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Sir Nigel Gresley overhaul – update 15

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The team in The Works are pressing on with the overhaul of Sir Nigel Gresley. Locomotive Engineer Darrin Crone provides us with an insight of recent weeks’ work.

This is the 15th update – you can catch up on the previous posts here.

Week commencing 7 April

New linings were fitted to the reverser clutch this week. This involved heating them in an oven to make them pliable then bending them to the correct curve to fit in the recesses in the clutch. The linings are screwed in place, and some of the old screws were apparently not of the correct thread type, so these were replaced as they were found to be damaged upon removal. The complete clutch was then assembled on the bench and the reverser shaft sheaves were used to test the fit. The linings certainly get a good grip.

The assembled reverser vacuum clutch with new linings in place tested with the reverser shaft sheaves in place.

The overhaul of boiler fittings and valves continued this week with the blower valve stripped and inspected. The valve seat lapping was completed and the valve repacked and reassembled. The valve is now ready for reuse. Work has now started on the overhaul of the manifold valves. Some see very little use in traffic, such as the shut-off valve for the boiler pressure gauge, but others, like the steam heat valve, don’t live such a quiet life and the wear is considerable. Upon inspection of this valve, it appears to be life-expired and will require replacement.

The new stud for the displaced thrust in the right-driving axle box was made and fitted this week. All the axle boxes are now ready for remetalling, though we still await the dimensions of the finished journals.

A tiny detail, but requiring making from scratch, a new locating stud has been fitted to the thrust insert in the right driving axlebox.

The painters have been busy again, applying the first primer coats to the inside of the saddle after a final coat with the needle gun. The painting team have been itching to get it painted for weeks.

Inspection of the bogie continued this week with the examination of the front and rear stretchers and all around the horns. The outside central sections of the frame plates are all that remains to be done. By the end of the week the first coat of primer was applied to the underside.

The upturned bogie frames have been extensively tested to ensure they are free from damage and defects.

The vacuum brake cylinders were dismantled this week, beginning their overhaul. There are three in total: two smaller ones mounted side by side toward the front of the loco, and a larger one mounted further back between the frames. The brake hangers and cross beams were mounted on the loco by the 007 Gang of junior volunteers last week, and this week the inspection of these components began.

The loco vacuum brake cylinder overhaul has begun. The larger cylinder nearest the camera is mounted between the driving and trailing coupled wheels and the two smaller cylinders are mounted in front of the leading coupled wheels. They are linked on the loco by brakegear that combines their brake force.

The outside cylinder bolt hole refurbishment continued this week. Only three remain to be done, since all the others have now been bored and reamed. The jig used so far to ensure accurate alignment will now require modification to access the remaining holes.

Inspection and assessment of the loco draw gear continued this week with the removal of the tender eyebolt and its rubber spring. The eyebolt passes through the front tender dragbox and the intermediate main drawbar is pinned in to it. This has now been measured and its current dimensions will be compared to drawing and permissible wear limits. It can then be decided if it requires any repairs or replacement. Measurement of the front drawhook shows it to be fit for further use – in fact, it’s surprising how little wear there is, but until 10 years ago it spent most of its time on the mainline, so the front hook probably didn’t get much use.

The tender eyebolt mentioned in this weeks report has been examined.

The right-hand leading combined brake shaft and spring bracket returned from repair this week and was trial fitted to the frames on Saturday. Measurements were taken of the trial position and compared to the position of the existing left-hand side. As you might expect from a hand-built 1930s locomotive that has seen a long and active life, things are not exactly as in the original drawing, so a certain amount of fitting is still required before finally locating the bracket. A cutter has been obtained and a set-up devised that will accurately drill mounting holes in the bracket to match the holes already in the frames.

The refurbished combined spring and brake shaft bracket trial fitted to the frames.

The final rivets were put into the right-hand footplating this week. The last ones went into the slidebar bracket. Attention was then turned to putting in the last rivet in the left-hand side footplate bracket. Shortly after completing this riveting, the footplating received its first coats of primer in preparation for refitting the oilbox brackets which sit on the footplate in this area.

Not mentioned in the report, the plates at the back of the bufferhead that compress the smaller rubber springs an the back of the buffer assembly have been skimmed to remove deformation from decades of use.


