Unimog 401

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Unimog 401
Unimog 401.jpg
401
Overview
TypeTractor
ManufacturerDaimler-Benz AG
Also calledUnimog
Unimog U25
Production1951–1956
AssemblyMercedes-Benz-Werk Gaggenau
Body and chassis
RelatedUnimog 402
Powertrain
EngineOM 636
(Diesel, 18.5 kW)
Transmission6-speed manual gearbox, two reverse gears
Chronology
PredecessorUnimog 2010
SuccessorUnimog 411

The Unimog 401 is an all-wheel-drive vehicle of the Unimog-series by Mercedes-Benz, developed as a tractor and equipment carrier. It was produced by Daimler-Benz in the Unimog plant in Gaggenau from 1951 to 1956. A total of 16,250 Unimog 401 and 402 were made.[1]

Initially, the Unimog 401 was made in the cabrio version only. The closed cab model Froschauge (German for frog-eye), with a cab made by Westfalia,[2] was introduced in September 1953.[3] An increased wheelbase model was developed, bearing model type 402. Both models were succeeded by the Unimog 411, available in both long and short wheelbases.[2]


History[edit]

After World War II, German engineer Albert Friedrich built the first Universalmotorgerät, however, Daimler-Benz declined to put it into series production. Manufacturer Boehringer in Göppingen on the other hand was interested and produced a prototype for the 1948 DLG-exhibition in Frankfurt. The Unimog attracted much interest, encouraging Boehringer to begin series production. Until 1950, approximately 600 Unimog 70.200 were made; their brand logo was an ox-head with U-shaped horns. In late 1950, Daimler-Benz purchased Boehringer moving Unimog production to Gaggenau, beginning series production in May 1951.[4] Initially, the Unimog's type number was 2010, changing to 401 in 1953, with the 401 becoming a new type. The Unimog 401 was the first Unimog to receive the Mercedes star on its grille.[5]

Unimog 401: Chassis cutaway model in the Unimog Museum

Technical description[edit]

The Unimog 401 is a very compact vehicle with an approximate length of just 3.5 metres. It has a U-shaped ladder frame, beam portal axles both in the rear and front, with four wheels of the same size. Each axle has additional reduction gears built in. Both front and rear axles are supported by a central joint and panhard rods. The 401 has coil springs and hydraulic shock absorbers. Daimler-Benz used 6.5–20" multi-purpose tyres, that are designed for both on and off-road applications. The brake system is hydraulic, the 401 having drum brakes for each wheel.[6] The 401 has a wheelbase of 1720 mm; the 402, 2120 mm.[2]

Engine OM 636 of the Unimog 401

Engine and gearbox[edit]

The 401 uses a car engine, type OM 636 VI. It is a water-cooled naturally aspirated straight-four-diesel with precombustion chamber injection, OHV-valvetrain and a displacement of 1767 cm3. Its standard power output is 40 PS (29.4 kW), reduced to 25 PS (18.4 kW) at 2350 min−1 for the Unimog. The OM 636 is mounted slightly inclined towards the rear, in the front of the Unimog. It has an electric starter.[6]

The Unimog 401 uses a Daimler-Benz six-speed constant-mesh gearbox with two additional reverse gears. It has clutch-independent switchable all-wheel drive and differential locks for the front and rear axles. The clutch is a Fichtel & Sachs single-disc-dry-clutch.[6] Daimler-Benz offered an additional two-speed crawler-gearbox as a factory option.[7]

Features and accessories[edit]

The 401 uses a 150 W Bosch alternator, a 12 V / 105 Ah lead-acid battery, two headlights, two rear lamps, electric trafficators, windscreen wipers and a horn. A plug socket for a trailer was offered as a factory option.[6]

A flatbed is mounted on the rear, measuring 1500 × 1500 mm, designed for a payload of 1000 kg. The 401 has a spring-mounted hitch in the rear and a standard hitch in the front. For additional equipment, it has an anchor rail.[6]

For power take-off, the Unimog was available with front and rear PTOs (DIN 9611, 540 min−1). The rated power is approximately 22 PS (16.2 kW). A 315 mm belt pulley was also available, with an output power of 22 PS (16.2 kW). Daimler-Benz also offered a spare wheel, rear twin tyres, a trailer-brake-system, a winch, a mowing bar and air compressors for the 401.[7]

The previous Unimog 2010 was offered as a cabrio with a foldable top, a conceiling windscreen, removable side windows and a rigid rear panel. It was available in the colour Unimog-grün. After developing the 2010 into the 401, the closed cab was offered. The cabrio version then became Version A while the cab-version became Version A/F. Unimogs with a trailer-brake-system were called Version B and Version B/F. Unimogs with a closed cab were available in the paint colours Unimog-grün, hellgrau and Mercedes-blau.[7]

Technical specifications[edit]

Unimog 402 long wheelbase (2170 mm)
Unimog 401 Froschauge with Westfalia-cab
Unimog 401[6]
Measurements and weights
Track width 1270 mm
1470 mm (after switching wheels)
Wheelbase 1720 mm
Ground clearance 380 mm
Length 3520 mm
Width 1630 mm
Height 2050 mm (with foldable top)
Turning clearance circle diameter 7600 mm
Bed 1.5 × 1.5 m,
2.25 m2
Mass 1680 kg
Payload 1000 kg
max. allowed mass 3150 kg
Drive train
Torque transmission to rear wheels, switchable all-wheel drive
Gearbox Daimler-Benz six-speed constant-mesh gearbox,
two reverse gears
Clutch Single-disc-dry-clutch by
Fichtel & Sachs
Top speed 53 km/h
Fuel consumption 10 l/100 km
Engine
Type OM 636 VI
Layout Straight-four diesel with precombustion chamber injection, OHV-Valvetrain
Cooling system Water
Bore × Stroke 75 × 100 mm
Displacement 1767 cm3
Compression ratio 19 : 1
Rated power 25 DIN-PS (18.5 kW) at 2350 min−1
Max. torque 10.3 kp·m (101 N·m) at 2000 min−1

Bibliography[edit]

  • Werner Oswald: Mercedes-Benz Lastwagen und Omnibusse 1886–1986. Motorbuch Verlag Stuttgart, 2008, ISBN 978-3-613-02943-9.

References[edit]

  1. ^ Werner Oswald, p. 320.
  2. ^ a b c Unimog-Community: Unimog U 401 (in German)
  3. ^ Werner Oswald, p. 321.
  4. ^ Werner Oswald, p. 321.
  5. ^ Unimog U 2010 – Unimog-Community (in German)
  6. ^ a b c d e f Daimler-Benz AG: Technische Daten Unimog 401 1955 (in German)
  7. ^ a b c Daimler-Benz AG: Preisliste für Unimog 401 1955 (in German)