December construction update

Following a highly successful A1 Steam Locomotive Trust annual convention which included a visit to Darlington Locomotive Works to see progress on Prince of Wales the workshop has returned to normal with much detail work being done including riveting of the smoke lifting plate joint strips and permanent riveting and bolting of the front footplating. The chimney has also had all its mounting bolts and studs fitted.

Frames – With delivery from North View Engineering of the remaining coupled wheel manganese steel faced hornblock liners, detail fitting of them is underway. This has involved ensuring that the liners are making full contact with the horn blocks followed by opening out the bolt holes and reaming to take driven bolts

The gaps between the hornblocks were measured and mapped, after which the 16 hornblock liners have been fitted and their surfaces measured and mapped.

Ian Matthews measures the hornblock gaps – Bob Hughes

The aim is to have both liners in each hornblock truly square to the frames and parallel with each other. Individual liners will then be surface ground where necessary to achieve this. The initial results of the mapping are encouraging, with the horn faces very close to square across the frames and all with a small amount of material left on to provide for adjustment when the axle and cannon boxes are fitted. This is illustrating the benefit of having the frame plates and hornblocks CNC (Computer Numerical Control) machined to close tolerances from the 3D models. The hornblocks and liners have gone together with minimal hand fitting.

Final machining of the last of the major frame stays (the leading brake stay) is nearing completion at North View Engineering Solutions in Darlington.

The leading stay during machining – David Elliott

Wheelsets – The plain coupled axles have at last been delivered from South Africa and are presently at Unilathe at Stoke on Trent for finish machining. In the mean time Unilathe has completed the initial machining of the crank axle stubs and crank pin, which along with the crank webs have been sent to South Devon Railway Engineering for assembly.  Meanwhile in order to assist in balancing the coupled wheels, they have been laser scanned to confirm that the centre of mass of each wheel is where we think it is!  As part of the process to check the results of the scanning, each wheel has been weighed so that the density of the wheels can be compared by calculation with the known density of cast steel.

Unilathe are making good progress with machining the crank pins (from axle material – specifically from axle stock made for Class 56 diesel locomotive wheelsets) and have delivered the bolts and rod retaining washers for the leading crank pins, plus 3 large nuts for the intermediate and trailing crank pins.

Crank pin nuts and bolts – David Elliott

Timsons at Kettering are making good progress with machining the cannon and axleboxes (new photo of driving axleboxes, photos of completed Cartazzi axleboxes and bearing spacers)

Axleboxes during machining – David Elliott

Part-machined axleboxes at Timsons – David Elliott

Fully machined Cartazzi axleboxes – David Elliott

Cartazzi roller-bearing spacers – David Elliott

Coupled axlebox trunnion guides at Timsons – David Elliott