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Off-road Vehicles

Updated: Jan 27, 2022


Always longed to explore nature- its hilly, rough terrains on a breathtaking four-wheeler!? Well, then you might just be dreaming of becoming an “off roader”. But before you go off roading, let’s take a dive into the world of those vehicles, that will quench our thirst for adventure.
Off road vehicles are designed to travel on and off, paved or gravel surfaces. They are generally characterized by large tires with deep, open treads, a flexible suspension or even caterpillar tracks.

Best features of off-road vehicles:


High ground clearance:
The body frame must be similar to that of SUVs like Chevrolet Tahoe, Jeep Wrangler or Toyota 4Runner. They have a higher ground clearance compared to car-based cross over vehicles. Purpose built SUVs like the Jeep Grand Cherokee, Land Rover Range Rover and Land Rover LR4 have adjustable suspension- that means the vehicles’ side height can be raised with just the push of a button- this feature makes them the perfect off-road vehicles.

Low range transfer case:
Low Range capability is important for travelling on steep hills. The low gearing provides extra pull when the wheels are taking a turn. Although, low engine and high wheel speed provide better fuel economy on paved roads but these factors do not work on the roads that are typically slippery and uneven. Also, low range gearing ease the vehicles moving downhill, thus aiding the driver to maintain control over the velocity of the vehicle.

Good torque output:
Higher the torque output, easier will it be to pull the vehicle uphill or a mud hole, provided the tires provide a sufficient grip on the ground.

Locking differential:
Most of the conventional four wheelers have limited slip differential, i.e., only have two- wheel drive- one front and one back. A locking differential is same as posi-traction, i.e., it locks the differential such that both the wheels on the axle can rotate at all times. Any off-road vehicle must have some form of locking differential. For example, Wrangler has a mechanical locking differential. Some trucks have full locking differential (all wheels can rotate at all times) while some like the “desert racing versions” of the Tacoma and the Frontier have lockers only in the rear axle.

Hill start assist and hill descent control:
The Hill Start Assist prevents the rolling back of a vehicle in case the driver lets off the accelerator. Hill Descent Control uses traction control and anti-lock brakes along with the low range gearing system to maintain a safe speed while going down a steep slope.

Tyres:
Mud Terrain Tires:
With more aggressive tread patterns, these tires offer excellent grip for the wheels in the most extreme terrain, particularly wet snow and mud. They are also very durable, with tough sidewalls to absorb the impact of rocks and damage from other off-road hazards.
Snow Tires:
In regions where the conditions are predominantly ice and snow, snow tires are used in off road vehicles. These tires stay soft and pliant even below 0° C. The tread has a series of tiny grooves and channels, that can dig into wet snow and ice to improve traction while driving in slippery conditions.

Skid plate:
A skid plate is a sheet of material fitted to an off-road vehicle, that acts as a barrier and protects the essential vehicle components from harsh, off-road conditions, such as rocks, hard ground, rocks, logs, etc. Skid plates are usually made from abrasion-resistant materials.


The physics of Off-roading:


One of the most important factors for success in off-roading is traction, or the grip your tires have on whatever terrain the car is driving on. Traction is largely affected by the type of tires being used, their size, and their air pressure, as well as whether the car is on four-wheel drive (4WD). For instance, some tires have bigger treads meant to give better traction when driving in mud. And using 4WD gives all four tires better grip and control on the ground. Lowering the air pressure of the tires also increases traction because it allows more of the tire surface to grab onto whatever the vehicle is driving over.
Momentum is also an important factor for off-roading. Momentum-the mass of the vehicle multiplied by its velocity (speed). Although the mass of the vehicle is fixed (mostly), the speed can be controlled as per requirement. Friction with the ground and the force of gravity acting on the vehicle decreases the momentum.
Before going off-roading, knowledge of these three different angles of this car: the approach angle, the departure angle and the break-over angle, is required.
Consider driving a car towards a ramp. If the ramp is too steep, the front bumper will hit the ramp, like a wall, before the tires are able to reach it. The maximum angle (from the ground) that a hill or obstacle can have and that the front of the car can still clear is called the approach angle. The same principle applies to the rear bumper and wheels on the car; this is the departure angle.
Likewise, when coming down off, say, a rock, we need to know how much clearance is there in the car's midsection so that it won't scrape the rock. The angle between your tires and the middle of your car's underside is dubbed the break-over angle. If the break-over angle of the car is not known, the car can wind up balancing on a rock with all the wheels off the ground. All of these factors are important to off-roading, but they differ depending on the terrain.

