Most desert driving over level ground and low dunes should be in High Range.
The constant use of Low range causes vehicles to over-heat and consume excessive fuel. Low Range should only be used in specific situations when negotiating an obstacle or for self-recovery exercises. When in Low Range the engine is reviving faster, at any given speed, when compared to being in High Range. But as the speed of the vehicle is slower, the wind flow through the radiator is reduced and the cooling process is diminished.
As low 1st has such a low ratio, it is rarely used in desert driving. In most situations is not a viable choice. For self-recovery from soft sand the first option is Low 2nd with a very light throttle pedal pressure. Excessive engine power only spins the wheels and you will go down - not forward or back!
Low Range has very useful characteristics especially for controlling your vehicle on steep descents by offering excellent engine braking. This means that when you remove your foot from the accelerator, the vehicle is slowed by the engine and you do not have to use your brakes. Retardation is applied evenly to all wheels through the transmission and the weight transfers associated with foot braking do not occur.
Reducing tyre pressures is essential once you leave the road and enter the desert. Experience and knowledge of your tyre and vehicle capabilities will tell you what pressures to use for different circumstances but as a guide the following information is relevant. Recommended Pressures for Dual Purpose Tyres:
Large 4WD vehicles - 18 psi
Small 4WD vehicles - 16 psi
Emergency only - 14 psi
If you ever have to reduce to emergency minimum pressures you must reinflate at the earliest opportunity to avoid tyre wall damage and danger from an unstable vehicle. Your onboard or portable inflator can be used for reinflation.
Tyre pressures should be taken when tyres are cold. Pressures will build up from use and in hot weather by anything from 5 to 7 psi. So if you get stuck in soft sand your first check should be the tyre pressures. If they have built up, reduce them and that may be enough for a self-recovery.
a) Shovel: Never go out without one. The best type has a rounded blade as opposed to a straight edge. Shovels with wooden handles come in various lengths - short, standard and extra long. The choice is purely personal and could be influenced by stowage space frequency of use or even how tall you are. Metal folding shovels as used by the military are excellent but obviously more expensive than a 'souk special.'
b) Tow Rope: Never go without one. Forget those cheap straps on sale at the auto accessory shops. They will break under the slightest strain. Better to buy an industrial lifting belt with a minimum breaking strain of 6,000lbs and attach a shackle at each end. Shackles are better than hooks as the latter can be bent straight under extreme pressure. A good recovery rope should be at least 6 to 8 metres long. One type of rope on the market is the KERR (Kinetic Energy Recovery Rope) made of nylon with 20 tons breaking strain. The rope is designed to stretch by 40 per cent over its normal length, when attached between a stuck and a towing vehicle, and in doing so stores up energy. The process of shrinking back to normal length generates sufficient power to move even the most deeply stuck vehicle.
c) Lump Hammer: A three or five pound lump hammer is a good persuader in a number of different situations. Bent fenders that are rubbing wheels can be knocked out of shape.
A First Aid kit is an essential item in every off-road vehicle as is the knowledge of how to use it to good effect. First Aid courses are run by most responsible companies and voluntary attendance may be the difference between life and death. Seat Belts are an important safety aid when driving over rough country. The inertia reel type will help to keep you firmly in place when traversing slopes or ascending or descending dune slopes
The desert is home to a variety of creatures including some who can give a nasty sting or bite. Scorpion stings are not always fatal but will cause swelling and extreme tenderness of the affected area. Camel spiders are unpleasant not only to look at but to be bitten by. When they bite they inject a form of anesthetic so the victim, usually a camel, is unaware of what has happened. The female spiders lay eggs in the wound and sometime later the camel is an unknowing host to new born spiders. The best recommendation for treating a person bitten by these creatures or a snake is to rush them to the nearest hospital for professional attention. At several places in the desert, you will see clumps of yellow, lemon-like fruit. If you happen to stop, do not pick it as it is poisonous. (the camels don't like it either).
