The OB has a wheelbase of 14 feet 6 inches (4.42 m), and is a semi-forward control model, designed to carry 26 to 29-passenger bodywork.
It is fitted with a 27.34 horsepower (20.39 kW) petrol engine, and has a four-speed manual gearbox and fully floating rear axle. The brakes are of the vacuum servo assisted hydraulic type.
Although only 73 were built prior to the cessation of production due to World War II, it reappeared in an unchanged form at the end of the war, continuing in production until 1951. A total of 12,766 were produced, making it one of the most popular buses of its type ever.
The Pre War OB
The OB was introduced in the summer of 1939 as part of a new range of models, which included the "O" type lorry chassis. The passenger version was named the 'OB' and Duple modified their 'Hendonian' body to fit the chassis, which at 14 ft 6 in (4.42 m), was longer than the previous WTB model. But the new model had a very short production run - with the advent of World War II, Bedford turned over to the war effort. Only 73 chassis were built and consequently the pre-war OB was very rare. The 28 horsepower engine, which had been introduced in 1938, was based on the model "O" goods chassis and the six cylinder overhead valve power unit with a capacity of 3519 cc developed 72 bhp (54 kW; 73 PS) at 3000 rpm.
The Post War OB
It was not until after the end of the war that Bedford restarted the production of the OB again.
The ash framework was reinforced with steel and the floor made from hardwood with softwood tongued and grooved boarding with the exception of the cab area which was finished with alloy chequerplate. Seating capacity was normally 29 with overhead luggage racks provided for passengers, whilst the rear luggage boot was also used to store the spare wheel.
The Vista remained Duple's standard OB body until production of the OB chassis ceased in the early 1950s.
The price of a complete coach, including finishing in a two colour livery, was £ 1314.10s for a 27 seater and £ 1325.10s for a twenty nine seater.
The OB is remembered by many for its characteristic gearbox whine which was a familiar sound all over the country. Even today many recall their happy memories of journeys to the seaside, Sunday school outings or just the regular school run.
From the end of the war until 1951 a total of 12,693 OB's were built.
The OB is one of the most popular coaches in preservation. There are known to be 180 still about and nearly 70 in roadworthy condition, and about 30 are fully PCV'd for private hire work. 2009 marked the 70th Anniversary of the OB and this was commemorated by a gathering in August. 30 OB's attended the event at Vauxhall Motors in Luton. The vehicles were all on display outside the Vauxhall Museum before making a road run to Bletchley Park. 2010's event was held in Derbyshire.