Cab Forward Steam Locomotives

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Cab Forward Steam Locomotives

Postby calroth » Thu Jul 10, 2014 9:20 pm

Today I was researching cab forward steam engines and read that one of the challenges was to feed coal or oil into the fire box. Can any one tell me how this was done?
Also I studied the modern diesel locomotive design and from the front hitch to the engineers seat there is a considerable distance, apparently the reason is that it provides an easement or cushion for the operator in case of a front end collision. The early roll back design such as used in the EM-FD7 was not as safe because of lack of distance between collision point and engineers seat was not as safe as later designs. Is that a accurate assessment ?
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Re: Cab Forward Steam Locomotives

Postby Allen Hazen » Fri Jul 11, 2014 12:41 am

Cab forward steam locomotives in American practice (basically this means Southern Pacific articulates, though there may have been a narrow-gauge non-articulated predecessor) were all(*) oil-fired, with the oil brought forward from the tender in some sort of pipe/hose arrangement: coal firing wouldn't have been practical. (Southern Pacific had one class of coal-fired 2-8-8-4 articulates: they were of "conventional" layout, with the cab behind the boiler.)

My guess is that the Southern Pacific cab-forward cab design would now be thought of as horrendously unsafe. Lots of things were tolerated in the old days that would now be considered horrendously unsafe: footboards on the pilots of locomotives, for example, that allowed a crew member to ride on the front end, next to the coupler, in switching moves. Presence of SOMETHING ahead of the engineer's compartment has been standard in American diesel locomotive design to protect the crew in the event of running into something: my impression is that the engineering to ensure that it actually provides effective protection has gotten steadily better over the years. The modern "wide-nosed" cabs on high-powered locomotives have many design features to enhance safety: extra-thick steel plate on the front ed, front doors designed not to admit buying fund if, e.g., you run into a tank truck at a road crossing, very robust internal structure ("collision posts"), sand boxes (holding the sand that gets squirted onto the rails in front of the wheels to improve traction) located to provide an additional barrier between the crew and anything the locomotive collides with…. Something similar happened in the 1930s with electric locomotive design. The Pennsylvanian Railroad's early electrics, including the original P5A design, had cabs at the ends: in operation, the crew was at the front. After, I believe, a grade crossing accident in which the locomotive crew was killed, they rethought the design, moving the cabs away from the ends with a "hood" (narrow enough to allow forward vision alongside it) in front of it: thus the classic GG-1 and P5A Modified designs.

(The EMD F-7 had a surprising safety feature: the frame had a weak point BEHIND the cab, so the whole locomotive would buckle upwards in the event of a collision. Since the energy-absorbing weak point was behind the cab, the cab structure itself was less likely to be crushed.)

(*) There are, of course, potential exceptions to any statable rule! There were a small number of coal-fired steam locomotives designed to be operated bi-directionally. (The New York Central had 2-6-6 and 4-6-6 "double enders," operated by its Boston & Albany subsidiary on Boston area commuter trains.) These locomotives would, technically, be "cab-forward" when operated in the direction that put the boiler behind the cab! The trick was that they were not designed for long distance operation, and so didn't need a large coal tender: they were tank engines, with water tanks and coal bunkers on the locomotive frame in stead of a separate tender. The coal bunker was behind, or ahead… anyway, the cab was between the boiler and the coal bunker (as the cab is between the boiler and the tender on a conventional steam locomotive), and narrow enough to allow forward vision when running back-up. The steam-turbine electric locomotives built for the C&O and the N&W very late in the steam era similarly had coal bunkers on the engine frame ahead (since their normal direction of operation had the cab ahead of the boiler) of the boiler.

Summarizing: you can operate a locomotive with the fire-box end of the boiler either forward or aft, but with coal fuel you're going to have to have the coal supply -- tender or on-frame bunker -- at the end where the firebox is. The fireman's station has to be at the firebox end of the boiler, so there has to be at least a bit of a cab there. The engineer doesn't HAVE to be there, so you COULD come up with a two-cab design, with the engineer's cab elsewhere. The "camelback" steam locomotives on a number of northeastern railroads (railroads burning anthracite fuel) had the engineer's cab on top of the boiler, for better visibility than thought possible behind the very wide fireboxes of these locomotives. (This design was later banned, on the grounds that safe operation depended on engineers and firemen who could communicate with each other, and -- back in the pre-cell-phone era -- this was thought to be achieved best by having them in the same cab.) I think I have seen a drawing of a steam locomotive with the fireman's cab in the normal place and the engineer's at the very front, in front of the smokestack end of the boiler, but I don't believe any American steam locomotives were built to this configuration in the 20th Century. For weird possibilities… look up the "Leader" class of Britain's Southern Railway and the similar "turf burner" of the Irish railway.
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Re: Cab Forward Steam Locomotives

Postby calroth » Fri Jul 11, 2014 1:41 pm

Thank you for the excellent dissertation. It might inspire me to write a small book on "weird" locomotives.
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Re: Cab Forward Steam Locomotives

Postby Allen Hazen » Fri Jul 11, 2014 5:00 pm

A book on… unusual… locomotives could be very interesting! For hints as to what to devote chapters to, there is a fun WWWebsite,
http://www.douglas-self.com/MUSEUM/LOCO ... coloco.htm

(It describes, among other things, at least one of the weirdos I mentioned, Bulleid (the designer) 's "Leader" for the Southern Railway in G.B.)
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Re: Cab Forward Steam Locomotives

Postby johnthefireman » Sat Jul 12, 2014 2:03 pm

The Railway Magazine in the UK recently had a two-part article on cab-forward locomotives. The second part dealt with the US ones, which were really the only ones that had a successful operating career, but the first part showed some interesting early examples from other parts of the world.
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Re: Cab Forward Steam Locomotives

Postby mikado-2-8-2 » Tue Sep 02, 2014 8:58 pm

Yes, the potential for a front end collision was one concern that the men in the cab had concern with in the early years of SP's Cab Forward locomotives. However their unobstructed forward view gave them a decided advantage over conventional locomotives and none were ever involved in one of the imaginary gory accidents that were imagined. My great uncle was an engineer on SP and ran cab forwards. My mom told me on several occasions she went on cab rides in them. As far as the fuel delivery the heavy oil they used for fuel it was heated in the tender by steam and it was pressurized by air at 5lbs per square inch to make it flow to the firebox.
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