Part 6: Frames—February to April 2001
The loco frame has just undergone extensive magnetic particle testing to check up on previous weld repairs. This followed on from heavy professional grit blasting after it came to Adelaide. It would not be an understatement to say that NM25 was sentenced to hard labour from the day it entered traffic, and that the sentence was rigorously enforced. The frames have been warped and cracked, welded and rewelded. Many of the welds are now shown to be cracked. This presents us with serious concerns about the long term viability of repair. We are aware of at least one case in heritage service where similar repairs have returned to cracks in a few years. Therefore, urgent steps have been taken to price compare the alternatives of repair or replacement. After doing this, and discussions with PRR loco and Executive people, it has been decided to make a new main frame. Whilst this sounds pretty radical, it will produce a far better long term result, for a relatively small additional cost over and above a repair job.
The left hand cylinder has (after the same grit blast job) shown up significant cracking due to a combination of poor casting quality, and an incident where it is believed the loco either took a short cut down an embankment, or suffered from a collision with an SAR T class loco. The cast iron smokebox saddle is also cracked, due to the tendency of the cylinder weight to pull the frames apart, and probably also the aforementioned incident. The fact that the QGR had gone to steel castings on the C17 probably says something. As with the frame, considerable effort has gone into evaluating the best options for corrective action in these vital areas. Accordingly, it is looking very much as though NM25 will be sporting one new cylinder. The right hand cylinder is somewhat newer, and is not expected to need replacement in this exercise. The saddle is likely to be strengthened using a patented metal stitching process, with assistance coming from as far afield as Mackay (QLD) and the USA.
TAFE have decided that building the new tender tank will be a great staff and student exercise. Accordingly, the tender underframe has been grit blasted and delivered to the Port Adelaide campus of Douglas Mawson TAFE, ready to provide a foundation for the new tank. Panorama campus are providing labour (at our cost) for a variety of metal fabrication jobs. This includes frame components such as a new rear drag box (the bit that connects the loco to the tender and therefore pulls the train along!), new smokebox, and new ash pan.
Two tradespeople, one metal trade trainee, and a part time trades assistant have been engaged, and are currently working on tender and loco bogies, spring hanger bushes and the like. Considerable effort is also being expended in getting components out to specialist suppliers for things such as grit blasting, spring repairs, and hard chroming. Items such as the all welded tender tank have required considerable engineering draughting work, to convert from the original riveted design, and to allow for currently available material sizes. To our horror, we have had to metricate some of this, because a lot of the modern world no longer has any concept of what an inch or a foot is. We have come up with a conversion that some modern people understand. A foot is roughly equal to the length of one school ruler!
The new frames for NM25 were cut on 4 April 2001 at Adelaide Profile Services.