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DEFENCE INDUSTRY: MILITARY VEHICLES


 Vehicles used in military applications not only need to withstand submersion (below) but also exposure to harsh terrains (bottom)


Managing submersion: it’smore than fitting a snorkel


Military vehicles often have to negotiate rivers or flooded areas, so the challenge is to ensure they can withstand not just water but other contaminants. Andy Pye talks to Cy Wilkinson, managing director of steering column specialist, Pailton Engineering


dangerous. 70 per cent of flood-stranded cars are completely written off by their insurers. If driving through flood water is completely unavoidable, Land Rover advises its drivers to creep into the water at a very low speed, building upmomentum to create a bow-wave in front of the vehicle as itmoves through the water. This bow wave pushes the water away


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fromthe engine and can be an effective way to keep the air intake of the vehicle clear of water.However, it is not a feasible method for vehicles that are regularly subject to wet terrain or are subject to being partially submerged in water. Heavy-duty vehicles that canmanoeuvre


through water that is severalmetres deep – often referred to as deep wading – are described as “semi-amphibious”.Many of us will have seen off-road passenger vehicles fitted with a snorkel that is higher than the normal engine air intake, usually level with the top of the cab. Usually, when these snorkels are fitted to


off-road vehicles they are used by hobbyists or those with jobs that require themto do a lot of off-road navigation. These vehicles do provide some wading capabilities, but not the level of submersion required for extreme ormilitary applications.


44 /// Environmental Engineering /// October 2017


tandard passenger vehicles are not designed to be driven through water. Driving your car through deep water is not only inadvisable, it’s also pretty


Truly semi-amphibious vehicles are


usually armouredmilitary vehicles that can bemostly or almost entirely submerged in water. These vehicles aremanufactured with the ability tomanoeuvre through wet terrain at the forefront of their design— above the aesthetics, comfort and speed specifications of a regular passenger vehicle or 4x4. To successfully navigate through water,


military vehiclesmust ensure that all components underneath the vehicle are completely sealed off to external elements —or designed in a way that ensures they are unaffected by exposure.However, it is not just water thatmilitary vehicles need to withstand; dust, grit and general rough terrain can also cause problems. Designing and producingmilitary


vehicles is not a cheap exercise, nor is it something to be taken lightly. Consider military steering systems as an example.


Many extreme applications expose the steering systemto salt, water, grit and mud. Generally, the bevel boxes on steering systems are not designed to handle this exposure, yetmany steering systems are standard in design. By choosing a bevel box that is designed


with extreme applications inmind, the manufacturer can ensure it can withstand these conditions, without affecting the durability or agility of the drive itself. Military vehiclesmust be able to


withstand tough terrain. So, when purchasing components for amilitary vehicle,manufacturers should never assume the part has been tested to its limits. Instead, theymust choose a supplier with a dedicated testing facility. In the case ofmilitary vehicles, the equipment should be adequately tested against the effects of encountering water,mud or grit while driving. Naturally, different types of vehicles require different testing procedures, and this is usually determined by the environment in which the vehicle will operate. Thorough testing procedures will not


only subject the components to different terrains, but will also simulate long distance driving to identify how the system will be affected over time. For example, rotary testmachines are a way to check the wear on bearings in universal joints, sliding shafts and othermoving parts of a steering system. EE


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