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By Darrin Crone on

Sir Nigel Gresley overhaul – Update 28

Further progress has been made in the workshop on the restoration of a historic locomotive.

Week commencing 7 May 2018

The removed coupled axlebox thrust inserts have now been measured and quotes for material obtained. Our repair method has been documented, including the specification of the material for the inserts, and when approved material will be obtained.

The painting team has now applied varnish to the coupled wheels and they’ve been prepped for their second coat. The outstanding bogie springs have been returned from the suppliers, with our new spare, and these are being painted prior to the assembly of the bogie.

The front coupling assembly that the loco carries in traffic varies from the original LNER/BR arrangement, as carried by 4468 and 60009. As we need to renew the front hook spring, we are in the process of manufacturing new springs to the original arrangement. To adapt this layout to our loco, an additional plate is required between the spring and the rear of the buffer beam. The plate is profiled to clear some rivet heads in the bufferbeam. To prevent it from moving and wearing the hook shaft, the plate is now held on pins in the bufferbeam. The plate is presently being bored to increase its clearance on the hook.

The rubber for the front hook springs is on order and the plates between the rubbers require blasting and deburring.

The last of the lower slidebars has now been dye penetrant inspected and no defects were found.

The outside of the smokebox door has been needle-gunned and painted. We’ve also worked on the door bar and dart, with the bar descaled and the dart cleaned for inspection. The dart threads are in good condition and have been dye-penned. No defects have been found and after a bit of tidying up will be fit for further use.

The last of the leading and upper cylinder and saddle fitted bolt holes have been spotfaced and bolts fitted. This has been an awkward and lengthy process, requiring tooling to be made to fit specific holes and locations. The bolts are also made to fit their specific holes, for diameter and length. In a couple of locations the seats for the bolt heads have had to be cut by hand with hammer and chisel. In other locations special washers have been required. However, the cylinders are now as well secured as they have ever been.

Close up of silver-coloured bolts on the frame of locomotive Sir Nigel Gresley.
New bolts have been fitted to the leading top of the saddle. These go through the saddle, frame plate and left-hand cylinder. The upper left only fits if the head is shaped and the face for the head was cut with chisels.

The loco bogie side bearer holes that are in the bottom cylinder flange have now all been reamed. The side bearers have been tried up and will need careful fitting—a method for the best way of doing this is still being worked on. As they are a relatively simple fabrication it may be easier to start with new material.

The final couple of horizontal hornstay bolt holes have been reamed. The holes now require countersinking, to ensure the countersinks remain on the hole centres. The countersink has been specially ground and has been received from our supplier.

Work continues on the safety valves, with quotes for material and machining from solid and patterns, so that we can decide the best way forward. Simultaneously, we have been talking to other loco owners about the possibility of purchasing additional parts on their behalf and so reducing unit costs to us. At the same time work continues on trying to determine original manufacturing dimensions and tolerances, as we only have access to worn valves.

We have now had visits from two lifting contractors with a view to obtaining quotes for the lifting of the tender tank clear of the frames. Both have described the same method of lift, which is the same as we had devised. Meanwhile, work continues on the tank with all of the corridor roof removed, and new steel work has been ordered. More stiffeners have been added across the corridor to the outside of the tank now that it is not supported by the roof. Descaling around the outside of the water tank, along the corridor and vestibule has uncovered some holing due to corrosion, though this seems to originate from outside of the tank. Most of the way up the corridor the tank appears to be in good condition.

The corroded inside of the tank of locomotive Sir Nigel Gresley.
Decades of paint, bitumen and filler have been removed in the corridor to determine the condition of the tank. This is a view into the vestibule end.

On the front of the tender, the GSMR user interface unit and the AWS battery box have been removed, as there is work to be done on the tender front platework.

The pipework fitting continues, with new pipe installation giving the assembly a very professional appearance. A number of joints are being relocated to enable easier access when in traffic. The air pump governor and its pipework have been refitted temporarily as the governor is to be relocated. This gives us an idea of the space required for the governor pipe runs.

