Progress of the restoration of the General Steam Navigation steam locomotive
The General Steam Navigation (GSN) Restoration Society has released its latest update on the restoration of steam locomotive Bulleid Pacific Merchant Navy Class No. 35011 General Navigation on Steam.
Inside the firebox, work continues on the boiler, with the last of the remaining boiler tube stubs removed last month. Rust is removed from the interior of the combustion chamber, the interior of the boiler is descaled, and the interior of the boiler and combustion chamber are cleaned before a scheduled inspection.
Progress continues in the design of the crank axle and the original drawing has been converted to an electronic CAD file. The next step is to design the chain drive sprocket and start conversations with a forger and fabricator to develop forging and fabrication drawings. Alongside the design work for the new crank axle, the thoughts turn to the balance weights. Rebuilt Merchant Marines had external balance weights on all three axles, but it is planned to remove the weight added in 1958 on the front and rear axles and rebalance the wheels, with weight in the pockets if possible.
The shape and material of the tie rods have yet to be decided, which will impact the amount of balancing needed on these axles. The goal is to mimic the classic Bulleid look with no visible balancing.
Originally, the crank webs and the inner connecting rod of the central driving wheel were balanced on the rim of the wheel, with a large plate on the back side of the wheels and lead in the pockets. By studying the designs of the original and rebuilt locomotives, the team now knows how to rebalance the drive axle.
From a mechanical point of view, the front and rear wheels will not need to be rebalanced, although from a cosmetic point of view it is expected to do so. It is also planned to install smooth rods like those installed in 1956 as they have greater tensile strength and are less prone to bending. The next step in balancing is to determine the layout of the lead in the pockets to achieve the desired counterweight. For the front and rear wheels, it is little more than a modification of the original design, but the center wheel requires additional design work to determine the center of gravity of the lead pockets and the weight plate of ‘balancing.
The five large brackets that held the external valve gear and screw-type diverter were removed from the frames. These are now surplus to requirements as there are plans to build Bulleid’s chain driven valve gear and fit a steam inverter. Removing them made it easier to access other areas of the chassis, and the last brake shoes and arms were removed from the front and rear axles.
All parts hanging from the frames will be removed later this year, allowing the frames to be raised, freeing the front bogie, front axle and trailing axle. The main bogie will then be assessed and prepared for professional restoration to mainline condition, while the drive wheels will be sent to South Devon Railway Engineering for rebalancing and profiling.
It is necessary to clean and examine the current condition of the frames, and to cut out and replace all corroded sections of the frame, rear platform and dragbox. It is also necessary to reverse some of the areas that were changed during the rebuild to allow for the installation of a new center cylinder and the replacement of Bulleid’s unique patented chain valve gear.
To help fund the work on the frames, a Funding the Frames call has been launched. All money donated to the appeal will be specifically earmarked for executives. If you can contribute to this project in any way, big or small, the company will appreciate your support. You can find out more here on their website
You can see the latest video update below
The company has a university project on the internal aerodynamics of a merchant navy. It builds on lessons learned over the past year, as well as a better understanding of the test data available on both the original smokebox and the rebuilt design. The project examines variations of the original exhaust design and variations of a Lempor exhaust to understand the impact of nozzle size, angle and target on smoke box draw .
As part of the project, a tour was arranged for students to visit the Loughborough shed to examine 34039 Boscastle.
2022 will be a very important year for the project with big goals in mind. To achieve this, society needs your help.
If you want to become a member of the Society, you can join for just £15 a year here on their website.