Heavy dump truck
M917A3 is a heavy dump truck (HDT) designed and developed by Mack Defense, a subsidiary of US-based truck manufacturer Mack Trucks to meet military transportation requirements of tactical and logistic missions. Mack Trucks is a part of multi-national manufacturing company the Volvo Group.
The HDT was presented at the Association of United States Army (AUSA) show held in Washington, DC in October 2018. The modern trucks are expected to replace AM General’s MM917, which has been operational with the army for more than 40 years.
The HDTs are intended for use by the active, reserve and guard components. The army will receive 50% of the vehicles, while the remaining 50% will be delivered to guard and reserve units.
Mack Defense M917A3 heavy dump truck development and testing
In October 2018, Mack Defense and Hendrickson won a contract from the US Army to integrate PRIMAAX® EX suspension systems on all Mack dump trucks.
In August 2019, Crysteel Manufacturing and Truck-Lite joined Mack Defense’s team of suppliers for the programme. Crysteel partnered with Mack Defense to develop the steel body for the M917A3, while Truck-Lite agreed to provide lighting systems for the truck.
JWF Defense Systems (JWFDS) was selected to provide the armoured cab system. The company is responsible for fabricating and painting the cab system before delivering it to Mack for installation.
Production work on five M917A3 HDTs started in February 2019, marking the start of the production vehicle testing (PVT) phase of the programme.
The first five non-armoured trucks were formally handed over to the US Army in June 2019 to undergo a 40-week durability testing at the Aberdeen Test Center in Maryland. The testing, which began in the second half of 2019, was intended to evaluate various performance metrics, including payload, mobility, and safety.
Initial testing excluded the testing of armour capability. The company tested the HDT in areas such as trench crossing, vertical step, and side slope during the test production and competition phases.
Mack Defense delivered six M917A3 trucks in armoured configuration to the US Army in September 2020. The vehicles participated in a 40-week PVT phase at the US Army’s Aberdeen Test Center, following the delivery. The performance and durability of vehicles were tested. The trucks also underwent live fire testing to evaluate the survivability of the occupants.
Orders and deliveries of M917A3
Mack Defense received a contract from the US Army to deliver M917A3 HDTs in May 2018. The $296m contract involves the supply of 683 armour-capable or armoured HDTs to the US Army to enhance operational effectiveness and readiness.
The next-generation armoured trucks will be delivered to US Army units across the world by May 2025. Mack Defense’s M917A3 HDT was preferred over the solution proposed by Navistar Defense. The company received an order from the US Army to deliver 99 M917A3 non-armoured HDTs in March 2021. The HDTs will serve both the US Army and the US Army Reserve.
Mack Defense commenced the production of the HDTs at the Mack Experience Center (MEC) in Allentown, Pennsylvania, in the first quarter of 2021. The company established a dedicated production line for the vehicle with an investment of $6.5m.
The first production vehicles were delivered to the US Army and the US Army Reserve in September 2021.
M917A3 truck design and features
The HDT is based on Mack Defense’s Granite axle-forward construction grade chassis and includes modifications to provide improved payload, mobility, and survivability in hostile environments.
The enhancements made to the Granite model include all-wheel drive, heavy-duty rear axles, and increased ride height suspension.
The truck is equipped with a force protection capability and comes with a standard cab and an optional armoured cab, which is designed to meet the blast requirements of the US Army. The HDT provides the capability to swap the standard cab with the drop-in armoured cab to meet mission needs. The truck can also be used as a radar carrier, tanker, wrecker, troop carrier, and heavy equipment transport vehicle.
In the 8×8-wheel configuration, the truck has a gross vehicle weight of 42.9t. The cab can accommodate two personnel, including a driver. The heated steel dump body has the capacity to carry 13.76m³ of dump.
M917A3 offers a payload capacity of up to 27t. Mack’s Cornerstone chassis allows the tuck to transform into multi-mission platform to serve the military’s logistical and tactical support needs.
The vehicle is fitted with a control module with a touch screen display that can provide information related to functionality and safety to the operator. The hub gives the driver control over the tailgate, tarp, hoist, thermostatic body heater system, material control system, and inclinometer.
The M917A3 HDTs will support the US Joint Forces in operations such as mobility, survivability, counter mobility, and sustainment.
The armoured cab designed by Tencate is fitted with Jankel BLASTech seating, which helps reduce the impact of a blast to increase the survivability of occupants.
The truck features eight cross-members along the frame rails to ensure better strength and stiffness.
Chemical agent resistant coating (CARC) is applied on the vehicles to protect them from corrosion, chemical, and biological weapons, and offer camouflage properties.
Engine and drive-line details of M917A3 heavy dump truck
M917A3 is equipped with Mack MP8® engine, which offers a maximum power of 440hp and torque of 1,660lbft. The engine is mated to Allison 4500 Generation 5 six-speed automatic transmission system.
The 13l turbocharged diesel engine is compatible with jet propellant-8 (JP-8) fuels.
The dump truck is integrated with Meritor’s drive-train solution including MX810 front drive steer axle with gross axle weight rating of 24,000lb, MTC-3220FV high-torque transfer case, ProTec Series 50 tridem drive beam axles and central tire inflation system (CTIS). The axles come with standard driver-controlled differential lock (DCDL) or automatic locking options.
The Meritor Permalube RPL Series drive-line supports gear-fast/run-slow drive-trains and applications that require high torque. Permanently lubricated and sealed for life to reduce operating and maintenance costs, it offers increased U-joint life for operations in challenging terrains.
The truck has a 243in (6.17m) wheelbase and 445/65R22.5 Michelin XZY3 front and rear tires with load range L. It also features 6S/6M anti-lock braking system (ABS). The braking system at front includes Meritor® EX+ disc brakes, while Meritor Q+ Cam Drum 16.5”x7” brakes are used at the rear. The forward suspension system is taper-leaf spring suspension (parabolic). The rear axle suspension is Primaxx® Pax 792 high stability type with a load capacity of 76,800lb (34,836kg).
The vehicle offers manoeuvrability and high ground clearance. It supports tie-down and towing and can be airlifted by military transport aircraft. An optional spare tire carrier is mounted between dump body and cab.
Designed to handle rugged terrains, the vehicle can operate in environments with austere conditions and minimum or no host nation support.
The truck passed vertical step, side slope, and trench crossing tests. It can ford a maximum water depth of 20in.
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