Alvis Stalwart Information

The Stalwart, formally classified by the British Army as Truck, High Mobility Load Carrier (HMLC), 5 Ton, 6 x 6, Alvis/Stalwart and informally known by servicemen as the Stolly, is a highly mobile amphibious military truck built by Alvis that served with the British Army from 1966 until 1992.

The Stalwart was a private venture by Alvis that was adopted and entered service with the British Army in 1966 as a general transport truck in preference to the FV431, the load carrier variant of the FV430 series. It was one of the same line of vehicles that included the Alvis Saracen, Saladin and Salamander. The high mobility and amphibious capabilities were considered ideal for resupplying units in the field, particularly those of the British Army of the Rhine.

The hull is the vehicle chassis, the engine is situated under the load deck in the rear of the hull and the gearboxes with differentials and transfer boxes forward of this. The load deck is open-topped with large drop down panels on either side. Waterproof seals ensure that these will not leak when in the water. The three-person cab has the drivers position in the centre and a seat for a passenger on either side. The cab can only be entered through roof hatches.

The Stalwart can carry 5 tonnes of stores, or tow 10 tonnes.

In the water it can be driven at about 6 knots by vectored thrust water-jet propulsion units.

The drive system, which includes the all-wheel drive, multiple gearboxes, and the water propulsion units, is complex and needed a lot of maintenance. When the amphibious qualities became unnecessary, it was common for the water jets to be removed to reduce weight and maintenance.

The Stalwarts over-terrain capabilities come from the fact that the six-wheel-drive system lacks differentials, using simple bevel gears to transmit drive. A centre mounted no-spin differential allows a certain amount of slip between the two sets of wheels on each side of the vehicle on hard surfaces, but there is no allowance for rotational speed differences between front and rear. The centre no-spin unit allows the wheels on either side of the vehicle with most grip to drive when off-road. This has the effect of making the vehicle appear to crab (move from side to side) when negotiating muddy conditions, thus making the Stalwart a true six-wheel-drive vehicle, with three wheels locked together and turning at the same speed.

However, this system causes "wind up" in the transmission (inter-component stress) as all the wheels are forced to rotate at the same speed, which during cornering is impossible. This led to rapid wear and breakage of the tracta joints within the drive train. If the vehicle was used on firm surfaces, such as tarmac or concrete – in off-road conditions, the natural slip of a loose surface, such as mud or gravel reduced wind up. This problem is of special concern for modern-day Stalwart owners – to get a vehicle to a show requires moving it by low-loader or driving it on the road, risking damage to the transmission. Alternatively, the front and rear driveshafts can be removed, eliminating wind up at the expense of off-road capability.

During military use, the problem of transmission wind up was solved by laying out railway sleepers (railroad ties) in a grid on flat ground and driving over them on long road moves; this allowed the transmission to unwind. On more than one occasion, servicemen drove Stalwarts into car parks and used the kerbstones separating parking bays for the same purpose. Another problem with the transmission was that the vehicle was designed to be driven loaded. Driving the vehicle unloaded caused increased wear on the drivelines to the wheels as a result of the increased angle of mesh of the joints.

Stalwart Mk 1 load carrier

Stalwart Mk 2 load carrier. This had a two-man crew although a third seat could be fitted to the right of the driver as a field modification. It could also carry 38 fully equipped troops or the Gloster SARO bulk refueling pack as alternatives to the five tonnes of cargo. The jet drive units in all the Mk 2 variants were much more efficient, giving a claimed 9 knots.

The most obvious visible difference between Mk 1 and Mk 2 variants is that the lower edges of the cab windows were now angled downwards rather than horizontal. This was to improve visibility at close-range, particularly when being marshalled by a banksman standing nearby.A total of 970 Mk 2 FV622, FV623 and FV624 Stalwarts were produced, of which the British Army purchased 946, with 24 sold to other countries.

Stalwart Mk 2 limber. An artillery ammunition supply vehicle for the Abbot self-propelled gun. There was an extra seat in the cab for the crane operator plus four rear-mounted seats for a seven-man crew. An Atlas 3001/66 hydraulic crane capable of lifting three tons was added to the cargo area to lift palletised loads of ammunition. The rear crew folding seats were separated from the main cargo area by a wooden divider, and protected from inclement weather by two folding PVC hoods on metal hoops.A total of 269 Mk 2 Stalwart limbers were produced.

Stalwart Mk 2 REME fitters vehicle, based on the Mk 2 Stalwart. Two extra rear-mounted seats were added to the main cargo area for a four-man crew. An Atlas 3001 hydraulic crane capable of lifting three tons was added to the cargo area. This differed from that of the FV623 variant by having hydraulic anti-creep check valves fitted. This modified crane was more stable (and safer) for lifting and holding engine, transmission, and other heavy equipment whilst manoeuvring them into position.A total of 60 Mk 2 Stalwart fitters vehicles were produced.

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