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The GM PD-4501 Scenicruiser, manufactured exclusively for The Greyhound Corporation, was a three-axle monocoque two-level coach used by Greyhound from July 1954 into the mid-70's. 1,001 were made between 1954 and 1956. The Scenicruiser became an icon of the American way of life due to its presence throughout the USA in cities and along highways and popularity with the traveling public. The high-level design concept of Scenicruiser resembles some of the rolling stock of the passenger-carrying railroads of the United States and Canada, particularly their popular stainless steel dome cars. This type of two-level motorcoach body was common in the late forties in Western Europe, including Great Britain where it was known as ''Observation coach''.〔(Whitson RC35C ) built on Maudslay, Leyland, AEC, and Foden chassis between 1949 and 1952 (accessed March 10, 2013)〕 The concept of two-level monocoque body had been used earlier in the Spanish Pegaso Z-403 two-axle coach, designed in 1949 and entered production in 1951.〔(Pegaso Monocasco (monocoque) brochure 1951 ) accessed March 10, 2013〕 ==Overview== The Model PD-4501 as GMC called it was the most distinctive American ''parlor'' bus design of the modern era. It was the result of seven years of effort by Greyhound and GM Truck and Coach Division. The first GX1 prototype was based on a design by Raymond Loewy as . Originally conceived as a bus, Greyhound later used a tandem-axle, prototype called the GX-2, also designed by Raymond Loewy, to lobby for the lifting of length restrictions that applied to the operation of buses longer than 35 feet in most states at the time. Power for the production models was originally provided by two GM Diesel 4-71 engines of 150 HP each connected by a fluid coupling because GM had never seen the need for a V8 version of its Series 71 diesel engine. Each coach had a single three speed manual transmission with a two speed splitter for six forward speeds. There were some problems when the coaches were new because all of Greyhound's other coaches had four speed manual transmissions that shifted differently than those in the Scenicruiser. This meant additional training for drivers, who mostly disliked the new system. Interestingly enough, This rebuilding started during October so it was not the first use of GM's 8V-71 engine in a coach. The first coaches to use this engine were 1961 NEW Silver Eagles made for Continental Trailways by La Brugeoise et Nivelles (now part of Bombardier) in Belgium. The 1960 models of this coach used Cummins NRTO engines. When the 8V-71 was announced the 1961 models were shipped to Houston without engines and the 8V-71's were installed there. This started shortly before GM's model PD 4106 was introduced. Late in 1961 Eagle production was moved to the new Bus & Car factory (the coaches were now known as Model 01 Eagles) and Continental started shipping the engines to Belgium for installation in the coaches on the assembly line. The first design prototype for the Scenicruiser, called GX1, was a double decker with access from the lower deck and the driver was seated on the upper deck. It was soon decided that a split-level design would be better because the GX1 was too tall for many Greyhound garages and lacked luggage space for 50 people. The GX2 had a lower level containing the driver's area and entrance with 10 seats plus a restroom on the driver's side and the upper level with 33 more seats. This arrangement also allowed a large baggage compartment underneath the second level and provided a 360-degree view from the upper level. This was called the GX2. Both the GX1 and GX2 were actually built by Greyhound in 1947 and 1949 with help from GMC. In late 1953 GMC started work on its first prototype called the EXP 331. It was completed in 1954 and had some unique features that were not used on the production versions. Interestingly enough. After the last PD 4501 was built, this prototype was rebuilt by GMC and left the factory with serial number PD 4501-1001. The Scenicruiser was equipped with air-ride suspension and air-conditioning. The coaches were also unusual in having 10 wheels. Each rear axle had four wheels and tires but only first one of them (seen from the front) was a driven axle. The Scenicruiser's popularity with the public inspired GM's later PD 4107 and PD 4903 Buffalo bus 35 and 40 foot models, which arrived nearly a decade later. They had a less obvious "second level" which ran most of the length of the coach, side windows from GMC's line of transit coaches and a smaller upper windshield in the front because the driver and first passenger seats were positioned higher. Unlike the Scenicruiser, these models were available for sale to all operators. The Scenicruiser also caused GMC's top competitors, Flxible and Beck to bring out similar offerings. Flxible introduced the semi deck and a half Vista-Liner 100, a 35 foot coach (208 produced between 1955 and 1959) and Beck produced three similar 35 foot coach models for a total of 29 coaches. Beck also built twelve 40 foot Scenicruiser lookalikes in 1955 powered by the 300 HP Cummins NHRBS diesel engine. They were Beck's model DH1040 and some were delivered new to Queen City Trailways (later Continental Southeastern Lines). Most of Beck's 40 foot coaches were sold to operators in Cuba and Mexico. Beck had to repossess several of them and they later returned to the United States and were resold as used buses. A number of Vista-Liner 100's and even at least one of the later Becks have been converted to motorhomes and are still on the road. Mack Truck and Bus also produced a single model MV-620-D prototype in 1957 that was also 40 feet long but it found no takers even though Greyhound leased it for several months. This coach still exists in private hands in Ohio. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「PD-4501 Scenicruiser」の詳細全文を読む スポンサード リンク
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