High Mobility a Critical Design Element
The CV90 user club continues to grow, with recent announcements from both the Czech Republic and Slovakia that they have will procure the vehicle to meet their IFV needs. They join seven other users deploying between them nearly 1,300 vehicles in multiple variants.
Several variants of the CV90 will be procured to replace the BVP-1 and BVP-2 series vehicles – variants of the BMP-1 and 2 respectively manufactured by Czechoslovakia, representing a significant improvement over those Soviet-era platforms. Both countries are expected to negotiate in a joint fashion for the vehicles, and BAE Systems states it will cooperate with their domestic industries to manufacture them.
The designer of the CV90, BAE Systems engineer Alfons Falk, has written extensively about the vehicle’s design process and what makes it unique. Its primary defining characteristic was the need for mobility in northern Sweden, including deep snow and swamps. This led to an extensive study period, including the use of terramechanics simulations to assess how ground pressure could be optimised.
A vehicle’s ground pressure dictates how far into soil or snow the vehicle’s tracks or wheels will sink, the depth to which it sinks dictating the resistance tracks or tyres must overcome. The defining factor of an off-road vehicle is typically weight – the heavier a vehicle, the deeper it will sink, the more resistance it will have to overcome, and the worse its off-road mobility will be.
A custom mobility test rig was built for the CV90 and extensively tested before full development commenced. A critical impact on the vehicle’s design was the UDESXX20, a tracked articulated vehicle designed to carry a 120mm gun. Despite exhibiting considerable off-road mobility, its track sinkage was found to be greater than the IKV91 reference vehicle – the result of track tension, which in turn led to the track tensioning system on the CV90. This affects the ‘attack angle’ of the tracks over the front roadwheel – too great an angle will increase sinkage and lead to loss of traction. It is therefore critical to adjust track tension according to the terrain.
Other design aspects also maximised mobility. The vehicle has seven roadwheels arranged as close together as possible – compare this with the six of Warrior, Bradley and KF41 Lynx – which works, together with the greatest track length possible, to distribute vehicle weight over a large area, thereby reducing ground pressure.
There are many elements that impact a country’s decision to procure one armoured vehicle over another, with politics, industrial/employment benefits and cost key considerations. However, the mobility of the CV90 must also figure prominently, especially for those countries with difficult terrain to cover and defend.
Sam Cranny-Evans of RUSI London for MON