Performance of Off-road vehicles:


Performance of an off-road vehicle refers to its ability to overcome motion resistance, to develop drawbar pull, to negotiate grades, or to accelerate in straight-line motion. Dependent upon their intended use, different criteria are employed to evaluate the performance of various types of off-road vehicle. In off-road operations, the motion resistance may include obstacle resistance, internal resistance of the running gear, and resistance arising from vehicle running gear (track or wheel)–terrain interaction. In order to evaluate the performance potential of off-road vehicles, the thrust that the vehicle running gear (track or wheel) develops has to be determined. There are two limiting factors to the thrust developed by an off-road vehicle -
Characteristics of the power plant and transmission.
Characteristics of shearing between the vehicle running gear and the terrain.
For off-road transport vehicles, such as off-road trucks used in construction, mining, and logging industries, transport productivity and transport efficiency are often used as performance criteria. Transport productivity is defined as the product of the payload and the average operating speed from the origin to destination on a given route, and transport efficiency is defined as the ratio of the transport productivity to the corresponding power input.

Some of leading off-roading vehicles:


Jeep Wrangler:
This 4 X 4 system features a full-time mode that will automatically shift from a 2 Wheel drive to 4-wheel drive as the conditions demand. The internal wheel speed and traction control sensors of this vehicle make driving in uneven terrains and adverse weather conditions safer and smoother while delivering superior efficiency when 4WD is not required.
Every Wrangler is equipped with skid plates to help protect critical components. Heavy-gauge steel skid plates protect essential parts like the fuel tank and transfer case, while skid bar safeguards the automatic transmission oil pan.

Ford F-150 Raptor:
Going from mild to wild on the most unforgiving terrain is where the Baja-bred F-150 Raptor excels with its extraordinary capability. It has the 24-valve, 3.5L twin-turbo HO EcoBoost with Ford port-fuel and direct injection (PFDI) system and 10-speed automatic giving a massive best-in-class 450 hp and 510 lb-ft of torque.
This high output Eco-Boost is also the standard engine for luxury travel in the top of the line F-150.

Toyota Land Cruiser:
The 2021 Toyota Land Cruiser is a product that has served for over 60 years of global adventures, it’s a sophisticated blend of off-road prowess, on-road comfort and unparalleled refinement. It also offers seating for up to eight passengers. Land Cruiser’s undercarriage is equipped with skid plates to protect crucial parts like front suspension, radiator, fuel tank and transfer case. There is a multi-terrain monitor to navigate the front, rear and side views. The Kinematic Dimension Suspension System always maintains an optimal traction, no matter how much uneven the terrain is. The multi-terrain Select helps control wheel spin and brake lockup to optimize driving performance over the most common off-road terrains- rock, loose sand, mud. When the terrains get tougher the CRAWL control system automatically modulates the throttle and brakes on five low speed settings. The Off-Road Turn Assist allows for a tighter turning radius in Crawl Control mode.

Mercedes Benz G-Class:
This started out as a military vehicle designed to go anywhere and withstand anything has become one of the most sophisticated off-roaders around. Three locking differentials in the four-wheel-drive system makes G-class perfect for the uneven terrains. It is powered by a twin-turbo 4.0-liter V8 making 416 hp and 450 lb-ft of torque, but go for the AMG fettered version, and the power ratings go to 577 hp and a brutal 627 lb-ft of torque.

