The object of the Trials – or Ordeal as they were later officially termed – was simple: The Railway required motive power able to cover the road between Liverpool and Manchester at a given speed, with a given load.
The stipulations were the result of careful thought to bring out from the contestants exactly what the Railway was looking for.
The main areas for consideration were:
- The engine’s ability to ‘consume its own smoke’ – this was considered very important and meant that coke had to be used as fuel. This remained the case until the much later introduction of the deflator plate and brick arch which enabled coal to be burned satisfactorily. Whilst the L & M R Act was imperative on this point, revised conditions referred to later contain no reference to this point and during the trials smoke was emitted. Stephenson and Booth were already looking at smoke elimination in experiments conducted with the Lancashire Witch where they had tried producing steam without smoke using bellows. Burning coke in itself did not ensure freedom from smoke. Smoke emitted by the Rocket during the trials was attributed to coal having been accidentally mixed with the coke.
- The second stipulation was regarding limiting boiler pressure to 50lbf/in, which in the 1830s was high for locomotives but low for road carriage practice where 300lbf/in was not unknown.
- The third stipulation called for the provision of two safety valves, although in fact a third was required for the mercury in the pressure gauge as required in stipulation six. Reports show the locomotive builders to have taken exception to the requirement for use of expensive mercury for the gauge for the length required, indeed Burstall who entered Perseverance, ignored the stipulations to the extent of substituting the gauge with a special valve he considered better.
- Stipulation four required the locomotive to be spring borne, and carried on six wheels unless the weight did not exceed 4.5tons when four would suffice. It also stipulated a maximum height of 15 feet.
Have you heard? Visit the Virtual Museum for contemporary accounts of the Trials.
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