PD-4501 Scenicruiser

كان النموذج الأولي الأول لتصميم حافلة سينيكروزر، GX-1، عبارة عن حافلة ذات طابقين ، حيث كان المدخل من الطابق السفلي، بينما يجلس السائق في الطابق العلوي. وسرعان ما تقرر أن التصميم ذو المستويين سيكون أفضل، لأن GX-1 كانت مرتفعة جدًا بالنسبة للعديد من مرائب شركة غرايهاوند، كما أنها تفتقر إلى مساحة كافية لأمتعة 50 راكبًا. لذا، تم تصميم GX-2 بطابق سفلي يضم مقصورة السائق ومدخلًا مع عشرة مقاعد، بالإضافة إلى دورة مياه على جانب الركاب، وطابق علوي يضم 33 مقعدًا إضافيًا. كما أتاح هذا التصميم مساحة واسعة للأمتعة أسفل الطابق الثاني. وقد سُمي هذا التصميم GX-2 . في الواقع، قامت شركة غرايهاوند بتصنيع كل من GX-1 و GX-2 بين عامي 1947 و1949 بمساعدة شركة جي إم سي. وفي أواخر عام 1951، بدأت جي إم سي العمل على نموذجها الأولي الأول، المسمى EXP 331. وقد اكتمل هذا النموذج في عام 1954، وتميز ببعض الخصائص الفريدة التي لم تُستخدم في النسخ الإنتاجية. بعد بناء النموذج الأولي الأخير من طراز PD 4501، أعيد بناؤه كنموذج إنتاج برقم تسلسلي PD 4501-1001 .

كانت عربة "سينيكروزر" مجهزة بنظام تعليق هوائي وتكييف هواء. تميزت العربات بوجود عشر عجلات، حيث كان لكل من المحورين الخلفيين أربع عجلات، لكن المحور الأمامي فقط كان مزوداً بمحرك.

كانت الطاقة تُزوَّد بها نماذج الإنتاج في الأصل بواسطة محركين من طراز GM Diesel 4-71 رباعيي الأسطوانات، بقوة 160 حصانًا لكل منهما، موصولين بوصلة هيدروليكية ومرتبين جنبًا إلى جنب على شكل حرف V ضحل. كان وجود محركين ضروريًا لأن شركة GM لم تكن قد أنتجت بعد نسخة V8 من محركها Series 71 Diesel. احتوت كل حافلة على ناقل حركة ثلاثي السرعات مع قابض يدوي ثنائي السرعات لست سرعات أمامية. واجهت الحافلات بعض المشاكل عند إطلاقها، لأن جميع طرازات Greyhound الأخرى كانت مزودة بناقل حركة يدوي رباعي السرعات يختلف في طريقة تغيير السرعات عن تلك الموجودة في Scenicruiser. هذا الأمر استلزم تدريبًا إضافيًا للسائقين، الذين لم يُعجبهم النظام الجديد في الغالب. لم يُحقق هذا النظام نجاحًا يُذكر، فأُعيد بناء الحافلات الـ 979 المتبقية في الفترة 1961-1962 بمحركات 8V-71 وناقل حركة يدوي رباعي السرعات من نوع Spicer بواسطة شركة Marmon-Herrington .

ألهمت شعبية حافلة Scenicruiser لدى الجمهور شركة جنرال موتورز لإنتاج طرازي حافلات Buffalo PD 4107 وPD 4903 ، بطول 35 و40 قدمًا، واللذين ظهرا بعد ذلك بعقد تقريبًا. تميز هذان الطرازان بوجود "مستوى ثانٍ" أقل وضوحًا يمتد على طول معظم الحافلة، ونوافذ جانبية مستوحاة من حافلات النقل العام من GMC، وزجاج أمامي علوي أصغر حجمًا نظرًا لوضع مقاعد الركاب في الصف الثاني أعلى من مقاعد السائق والصف الأول. وعلى عكس حافلة Scenicruiser، كانت هذه الطرازات متاحة للبيع لجميع شركات النقل.

As introduced, the Scenicruiser had some significant problems, particularly the drivetrain and cracking of the frame structure around the side windows in the rear quarter of the coach. GMC was not about to put a non-GM engine into its flagship coach nor did it have a V8 version of its Series 71 Diesel engine at the time. Therefore, GM's solution was to use a pair of 4-71 engines. One Greyhound historian wrote of the Scenicruiser's early technical issues:

"Maintenance on the Scenicruiser was a constant headache – partly because of the complicated nature of some of the new systems (in the manner of Rube Goldberg, some of the critics suggested), partly because some of the components were too new and unimproved (using new, unproved, and unimproved technology), partly because the diagnostic tools and techniques were inadequate, partly because the training and availability of mechanics (and maintenance supervisors and managers) for the new model were less than optimum, partly because the technical support and repair-parts support were less than optimum, and largely because of a combination of several of those factors – along with a few other explanations – including, sadly, occasional incidents of careless or intentional abuse of the new coaches by disgusted drivers or mechanics."^[3]

GMC solved one major problem in the factory as the 1955 models were being produced. The original clutch was electrically operated. That meant the drivers could not make the clutch smoothly engage; it was either in or out. This caused lurches and jolts every time the driver started from a stop or changed gears. Both the passengers and drivers didn't like it. The electrical clutch linkage was replaced by a mechanical one which solved the problem. GMC gave Greyhound enough sets of parts to convert all of the previously made coaches. At the same time the windshield wipers were changed to a pantograph design, which kept them in full contact with the glass at all times and this was also retrofitted to older coaches. The other problems were mostly solved starting in 1961 when all 979 Scenicruisers were rebuilt, costing Greyhound over US$13 million.

The Scenicruiser 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 100s and at least one of the later Becks have been converted to motor homes 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. Other two-level models introduced after the Scenicruiser were the Western Flyer T-36-2L, and the impressive four-axle twin-steer Sultana Crucero Imperial.

The problems with the Scenicruisers greatly soured relations between Greyhound and GMC. Greyhound continued to buy GMC coaches with the PD 4104 up through 1960 and the PD 4106 from 1961 to 1964. Given the problems with the PD 4501, Greyhound had no interest in asking GMC to produce a second version of its signature coach based on the PD 4106's mechanicals and styling. Greyhound also bought some PD 4107 buses from GMC which were known as the "Buffalo" model. Greyhound purchased 362 of these buses in two orders (162 in 1966 and 200 more in 1967, with the 1966 units being trouble-prone). The company never bought another GMC coach afterwards. In 1958 The Greyhound Corporation acquired a controlling interest in Motor Coach Industries (MCI), Limited, of Canada and by 1961 had full ownership of it. This led to the end of its need for GMC coaches by 1968. GMC's sales soon went into terminal decline as both Greyhound and Trailways were building their own coaches.

Beck left the bus and coach market in 1957, a year after being taken over by Mack. In 1960 Mack left the market except for a short time as an importer of rebadged Renault FR1 coaches between 1986 and 1989. In 1978, Flxible was sold to Grumman, with the sale including the sale of two prototypes of what would become the 870. Flxible built its last intercity coach in 1969 and its final transit coach in 1995. GMC exited the new coach market after producing the 1980 models and continued transit coach manufacturing until 1987.