Toyota 4Runner:
4Runner is built on an independent double-wishbone in the front and a 4 link and coil-spring setup in the rear. It has features like body-on-frame construction, advanced off-road technologies and tough powertrain. It is equipped with the feature of electronically controlled locking differential that helps maintain a controlled pace over obstacles. Similar to the Land Cruiser under the same family, it also has the CRAWL control feature and the Kinematic Dimension Suspension System(KDSS). It is designed to run on all terrains. All 4Runners have the skid plates to protect the front suspension, fuel tank and the engine; 9.6 inches of ground clearance, an approach angle of 33 degrees and departure angle of 26 degrees. All these features make 4Runner a perfect choice for an off-road vehicle.


Market Survey:

Improving economic conditions along with increasing discretionary spending and credit availability are positively influencing off road vehicle demand. Market players including Polaris, and Kawasaki are introducing low cost models to attract more enthusiasts. New technological developments including GPS tracking and mobile tracking to improve driving experience will boost industry growth.

Off-road Events:


While in some parts of the world, off-roading is strictly regulated, others promote it by organizing events like, Dakar Rally, Spanish Baja, Africa Eco Race, Abu Dhabi Desert challenge, Russian Baja Northern Forest, San Felipe 250 and Baja 500 and 1000.
There are certain off-road parks and motocross tracks that host a number of events and may be the only legal place to off-road in the area. Events include jamborees, rock crawling competitions, Mud Bog races, Top Truck Challenges and sand racing as well as many other events, such as the Tank Trap. The popular Ultra4 off road racing series organizes races such as King of the Hammers. Those Ultra4 cars combine desert racing and rock crawling in one car. Russia has very busy off-roading championship- 5 to 7 starts every year. Also, every club has its own events- in Tambov, off-road club Chernozem has 4 traditional races and the most popular off-road race in Russia is Ladoga Race in Karelia.

Off Road events in India:
Off-Roading Trophy sponsored by Mahindra, is the competitive side of Great Escapes. Held alongside Great Escape Trail Drives in select locations, the Off-Roading Trophy features tougher challenges where the best off-roaders come together to conquer obstacles with their vehicles. The Off-Roading Trophy format is such where drivers must pick up as many flags as possible without knocking over any cones. Every cone carries a penalty while every flag gives them points. Here, the best off-roaders from around the country converge over two days of fierce off-road battle where the winner takes home, apart from the title of the “Best off-roader in the country”, a brand-new Mahindra Thar CRDe 4X4.

The Palar Challenge:
The event is an annual team-based off-road competition held around the Independence Day weekend. Each team consists of 3 vehicles and 6 competitors. The first event was flagged off with around 21 members of the Jeep Thrills community.

Over the last couple of years, the event has seen international off-road drivers of repute competing with the best Indian off-roaders. The event is spread across 4 days on a terrain of rocks, slush, sand and gravel over carefully planned obstacles. This is to ensure that the level of competition is very high and for competitors to ensure that they change their driving pattern based on sudden changes in terrain.

References:

https://en.wikipedia.org/wiki/Off-road_vehicle
https://adventure.howstuffworks.com/outdoor-activities/off-roading/off-roading1.html
https://www.autotrader.com/car-news/best-off-road-features-169320
https://www.popularmechanics.com/cars/trucks/reviews/g129/the-10-best-off-road-vehicles-you-can-buy-right-now/
https://www.sciencedirect.com/topics/engineering/off-road-vehicle
https://www.jeep.com/wrangler.html
https://www.ford.com/trucks/f150/2020/models/f150-raptor/
https://www.toyota.com/landcruiser/
https://www.mercedes-benz.co.in/passengercars/mercedes-benz-cars/models/g-class/suv-w463/explore.html


Report by:


Ritaja Ghosh
Suspension team
Team XLR8
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