Overview of preparing a 4x4 truck for overland travel
This is an article I wrote for Chris Scott's upcoming book, Overlanders Handbook. I've reproduced it here for interest's sake. Over time I will expand on the information in their own individual sections.
Preparing a 4x4 truck for overland travel.
Using a truck for overland travel allows you the luxury of space; space to have a permanent bed, space for a toilet and shower-room, and space for kitchen and seating areas. However, a simple motorhome will not suffice, as the demands overland travel in remote areas places on your vehicle are sufficient enough to require specialised techniques.
First and foremost you need to find a suitable 4x4 truck, one rugged enough to be able to withstand rough roads, tough terrain and extreme conditions. Don't go for a 2x4 truck, as you will be limited in the areas you can travel to, which will disappoint and in many people's minds, defeat the whole point of overland travel, which is to go to places off the beaten tourist track. When choosing your truck, remember that no matter how strong it is, and no matter how many spares you carry, you can never plan for every occasion, and at some point during your travels, something will break and you won't have a spare on hand. For this reason it is advisable to bear two things in mind when choosing your vehicle. First, favour a truck which is prevalent in the areas you wish to travel, and secondly, favour a truck with a pure mechanical design over one with electronic components.
When something breaks which is beyond your capabilities to fix, it will be far easier to find a mechanic if they are familiar with your truck's design, and in the event you do require a spare, the ability to source one locally will often be both far cheaper and quicker than if you need to have one shipped out to wherever you are. Even if you can afford the often exorbitant cost of couriering a spare out to some remote corner of the world, remember that customs duties payable are often100% or more, and you can't choose where you break down... if you are in a remote area without telephone contact you will have to face the difficult choice of splitting up as someone goes to make contact with the outside world, or if you don't feel comfortable with breaking up your group, leaving your truck where it is, and perhaps returning to find excessive pilfering has taking place. Mercedes trucks are most prolific around the world, and you should favour this manufacturer if at all possible.
A truck which relies on mechanical components rather than electronic is king, as electronic components are notoriously non rugged, susceptible to dust and moisture, and when deep in some remote jungle or desert, if your electronic components fail, often your truck will become stranded until you can fit a computer to diagnose the problem. These days newer trucks rely on electronic components more and more, so go for an older truck which has a simpler design... remember the old adage:Keep it simple stupid! A good source of suitable trucks is the armed forces. These trucks are notoriously simple in design, extremely rugged and more often than not, are 4x4 as standard, since the nature of the armed forces requires they can travel in extremely rough conditions.
Once you have your vehicle you can concentrate on the conversion. Your first concern is the torsion-free subframe. 4x4 vehicles are designed to allow considerable chassis twist, allowing the chassis to accommodate undulations in the terrain, thereby keeping all four wheels on the ground. If you take a box and connect it directly to the chassis,twist in the chassis will be transferred through the walls of the box. If the box is strong enough to withstand this twist, it will prevent the chassis from twisting itself, reducing the capability of the vehicle to keep its wheels on the ground. However, a much worse situation is when the box is not strong enough to withstand this twist; in this scenario the walls of the box will buckle, perhaps even break apart! Any cupboards or similar furniture fixed to the walls of the box will themselves buckle and break or fall off the walls. The solution is to allow the box to move separately to the chassis, and this is achieved by means of the torsion-free subframe.The Mercedes-Benz Unimog uses a geometric cantilever system, and is the industry-leading example, but many different approaches will do the trick. One approach is to use two supplemental rails, sat on top of the chassis rails. Each is connected to its respective chassis rail with a hinge at the front and a spring at the rear. When the chassis rails twist, the spring will extend rather than cause the supplemental rails to twist. Another option is to seat the box on the chassis and connect it with springs at regular interval. Again twist will cause the springs to extend in-situ, preventing the torsion force from being transferred to the box.
Once you are confident your box will withstand the twist your chassis will be subjected to,you can concentrate on making it liveable. There are five main things to consider - your furniture, power system, water system,refrigeration and cooking.
1. Furniture:
You want to ensure your furniture is light-weight. Using chipboard, which is most often used in kitchen cupboards and much other furniture at home is not advisable as it is very heavy. A far better option is to use plywood, as this has the benefit of good strength while being relatively lightweight. For building your bed and seating areas,consider adding a metal frame to your plywood to provide extra strength. Ensure you build your furniture with ruggedness in mind,corrugations experienced on many roads in remote areas will surely shake apart furniture that is not built strong enough. A high-strength glue which sets allowing a little flexibility is advisable, as glue with no flexibility will most likely crack.
If you want a permanent bed, consider locating it across the width of the box. This will allow you to position windows on either end, which when open can provide a flow of air across the bed. When sleeping in extremely hot and/or humid areas, insufficient air-flow across the bed will make for a very uncomfortable night's sleep.
