Below: Coffee Pot No.1 has been quite a regular performer on our Colliery railway since restoration was completed in 2010. However, over recent steamings we have had some issues with loose bolts where the crankshaft mounting casting is attached to the boiler. The bolts themselves screw into blind bushes (so no danger of steam leaking out and enabling an easier installation of castings onto the circumference of the boiler). However, when running in reverse, the design of the engine is such that the small pinion gear attempts to climb over the larger gearwheel mounted on the front axle. The result of this plus the vibration is loose bolts. However, whilst tightening them to some extent temporarily fixes the problem, long term wear has become manifest as the image below shows. These are two of four bolts which hold the centre of the casting to the boiler shell. Note how they have ‘necked’ and now look more like stays – the shank was once the same diameter as the outside of the threaded section. Also note the hammering of the threads on the left hand bolt.

Below: This is the main casting for the crankshaft assembly showing the two bolts removed. The simple solution would be to fit new bolts, but the movement of these over the last two years (and probably thought out the engine’s working life) has elongated the holes in the casting, rendering a possible fix of a ‘fitted’ (i.e. very tight) bolt shank to take up the wear impractical. So, we intend to replace the bolts and restore the full interface of thread within the bush, but also fit Nord-Lock washers which serve to prevent movement of a bolt under extreme stress or vibration. Hopefully this combination of effort, plus a restricted loading for the engine in terms of train weight, will enable us to carry on operating the locomotive. In the longer term the crankshaft casting will need removing and the holes boring to a true circle (and probably bushing) to enable us to fit fitted bolts (at the shanks) and therefore improve the overall fit in this area. However, as it is always a point of weakness due to the load and vibration (and thrust from the cylinders against the crankshaft pedestals) then we will have to monitor this area of the engine very carefully. A good example of the constant maintenance and care a 141 year old steam locomotive requires!