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News | June 30, 2016

A Proper Fit

By Michael Molinaro, DLA Land and Maritime Public Affairs

The manufacturer’s tooling was in bad shape. Depots were supplying remanufactured used parts in insufficient quantities. It was already taking 120 days to get the part to the troops, and demand was heavily outweighing production.

Fortunately for the warfighters, a team from DLA Land and Maritime and the Ohio Army National Guard came up with a solution to keep the Humvee rolling along in Afghanistan and elsewhere — demonstrating how innovation combined with determination help better serve the warfighter.

The Humvee torque converter experienced a surge in demand from the Afghan National Army in September 2014. This surge, coupled with monthly use of 240 converters, placed a huge burden on DLA Land and Maritime to keep up. In an automatic transmission, a torque converter transmits or multiplies torque, the twisting force an engine generates to rotate a driveshaft, which in turn rotates the axle connecting the wheels.

At the same time, the approved sources, General Motors and AM General, experienced shortages of remanufactured used parts, or cores, in the supply system, and the tooling shared between the two suppliers had capacity problems that limited production to 150 per month.

Faced with this shortage, GM designed a new torque convertor that could be used in commercial and military vehicles. This proposed “hybrid” part has a production lead time of 30 days versus 120 days and comes with a cheaper price tag, falling in line with DLA’s culture of continuous improvement.

“The hybrid can be used in commercial and military vehicles, so with adequate demand, they can keep a line running and increase throughput,” said Dan Krist, an engineer with DLA Land and Maritime. “The adequate supply of cores would probably contribute to reduced lead time as well.”

Meanwhile, obstacles still stood in the way. The tooling operation wasn’t functioning correctly, and its representatives said GM could not increase production for new parts. Army depots were supplying cores to obtain remanufactured parts but still in insufficient quantities. The only option was to convince the Engineering Support Activity at TACOM Life Cycle Management Command in Warren, Michigan, that the commercial hybrid would meet Humvee fit and function requirements.

To see if the new torque converter would work as an alternate item, a fit check was needed to ensure it would be compatible with the Humvee engine and transmission. But the ESA had facility and funding problems that kept it from doing the testing.

So personnel at DLA Land and Maritime began searching for an in-house alternative. Mohammed Cisse, the Land Supplier Integrated Support Team chief, asked the Engineering and Technical Support directorate to evaluate options. Cisse and his team ensure the right contracts get awarded and expedited, so that troops in theater get the parts they need on time. He didn’t have time to wait for others to come up with a solution. Little did he know one was a few blocks away at Defense Supply Center Columbus.

Right down the road on the DSCC installation is the Ohio Army National Guard’s Combined Support Maintenance shop. Engineers from DLA Land and Maritime had worked with the Guard on other Humvee fit tests on parts such as windows, so they gave it a shot and called down to the shop.

“That day they just happened to have a vehicle disassembled with a 6.5-liter Humvee engine block available for the fit test,” said Joe Crum, a DLA Land and Maritime engineer. “It was simply a matter of timing and luck.”

GM shipped the new torque converter, and Sgt. 1st Class Joshua Brown performed the fit test as DLA Land and Maritime engineer Jeffery Carpenter watched and prepared the report for TACOM. The item was very similar in appearance to the original, and the differences were so slight that it’s unlikely a maintainer would be concerned that the part was not a valid replacement part. The engineers checked the thickness of the two torque converters; they were the same, and  the torque converter seated well. When the testers rotated it by hand, they noted no unusual resistance and no scraping sound.

Carpenter said tests with both torque converters showed no significant performance margin relative to the specification. It passed.

Aside from the fit test, TACOM also had a requirement for a function test using a transmission dynamometer — a device for measuring twisting force (torque), or horsepower (the ability to produce torque at speed). For example, the power produced by an engine, motor or other rotating prime mover can be calculated by multiplying torque and rotational speed, or revolutions per minute. A commonly cited general formula is HP = Torque x RPM ÷ 5252.

“TACOM was going to contract out this test and bill us — it would have been very expensive and time consuming,” Crum said. “It just so happened the Army National Guard had a dynamometer and agreed to perform the function test for free. We had no idea they had one of those.”

To run the test, the transmission subassembly is mounted on the dynamometer. A short lever allows the technician to manually shift gears between park, reverse, neutral and drive. Other connections allow control and data signals to pass between the control console and the transmission. Once the transmission is at operating temperature, the automated test measures stall torque and then takes a series of measurements of the main pressure under 12 conditions of input rpm and gear selection.

A transmission test of a current configuration transmission and torque converter conducted on the same dynamometer was used as a baseline for evaluating the similarity of the proposed torque converter. According to Crum, the performance was nearly identical. In addition to the data in the appendix, the console had an indicator light that showed the torque converter locking up as expected during the test. The data showed that both subassemblies met the specification and that their performances were very close together in the band of compliant hardware.

Only five days elapsed between the time the torque converter was received, tested and approved. After some apprehension by TACOM, this effort allowed the ESA to approve the new hybrid design. Cisse said “a little proactivity and a lot of luck allowed us to complete the tests in such a short period of time.”

“This collaborative effort will improve the [inventory] health of this and increase DLA Land and Maritime’s response to the warfighter on all future demands,” Cisse said. “Fort Hood is planning to use over 3,200 of the torque convertors by Fiscal 2017 to rebuild the Humvee transmissions. It’s definitely a win-win in warfighter support.”

By analyzing and developing a process management solution that consolidated, standardized, and integrated the total DoD supply chain, DLA Land and Maritime realized savings, avoided costs and improved warfighter support all at once.