Storage is highly valuable, as you will most likely want to bring along a fair amount of equipment (outdoor equipment (camping chairs, table, lamps etc),vehicle spares, books, games, electronic equipment, medical kit,extra toiletries and perhaps dry food and tins for when local produce is not available.) If you position the bed fairly high up you can utilise the space below the bed as a large storage space. The dining area's seats can be built as seat-boxes, having large storage space below the seats. Consider also having access from outside for part of the storage. A good combination is to have the area under the bed accessed from outside, and the area below the dining-area's seats for inside storage.
2. Power:
Several deep-cycle batteries (also known as leisure or yacht batteries) will be used to provide lights and power for accessories. Most trucks run on 24V systems. For simplicity it is advisable to keep your accessory system 24V instead of dropping the truck's voltage to 12V for your leisure system. 24V has the added benefit of being more efficient than 12V. When you start your research you will find that most camping, caravan and motorhome accessories are available in 12V format. This is because these accessories traditionally cater to the caravanning world. Caravans are normally pulled by cars, hence the 12V system. 24V accessories are available, but are generally more expensive than their 12V counterparts, economies of scale working in the favour of the 12V system. Instead you should turn to the yachting industry to find your 24V accessories. Perhaps this doesn't sound intuitive, but if you give it some thought you will realise that all you are doing is creating a mobile home – if it is moved by means of a yacht or a truck it is, in fact, no different internally. Generally speaking the yachting industry has more expensive components, but remember that you get what you pay for.
If you are intent on having a 12V system, then you will need a 24-to-12V battery-to-battery charger to drop the 24V alternator output to a 12V charging source for your 12V system. Avoid the temptation to use a DC/DC converter as this puts out a set voltage which will only be able to charge your batteries to about 80% of their capacity. If you use a 24V system then you can just use your alternator's output to charge your batteries, keeping the system simpler and making for fewer points of failure. You should definitely have a split-charging system that will charge your truck batteries first, and only once they are charged, divert the current to charge your leisure batteries. You should also look into upgrading your alternator regulator, to utilise multi-stage charging. Batteries require different charging voltages and currents to be charged to 100%, and a specialised alternator regulator will be able to achieve this.
Deep-cycle batteries are damaged and do not have a long life if they are constantly discharged before being recharged. They will last much longer if used where the rate of discharge is close to the rate of charge. For this reason it is a good idea to use low-power accessories, such as LED lights over Halogen or similar inefficient lights, and forego current-hungry accessories such as microwaves, air conditioners, electric heaters, etc.
Recharging the batteries is most often provided for by the vehicle's alternator. However, this only provides charge whilst moving. If you want to park up for several days you will need other means to recharge your batteries. You will certainly want to have a mains charger that can take a shore-hookup from mains power and charge your batteries, but this is only useful when you are near a mains supply. If you're building an overland camper then you will naturally want to be exploring off the beaten track, and often there won't be mains available. These days solar panels are becoming efficient enough to provide sufficient current to keep your batteries topped up at an affordable price. You will need a good solar charge regulator in conjunction with your solar panels to regulate the charge being provided to your batteries.
Another option is to use a generator, useful when in overcast conditions or when you wish to use accessories that use more current than solar panels can provide. Something to be aware of is that some battery chargers do not live well with the AC wave-form generated by certain generators. Make sure your generator and battery charger work together, otherwise your charger will be cooked! A downside to consider is the noise your generator creates, which can be a considerable bother, especially at night. Silent generators are available these days, but are fairly expensive and use petrol; since almost all trucks run on diesel, you will be forced to carry two fuels.
How much battery power do you need? Deep cycle batteries are rated in Amp/hours. This is the number of amps they can provide for a certain length of time. For example a 100 Amp/hour (Ah) battery can provide 1A for 100 hours, or 100A for 1 hour, or 50A for 2 hours, etc... You need to calculate how much power your accessories will use during a 24h period. Each of your accessories will come with documentation showing either its current draw or its power usage. If an accessory, say a water pump, draws 7A, and you anticipate using the pump (for your shower and basin, sink etc) for a total of 1 hour each day, then over a 24h period the pump will draw 7Ah (7 Amps x 1 hour). If another accessory, say a heater, has a power rating of 300W then you use the formula I = P/V to calculate the current draw. If you're using a 24V system, then the current draw will be I = 300W / 24V, or 12.5A. If you anticipate using your heater for 3 hours each day, then your heater will draw 37.5Ah (12.5 Amps x 3 hours). Do these calculations for each accessory you have, add up all the resulting Ah figures, and you will get a total amount of Ah you need in a 24 hour period. Let's say the total is 100Ah. It is a general rule of thumb that you should provide 3 times the total you require, so for this example you will need to provide 300Ah.
Previously it was mentioned that if deep cycle batteries are extensively discharged then they are damaged and become less and less able to hold charge. If you want your batteries to last then you don't want to discharge your batteries to less than 80% of their capacity. So, for our example of using 100Ah in a day, and having a battery bank capable of providing 300Ah, we don't want to use more than 60Ah before we start providing some charge back to the battery bank. This is done by either being on the move (charge being provided by the truck's alternator), being on shore-hookup (charge being provided by mains charge), or by getting charge from an alternate source, such as solar panels.
