The Unimog 411 is a vehicle in the Unimog series from Mercedes-Benz. Daimler-Benz AG built 39,581 units at the Mercedes-Benz plant in Gaggenau between August 1956 and October 1974.Vogler, p. 14. The 411 is the last series of the "original Unimogs". The design of the 411 is based on the Unimog 401. It is also a commercial vehicle built on a ladder frame with four equally sized wheels and designed as an implement carrier, agricultural tractor and universally applicable work machine. Like the 401, it had a passenger car engine, initially with 30 hp (22 kW).Vogler, p. 13.
There were a total of twelve different models of the 411, which were offered in numerous model variants with three wheelbases (1720 mm, 2120 mm and 2570 mm) and could be supplied in the conventional convertible version, as a drive head and with a closed cab, which was manufactured by Westfalia as with the predecessor. The closed cab was available in two versions, the Type B resembled the cab of the Unimog 401, the Type DvF resembled the cabs of the Mercedes-Benz trucks of the 1950s and 1960s with headlights in the radiator grille and chrome strips.
During its long production phase, the Unimog 411 was technically revised several times. Due to the large number of changes that the 411 series underwent, four types of the 411 series are distinguished for better differentiation: the Ur-411, 411a, 411b and 411c.Vogler, p. 12. Although the 411 was technically based on the 401, design features from other Unimog model series were also adopted for the 411, including the axle design of the Baureihe 406, which was used in modified form on the 411 from 1963. As the last classic Unimog, the 411 had no direct successor, but from 1966 the Unimog 421 was in the Unimog range, which was technically based on the 411 and was positioned in the same product segment.
Vehicle history
Development
The Unimog 411 was not a completely new development, rather Daimler-Benz derived the 411 series from the predecessor 401 and 402 series. In the 1950s, the Unimog design department under the leadership of Heinrich Rößler took a wait-and-see approach to new developments, even though consideration was given to offering the Unimog 411 with a 40 hp (29.5 kW) diesel engine and an 80 hp (59 kW) petrol engine. However, these ideas were only implemented in later model series. The developers' hopes were pinned in particular on the 411 with an all-steel cab. The most important focus of the development department was primarily on demonstrating, testing and improving the Unimog as such.Vogler, p. 18. The main changes to the 411 compared to its predecessor were an increase in engine output by 20%, reinforced shock absorbers, reinforced crossmembers for the engine, from 1959 plain bearings instead of roller bearings for the manual gearbox and enlarged tires with the dimension 7.5-18″ (optional equipment: 10-18″), which made a new wheel arch necessary; on the 411, the front wheel arches are slightly longer at the top than on the 401, so that the tires do not drag when turning the steering wheel.Vogler, p. 33. In addition, the front end of the 411 was redesigned, with wider beading on the hood. The radiator grille was also made smaller; it was now a square grille painted in the vehicle color instead of the struts of its predecessor.
Series 401 convertibles were already equipped with the cab of the later 411 series from June 1955, so that there are some hybrid vehicles. The 411 was then presented at the DLG exhibition in Hanover in September 1956. As many changes were made to the Unimog 411 during the entire period of series production, the Daimler-Benz works literature divides the 411 series into four types to make it easier to distinguish between significant technical changes: the original type "411" (1956-1961), "411a" (1961-1963), "411b" (1963-1965) and "411c" (1965-1974).Vogler, p. 22.
With the Unimog 411, Daimler-Benz set itself the target of selling 4,000 vehicles a year. In order to meet the requirements of the Unimog 411, customer wishes were incorporated and taken into account in the further development of the series.Vogler, p. 87. Nevertheless, the 411 was more of a small vehicle with an output of just 34 hp (25 kW) powerful diesel engine, which was considered too underpowered for some applications. Analysts at Daimler-Benz warned that the annual production rate of the Unimog 411 would fall below 3000 vehicles after 1960. This point was reached in 1964. Daimler-Benz therefore introduced a larger Unimog in 1963, the 406.Carl-Heinz Vogler: UNIMOG 406 – Typengeschichte und Technik. Geramond, München 2016, ISBN 978-3-86245-576-8, p. 12, 14, 16. The 411 was thus transformed from the former core product of the Unimog range into a light series. However, the further development of the Unimog 411 did not end there; from 1963, the axles of the Unimog 406 were also fitted to the 411 in a modified form. These axles are more stable, cheaper and easier to maintain.Vogler, p. 93. From 1967, the 411 received the same bumper as the Unimog 421.Vogler, p. 102.
After the introduction of the type 411c in 1965, the 411 series was no longer developed further on a large scale; the models with an extra-long wheelbase were the last major innovation to be added to the Unimog model range for the export market from 1969.Vogler, p. 17. In March 1966, the Unimog 421, a technically similar vehicle with a much more modern appearance, was presented in the same segment. The 421, which had the technology of the Unimog 411 and a 2-liter pre-chamber engine of the type OM 621 with 40 hp (29.5 kW), was actually designed as an inexpensive addition to the 406 series,Unimog-Community Unimog U 421 [1966 bis 1989] But from 1970 onwards, the Unimog 421 was already much more popular than the similar but older and weaker 411 and was preferred by customers.Vogler, Graphic on p. 105. Dhe Unimog 411 continued to be built unchanged. Production was only discontinued in October 1974 after 39,581 vehicles. Presumably some vehicles were produced again in 1975 for a military customer.Vogler, p. 137.
