Ömazislav/Gorganstien Delticron (Bus)

The Ömazislav Delticron, later referred to as the Gorganstien Delticron, is a line of intercity and commuter motorcoaches and transit buses that come in nominal lengths of 35' rigid, 40' rigid, and 60' articulated. They were initially made as 35 and 40 foot rigid buses by Ömazislav Otobüs from 1967 to 1979. From 1981 to 2002, the Czechoslovak-Turkish Gorganstien Otobüs subsidiary of Gorganstien trucks (which was formed from the remains of Ömazislav Otobüs after their acquisition by Gorganstien Trucks) took over production of the buses and introduced a 60 foot articulated variant alongside the 35 and 40 foot buses. In addition to the various lengths available, the buses are marketed with a variety of engine technologies, initially beginning under production by Ömazislav Otobüs with gasoline, conventional diesel, and diesel-electric hybrid; Later buses by Gorganstien Otobüs added more powertrain options such as compressed natural gas (CNG) and battery electric.

The original Delticron was based, in particular, on the GM "old-look" transit bus and was directly adapted from the GM TDH-5108 body style. With a steeper windshield and the option to remove the middle door, the Delticron distinguished itself from the GM "old-look" more than the Saribus did. Delticron buses were typically powered by the Detroit Diesel 6-71 inline six-cylinder diesel engine or the Detroit Diesel 4-71, a four-cylinder version of the same diesel engine, with the 4-71 being used for shorter variants. Occasionally, however, they were also propelled by a Tatra diesel or a Mercedes diesel engine.

The Delticron was designed primarily for transit usage, but it also differs substantially from the "old-look" in that, while being 40 feet long, it can accommodate 81 passengers instead of 51 thanks to a more flexible seating arrangement made possible by the removal of the middle door. A few Delticron models had lengths greater than 40 feet, and a few more models even had a "triangle 6" Napier Deltic-style engine, however these were rather prototypes and only three examples were produced. Only three of these small Deltic engines were created by D. Napier & Son under license for the three aforementioned specimens which were produced for the Soviet Union. This decision was coicidential; It was an unusual decision to put the Napier Deltic in the Delticron since the Napier Deltic 2-stroke diesel engine was originally used in Royal Navy high speed patrol boats and later adapted for use in railway locomotives. In reality, it was the consequence of a design modification performed in 1971 that required changing the bus body to better fit on a custom chassis manufactured by Ömazislav under license from Gorganstien, which itself was taken from Gorganstien's 596DT Trinity truck in its unaltered form. However, because the Delticron was derived from the GM "old-look," which is constructed as a monocoque, the body had to be further altered in order to integrate the mofified 596DT frame into the bodywork.

First generation
Outside of Turkey and Czechoslovakia, Ömazislav assembled GM's model TDM-3207 and TDH-3610 under license, in place of developing an all-new model line from the ground up. These started production in 1955 and came to be known as the "Sarıbüs" (from "Yellow bus", in reference to Yellow Coach and anglicized as Saribus) and were first assembled with a Tatra diesel, but supply problems caused Ömazislav switch to the Detroit Diesel 6-71, also built under license. The licensed TDM-3207 was known as the Saribus ST-732 and in turn the TDH-3610 went to be known as the Saribus ST-1036. Because of persistent problems with the dependability of the drive-train parts, the Sarıbüs underwent changes and finally evolved into the Ömazislav Delticron.

The removal of the riveted metal body panels from the GM old look design was the most noticeable of all these alterations. While it would have been obvious to add more fasteners, Ömazislav engineers decided against doing so since there were effectively too many body panel joints. Instead, the body panel joints were entirely removed because there were simply too many of them, and the bus body was partially redesigned so that the main exterior shell would be made of three aluminum sheets. This resulted in a 12-piece body shell with three main pieces that are welded rather than riveted. (instead of the GM "old-look," on which it is based, having almost four times as many body panels) Similar to the body panels, the roof panel would be made as a three-piece component that would be welded into place. As a result, the only components of the bus that now needed fasteners were the interior, the hinge joints, and the rear where the engine is located.

