took its name from H.W. Kent and E.K. Worthington who had been directors of its predecessor company, the Gersix Manufacturing Co. Their early days were helped by the failure of the only other truck makers in Seattle, H.R.L. and Vulcan, from whom Kenworth bought parts. Early Kenworths came in three sizes, 1 Y2-, 2%- and 4-tons, all powered by 4-cylinder Buda engines. The first year’s production was 78 trucks of which only two were the 4-tonners. By 1925 there were five models, from one to five tons, and in 1926 annual production reached 99 trucks. At this time and for many years afterwards Kenworth production was sufficiently small for a wide variety of customer’s requests to be incorporated, so it is misleading to speak of a standard range; almost any type of vehicle would be built if asked for. In 1927 a new 78 hp 6-cylinder engine was used, and Kenworth began to cater more noticeably for the West Coast market, with 7-speed transmissions, stronger axles and sometimes supplementary springs at the front. In 1929 Kenworth set up a branch factory at Vancouver, B.C.
He identifies the bus on the left as a 1931 Heiser scratch build, and the one on the left as a 1935 Kenworth with a Heiser body
In 1932 Kenworth became the first American truck maker to offer a diesel engine as a factory option; this was a 4-cylinder 100 hp Cummins HA4. Other developments of the early 1930s included torsion-bar suspension and vacuum boosters for the hydraulic brakes. New types of vehicle included 6-wheelers, either with trailing 3rd axle or tandem drive, and fire engines. Buses had been made from the late 1920s, and were a small but interesting part of Kenworth’s business until the late 1950s. They were mostly intercity coaches, some with ‘one and a half deck’ bodies, and either conventional or forward control. Some in the late 1930s had underfloor pancake engines, while an interesting hybrid built in 1951 for Northern Pacific Railroad was the ‘Bruck’, a combination bus and truck for 17 passengers at the front and a taller cargo van, 18 ft long over the tandem axle at the rear. It was powered by a 136 hp Hall-Scott engine.
In 1935 Kenworth began to build their own cabs and sheet metal, a result of which was an attractive chrome grille which is still recognizable in the appearance of today’s Kenworths. Although special requests could still be made, such as chain-drive trucks in order to get an axle capacity for a larger load, there was a standard range of Kenworths in the late 1930s from 2- to 10-ton trucks in the price range $1245 to $11646. Basic power plants were Hercules, Buda and Herschell-Spillman gasoline, and Cummins diesels, all 6-cylinder engines. The first four-wheel-drive truck was made in 1937, and cab-overs appeared in the same year. Other special models were low-bed trucks, milk delivery trucks and sleeper boxes in the rear of the cabs. In 1941 Cummins built the world’s first aluminum diesel for installation in a Kenworth at the request of the company.
During World War II Kenworth made some 1900 MIA wrecker trucks similar to those of Ward LaFrance, and also pilot models of an 8-ton 6×6 truck. Using the experience gained in war-time metallurgy, Kenworth engineers developed in 1944 an extruded aluminum truck frame, and extended the use of aluminum to cabs, hoods and transmission housings. In 1945 Kenworth was bought by Pacific Car & Foundry who relocated it in the former Fisher body plant in Seattle where it has operated ever since. Later a Kenworth plant was established in Kansas City which specialized in extra-heavy duty models.
Production of civilian trucks never entirely ceased during the war, though it was down to only 87 units in 1943. In the late 1940s it climbed to some 600 per year, and passed the 1000 mark in 1952. Conventionals and cab-overs were made, together with fire engines and a dwindling number of buses. The radiator on the conventionals had become vertical in 1940 in place of the sloping grille used since 1935, and this vertical design has been steadily developed up to the present without any radical change. In 1947 Kenworth developed desert trucks for oilfield work in the Middle East, culminating in the Model 953 of 1958 which had a Cummins NTC350 engine, tire sizes of up to 29.50, and cost over $100,000. These trucks are so large that a low sports car can be driven under them, and they have been used for transporting full-sized locomotives across the desert. In 1950 a Boeing turbine was installed in a Kenworth and although it did not go into production it was the first gas turbine in scheduled freight service. Another special project was the
T-10 Heavy Equipment Transporter for the US Army, a double-ended unit with tractors in front and rear of a 250mm gun, with a total weight of 85 tons.
In 1953 Kenworth introduced an original cab-beside-engine design for line-haul work in the mountains where the drivers wanted maximum visibility. Some were 6x4s with the sleeper box behind the engine and entrance to the cab. This was really a single-seater, though a small canvas seat behind the driver could carry a passenger. The cbe style was too unconventional to last for long. Another Kenworth original developed in conjunction with Pacific Intermountain Express, in 1956 was a 4-axle ‘Dromedary’ with twin steering axles and a short cargo van between the cab and the 5th wheel coupling for the semi-trailer. Peterbilt also built ‘Dromedaries’ for P.I.E.
From the late 1940s onwards, tractor-trailer units began to gain increasing importance in Kenworth production compared with straight trucks, and today make up the bulk of trucks built. The familiar flat-faced full-width cab-overs (K Series) have been made since 1950 with little change, this cab being shared today with Peterbilt. For the past 20 years or so all Kenworths have used diesel engines, the basic units being Cummins, with Caterpillar or Detroit Diesels as regular options. In 1971 came the PD series, later renamed the Hustler; this was a straight cab-forward design mainly intended for the urban delivery trade, and used the same cab as Peterbilt’s 200 series. In 1973 a new model was the Brute, a 6X4 conventional intended for the construction industry. Current models include the Brute and Hustler, W-series conventional line-haul tractors and K-series cab-over line-haul tractors. GVWs range from 50,000 to 89,000 lbs. for the construction models, and GTW s with semi-trailers for the Wand K series from 76,800 to 130,000 lbs. Production has grown dramatically in the past 15 years, from under 2000 in the early 1960s to 10,000 to 11,000 in the mid-1970s. In addition to the Kansas City plant, Kenworth has factories at Mexicali, Baja California and Bayswater, Victoria in Australia where some special models for the local market are made including ones with tandem front steering axles. Kenworth has gained an unusual record in being the fastest recorded truck in the world, with speeds of 132-154 mph for a tractor, and 92.083 mph for a tractor and semi-trailer. Both records were set in 1975.
1958 Kenworth bus Buddy Holly Tour of Stars
Kenworth » CargoCoach Bruck © Greg Pascut
That’s all the Kenworth Buses I could find.