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H-drive
An H-drive drivetrain is a system used for heavy off-road vehicles with 6×6 or 8×8 drive to supply power to each wheel station.
H-drives do not use axles but rather individual wheel stations, usually carried on a punt chassis. A single differential splits the drive into separate left and right drive shafts, which each run fore and aft inside the bottom corners of the chassis. At each wheel station a bevel box drives the half shaft out to the wheel.
H-drive is not commonly used for 4 wheel vehicles, as it is relatively complicated for small vehicles. It has been used most widely for military 6×6 chassis in the West. Vehicles of the Warsaw Pact, such as the Tatra 813 and MAZ-535 series, were instead based on narrow backbone chassis with a central propeller shaft.
H-drive was first developed by Hub van Doorne of the Dutch truck maker DAF. It was a derivative of their Trado conversion to produce a 6×4 off-road truck from a commercial 4×2 chassis. The Trado used a bogie rear suspension for both sets of rear wheels. This suspension, best known through the Scammell Pioneer of 1927, uses a single central axle, or driveshaft, that in turn drives two walking beams (balanceur, in Dutch) one on each side. The wheels are supported by overhung stub axles. The conversion added the walking beams to the ends of the original truck beam axle. From that point, the drive between the axles of each side was separated side by side.
In 1938, a later version of the Trado 3 conversion added drive to the front wheels and so converted a 6×4 vehicle to 6×6 drive. Unlike most all-wheel-drive vehicles, the front axle was no longer a live beam axle with added articulation for steering, but used two separate drive shafts, one to each front hub.
This principle of divided drive already being established for the front of the Trado, it was a minor step for van Doorne to divide the drive to the rear wheels as well. The DAF YA-328 used walking beams where the axle was no more than a pivot and the drive was supplied entirely by external longitudinal drive shafts, one on each side. As was usual for heavy vehicles of this period, the final drives and right-angle drive to the stub axles were combined through a worm gear box. This also had the advantage that it is easy to connect such boxes in series, using the rear end of the worm shaft as an output.
This type of drive was used by DAF for several types of military vehicles:
DAF also made cars and were particularly known for their Variomatic continuously variable transmission, introduced with the DAF 600 in 1958. Although at a different scale to their military vehicles, these also used the unusual principle (outside DAF) of a side-by-side divided drive.
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H-drive AI simulator
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H-drive
An H-drive drivetrain is a system used for heavy off-road vehicles with 6×6 or 8×8 drive to supply power to each wheel station.
H-drives do not use axles but rather individual wheel stations, usually carried on a punt chassis. A single differential splits the drive into separate left and right drive shafts, which each run fore and aft inside the bottom corners of the chassis. At each wheel station a bevel box drives the half shaft out to the wheel.
H-drive is not commonly used for 4 wheel vehicles, as it is relatively complicated for small vehicles. It has been used most widely for military 6×6 chassis in the West. Vehicles of the Warsaw Pact, such as the Tatra 813 and MAZ-535 series, were instead based on narrow backbone chassis with a central propeller shaft.
H-drive was first developed by Hub van Doorne of the Dutch truck maker DAF. It was a derivative of their Trado conversion to produce a 6×4 off-road truck from a commercial 4×2 chassis. The Trado used a bogie rear suspension for both sets of rear wheels. This suspension, best known through the Scammell Pioneer of 1927, uses a single central axle, or driveshaft, that in turn drives two walking beams (balanceur, in Dutch) one on each side. The wheels are supported by overhung stub axles. The conversion added the walking beams to the ends of the original truck beam axle. From that point, the drive between the axles of each side was separated side by side.
In 1938, a later version of the Trado 3 conversion added drive to the front wheels and so converted a 6×4 vehicle to 6×6 drive. Unlike most all-wheel-drive vehicles, the front axle was no longer a live beam axle with added articulation for steering, but used two separate drive shafts, one to each front hub.
This principle of divided drive already being established for the front of the Trado, it was a minor step for van Doorne to divide the drive to the rear wheels as well. The DAF YA-328 used walking beams where the axle was no more than a pivot and the drive was supplied entirely by external longitudinal drive shafts, one on each side. As was usual for heavy vehicles of this period, the final drives and right-angle drive to the stub axles were combined through a worm gear box. This also had the advantage that it is easy to connect such boxes in series, using the rear end of the worm shaft as an output.
This type of drive was used by DAF for several types of military vehicles:
DAF also made cars and were particularly known for their Variomatic continuously variable transmission, introduced with the DAF 600 in 1958. Although at a different scale to their military vehicles, these also used the unusual principle (outside DAF) of a side-by-side divided drive.