Week commencing 14 April

With the footplate riveting finished, paint has now been applied around the riveted areas. This has enabled the two large oil boxes to the rear of the saddle casting to be fitted on freshly painted brackets. These were retrieved from store earlier and given a finish clean and some minor attention to the connection threads.

The large oil boxes located just to the rear of the saddle were refitted this week over the recently fitted footplate rivets and newly painted footplating

Earlier in the week all the axle box mechanical lubricator copper piping was retrieved from store. The pipework, as usual, was given a further clean through and is now going through the process of inspection, repair and annealing. The mechanical lubricator has now been returned from overhaul, which has been carried out by our CME.

The brackets supporting the unions between the flexi pipes that run from the axle box lubricator copper pipes have been stripped down and are currently being painted. I had planned to fit them to the loco and have them painted in situ, but the painting team vetoed that decision as a better job can be done on the bench. The unions themselves have been cleaned and had repairs made to some damaged threads.

A view of the painting bench with the bogie side control springs in bright red, ready to refit in the bogie. In the foreground is one of the oil boxes, which received its last inspection before fitting to the loco.

The trial fitting of the leading right-hand combined spring and brake bracket has required some dimensional investigation to ensure that when left and right brake shaft bearings are placed on the same centre line, the right-hand bracket positions the centre of the spring under the centre of the axle box. We also have to ensure that there is sufficient clearance for the spring to move while in traffic. To achieve the common bearing centre line, we still need to remove some material from the trailing edge of the bracket for final fitting, as when trialled it was very near the hornstay.

Work on the manifold assembly continued this week with attention turning to the manifold casting itself. All the valves have now been refurbished except for the manifold shut off valve, which is an integral part of the manifold casting. Work started by removing wasted studs, then cleaning and carefully abrasive blasting the surface. This will allow a detailed inspection of the surface.

The manifold that normally sits inside the cab on top of the firebox and supplies steam to various systems on the locomotive under the control of the crew. The flanges are normally coupled to valves. The manifold has been cleaned and some of the damaged mounting studs have been removed and will be replaced with new ones.

The inspection of the bogie frames was completed this week, and the painting team wasted no time in finishing applying the undercoat. We are concentrating on painting the underside of the bogie before we turn it back the right way up and these areas cease to be easily accessible. The side control springs, to be fitted before turning the bogie frames, were painted this week. The spring cups, spacers and other parts were painted some time ago.

The inside of the upturned bogie frames receiving an undercoat, now that the frames have been proved defect-free.

By the end of the week, undercoating of the bogie frames was completed. This will be glossed next, but painting of the outside frames and upper surfaces will be completed when the frames are back the right way up. This is a view from the front of the bogie. The brackets on the front of the bogie support a beam, on which is mounted the AWS receiver.

The bogie axle boxes have been closely examined and measured by our CME, but to ensure their soundness we dye penetrant inspected the flanges of the axle boxes to ensure there are no cracks. All are free of defects.

The bogie axle boxes have been dye penetrant inspected to ensure there is no cracking in the corners of the flanges that control the lateral position of the axle box and wheelset.

Cylinder and saddle bolt boring continued this week with the boring of the first of the ‘really challenging’ holes. This hole was bored through and partially reamed. There are now only two holes left – these are the ‘really, really challenging’ ones. At the trailing end of the saddle, the last of the life-expired bolts that fasten the saddle to the middle cylinder casting were removed this week. The holes were then cleaned out to remove corrosion.

The boring of the front top cylinder flanges continued this week, with the uppermost in this photograph just bored through. This is the right hand side. Just one more to do each side, then this marathon is over.

Work began on the Cartazzi refurbishment as we removed paint from the wheelset axle. This was something of a challenge with it still in position, and the engineering team coped very well as always. The team also continued the examination of the vacuum cylinders, examining the piston rods for wear and distortion. The loco drawbar gear has been removed and measured over the last few weeks. Work continued this week on these parts and we gave them a good clean before they receive their crack detection examinations.

The piston from one of the vacuum cylinders sees daylight infrequently. Dated 1953, it looks to be in as new condition.

Written by Sam Terrace

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  1. Paul Leadbeater

    Hi Sir Nigel,

    Get well soon. Miss you already.

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