On its most fundamental level, the “Stephensonian” design of steam locomotive requires the exhaust to generate a draft to pull oxygen through the firebed and, thereafter, hot gasses through the flues to create steam. The more steam the locomotive uses, the higher the flow of oxygen through the fire, and the higher the generation rate of steam. This positive feedback loop requires a well-tuned machine.
While an efficient exhaust is important to generating draft, the flow of hot gasses through the smokebox of steam locomotives is almost as important. If one thinks back to the old “wild west” movies, the steam locomotives in those films had “balloon” stacks, the design of which employed a series of screens in the stack to arrest sparks. As the design of locomotives changed, so too did the mechanism of preventing lineside fires. As the size of smokeboxes increased and the understanding of fluid dynamics improved, spark arresting netting moved into the smokebox of the engine.
The solution developed in the U.S. over the first two decades of the 20th Century, known as the Master Mechanics’ Front End (MMFE), is an efficient way of arresting sparks and maximizing flow of gases through the smokebox. Named for the Association tasked with developing the design, the MMFE [ABOVE] employs a series of baffles [red] and screens [blue] to first break up then sift any burning cinders carried through the tubes.
In Germany, however, no system as efficient as the MMFE was employed. The diagram [BELOW LEFT] shows the existing arrangement of spark arresting on the 0-4-4-0Ts operated by the HSB.
The diagram [ABOVE RIGHT] shows a conceptual overview of the engineering work CSR is performing on behalf of the HSB. Both the new Lempor Exhaust and MMFE will fit into the existing historic envelope of the steam locomotive, yet the locomotive will be both lower in maintenance and more efficient to operate.
The Master Mechanics' Front End never caught on in Germany, rather they employed an alternative arrangement that, while in principal performs the same spark arresting function, in practice causes some operational headaches. The image at LEFT shows the existing system in 99 5906 [partially disassembled to show the netting]. The steel baffle is a first line of defense while the stainless steel netting strains out fine particles. This design does not, however, increase the velocity of gasses through the smokebox and it is prone to plugging.
CSR has undertaken hundreds of detailed calculations associated with the design and construction of the new components, from the optimal size of spark arresting screening to the best dimensional proportioning between stack and nozzles. At a glance, the detailed work going into the engineering project on the HSB, which is headquartered 4,300 miles away from Minneapolis, may seem a bit “far afield.” In reality, it has been an invaluable opportunity for the engineering team at CSR to work together towards a facet of our mission: research and develop sustainable railroad locomotives.
Already as part of this unique project, CSR engineers have digitally instrumented a near 100-year-old steam locomotive, re-engineered a smokestack and front end with fuel and power saving improvements, and have done so without jeopardizing the historic integrity of the engine.
This hands-on work has prepared our crews for taking on the next steps with ATSF 3463, including the application of a MMFE and advanced exhaust. It will be key with 3463 that the exhaust create sufficient vacuum in the smokebox to allow application of a Gas Producer Combustion System while not hampering the mechanical performance of the engine. The real world application of a Lempor the 99 5906 is a key step in preparing our engineers to take on “the big engine,” and performing improvements that do not detract from the artifact is a key consideration.
This research has also lead to some very interesting developments in the application of modern materials sciences, computer aided design [RIGHT], and digital instrumentation to the world of steam locomotive development. CSR has modeled, in excruciating detail, the planned improvements to 99 5906.
Working with the professional staff at HSB has also provided a unique opportunity to view what it takes to operate a tourist railroad that hosts more than one million passengers per year (in comparison, the Durango and Silverton Narrow Gauge railroad hauled approximately 175,000 passengers per year in the pre-recession mid-2000’s).