Until recently, there has not been enough spare time to make much progress on Queen Anne, but we now have something to report.
Radiator Grille
The original radiator grille was made of mild steel mesh
with a mild steel strip around the edge.
Not surprisingly, the bottom part of the grille was a rust trap and was
badly corroded along with lower part of the bonnet that it was bolted to. So it was decided to replace it with
stainless steel this time.
The old grille used ¼ inch 16 gauge woven mesh. The nearest stainless steel equivalent that
can be obtained in small quantities is ¼ inch 18 gauge. We hope no-one will notice the difference. Suitable stainless steel U-section strips
were also obtained to act as a “hem” for the edges of the mesh. The grille had been fixed on by 5/16 inch
Whitworth dome-head bolts, so suitable replacements were turned up in stainless
steel.
The mesh was cut to size and the U-section strips were
mitred and fitted round the edges. The
mitred corners were then TIG welded together.
The mesh was positioned over the aperture in the bonnet and the
U-sections drilled to match the mounting holes. The resulting grille is better than new.
Radiator mesh and edging strips |
The bonnet with its new grille |
Compression Testing
When running the engine, it was noticed that cylinder No. 1
did not appear to be firing, and simply generated clouds of unburnt
diesel. The rings and cylinder liners
are new, and we had previously pressure-tested the cylinders. The test showed that there was very little
leakage past the valves or pistons on any of the cylinders. The spray patterns of the injectors seemed
OK, so it was decided to do a compression test.
A simple automotive compression tester kit was bought. This came with lots of adaptors for modern
engines, but none for a Ruston 4VRH, so an adaptor was made to fit the Ruston
engine. The non-return valve was fitted
at the bottom end of the adaptor to provide the best reading. The tester with the Ruston adaptor is shown
below.
Compression Tester and Adaptor |
The compression tester was fitted to each cylinder in turn
and the engine cranked round. Pressure
readings were as follows :-
- 290
- 330
- 320
- 310
The test clearly showed that cylinder No. 1 had
significantly lower compression. It was
probably no coincidence that this cylinder had the slightly bent con rod, so it
was decided to remove the cylinder heads No. 1 and No. 2 and take some
measurements.
The cylinder heads are essentially flat and the piston has a
large recess in the crown to form the combustion chamber. The top of the piston crown at its highest
point should ideally be level with the block.
By using a dial gauge, it was found that No. 1 was 40 thou below block
level, suggesting that the con rod was short.
This was almost certainly due to the fact that No. 1 and No. 2 cylinders
were seized due to water ingress through the exhaust after the loco had been
abandoned.
Subsequently a measurement was made of the volume of the
recess in the piston crown by filling it with water. Knowing that the cylinder capacity is 4 ½ inches diameter by 5 ½
inches stroke, the compression ratio comes out at 13.5 to 1. This is very low for a diesel (modern ones
are usually at least 16 to 1), but in 1948 they were probably happy to have a
low compression ratio because although the efficiency is less, the crankshaft
and crankcase do not have to be so strong and heavy. The extra 40 thou of clearance on No. 1 reduces the compression
ratio to about 12.5 to 1, which is borderline for a compression-ignition
engine.
Extensive enquiries were made to see if a replacement con
rod could be found, but the search drew a blank, so Plan B was put into
operation. This involved making a new
little end bush and boring it eccentrically to bring the piston to the correct
height.
No. 1 Con Rod with eccentric bush & old bush |
The con rod and piston were re-fitted and the height of the
piston re-checked and found to be correct (level with the top of the block
within a few thou). The heads have now
been replaced and the engine awaits testing.
It will be tested initially without the exhaust manifold so that the
exhaust from each cylinder can be compared.