A curved section of copper-coloured pipework from locomotive Sir Nigel Gresley.
A section of the new air brake pipework before fitting to the loco. The curved pipes furthest from the camera are recovered from the current installation.

The ashpan is very near completion. The ashpan damper door screen requires new hinges and these are now being made.

The temporary screws holding the middle cylinder cladding have been replaced with permanent fasteners. Now that’s sorted, the ends of the drain cock cables to the linkage that runs under the cladding have been finally fitted. The cab handle has been operated and the linkage works well.

The drain cock operating rods are supported in cast slots in the side of the drain cock valves. As they are steel, the links wear the slots. It is apparent that they have been repaired before by rebuilding with bronze weld, so we decided to do the same again. This has now been done and a really good job has been achieved. During this repair it was discovered that one of the valves had a pin hole, which would allow cylinder steam to escape. Upon inspection of the other valves, we found that some show a surface defect in this same location, so it appears to be a common casting defect. Two valves were found to require the repair of a pin hole, and both have now been repaired.

Copper-coloured parts from the locomotive Sir Nigel Gresley on a workshop bench.
The drain cock bodies in which the pin holes were found have been repaired. All the outside draw-in cocks have had the side slots rebuilt.

After a reorganisation of the workshop the large vacuum cylinder was moved to the rear of the loco and was getting in the way, so we decided it would cause less obstruction in the loco frames. This has now been fitted. Before fitting, the stirrups that accept the cylinder trunnions were cleaned out and edge wear carefully removed. The stirrups were greased and the cylinder fitted. To stop it flapping around the cylinder has been tied up. The flexible hoses to the cylinder we tried on, since there was concern about their fit as they have a larger outside diameter than the ones removed from the loco (the smaller ones are no longer available). The new hoses fit fine.

Engineer in a blue hard hat working on the frame of locomotive Sir Nigel Gresley.
The trailing vacuum cylinder was lifted into the frames and secured.

The superheater header continues to occupy us. The middle sealing face and the one at the end of the header, which has a blanking plate, have been dressed to fit their respective covers. The middle face is fitted with a gasket and a template has been made for the purchase of a new gasket. New studs have been obtained and these are yet to be fitted.

The reverser stand has been examined for wear in its bearings and it was decided that the outer shaft bearing required adjustment. As this is a split bearing this is relatively easy to do using the existing bearing, and this has now been fitted. The bearings that support the trunnions of the reverser nut housing will be replaced.

The base of a locomotive reverser on a wooden pallet
The base of the reverser has a shaft that rotates and operates the reverser reach rod. The bearing nearest the arm has been re-machined and fitted to remove wear.

The new valve heads have been fitted to the valve spindles. They are all a good fit on the diameter of the spindles and butt up well to the spindle collars. The spindles have also been closely examined for knocks and burrs and any found have been carefully removed. The overall distance over the head ring grooves will be accurately measured and set to correspond to the distance between the valve liner ports, then the heads will be finally keyed to the spindles.

Piston valve heads and spindles for the locomotive Sir Nigel Gresley on the workshop floor.
The new piston valve heads are fitted to the valve spindles. Only the middle and right valve heads are new, as it was only these valve liners that required renewal.
Two bronze bearing discs from locomotive Sir Nigel Gresley.
The bronze bearing discs that are fitted between the loco and bogie are being machined. One has been faced, the other is still a raw casting.

Week commencing 14 May

The air pump governor has been remounted on the driver’s side of the loco this week. It was mounted on the fireman’s side, but we decided to move it to the driver’s side, as this is the safer side of the loco. If a fault develops with the governor it can affect the operation of the air pump, which it controls. The control can be overridden to keep the air pump going and maintain the operation of the air brake system. To do this requires access to the governor. On the driver’s side that means accessing the governor possibly next to another running line. The fireman’s side is more likely to be facing the lineside.