Being aware of your power utilisation and accommodating your needs with sufficient battery power and the associated charging needs will keep your electrical system in good health and able to work for you without being damaged. Having an inadequate system will result in chronically discharged batteries which will soon be too damaged to provide you with sufficient power. If this happens while you are off the beaten track you may find you have quite a few problems!
3. Water:
Assuming you don't want to use a jerry can as your water source in your overland camper, you will need a fresh water tank to provide water on demand.It is also advisable to have a grey water tank to hold your grey water until you are able to empty it. Some people allow grey water to flow directly to the ground outside, but in many places this is illegal or just plain embarrassing. It is also often unhygienic. If you will be emptying your grey water tank onto the ground (often the only option), consider using bio-degradable soaps, as normal soaps are hazardous to the environment. Many people also have a black-water tank for the toilet, but far more convenient is to use a cassette-toilet. If you have a black-water tank you will need a means to pump the tank's contents into a WC, which is often not conveniently located near the truck. A cassette-toilet has a black-water cassette which can be removed when full and carried to a WC where it can be easily emptied.
Water is a very heavy substance, so it is highly advisable to locate your water tanks in a low position, so as to give them a low centre of gravity. Locating them high-up, such as on your roof, is not advisable as when full the weight can make your truck top-heavy and cause stability problems when cornering. Furthermore, baffles should be located inside the tanks to restrict the surging effect of the water which can again cause stability problems when braking or cornering. When designing with size of your fresh water tank, consider the size of the tank.There is a trade-off to be had between too small, which means you will have to refill it often, and too large, which will add excessive weight to your truck when full.
Since the water tank will be located in a low position, you will need to pump your water. A diaphragm pump is your best option. It detects a drop in pressure (eg: a tap opening), and turns on, providing a flow of water. It can be used by itself, but a better option is to use it in conjunction with a pressure accumulator. The pressure accumulator will accommodate a build up of pressure (more than that used by the flow of a tap), thereby preventing the pump from cycling and prolonging it's life. (When a tap is opened, flow will be provided by the pressure accumulator until the pressure drops sufficiently for the pump to turn on; the pump will run until the pressure accumulator is filled, and turn off again.)
A means to purify water is essential for overland travel, because often water sources are of dubious quality. It is possible to purify water on an ad-hoc basis by boiling and/or using chlorine or water purification tablets, but a much more convenient option is to use a filer. It is not necessary to filter all your water, but definitely you want to filter your drinking water. There are several filtration techniques available,one example is reverse-osmosis. It is advisable to pre-filter your water (ie: before it gets to your water tank) with a basic filter (10micron is suitable) to remove sediment. This will keep your tank cleaner and prolong the life of your drinking water filter.
Finally, if you wish for the luxury of hot water, you need to consider a heating system. There are two main options, an on-demand gas heater or a calorifier in conjunction with a heat-exchanger. The on-demand gas heater is good because it heats only the water you wish to use, but beware of the amount of gas it uses, as often this can be hard to come by in remote areas. The advantage of calorifier option is you can connect it to your truck's coolant system and make use of excess heat generated by your engine to heat your water. However the downside to this system is that the amount of hot water is limited to the capacity of your calorifier, and when parked up for several days the engine isn't running, therefore you will have no hot water. To overcome this you can tee in a supplementary heat-exchanger that heats the coolant running through the calorifier. There are several small diesel heat-exchangers available on the market that you can connect to your truck's fuel system and turn on half an hour before you want hot water.
4. Refrigeration:
Some people can do without refrigeration, but this is a luxury most people would dearly like to afford. There are two main technologies:Absorption or compression refrigeration. Absorption refrigeration is inefficient when compared to compression refrigeration, but can be run on mains (AC) voltage, DC voltage and gas, which gives you flexibility regarding power supply. However, absorption refrigeration is so inefficient that running it with a DC power supply is all but impossible. Practically the only time this is possible is when the truck is running and the alternator is providing the DC voltage;connected to just your deep-cycle batteries they will quickly be depleted, your batteries will be damaged and your fridge will stop working. Therefore, you will find you almost always use the gas option. Preferable is DC compression refrigeration. DC compression fridges available on the market are so efficient that it is affordable to buy solar panels with a sufficient power output that can keep the fridge running practically indefinitely.
Another consideration with refrigeration to be aware of is front-opening vs top-opening (ie: upright vs chest) When you open a front-opening fridge all the cold air rushes out and the fridge has to operate again to maintain its specified operating temperature. Since cold air sinks, atop-opening fridge looses only a fraction of it's cold air when open.
5. Cooking:
Here, LPG (liquid petroleum gas) is king. It provides immediate heat, and gas is available in practically every country in the world. If you make use of the on-demand gas-heated hot water option, and/or the gas-powered absorption fridge, you can use a single gas bottle to provide for all your gas-powered systems. You can easily fit a gas-powered oven and hob in your overland camper, giving you all the cooking flexibility of home. However, do remember to fit both a smoke and carbon monoxide alarm when using gas, and have a suitable fire-extinguisher to hand.