As military vehicles and equipment have evolved into complex machines with advanced powertrains and electronics, enhanced performance test procedures have been developed to put them through their paces.
An important apparatus for this is the mobile field dynamometer, a massive vehicle capable of putting up to a 60,000 pound load on the Army’s heaviest vehicles, such as the M1 Abrams Main Battle Tank.
Adding additional mobile or trailer dynamometers can increase the load even more, sometimes exceeding 100,000 pounds.
“All vehicles that go through testing at YPG—tracked and wheeled—need to be stressed,” said Jose Rodriguez, electronics team lead in YPG’s Engineering Support Branch. “You want to stress the internals like the transmission and the engine to their breaking limit, and the way to do so is to put them under a load.”
The parameters are dictated by a given test plan, but the most punishing of the tests can add years worth of strain to a vehicle in a matter of hours.
“One of the most excruciating tests is a full-load coolant test,” said Rodriguez. “You are measuring the temperatures of the engine coolant, transmission fluid, hydraulic fluid. Even under stress they need to stay within certain thresholds.”
“It’s hard to wrap your head around the amount of loads we are putting on these vehicles,” said Francisco Chavira, automotive instrumentation supervisor. “We’re talking about a huge military vehicle with the gas pedal pressed all the way to the floor, the vehicle giving us every bit of horsepower and torque it can possibly give us, and traveling at two miles per hour.”
YPG has three massive mobile dynamometers: the newest was built in 1989. Like its two older counterparts that date from the 1960s, it was manufactured with analog controls. In fact, replacement parts are no longer available on the commercial market: they have to be specially fabricated, a costly and time-consuming process.
“The systems are obsolete: they are end of life cycle because there is no support for them,” said Gavin Mackenzie, an engineer in YPG’s Engineering Support Branch. “The companies that used to support those systems are no longer in business. If there is an issue, we have to troubleshoot it and fabricate our own repair or parts.”
Recently, YPG completed a multi-year $605,000 project to fully digitize the newest of the three dynamometers. The modern digital controls improve the precise control of the vehicle’s speed and loads applied to vehicles during evaluations, which means more accurate test data for customers.
“The previous analog method was really labor intensive,” said Mackenzie. “Now it is really simple for one operator to input on a computer screen, when previously it was dials and knobs monitoring all of the different functions and having to keep it within a certain threshold of parameters.”
“In the past it wasn’t possible to maintain a speed,” added Rodriguez. “As a test vehicle slowed down, the adjustments would have to be dialed in by a person in the seat of the dynamometer. Now with the logics and digital circuits behind it, it is capturing that distance and making adjustments on the fly.”
The digitized controls also allow for repeatability of test conditions across many days and multiple different human operators.
“In some cases, when we perform these tests we have different technicians on different days with different manners of loading these vehicles, which gives a different data set at the end of the day,” said Chavira. “With our modernization and the computer doing all of the controls, there could be multiple technicians entering the same numbers with the computer acting in the exact same fashion every time, all the time.”
Additionally, replacement parts for the upgraded dynamometer are readily available on the commercial market.
“It eliminates components that would require specific knowledge to repair or replace if it goes bad,” said Mackenzie. “Now it is all modern parts and technology that we can easily replace if there is an issue.”
Though future dynamometers will likely be the trailer variety that come with less maintenance needs, the digital upgrades give the manned dynamometer a new lease on life. A new dynamometer comparable to the upgraded one would cost north of $2 million.