All of the components to assemble the frames have now been manufactured and machined, they are currently being assembled. We have spent a lot of time in checking the frame alignment and the fit of the
frame plates on the cast steel stretchers. In September 2019, specialists from Hexagon Metrology came to measure the frames with their latest laser scanning systems. This proved that the alignment was
virtually correct and a small amount of correction was needed. In September 2020, the frames were transferred to the assembly shop at CTL Seal for the important machining of the hornguides. The hornguides are the 3 per side, U shaped openings in the frames which contain the axleboxes for the driving wheels. The hornguides have been machined so that they are in line across the frames.
The cast steel frame stretchers, which ensure that the frame plates are the correct distanced apart, differ from those of the first 10 Clans which were fitted with fabricated stretchers. This was a lot 242 modification which followed the change for 71000 Duke of Gloucester; this having cast steel stretchers in an attempt to avoid frame cracking in the area of the hornguides.
A large part of 2022 has been fitting the frame extensions to the main frames - a critical join. Also in the same area is the front firebox support stretcher and pony truck pivot. In some places, a bolt needs to go
through 4 different components. Each bolt hole has had to be drilled and reamed until it is truly circular and parallel. The hole is then accurately measured and a bolt manufactured to fit that hole. This is virtually complete. The final job in this area is to fit the bracket that supports the rear driving wheel suspension spring.
In 2022, SSLC discovered that a new design of dragbox had been designed by British Railways as existing dragboxes were becoming distorted. Our drawings are now complete and we expect to place an order shortly. The front buffer beam has been riveted in place.
The manufacture of the pattern and the casting of the main cylinders is a long term job and we reckon that it will take 3 to 4 years to manufacture the complex pattern. Work is well underway on this job and our pattern maker, Tony, has provided a comprehensive step by step account of how you make a complex pattern, as is required for the cylinder casting. You can follow progress by clicking the link below. All CAD design work is complete and the motion cylinder pattern is complete. Work is in progress on the valve cylinder pattern and the main flange that allows the cylinders to be bolted to the frames. The complex part of the job is creating the 'cores' for the internal air spaces and the necessary transfer passages and unions. We have a sponsor for the casting of the cylinders.
The design team have completed work on the front bogie. We have all the drawings and have built the CAD model for the complete bogie. All of the components for phase 1 of the bogie construction are in
stock and assembly has commenced. A challenge is the side control springs which are a rectangular section, coil spring. At the moment we have not located a supplier who has the capability to produce a spring of this size.
The bogie wheelsets have now been manufactured. Assembly took place at South Devon Railway Engineering and we expect the wheelsets to be delivered to Sheffield shortly. This represented a
particular challenge as the axleboxes were a Timken design and detailed drawings were not available. With assistance from Timken, we developed our own drawings and these have been manufactured an
Trailing Truck or Pony Truck.
The next task in the build plan will be to manufacture the trailing truck. With the front bogie and trailing truck fitted to the frames, we have the ability to more easily move the frames, if required. The trailing or
delta truck for the lot 242 Clans follows the same design of 71000 Duke of Gloucester in having a coil sprung truck. Keith Collier who was the Chief Engineer for 71000 (and who worked at Crewe Works) has said that 71000 was one of the best riding locomotives he travelled on. We expect to start detailed design work on the trailing truck soon.
Although we have reproductions of most of the British Railways drawings for Hengist, we are finding that a drawing to modern standards is appreciated by suppliers. Most suppliers operate in metric
measurements and the BR drawings are imperial. First we create a 2D drawing to modern standards, converted to metric. Then we take the 2D drawing and transpose it into our 3D model. This identifies any
errors before metal is cut.
The tender can be developed in parallel with the locomotive so we are looking at policy decisions for the tender. There were a range of British Railways Standard Tenders which would be suitable for Hengist and
we will adopt a design which allows for the maximum water capacity. On the modern railway, water facilities are limited.
The boiler is a long lead item and we already have had discussions with potential suppliers. The main changes from the original design fall into 2 main categories. First, the boiler will be welded rather than riveted in the original. Modern boilers are riveted and the lack of overlapping joints in a welded boiler will result in a weight saving. Secondly, the original locomotives had a copper inner firebox. We will replace this with a steel inner firebox. This will be cheaper and save weight. With modern water treatment of the water used in the boiler, there is little advantage in using a copper firebox. Whatever we do, there is a considerable amount of design work required before we can consider placing an order for manufacture. The smokebox and cab have already been built to provide a showcase for the project.