Distribution
On the West German market, the basic version of the Unimog 411 cost DM 12,500 as a convertible when it was launched in 1956. It initially had the OM 636.914 engine, which produced 30 DIN hp (22 kW) at 2550 rpm.Vogler, p. 21. As the Unimog 411 was too expensive for some customers, an "economy model" was offered from 1957 to 1959, the U 25. The U 25 was given the independent model number 411.116. It lacked the windscreen, side windows, windscreen wipers, soft top and other small parts, the seats and engine came from the Unimog 2010, and the transmission ratio of the portal axle was also changed. It was a failure, only 54 units were sold. Vogler, p. 26. At the end of the 1950s, the 411 model series was also exported to the USA, where Curtiss-Wright sold the 411.112 and 411.117 models; the Mercedes-Benz brand name was retained.Vogler, p. 64. In 1965, the basic version cost 15,300 DM.Vogler, p. 103. Daimler-Benz AG achieved the largest turnover with Unimog sales in West Germany. In 1962, worldwide sales of the U 411, excluding the spare parts business, amounted to 54,870,000 DM.Vogler, p. 88.
Prototype for the French army
At the request of the French army Daimler-Benz built a prototype based on the 411 series with a gasoline engine in 1957. The vehicle was given the chassis number 411.114 75 00939 and was assigned to type 411.114, which was reassigned to the extra-long wheelbase models in 1969. The prototype 411.114 had the long wheelbase of 2120 mm, transmission and clutch of the Unimog S and tires of dimension 7.5-18″. The desired and installed four-cylinder engine was the M 121 with a displacement of 1897 cm³ and an output of 65 hp (48 kW) at 4500 min-1 as well as a maximum torque of 128 N-m at 2200 min-1, as it was also used in the Mercedes 180. The top speed is 90 km/h. The reinforced windshield with the windshield wipers at the bottom is a distinctive feature. The French army tested the vehicle over a period of almost 9000 operating hours and decided not to procure it due to its high center of gravity. On the basis of this prototype, Daimler-Benz developed further military vehicles with a payload of one ton.Vogler, p. 42.
Westfalia cab
Like the Unimog 401 and 402 before it, a closed cab was also offered for the Unimog 411, which was manufactured by Westfalia in Wiedenbrück. Daimler-Benz equipped the Unimogs with this cab ex works. When production of the 411 series began in August 1956, the type B cab, which had already been built for the Unimog 401, was modified for the new Unimog 411 chassis and continued to be built almost unchanged on the outside. It has the model 411.520. This cab is nicknamed the frog's eye and was only built 1107 times, the models 411.111 (1720 mm wheelbase) and 411.113 (2120 mm wheelbase) were equipped with it until they were discontinued in October 1961. Westfalia had already produced a new cab for the Unimog 411 in 1957. It has the model 411.521 and is designated as cab type DvF.It was only built for the 411.117 and 411.120 models with 2120 mm wheelbase. DvF stands for Type D, widened cab. As the name suggests, its dimensions were significantly larger than those of the Type B, it has a 30% larger volume and is wider than the Unimog's loading platform. The windshield is undivided and the ergonomics have been significantly improved. The shape follows the truck design of the Mercedes-Benz brand in the 1950s and 1960s with an elliptical radiator grille with headlights framed on the outer edge and lavish chrome trim. Unlike the convertible models, the front bumper is more rounded and more strongly curved at the ends. On request, Daimler-Benz equipped the DvF cab with a heater. A disadvantage of the DvF cab was the high heat load caused by the engine exhaust heat. The reason for this is the engine cover, which protrudes far into the passenger compartment and does not sufficiently insulate the cab from the engine. Production of the Unimog 411 was discontinued in 1974, but Westfalia continued to build the DvF cab until 1978.Vogler, p. 44–47.
In the mid-1960s, Westfalia also tested a GRP hardtop for the convertible versions of the Unimog 411. It offered better protection from the weather and better visibility to the sides than the fabric top. Although brochures were printed and the hardtop was included in the official Unimog catalog, it was hardly ever sold. It is not known how many hardtops were produced.Vogler, p. 108.
Annual series change
Prototype 411
1957
The 411 was extensively modified in 1957. The indicators were removed and replaced by conventional car indicators. Other external innovations included the new Mercedes badge on the hood and the modified rear lights. The engine output was increased to 32 hp (23.5 kW) from March and the transmission synchronized could be supplied on request, in July new springs with a wire diameter of 19.5 mm instead of 18 mm were fitted to the rear axles, and from September a reinforced steering system with a three-spoke steering wheel from Fulmina was installed. In the convertible models, the side windows made of Cellon were replaced by polyvinyl chloride windows as early as May 1957 .Vogler, p. 31. Mercedes-Benz also introduced the economy model U 25 in May. The new Westfalia type DvF cab was presented at the IAA in September; a trailer brake system was available from October.
1958
From March or April 1958 the Unimog 411 was equipped as standard with a 60-liter fuel tank instead of just 40 liters. Other changes were rather minor, including modifications to the brake system, the installation of a combined pre-glow and start switch, a reinforced power take-off and the installation of hinged windows on the Westfalia cab type DvF.Vogler, p. 40.
1959