What is the “ladder frame” used for off-road 4WD?
The Suzuki Jimny 5-door is finally here, and there are rumors of a full model change for the Toyota Land Cruiser Prado in 2023, so there are signs that off-road 4WD is likely to get even more exciting.
Speaking of off-road 4WD, the word “ladder frame structure” is often heard.Today’s cars have a “monocoque structure,” a “ladder frame structure (also known as a separate frame),” and a “frame-in-monocoque structure,” which has the advantages of both.
The monocoque structure is a body structure that achieves both lightness and robustness by bending thin steel plates into a box shape. Imagine a box of tissue paper. That box is also made of folded paper, but if you push it from all sides, you will find that it is surprisingly sturdy.
oneA ladder frame is a form in which a separate upper body is placed on a sturdy ladder-shaped frame made of metal.In the early days of automobiles, wooden frames were used, but from around 1900, they were replaced by metal frames.
The initial merit of using the ladder frame was that it was easy to increase variations.Not only can a single chassis be shared by various body variations such as sedans, roadsters, and trucks, but it can also be used for new design cars.
The advantage of the ladder frame is its robustness and high load-bearing performance.
Source: wikipedia.org Author: Ricardo Tulio Gandelman CC Attribution 2.0
Of course, before the 1960s, monocoque structures were not introduced into automobiles, but ladder frames have other advantages as well.that isRobustness and load-bearing capacity. By strengthening the material of the ladder frame and adding cross members to the frame, it is possible to make it a stronger skeleton.
These reinforced ladder frames were mainly used for trucks that carried heavy loads.
But in 1941,A car with a compact and tough ladder frameis born. It is a Jeep called Ford GPW/Willis MB, which has been selected as one of the “famous cars of the 20th century.”
Jeep, which was born as a military vehicle, was developed on the premise that it would be used on the battlefield, so robustness and durability were the most important performance.It is considered to be able to tow weapons and vehicles heavier than the own vehicle, and parachute descent from the sky in airborne operations, so it would be a problem if it breaks down just a little.
In fact, he even pulled trains on occasion. One of the factors that supported its toughness was the ladder frame.
It also has the advantage of being easy to manufacture, maintain, and repair.
Furthermore, by making ladder frame structure,Easy to produce, maintain and repairIt was also an advantage.
The suspension of the early Jeep was a rigid axle type of leaf spring, so it was veryThe structure is simple and the number of parts can be reduced. This made mass production possible, and even if it broke on the battlefield, it was possible to speedily maintain and repair it.
It also had the advantage that even if the upper body on which the crew was riding was damaged, it could still be used as long as the bare chassis was movable. The fact that it is durable and can be used for a long time is another reason why the Jeep was loved.
More than half a century has passed since the first military jeeps were produced, but there are still quite a few vehicles in active service.
After the war, thisA number of four-wheel drive vehicles were born that imitated jeeps.These include the Toyota Land Cruiser (originally Toyota Jeep BJ), the Nissan Patrol (sold under the name Safari in Japan), the Mitsubishi Jeep, and the Suzuki Jimny. The Land Rover Series I overseas and Mercedes-Benz’s slopes (now G-class) were also built with reference to the jeep structure.
Although the monocoque body has become mainstream, the ladder frame is the optimal solution depending on the region and operation.
In the 1960s, when monocoque body structures using aviation technology became popular, the number of small cars using ladder frames decreased. Basically, it’s going to be about a four-wheel drive car.
Even in the world of four-wheel drive vehicles, a wave of light cross-country vehicles (later SUVs) arrived in the 90s, and in the early days, a frame-in-monocoque structure combining a ladder frame and a monocoque body reduced weight. As a result, we have improved the exercise performance and environmental performance.
In the 2000s, it became standard for SUVs to have the same monocoque body as other passenger cars, and there were very few models that used ladder frames.The main compact cars that still use ladder frames today are the Land Cruiser, Jimny, Jeep Wrangler, and Mercedes-Benz G-Class. The G-Class is said to be monocoque in the next full model change, similar to Land Rover’s Defender.
The reason why the aforementioned car model stubbornly uses the ladder frame isRobustness and durability are the main focus of development.I guess.All models are often used in areas where road infrastructure is inadequate, and moreover, many people ride and carry heavy loads on a daily basis.It’s from
The ladder frame structure is old-fashioned, but it is the most suitable for long-term hard use in harsh environments.
At the Tokyo Auto Salon 2023, Toyota Auto Body exhibited a vehicle called the Land Cruiser 40V at the top and the Land Cruiser HZJ71V at the bottom, which attracted a lot of attention. It can be said that it is the ladder frame structure that makes it possible to build such a “Nikoichi” vehicle.