The ashpan hopper and damper operating gear was retrieved from store this week and fitted to the loco. The installation of these parts will assist in the rerouting of the pipework to and from the governor.

Piping of the air brake system continues at the rear of the loco. Our Chief Mechanical Engineer and the pipe fitting team have reviewed the system schematics and a number of modifications will be made to allow the repositioning of tees and gauge take offs, in order to ‘tidy’ the system and improve accessibility.

The new rings for the air pump shuttle valve were brought in this week and fitted. The air pump was tried but operation was not much improved on when the old rings were fitted. Again, operation was satisfactory when valve packing was used in one of the ring grooves. Attention then turned to the shuttle which does have a very large clearance in its bore, so that there is very little of the rings in the shuttle piston groove, perhaps leading to excessive leakage around the inside of the rings. It was decided that a new shuttle will be made and tried, reducing the shuttle piston clearance.

New hinges have now been fitted to the ashpan damper screen and some tweaking will be required to get the fit just right. Some small gaps here and there around the damper door hinges are being filled by small pieces welded in.

The bogie reassembly took place this week, now the painting team have finished painting the bogie springs. Just about every Engineering Team member in attendance this week played a part in it. All the bearing surfaces were scrupulously cleaned and lubricated with new oil. As we have the bogie on the wheel drop, under the overhead crane it was a relatively straight forward job, after easing the fit between the axleboxes and underkeep trays. After the wheels were in, the leading guard irons were refitted. There are still a few niggling things to sort out though.

The axleboxes are lowered onto the journals of the bogie wheelsets, guided in to position by Peter Brackstone and watched by CME Richard Swales.
With all the axleboxes in place, the frames are lowered, with a member of the Engineering Team at each corner to ensure that the axleboxes enter the bogie frame horns.
Men in overalls working on the bogie frames of locomotive Sir Nigel Gresley.
The axleboxes entering the horns as the bogie frames are lowered.
Working on the frames of locomotive Sir Nigel Gresley
After the frames are down on the axleboxes, the weight is held on the crane while the hornstays are refitted. The hornstays close the gaps in the frames under the axleboxes.
The assembled bogie on the wheel drop in the National Railway Museum workshop
The assembled bogie stood on the wheel drop in the National Railway Museum workshop

At the front of the bogie are brackets and carriers for the AWS/TPWS equipment. These were retrieved from store, cleaned and are now painted in primer. These will be refitted to the bogie before the bogie is refitted to the loco.

Parts of the AWS/TPWS assembly from locomotive Sir Nigel Gresley.
Parts of the AWS/TPWS assembly that is fitted to the front and underneath of the bogie.

New studs were fitted to the superheater header this week. Unfortunately some of the studs have gone further into the header than expected so they will have to be replaced by longer studs.

New plate has now been supplied for the tender corridor roof—six sections in total, rolled to the correct dimensions, reproducing the individual sections originally fitted to the tender. All the quotes have now been received for the tender tank lift.

The new piston valve heads for the right and middle engines fitted last week were measured for positioning on the spindles this week. Everything looks to be pretty much to drawing. Rings will be ordered and final measurements over the end rings will be taken. The valves are driven from the return cranks on the driving wheels so attention has now turned to this system. The expansion links were retrieved from store and dismantled by our 007 Gang of junior volunteers. After laying out the component parts they were thoroughly cleaned as they will require testing for defects. The clearances between the die blocks and running surfaces of the expansion links were checked.

Expansion links from locomotive Sir Nigel Gresley
The expansion links are now ready for testing and measuring.

The right-hand return crank has been separated from the return crank rod and will require fitting to the crank pin. The crank pins on the driving wheelset are new, being fitted during retyring. Initially measurements of the crank and crank pin end were taken and then the crank tried on, confirming that there is a quite a bit of fitting work required here.

The right-hand return crank of locomotive Sir Nigel Gresley
The right-hand return crank has been removed from its rod and tried on the crank pin.


This is the 28th update. You can read all the previous instalments here.


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