The termcab forward refers to variousrail androadvehicle designs that place the driver's compartment substantially farther towards the front than is common practice.
Insteam locomotive design, a cab-forward design will typically have the driver's compartment orcab placed forward of theboiler at the very front of the engine. On a coal-fired locomotive, the fireman's station remains on the footplate behind thefirebox so as to be next to thetender. On anoil-fired locomotive, the fireman's station could be (and normally is) in the forward cab. This type of design was adapted for a few locomotives throughout Europe in the first half of the 20th century, often in conjunction with an enclosed body design and/orstreamlining.
Visibility is greatly improved when the cab is in this position, and in tunnels it does not fill with fumes from the chimney. However, the crew's prospects in the event of a collision are worse, and if the driver and fireman are in separate places it is difficult for them to communicate, just as inautotrains.
In Germany, Borsig in Berlin built a one-off streamlined cab-forwardDRG Class 05 (serial number 05 003)4-6-4 in 1937, with further development stopped by World War II. Fueled by pulverized coal and with thefirebox at the forward end, this loco was built with huge driving wheels, 2,300 mm (91 in) in diameter. The design speed was 175 km/h (109 mph), but its conventional layout sister 05 002 set a newworld speed record for steam locomotives on 11 May 1936, after reaching 200.4 km/h (124.5 mph) on theBerlin–Hamburg line hauling a 197 t train, a record it lost two years later to the BritishLNER Class A44468 Mallard. In 1944, the streamlining was removed, but the 05 003 had by then already lost its cab-forward layout.[1] After the war, it pulled express trains in West Germany until 1958. It was scrapped in 1960.
The state-owned ItalianFerrovie dello Stato had several cab-forward locomotives,Class 670 and 671. These4-6-0 engines had a three-axle tender, and were nicknamed "mucca" (cow). The engines (construction year 1902, top speed 110 km/h) were used to haul passenger trains on theMilan–Venice railway. A single Class 671 cab-forward was rebuilt as aClass 672 with aFranco-Crosti boiler in 1939.
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Matthias N. Forney was issued apatent in the late 1860s for a new locomotive design.[2] He had set out to improve thefactor of adhesion by putting as much of the boiler's weight as possible on thedriving wheels, omitting thepilot wheels from beneath the front of the boiler. Such a design would not have been stable at high speeds on the rather uneven tracks which were common at the time. Instead, he extended the locomotive frame behind the cab, placing a four-wheeltruck beneath the water tank and coal bunker. In conventionalWhyte notation, this resulted in a0-4-4T locomotive, but when run in reverse it was effectively a4-4-0T, with the track stability of that popular wheel arrangement, along with unobstructed visibility for theengineer, and improved dispersal of smoke and steam.[3]
Forney's design proved ideal for the small, nimble locomotives forelevated and commuter railroads, and he licensed the patent design to many manufacturers. Large numbers ofForneys served inNew York City,Boston,Chicago and elsewhere, but were superseded at the end of the nineteenth century byelectrification and the development ofsubways.
Ariel andPuck were2 ft (610 mm) gauge locomotives built to the Forney cab-forward design for theBillerica and Bedford Railroad in 1877 byHinkley Locomotive Works of Boston.[3]
The best known example of the cab-forward design in the United States, the Southern Pacificcab-forwards (also known to a lesser extent ascab-in-fronts andcab-aheads) placed the cab at the front by essentially turning the locomotive, minus thetender, around, and rearranging the controls for the operators to face away from the boiler. This arrangement was made possible by burningfuel oil instead ofcoal.
The cab-forward design was widely used by theSouthern Pacific Railroad.[4] The design was able to deal with the peculiar problems of its routes. The 39 long tunnels and nearly 40 miles (64 km) ofsnow sheds of theSierra Nevada could funnel dangerous exhaust fumes back into the crew compartment of a conventional locomotive. After a number of crews nearly asphyxiated, they began running conventional locomotives in reverse to keep the fumes behind the crew. This meant that the tender was now leading the train, which introduced new problems. The tender blocked the view ahead and put crewmen on the wrong sides of the cab for seeing signals. The tenders were not designed to be pushed at the lead of the train, which limited speeds. Southern Pacific commissionedBaldwin Locomotive Works to build a prototype cab-forward locomotive, then ordered more units before the prototype had even arrived.
All of the cab-forwards were oil-burning locomotives, which meant there was little trouble involved putting the tender at what would normally be the front of the locomotive. The oil and water tanks were pressurized so that both would flow normally even on uphill grades. Visibility from the cab was superb, such that one crewman could easily survey both sides of the track. There were concerns about what would happen to the crew in the event of a collision, and at least one fatal accident occurred on the Modoc Line inHerlong, California when a moving locomotive struck a flat car.[5] Turning the normal locomotive arrangement around also placed the crew well ahead of the exhaust fumes, insulating them from that hazard. One problematic aspect of the design, however, was the routing of the oil lines; because the firebox was located ahead of the driving wheels (instead of behind them, the usual practice), an oil leak could land ahead of the wheels and cause them to slip. A nuisance under most conditions, it resulted in at least one fatal accident. This occurred in 1941 when a cab-forward with leaking steam enteredthe tunnel atSanta Susana Pass, near Los Angeles. The tunnel was on a grade, and as the slow-moving train ascended the tunnel, water on the rails from a leaking cylinder cock caused the wheels to slip and spin. The train slipped backward and a coupler knuckle broke, separating the air line, causing an emergency brake application and stalling the train in a tunnel that was rapidly filling with exhaust fumes and steam. The oil dripping on the ties then ignited beneath the cab, killing the crew.[6]
No other North American railroad ordered full-scale production of cab-forward locomotives, although some, likeWestern Pacific, did consider the type. Built to deal with difficult terrain, these locomotives became an easily recognizable symbol of the Southern Pacific. In total 256 suchMallet-type articulated locomotives, in three different wheel arrangements, were placed on SP's roster. One example of the type,Southern Pacific 4294, is kept at theCalifornia State Railroad Museum inSacramento, California. It is a4-8-8-2 locomotive and is the only one of SP's cab-forwards that has not been scrapped. It was also SP's last new steam locomotive, built in 1944.