Wearing gloves will protect hands and fingers from cuts, bruises and burns. The latter can be very painful in hot weather and the best treatment is to soak the affected area in lots of cold water. Burn creams are not recommended as they reduce the cooling process.
Learn to distinguish between different types of surfaces in the desert. You only have to look at a large expanse of desert to notice different shapes of dunes, different colours and textures of the sand and the presence or absence of vegetation. Each aspect of the ground has a message for the skilled driver.
Stretches of sand with a rippled surface are likely to offer a firmer grip than smooth sand. Pale yellow sand is generally of a coarser nature than the fine grains of the golden red sand and will be easier to drive on - to a degree.
In the bottom of a blowhole or a hollow between large dunes there will be loose sand that has been blown off the top of adjacent peaks. These hollows are potential danger spots as the sand is soft and powdery and offers little traction. If you find yourself in a blowhole keep moving, don't stop, until your vehicle is on the slope of the hollow. Better still, drive on and get out of the hole. If you stop on the side of the slope you can then use the Forward and Back routine to get out of the hole.
Dunes come in three basic types - the crescent shaped called Barchan, the ridge type called Seif and the mini-mountain type called Draa.
The Barchan dune's crescent shape is created by the prevailing winds which form a shallow slope on the side facing the wind. The reverse, or lee, side is much steeper and can be a 30 to 45 degree slope with a concave profile.
Running along the top of these dunes there is usually a narrow peak which slightly overhangs the lee slope. These peaks cause the inexperienced driver some concern as he has visions of tumbling over the top and cart-wheeling to the bottom of the slope. In practice these peaks will crumble away with the weight of your vehicle providing you are brave and do not stop with your wheels astride the peak. Stopping in this position is one of the most common causes of getting stuck.
If you are unsure of the way ahead, stop the vehicle in a place where you can start off again - NOT on the slope near the top of the dune. Walk ahead to see the lie of the land before going over the top. If you stop on the approach to the peak or astride the peak you may need to do some serious recovery work.
After rains you may find the peak has firmed up and will not crumble under the weight of your vehicle. In such a case, you may have to dig out the sand from underneath the vehicle so that the wheels regain contact with the sand for a good grip.
Seif dunes owe their shape to the prevailing winds not always blowing from the same direction. The dunes assume a profile similar to that of a wavy edged sword with a central ridge down its spine.
It is not unusual to find Barchan and Seif dunes occurring in isolated pockets in otherwise generally hard and flat sandy regions. A large continuous area of soft sand is called an Erg and it is in these areas that the high Draa dunes are found.
Most 4WD vehicles are regularly used by their owners as everyday transport and off-road excursions are weekend trips, once or twice a month. However, going off-road will put additional strain on the vehicle and small problems that would not normally arise with normal use may cause serious problems if you are out in the middle of nowhere.
Every off-road trip should be approached seriously and systematic routine checks must be made before starting. The items to check are as follows:
1. Condition of the tyres: Check for cuts, bulges or other signs of damage. Also check that the spare tyre (always take one with you) is inflated and serviceable. If the spare is mounted underneath the vehicle or on the rear door, make sure it is firmly secured with the necessary wheel nuts or other fittings.
2. Water level in the cooling system: Most modern vehicles have a water catch tank fitted and it is this that is topped up rather than the radiator itself.
3. Engine oil level: If your vehicle has automatic transmission, check the level of the auto box.
4. Hydraulic clutch and brake reservoirs should also be checked.
5. Battery check: If you are adventurous when going off-road, you may have placed your vehicle at steep angles, front, rear or sideways and there is a possibility that some battery acid has spilled onto the top of the battery. It is advisable to wipe it clean as acid corrodes surrounding parts including the clamps. Make sure these clamps are firm and tight before you start. A loosely fitted battery can cause a lot of damage under the bonnet if it breaks free from its mountings. Top up the fluid if needed.
