Tatra 813

Engine

The naturally aspirated V12 engine T-930 was created by adding four additional cylinders to the existing T-928 75° V8 engine, used in the Tatra T138. The crankshaft consisted of six individual journals bolted together with front and rear pins all running on the main roller bearings and located on the axial friction thrust washers. The military version was multi-fuel capable, running on any mixtures of diesel fuel, petrol and aviation kerosene fuel.

Chassis

The chassis is a full-length backbone tube with independent swing half axles available as either 4×4, 6×6 or 8×8 model. 4×4 models had a front axle suspension system with adjustable torsion bars, in the 6×6 and 8×8 models front and rear axles had longitudinal semi-elliptic leaf springs. For the 4×4 configuration the rear axle had air suspension. Permanent all-wheel-drive, front twin steer (6×6, 8×8) drive via homo-kinetic drive shafts, lockable differentials, inter-axle differentials with locks and planetary hub reductions were standard for all models. Unlike many six-wheeled vehicles, which have a single front axle and tandem rear axles, 6×6 versions used twin steering front axles- as with the 8×8- and a single rear axle.

• Front track
  • 2050 mm (KOLOS)
  • 1990 mm (6×6 Hauler, S1, 8×8 Chassis)
  • 2030 mm (NT, NTH Prime movers)
• Rear track
  • 2000 mm (8×8 KOLOS)
  • 1950 mm (6×6 Hauler, 8×8 Chassis, S 1)
  • 1990 mm (NT, NTH Prime movers)
• Wheelbase
  • T813 KOLOS - 1650+2200+1450 mm
  • 6×6 Hauler - 1650+2700 mm
  • 8×8 Chassis - 1650+3200+1450 mm
  • S1 8×8 - 1650+2800+1450 mm
  • NT, NTH 4×4 - 3700 mm
• Ground clearance
  • 380 mm (KOLOS, 6×6 Hauler)
  • 330 mm (8×8 Chassis, S1 8×8)
  • 300 mm (NT, NTH Prime Movers)

Transmission

The main gearbox was located behind the cabin and connected to the engine clutch housing via a short cardan shaft (this design enables a so-called flat floor cabin.) The main gearbox was bolted to an auxiliary gearbox, to a transfer case and then to a backbone tube and formed the main part of the chassis structure. A rear power take off and a winch drive were available as a factory option. Main and auxiliary gears were fully synchronized except the first and reverse gear. The new feature was a unique 2-speed planetary overdrive system bolted between the front and rear axles. The overdrive could only be selected manually while the vehicle was not moving. The auxiliary gearbox had a neutral position which allowed the winch and a power take off to use the main gearbox gearing for variable speed operation. From the backbone tube the torque was transmitted to the wheels via Tatra gear differentials with differential locks, offset drive shafts and planetary hub reductions.

• Main gearbox - 5+1 (2-5 gear synchronized) (KOLOS 8×8 & Hauler 6×6)
  • gear ratios - (1)9.97, (2)4.96, (3)2.83, (4)1.68, (5)1.0, (R)8.58
• Main gearbox - 5+1 (2-5 gear synchronized) with splitter direct and overdrive (S1 8x8, Chassis 8x8,NT & NTH 4×4)
  • gear ratios - (1)9.97, (2)4.96, (3)2.83, (4)1.68, (5)1.0, (R)8.58
  • splitter ratios - 1.0 (Direct), 0.75 (Overdrive) (electro-pneumatic control via switch on the gear lever and clutch pedal activated )
• Auxiliary gearbox - 2-speed (electro-pneumatic control via switch on the gear lever and clutch pedal activated )
  • gear ratios - 2.2, 1.62 (KOLOS & Hauler 6×6)
• Step down transfer case - single
  • gear ratio - 1.68 (S1 8×8, Chassis 8×8, NT & NTH 4×4 only)
• Planetary overdrive
  • ratios - 1.0, 0.62 (KOLOS 8×8 & Hauler 6×6 only)
• Clutch - 3× plate dry (clutch pedal hydraulic and air power assisted)
  • - 2× plate dry (clutch pedal hydraulic and air power assisted) (NT & NTH 4×4 only)
• Differentials
  • 2× front and 2× rear (8×8 models)
  • 2× front and 1× rear (6×6 models)
  • 1× front and 1× rear (4×4 models)
  • final drive ratio - 2.71
• Planetary hub reduction ratios
  • 2.14 (KOLOS 8×8)
  • 2.12 (Hauler 6x6 & S1 8×8)

Brakes

Full triple circuit air "S" cam drum brakes acting on all wheels drums via slack adjuster, all brake cylinders were remotely vented. First brake circuit acts on front wheels, the second on rear wheels and the third controls trailer service brakes. Unique design feature was remotely mounted brake valve which was operated via hydraulic master and slave cylinder principle on the Hauler 6x6 or via mechanical linkage on 8x8 models.

• Main wheel brakes ----> dual circuit drum brakes "S" cam type
• Park brake ----> mechanical via output shaft and drum at the back of the gearbox
• Supplementary brake ----> exhaust brake electropneumatic brake

T813 KOLOS military specs with dozer blade

Bodywork

Cabin is all steel construction of COE design but not tiltable, the access to the engine was provided via removable engine cowlings inside the cabin compartment. The cab came in two versions, the "short" two-seater two-door version and in the "long" "crew cab" seven seater four-door version. The military specs cabs included the roof hatch or two in the case of the crew cab. All cabs were equipped with self-contained diesel cab heater which could also be used in the winter to warm up the engine before starting it. Another military feature was CTI central tyre inflation system controlled from the cab for each wheel independently and an ability to pressurize gearbox and differentials housing during water crossing. The 8x8 models had abilility to cross trenches up to 1.4 metre wide and vertical obstacles up to 0.6 metre high. Water crossing depth (static including the wave) was up to 1.4 metre (KOLOS 8x8). The vehicle top speed was 92 km/h (NT & NTH), 80 km/h (KOLOS), 70 km/h (hauler), 60 km/h (S1) @ 2000 engine rpm.

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