings, if the original brass(yes, they appear to be brass) bushes are replaced with leaded bronze, phosphor bronze or sintered bronze bearing material and the shaft polished to have a good smooth finish then the bushes will perform very well for many years. I would, as others have also suggested, change the oiler to a grease nipple to help stop the problem of getting oil on the belts. So why did I go to ball bearings,,,,, well, um, ar ,,,,, so why do people climb Mt Everest?????
I wll refer to this Aluminium part as Part A, the back face being the end face closest to the cog tooth end. Before I dismantled the pulley assembly I measured the distance from the flanged bush at the back to the back face of this part, on mine it was about 3mm. I shall use the back face as a datum point. I set this part up true and bored it out to be close to the spring retaining holes, this bored hole will receive a bronze bush.
This part, which is made of steel, I shall refer to as Part S. Here I have it on a simple parallel mandrel the back end of which has a short very low angle taper so that it will jamb on the taper. I checked that the the pulley was running true, it was. I have machined the bearing surface true and parallel. At this stage of the modification I was only going to put new bushes in the whole lot. It was only after I got started on the project that I decided to change to an earlier idea to mount the pulley assembly on ball race bearings. The change caused me to come back later to this side to remachine and shorten it.
I rechucked it and bored the front end to receive this steel part I machined, it's about 1/2 to 3/4 thou inch interference.
After being pressed in.
I then rechucked true and bored to take ball race bearing. I made the bore to give about 2 tenths of a thou inch interference. The bearing recess is true to the journal. The ball race bearing is a 12mm ID x 28mm OD x 8mm wide.
On the back end you can see that I have now shortened the journal surface, I also machined it's diameter down to get rid of the wide lubrication groove that was in it. I machined in a shorter lube groove and smoothed and polished the sharp edges of the hole. This journal will run in a bronze bush.
Drilling two grease retaining holes in each end of the bush that I made. The material is leaded bronze bearing material.
For beginners who might not know. Here is the drill being oil stoned on it's cutting lips, only a small flat has to be put on each lip to stop the drill from biting in too fast in bronze and brass. Also good to do if enlarging a drilled hole in steel etc where the drill is just a bit larger than the hole you are going to enlarge.
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