6.Equipment check: : A standard checklist is provided here and, while it may seem over-comprehensive, it is better to be safe than sorry.
7.Fuel tanks: : Fill up before you leave and start with a full tank. If you find yourself worrying about how much fuel you have left, you may not be concentrating properly when tackling those tricky sections.
8. Interior Stowage: Make sure all equipment including tool-boxes, camping gear etc is firmly secured in the back of the vehicle and not liable to start flying around when going over rough ground or up or down steep slopes.
Driving over the ridge of a dune must be a careful process especially if you cannot see what is on the other side. (See earlier section "Look For What's Next").
The important thing to avoid is getting stuck with the front wheels on one side of the ridge and the rear wheels the other side with the vehicle resting on the chassis.
Most ridges will collapse from the weight of your vehicle but if one doesn't and you get stuck you have to dig out the sand from underneath the chassis to allow the wheels to make good contact with the ground or accept a pull from a colleague.
The unknown on the blind side of the crest of a dune should always be treated with respect. In the majority of cases the reality is far less worrying than the thought of what might be there. Here again learn to anticipate what lies ahead. If the series of dunes you have been crossing is low in relation to the surrounding countryside it is unlikely there is a long steep slope on the other side of the next dune.
Whether this is your first or hundredth time on the dunes, everyone can benefit from brushing up on their technique to get the most out of their drive. Here are few ideas for improving your desert driving techniques.
WHEN you hold the steering wheel do not grip it with your thumbs inside the rim. Keep your thumbs out and resting along the top face of the wheel. The reason is very simple. A sudden deflection of the wheel from contact with a pothole, hard lump in the ground or tree stump will cause the wheel to spin out of our hands. If your thumbs get caught by the spokes of the steering wheel it can be very painful indeed.
Line Of Least Resistance
TRY to take the line of least resistance when tackling an obstacle. Whilst you should always tackle smooth slopes in a straight line there are some climbs where the ascent can be better made by a meandering route which follows step by step ascent thus reducing the overall angle of climb.
Keep Your Distance
WHEN TRAVELLING in convoys some drivers have a bad tendency to drive too close to the vehicle in front of them. This causes serious problems if the leading vehicle runs into difficulty or has to stop suddenly or wishes to reverse back along his tracks as the follower has little time or space to take evading action and he himself becomes stuck
A reasonable distance to maintain is about ten vehicle lengths when driving over dunes and rough ground. This will give a clear view and sufficient reaction time if problems occur. When driving in convoy on tracks at faster speeds, use 100 metres as a minimum distance between vehicles.
Don't Stop Where You Can't Start
THIS APPLIES mainly when ascending slopes and failure to observe this rule is the main cause of inexperienced drivers getting stuck. Never stop on the top of a dune - go over the top and stop on the downward slope so that you can start off again. Never stop astride the ridge on top of a dune. Always stop on a downhill slope whenever possible.
Survival & Safety
THE basic requirements for survival are food, water and shelter. Human beings can survive far longer without food than without liquid intake. In summer months temperatures exceed 120 degrees F in the desert and the body will lose a tremendous amount of its fluids from sweating. If this fluid is not replaced your condition will be quickly affected. Official recommendations state 10 litres of liquid per person per day is needed in very hot climates. Taking salt tablets to replace the salt that you lose from sweating is also strongly recommended. Cold water helps to reduce body temperatures. Freeze some bottles of spring water in your freezer after decanting an inch or so to allow for expansion on freezing. These frozen bottles, if kept in a cool box will thaw out gradually and even after 24 hours are still partially frozen.
If you have broken down in the heat of the day and have decided to get yourself out by digging and pushing, be careful not to over-exert yourself and provoke an attack of heat exhaustion. Work for a short while and then retire to the shade of the vehicle to recover and rest for a while. Alternate between working and resting in equal stints until you have effected your recovery. Drink plenty of fluids at the same time.When the temperature and humidity are high and the air is still with little breeze the body is at highest risk as its cooling system may be inadequate to maintain a safe body temperature. Keep in the shade as much as possible, avoid long periods of activity and maintain your cool - metaphorically!
