The first of the large frame stays which have been re-designed as fabrications is presently being manufactured by North View Engineering Solutions in Darlington. This is the Frame Stay and Inside Motion Bracket.
Apart from holding the frames together, it also supports the inside cylinder slide bars. On the original P2 design it also had a saddle incorporated to support the front of the boiler where it joins onto the smokebox.
Apart from the decision to use Tornado’s shorter boiler causing the saddle to be in the wrong place, firmly attaching the back of the smokebox to the frames, in addition to bolting the front of it to the saddle on the top of the cylinder block gives the potential for cracks in the smokebox. This arises from the smokebox becoming much hotter than the frames when the locomotive is operating setting up severe stresses due to the smokebox expanding more than the frames.
Original P2 frame stay and boiler support
Modified stay for No. 2007
This problem was avoided with the A1 design by supporting the front of the boiler (and hence the rear of the smokebox) on a sliding foot to permit expansion. We are using the same arrangement for Prince of Wales. Meanwhile the next of the large frame stays, the Intermediate Frame Stay which as well as being redesigned as a fabrication has been modified to carry one air brake cylinder and an air pump instead of the original two vacuum cylinders has been ordered from North View Engineering Solutions.
Application of the Finite Element Analysis simulation package recently acquired to use in conjunction with Solidworks 3D CAD has indicated that the revised design has similar strength margins as the original, even with the addition of a 370 kg air pump.