As a consequence of this new body production method, the original front end of the GM Old Look bus became too complicated to manufacture since the newer body shell was made from just three metal sheets. Later, the front was modified to make it less complex, which had made the windshield steeper, in turn making the front end resemble that of a Gillig Transit Coach. The rear was also slightly updated to accommodate the Detroit Diesel 6v53 engine and subsequently the similarly sized Napier Deltic D6 Series II, which was initially built by Napier under a joint venture for the 596DT Trinity Truck.

The Delticron was launched in 1967 and was originally powered by a Detroit 6v53 engine coupled to a 6 speed gearbox. The Delticron was also available in several lengths ranging from 25 feet (7.6 m) to 41 feet 6 inches (12.65 m), though the first model was 40 feet long. Most Delticron buses were 96 inches wide, but 102-inch and 110-inch wide models were offered beginning in 1971.

While produced largely for transit use, this generation of the Delticron also departs significantly from the "old-look" in that despite its 40 feet length, it is available in capacities up to 81 passengers as opposed to 51 passengers. A few first generation Delticron models reached above 41 feet in length, and a few more models even had a "triangle 6" Napier Deltic-style engine, however these were rather prototypes and only three examples were produced.

Deltic engines
Both Ömazislav and Gorganstien were both keen in adapting the Napier Deltic for highway use and to demonstrate the engine's practicality in a heavy duty vehicle, The identical D6 Series II engine from the then experimental Gorganstien 596DT Trinity Tractor unit version was installed in a pre-1971 Delticron transit bus during testing done by Ömazislav in 1969. Although the 6-cylinder Deltic produced power and torque comparable to a Detroit Diesel 2-149 diesel and weighed as much as a 6-71, it was six cylinders arranged in two banks of three cylinders rather than essentially a downsized 9 cylinder Deltic. However the 6-cylinder Deltic was bogged down by fuel consumption, the placement of the exhaust and intake manifolds, and the high power-to-weight ratio of Napier Deltic engines as a whole, which proved to be insurmountable challenges. The D6 Series II was originally intended to be installed in the 596DT Trinity Tractor unit, which was intended to haul road trains, thus having power figures of a theoretical 2-149 Detroit Diesel as mentioned earlier. (Note that the description of a "2-149" is used to refer to the power of two single cylinders from a Detroit Diesel 149 series engine and that Detroit Diesel themselves did not produce 2-149.) In fact, the 596DT Trinity in both its tractor and chassis cab configurations are deceptively powerful despite being classified as medium-duty trucks. As its intended usage is hauling road trains, the truck was thus designed to use a smaller displacement version of the Napier Deltic as the sole power plant, being six cylinders arranged in two banks of cylinders rather than essentially a downsized 9 cylinder Deltic. In addition, Napier engines in general were typically half as big as equally powerful engines and about one fifth as heavy.

The installation of the 6 cylinder Deltic in later production buses also resulted in the Delticron being the only production bus in the world to solely be powered by a Napier Deltic engine until the Solaris Deltoid, which was powered by the same tiny displacment Napier Deltic engine, overtook it in 1987. Only with the Delticron II's debut in 1992 did the Delticron recover recognition as a Deltic-powered bus. (On the other hand, the reason why the Deltic ended up in the truck was due to the fact that a turbo-diesel would be the perfect engine choice because the truck was intended to run on a high-power, lightweight diesel engine, but because this was the 1970s, such an engine wouldn't be that common; nonetheless, the fact that Omazislav selected Gorganstien as a chassis supplier for its Delticron series is also a coincidence because Gorganstien would later acquire Ömazislav Otobüs in 1979.)

Deltic-powered Soviet Buses
On the opposite end of the deltic-powered bus spectrum, D. Napier & Son built three smaller displacemnt Deltic engines under license by Ömazislav for the three aforementioned Deltic powered examples that were made for the Soviet Union.