A decade before SP's first cab-forward, theNorth Pacific Coast Railroad, later part of the SP-ownedNorthwestern Pacific company, rebuilt an 18754-4-0 into an oil-fired cab-forward locomotive. This innovative engine was built by William (Bill) Thomas, the NPC master mechanic who was nationally known[7] and holder of a number of patents. Thomas used the running gear and frame from NPC locomotive 5, the "Bodega", which had been wrecked in 1897, to build NPC 21. With the addition a new and unusual marinewater tube boiler and an all-steel cab, installed in reverse order from standard engines, this unique creation earned Thomas a patent on the locomotive design. No. 21 entered service in 1900, but only lasted a few years. Although it reportedly steamed well, though with a sooty exhaust, the crews found it difficult to operate, and with fears of the possible results of a collision they dubbed it "The Freak". A negligent fireman allowed the water level to drop, damaging the boiler, and it was not repaired.[8]
Both theChesapeake and Ohio class M-1 andNorfolk and Western 2300 were experimental steam turbine locomotives that used a cab-forward arrangement. These highly unusual engines both placed their cabs in front of the boiler, and a coal bunker was then in front of the cab, while their tenders were purely for water.
L.D. Porta proposed a2-10-0 cab-forward, triple expansion,modern steam locomotive for fast-freight work for theACE 3000 project.
Experimental Prussian T 16 (seein German)2'C2' (4-6-4T) had control cabs at both ends.
Oliver Bulleid's ill-fatedLeader is sometimes referred to as a cab-forward locomotive, but since it had a cab at each end like a typical modern diesel or electric locomotive, this designation is not entirely appropriate.
The cab-forward design allows the passenger volume to be larger than in other similar sized automobiles.[9]
The first modernmass-produced U.S. automobile using the cab-forward concept was thePacer, introduced in 1975 byAmerican Motors Corporation (AMC).[10][11][12][13] The company did not call itcab-forward, but the Pacer's layout placed the passenger compartment farther forward than was typical to that time.[14] ItsA-pillars were moved forward and the windshield was placed over part of the engine compartment. The Pacer's "wide track and cab forward design actually lets it handle pretty well" given its body roll like competing contemporary models.[15]
Cab forward was used byChrysler Corporation starting in 1992, the first for a full-sized car,[16] to describe styling and engineering features that were similar to those seen on the AMC Pacer and theLamborghini Portofino, which improved cornering and interior space[17] The passenger cabin was forward, relative to typical designs, so that the front wheel well directly abutted the leading edge of the front doors, and the windshield extended forward over the engine, while the rear wheels were shifted towards the back corners of the vehicle. Moving the wheels to the edges allowed designers to enlarge the interior while improving ride and cornering.[18]
Numerous models built from 1993 to 2004 on theChrysler LH platform, theJA and JR platforms ("cloud cars"), and thePL platform (Neon), were specificallymarketed as cab-forward cars. Chrysler claimed to be the first to apply these features to afull-size car.[19] Likewise, the Dodge Stratus and Chrysler Cirrus have a hood that is wider than it is long because engineers established a goal of packing the engine and everything else that is located ahead of the passenger compartment into a much smaller space and then the designers developed the car's outer body to offer more interior roominess than competing models in their size class.[18]
In road vehicle design,cab-forward, also known ascab-over,COE (Cab Over Engine), orforward control, is a body style oftruck,bus, orvan that has a vertical front orflat face, with thecab sitting above the frontaxle. This body design allows for a more compact configuration. For example, theJeep Forward Control model was the first time the payload (or pickup box) had a record-breaking 74 in (1,880 mm) length (with the tailgate up) on an 81 in (2,057 mm)wheelbase as well as the first time offering a model where a 9-foot (274 cm) box exceeded the wheelbase of a truck.[20]
The cab-forward truck configuration is currently common amongEuropean andJapanese truck manufacturers, because the laws governing overall vehicle lengths are strict and the body style allows longer trailers or a longer cargo area for the same overall length than a standard truck (with an engine compartment ahead of a conventional cabin). Better visibility and maneuverability in tight quarters, such as for city delivery, are benefits of locating the truck's cab up front. Large trucks of this type are most often described ascab over engine (COE) orcab over models.
First domestic car with cab forward design
If there is a consistent formula used by Chrysler's designers and engineers, it is to expand passenger space, lavish attention on the interior and increase the driver's feeling of control by pushing the cabin out over the front wheels, while shoving the wheels out to the corners of the car to give the sense that it clings to the road.