Started the week by fitting a new castellated nut to the rear N/S shock absorber shaft, to  replace the wheel nut that was on there temporarily.  That took much longer than it should have, as I had to straighten the thread with a die nut.  The next job was to spray some silver on various parts under the bus that needed it, including the N/S chassis which I primed last week.  I then turned my attention to the matter of replacing the main vacuum pipe, which was in very poor condition.  I decided to retain the ends, which screw onto the exhauster pump and the main junction to the vacuum reservoir and front brakes, and add a flexible hose section in the length above the chassis member.  I started cutting the lengths of new copper tubing and a length of flexible hose, then soldered on olive rings to provide a seal for the hose on the horizontal lengths of tube.  Next, I silver-soldered the sections of pipe together.