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M939 / M35 Crew Protection Kit

Responding to information that Central Command truck drivers needed better protection against small arms fire and explosive devise fragments, in March 2004 Col. Robert Groller, program manager-tactical vehicles (PM-TV) contacted the US Army Tank-Automotive Research, Development and Engineering Center (TARDEC) to find a survivability solution. Soon prototype armor kits for the M939 and M35 series vehicles were under development. Noting TARDEC's work to quickly and successfully field the HMMWV Armor Survivability Kit, Col. Groller requested that TARDEC develop prototype kits for testing and evaluation in 90 days.

TARDEC was up to the challenge, and within a day of the request a matrix team was organized for the project. It included members from TARDEC's Research Business Group, Emerging Technologies Team, Development Business Group Digital Design and Physical Prototyping Teams, as well as individual members representing Quality Assurance, Safety, and representatives from PM-TV to ensure the customers needs were met. Representatives from PM-TV defined protection performance parameters to be that of the successful HMMWV Armor Survivability Kit. Taking that parameter, an armor solution now had to be found for these larger trucks.

TARDEC engineers first looked at an existing solution. Although not great in numbers, 165 armor kits were developed for the M939 during operations in war-torn Bosnia and still existed in Army warehouses. Developed in the early 1990s, this crew-protection kit would first need to be upgraded to provide enhanced side protection.

One full kit and enough parts remained at TARDEC to complete an increased protection upgrade for the Bosnia kit. By 21 May 2004, the TARDEC team had completed necessary changes, fabricated, assembled and shipped two prototype kits to be tested at Aberdeen Test Center (ATC). ATC would determine the performance of these kits against the Operation Iraqi Freedom (OIF) threats. While providing an interim solution, the Bosnia kits did not meet the full OIF requirements. Testing was delayed while a new kit design and prototype were completed.

Upon completion of this effort, attention turned to the production of new kits for the M939 vehicle system; a firm requirement for 2,229 M939 series kits was established in mid April. No firm number of kits was established for the M35 system, hence the priority on the M939 prototype kit development.

The ballistic threats that the OIF M939 kit would need to defeat greatly exceeded the Bosnia kit's capabilities. In addition to meeting threats, Central Command identified requirements to have movable side windows for ventilation and firing of all infantry weapon types, a gun ring that would permit mounting and firing of the M2 and M60 machine guns, M249, Mk19, a weapons platform, digital rack, and cab air conditioning unit. These requirements would prove to be a significant challenge.

There was great concern that the weight of the original Bosnia crew protection kit was at the ragged edge of what the vehicle's axle could withstand. To meet these additional requirements and not decrease the level of threat protection, the increased weight would need to be partially borne by the non-cab vehicle structure. Additionally, movable windows would be a design challenge since the estimated weight of the applied armored window transparency would be more than 100 pounds. Air conditioning space claim and cooling rate likewise posed a great challenge.

A start of work meeting occurred on 20 April 2004 during which it was indicated that M939 A1 and A2 vehicles would need to be supported by this new protection kit. M939 base vehicles would require upgrade to the A1 as part of the process, with front winches removed to accommodate the anticipated weight of the protection kit. Information provided by the PM-TV indicated that there existed 9 versions of the A1, A2 and M939 base vehicle with a total of 27 possible variations. The kit would need to fit 18 of these further complicated by realizing that approximately 40 percent of the vehicles in use in southwest Asia were the M939 base variants needing their winches removed.

Although funding was authorized for the project on 18 April 2004 by PM-TV, TARDECs Emerging Technologies Team had already commenced armor design efforts on 25 March 2004. This was and continued to be an all-out effort that has no margin for error. Every delay or mistake results in potential casualties to troops. There is no greater motivation than to have the ability to provide life-saving equipment.

In an effort to optimize the material and reduce unnecessary weight, numerous armor material combinations were considered for the various areas of the cab. Readily available armor materials and windshield transparency materials were given highest priority, as this approach would lead to lowest schedule and cost risk. Several other novel armor technologies were investigated and considered, but the combination of schedule, availability, fabrication ease, multi-hit performance and cost ruled out their application.

Design and digital modeling continued throughout April and May 2004, with 02 June 2004 established as the date to complete designs for the M939 kit. Fabrication of parts commenced prior to Memorial Day with fabrication revisions completed two weeks later. The final product consists of an armored cab, fire-wall protection, floor/fender mine protection and air conditioning.

To meet the most important requirement, crew protection, TARDEC engineers developed and manufactured an entire new cab from roof to floor and from door to door. Upon removal of an existing M939A2 cab, the new armored cab was installed consisting of armored cab walls and doors, which include the applied armored glass. Powered actuators to assist in moving the heavy doors and a powered protected door assembly that can move the side transparencies up and down for ventilation and firing purposes were included. To be able to mount the required weapon platforms, engineers fitted the armored cab's roof with the gun port ring used on the HMMWV lightweight gun ring. To add a bit of creature comfort and to make room for the vehicle's air conditioning and gunner platform, two new air ride seats were installed. Once complete the kit fits both the M939 basic, A1 and A2 series vehicles.

Adding even more protection, TARDEC technicians using a variety of water jet cutters and computer aided design, added contoured armor plate under the M939 hood and inside the dash board to reduce the threat of small arms fire through the hood region. Armor plate was also mounted inside the floor of the cab as well as under the front wheel wells to reduce the threat of fragments from land explosives.

Lastly, the problem of air conditioning was tackled. Collaborating with the Red Dot Corporation of Seattle, Wash., TARDEC modified an existing HMMWV air conditioning kit to fit in the M939. The thought was to adopt commonality between vehicle systemsin order tosimplify the number of parts and repair procedures required. Once the system was selected, additional room had to be made in the vehicle to mount it.

To make room for the evaporator cooler fan console, the bench seat along with the battery box were removed and relocated. The console was then mounted between the two new bucket seats; a new gunners platform was mounted on top of the console. Within two weeks of inception, a functional air conditioning system was installed. Upon successfulcompletion oftesting, a robust easy-to-install kit will be packaged, with an estimated cost per air conditioning kit per vehicle at $3,000.

The prototype design of the M939 armor kit required more than 300 drawings (to date) and consists of 260 individual components and it is estimated that the kit adds from between 1100 to 1500 pounds to the front wheels of the various M939 series vehicles. TARDEC's Physical Prototyping Team completed assembly and installation of the armor and air conditioning kits by 21 June 2004. The next day, the first two kits departed for ATC to under go automotive and safety testing, with one kit to become the Yballistic turret & hull for live-fire testing against the standardized OIF threats.

Concurrent to design, TARDEC is actively working with the Armys Ground Service Industrial Enterprise (a relationship that was cemented during the design and production of the Armor HMMWV kits) to identify and begin production of low-risk, long-lead items. This pre-production greatly helped to expedite fabrication of complete kits upon favorable automotive and ballistic evaluation by ATC.



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