We are delighted to bring our supporters the news that the main frame plates for ‘Prince George’ have been ordered from Tata Steel Profiles. As soon as this week material will be at the Wednesbury plant to await its slot in the production schedule. This marks the start of a programme of work on the foundation of the locomotive, manufacturing the major components such as hornblocks, stretchers etc as shown in the CAD image. Note that the colours are purely to highlight the different major components.
MAJOR COMPONENTS OF MAIN FRAMES
FRONT FRAMES (ALREADY EXISTING) ATTACH TO FRONT END OF MAIN FRAMES
|1||Main Frame Plate||Profiles ordered|
|2||Motion Plate||Supports slide bars|
|3||Driving Axle Hornblock||Guides axle bearings|
|4||Frame Stretcher||Maintains frame spacing|
|5||Splasher & Boiler Slide Bracket||Supports splashers and rear end of boiler|
|6||Trailing Axle Hornblock||Guides axle bearings|
|7||Dragbox||Maintains frame spacing and braces against racking loads: houses drawgear to tender|
|8||Step & Cab Support Bracket||Supports cab and steps|
The front and rear frame plates of the George were overlapped between the cylinders and the motion plate. This was because of the limited size of machine tools available at Crewe . We already have the front frame plates; however we will be concentrating on the main frames as the main structure of the locomotive.
LNWR express locomotives gained a reputation for cracked frames during the LMS era. Possible causes include removal of the centre frame supporting the crank axle centre bearing, as ordered by Hughes, but very likely they were simply too lightly built. Our locomotive’s frame plates are 30mm thick as against the original 1” (25.4mm) and they are deeper between the driving axles.
Unfortunately not all parts can be manufactured identical with the original. For example, the dragbox supports the brake cylinder and a bell crank lever. The first 20 locomotives had the rather unusual LNWR vertical steam brake cylinder. This worked a linkage to operate both locomotive and tender brakes. Later locomotives had separate cylinders on engine and tender, much more sensible except for that it was vacuum brake with huge 21” diameter cylinders. Most steam locomotives had steam brake cylinders on locomotive and tender. The LMS and BR used the same 10” cylinder to the end of steam construction in 1960, so that is probably what we will use.
Hornblocks will be designed around roller bearing axleboxes and manganese liners to improve reliability and reduce overhaul costs. In order to be confident in our frame plate dimensions, it was necessary to select the bearings and model the axleboxes in some detail, which will pay dividends when we move on to them. Before committing to machining the frame plates we need to ensure that we define all the holes required for mounting the multitude of smaller details, such as brake hanger brackets, valve motion, attachments for cylinder cock and damper operating links, sand boxes and pipes.
We are now setting about detail design of the major components shown and getting costs for them, and their assembly into the locomotive frame. After that we will work up a fund-raising appeal so we can assemble the frames.
I am really excited about the prospect of getting the main frames assembled thereafter assembling our existing parts on the frames and giving shape to number 2013 ‘Prince George’, and I hope our supporters will be equally enthused.