Exposure to excessive heat may provoke one of two different conditions - Heat Exhaustion or Heat Stroke. Heat Exhaustion is brought on by excessive sweating or lack of fluid intake and the symptoms include feelings of exhaustion, thirst and nausea accompanied by a violent headache. The skin is clammy but cool. First Aid level treatment involves administering copious quantities of fluid and salt and keeping the victim in the shade.
Heat Stroke occurs due to build up of body heat from high ambient temperatures and humidity and lack of cooling breezes. The main symptom is a sudden rise in temperature and the skin becomes dry and very hot as the cooling sweat process stops. First Aid level treatment requires the victim's body temperature to be reduced as soon as possible. One effective method is to soak a sheet with cold water and wrap it around the victim. Fanning will also assist and if you carry a 12V battery operated fan use it without delay.
In either case if the victim remains conscious he/she should be lain on the back with feet raised resting on a block. If unconscious the best recovery position is front down with head and neck extended sideways to prevent blocking of the air passages.
Fun Drivers must acquire a basic knowledge of First Aid treatment as described above, but as human life is at risk, if in doubt urgent medical treatment must be sought as soon as possible.
Ascending the steep slopes of a dune or a ridge requires one basic ingredient - MOMENTUM. There is no substitute for momentum. If you start to lose forward momentum your vehicle may falter and then dig in. Climbing steep sand slopes is a different process to climbing earth or stony slopes. When the ground is hard and firm the technique to use is one of slow and steady progress picking your way carefully up the slope and using the path that offers the best grip you can find.
Sand surfaces do not offer the same degree of traction as a hard surface so you need to build up a head of steam on the approach to the slope to allow the momentum of the vehicle to assist the driving force of the wheels once you are on the slope. An example of momentum at work is seen when driving on the highway at, say, 100 kph and putting the vehicle into neutral. The momentum of the vehicle will make it continue for several hundred metres before it eventually comes to a halt. The same principle is used for climbing dunes but in a controlled manner.
You must learn to judge just how much momentum is needed and how much speed you need to build up on the approach run to a slope. It can be dangerous to use excessive speed and risk losing control of the vehicle if it hits an unseen bump in the ground. The choice of gear is also important on your approach run. Select a gear that will enable you to build up momentum and which can be used for the ascent without having to change once on the slope.
Driving down a steep dune several hundred feet high is a daunting prospect for the first-timer. Apart from the courage required you also need to know what to do and what not to do. Gravity is a powerful force and a 2 ton vehicle on a 35 degree slope needs to be controlled by the driver.
After you have made your visual check of the slope and decided which path to take, remember the basic rules for descending sand dunes.
1. Always drive straight down a slope - not at an angle.
2. Do not use your brakes on a steep slope - the act of braking transfers the weight of the vehicle onto the front wheels which will dig into the sand. The rear of the vehicle becomes lighter and will have a tendency to slide sideways and the risk of overturning is very real.
3. Never try to coast down a slope in neutral or with the clutch pedal depressed. The soft sand will not allow the vehicle to roll forward and it may start to slide sideways and roll over.
4. Always be in gear and DRIVE down a slope with the engine pulling the vehicle. The choice of gear is very important - if you are in High Range your speed may become too fast and you will be tempted to use the brakes - with disastrous results. Better to select Low 2nd or 3rd gear for the descent. If your speed is becoming too fast all you have to do is lift off the accelerator pedal and engine braking comes into effect.
Retardation from engine braking is applied equally to all four wheels and will not unbalance the vehicle due to weight transfer as wheel braking would do.
Everyone gets stuck from time to time and here are a few tips and ideas to reduce the agony of self-recovery. Every vehicle needs to carry certain equipment on board to assist in the recovery process.