Cab Progress

Other work has meant that progress has been slow on Queen Anne.  The engine is running better (of which more later), but most work has concentrated on the cab.

The New Cab

The edges of the "doorways" into the cab are reinforced by what is known as "Half-round Feather Edging" which is riveted to the side platework.  Because the edges are curved in places, the feather edging has to be bent to the same shape as the platework.  To do this a jig was made from a 10mm flat metal plate and circular discs which had been turned to the radii of the curves on the cab sides.  The discs were held in place by 10mm bolts and other 10mm bolts were used to hold the feather edging in place and guide the bending process.

By carefully heating the feather edge to orange heat using an oxy-propane torch, the feather edging was bent to the required profile.  Care has to be taken in heating the metal.  Too much heat and the edging will kink to a radius that is too small.  Too little heat and the edging will not follow the circular arc.  The heating and bending has to be done carefully and slowly.  Some hammering is required to keep the edging flat.

Feather Edge - Making the first bend

Feather Edge - Making the second bend

The finished edging was offered up to the cab platework and found to be a close match requiring very little fettling.  A special jig was made to help drill 6mm holes in the centre of the edging and each piece (there are 8 in all) was drilled to take the rivets.  The edging was clamped to the platework and matching holes drilled through.

All 8 shaped Feather Edge strips

Feather Edge being fixed to the cab side

The edging on the upper sections of the cab has to be merged with the edging around the roof, so these panels had their edging bolted on as we are not yet ready to work on the roof.  The edging for the lower panels was cold riveted in place using custom-made 6mm countersunk rivets.  Before riveting, a thick layer of red oxide paint was applied to both surfaces, and some oil-based mastic was applied around the curved parts where the edging is not absolutely flat.  The paint and mastic are used as an interfay compound to fill up any imperfections and prevent corrosion setting in between the two pieces of metal.  The edging is riveted while the interfay compound is still soft.

To date, the lower right-hand side of the cab has been assembled using angle iron to join to the front and rear cab platework.  At the moment this has been done entirely using specially made stainless steel domed Whitworth screws to match those used on the original.  On the original cab the angles were fixed using domed rivets on one leg and domed screws on the other.  We will be doing the same, and the domed rivets have already been made, but this will only be done once all the angles etc. have been drilled.  When finally riveting and bolting the cab together, wet red oxide paint will again be used as an interfay compound.

Lower RHS of cab in place

Side View

Front View

Lower RHS of cab viewed from inside

Engine Progress

The engine is now running better without the grey smoke caused by unburnt diesel.  One of the original injectors was not really serviceable and suffered from severe back leakage.  Fortunately a local injection specialist happened to have a reconditioned VRH injector in stock that still worked, which has now replaced the bad injector.

Paint Colours

Someone (I believe he was working on an 88DS shunter) sent in a question about the proposed "Ruston Green" colour, but unfortunately it was accidentally deleted.  The sender queried the original blog post that suggested using Lincoln Green (BS381C 276).  The acknowledged expert on all things Ruston, Ray Hooley, states that Ruston Hornsby used Deep Bronze Green (BS381C 224) and we have one of his paint samples.  Deep Bronze Green is very dark, and seems much darker than the green paint that has been exposed by rubbing down.  Further tests on the old paintwork will be carried out, and comparisons made with a batch of shade 224 paint.  The actual shade that will finally be used is subject to further study.

Radiator Grille & Compression Testing

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 :-

1.    290 
2.    330
3.    320
4.    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.