Novelty was an early steam locomotive built by John Ericsson and John Braithwaite to take part in the Rainhill Trials in 1829. It was an 0-2-2WT locomotive and is now regarded as the first tank engine. It had a unique design of boiler and a number of other novel design features (perhaps explaining the choice of name); however several major components had significant design weaknesses which ultimately resulted in its failure at the Trials.
Novelty in the Rainhill Trials
Ericsson and Braithwaite Partnership
During the late 1820s Ericsson and Braithwaite were working together building horse drawn fire engines with steam pumps. These used a boiler designed by Ericsson and were built in the London works of John Braithwaite. These fire engines were known for their ability to raise steam quickly and looked similar to Novelty. Charles Vignoles has also been associated with Novelty, but his practical involvement is not known. He may have aligned himself with the engine because of a continuing feud with George Stephenson.
Building the engine It is said that Ericsson and Braithwaite only found out about the Rainhill Trials seven weeks before the event was due to take place, when Ericsson received a letter from a friend referring to a "Steam Race". This incredibly short space of time has led people to suggest that Novelty is in fact a converted fire engine. It is more likely that it used a number of the same parts as their fire engines and these parts may even have been built for an existing order and diverted to Novelty. Novelty was constructed in the London Workshop belonging to Braithwaite and transported to Liverpool by boat. There was no time to test Novelty in London before transportation, and following test runs at Rainhill before the trials, modifications were carried out with the help of Timothy Hackworth.
The boiler
The boiler used on Novelty was designed by John Ericsson. The design was scientific for the era but proved to be hard to build and maintain compared with the boiler design adopted for Rocket and most steam locomotives since. The most prominent feature for the boiler is the vertical copper firebox (the large vessel to the right in the illustration here). Within the vertical vessel was the inner firebox and the space between the two was filled with water (to a level just about the same as the driver’s ankle). (Coke) fuel was added from the top, where a tube passed down through the top of the firebox. This firebox construction was not dissimilar to some types of vertical boiler, but this was only part of Ericsson’s design. Like George Stephenson, Ericsson understood that a large area was needed to extract heat from the hot gases. This he did in a long horizontal tube filled with water which ran under the full length of the engine. It can be seen in the illustration on top of this page, sticking out to the right, with the vertical chimney attached to it. Within the horizontal section was a tube carrying the hot gases, this formed an ‘S’ shape so the gases made three passes through the water. This S-shaped tube was also tapered causing the gases to speed up as they cooled down. In practice this tube is almost impossible to clean. The resulting boiler was the shape of a hammer and was required to be fitted to the frame before the footplate, cylinders or blower could be added. The boiler used a ‘Forced Draught’ provided by a mechanical blower (the triangular structure on the right in the illustration). This forced air along a pipe and into the sealed ashpan (below the fire). Few steam locomotives have ever used a forced draught like this, the main reason is that in order to add fuel either the draft must be stopped or some form of airlock fitted. Novelty used an airlock to feed the fuel in, but there was still a chance of flame and hot gases being blown into the face of the fireman. The blower was driven from the rods linking the cylinders to the wheels, thus the draught was proportional to the speed of the engine, not to how hard it is working as with a blastpipe. It is assumed that either the blower was worked by hand when the engine was standing or the drive wheels were lifted off the rails. Details of the blower design are not known for certain. Water was forced into the boiler using a pump driven off one of the cylinders (this was normal practice at the time).
Drive to the wheels At this time, engineers were worried about uneven wear on pistons and cylinders when they were mounted horizontally, so most were mounted vertically, but vertical cylinders driving directly on the wheels (as on Sans Pareil) caused problems with poor riding and did not work well with the springs.
On Novelty, the cylinders were mounted vertically towards the rear of the engine (to the right of the men in the illustration). Directly below were bell cranks which changed the drive to horizontal. Connecting rods linked the bell cranks to the crank axle (the axle on the left in the illustration). The valve gear took a similar route to the drive. One effect of this was it had multiple pins and links, resulting in lost motion. The wheels themselves were of the suspension type (similar to a bicycle wheel). While Novelty appears to be an 0-4-0 locomotive as it had equal-sized wheels, it is actually an 0-2-2WT. Only the wheels under the firebox (those to the left on the illustration here) were driven, the other wheels were not normally connected to the drive, although they could be coupled by a chain 'when necessary'.
The first tank locomotive Novelty was the first tank locomotive as it carried its water in a well tank between its wheels. As one of the rules for the Rainhill Trials related to the weight of the engine without a tender, a special allowance had to be made for Novelty.
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