Denver, CO — Brent Oman is an 18-year Gates Corporation employee, a manager in the Denver, Col., firm’s Power Transmission Product Application department and a forensic scientist, of sorts, for Gates motorsports program.
His brand of forensic science is not associated with law, but it loosely fits the textbook definition. One of Oman’s engineering responsibilities is “to search for, and examine, physical traces of evidence that might be useful for determining the performance of Gates PolyChain GT2 blower belts.”
For the past 20 years, Gates polyurethane toothed belts have the been used by nearly all the Top Fuel and Funny Car teams in National Hot Rod Association drag racing. In two decades, the belt has gone through a few product evolutions, and many of the improvements can be traced to the forensic work of Gates engineering experts.
Gates has product testing agreements with several of the top teams. In exchange for being able to run with Gates latest belt technology, the teams supply Oman with their used blower belts.
During the week following an NHRA event, Oman receives the belts and descriptions of how they performed. Some of the race-day circumstances are puzzling, Oman admits. “If the team is on a tight travel schedule, I’ll get a belt that is hastily tagged ‘Broke,’ or it might simply say, ‘Went bang’.”
He adds that many of the returned belts are intact, and may have a notation about a track setting record.
Regardless of the physical condition of the belt, Oman wants to know why it looks near-new or worn, or why it separated from an engine that produces power at 11,000 rpm.
It’s Oman’s experience that belt failure is nearly always caused by improper installation, insufficient belt tension or overloading.
“When the belt is installed and aligned on the crankshaftblower drive, there is a margin of error of 1/4,” Oman declares. “Sometimes this critical measurement can be overlooked when the crews have only an hour to completely change the engine setup between races.”
He also looks for symptoms of improper tension. “Today’s nitro-burning engines are so powerful, that at the highest rpm, the crank and blower shafts actually bend towards each other, which reduces the pre-set tension,” Oman explains. “When tension is lost, the sprockets eat up the belt teeth and destroy them.”
But the biggest “belt-eater” according to Oman, results from “pedaling.” This normally occurs within 300 ft from the starting line, when the drive feels the rear tires begin to slip and they smoke up the track. “The engine crankshaft is accelerating from 9,000 to 11,000 rpm, and then when the driver lets up on the gas, it slows to 2,000 rpm,” he says.
“But, at the same time, the blower is accelerating and building up inertia. The engine and the blower are working against each other, and the belt breaks from the force of stress and the two opposing speeds,” Oman says.
The Gates engineer looks for other symptoms of actual or near failure — such as a bolt lodged in the underside of the belt — updates his log book, and forwards the belts to Gates laboratory in Elizabethtown, Ky.
Here at the plant where Gates manufacturers the PolyChain GT2 belt, other engineers perform “pull tests” that determine the remaining strength characteristics of the belt.
“Belt strength equals belt life,” Oman says. “Our goal is to optimize the configuration of the Kevlar tensile cords so that they remain flexible, lightweight and will be able to handle shock loads from acceleration and deceleration, and any malfunctions with the engine or blower.”