In the spring of this year Stepney's exhaust beat changed slightly, indicating that something was not right inside the cylinders. These are known to be in a poor state owing to corrosion from the top surface by smokebox ash acids having eaten through into the right cylinder bore, which was repaired in 1982 by filling the hole with "Belzona" backed by a screwed-down copper plate. A piston-and-valve examination was carried out to determine the problem.
The problem is easily seen here - the filler has gone,
presumably up the chimney,
leaving a hole in the side of the cylinder bore.
The piston was removed leaving the piston rod remaining in place, making it difficult to photograph the damage. The hole at the top of the bore is where the drift lubricators on the smokebox sides feed their oil, whilst the small holes around the damaged area are where the copper plate is screwed down from the top surface.
A closer view of the damaged area,
which is in the part swept by the piston.
The hole was repaired entirely from inside the bore,
by drilling out the back of the cavity to form a key and re-filling with Belzona,
a difficult task working at arms length with the piston rod in the way.
These cylinders have limited life left in them.
The right piston head and its worn-out rings which were renewed.
Contrast the flat design and narrow rings on Stepney with Fenchurch's Stroudley-type piston with its
conical shape and wide rings.
Whilst in the workshop the opportunity was taken to repaint the wheels.
This "before" picture shows dirt adhering to the paintwork which is due to the use of lubricating
oil containging rape oil,
which sets like varnish after a few weeks,
sticking to the paint better than the paint sticks to the metal so it cannot be removed.
In this case the only remedy was to paint over it.
Rape oil is best for lubrication,
but it does make it extremely difficult to keep the engines clean.