Titanium may seem like a pricey choice for the housing of an impact wrench. After all, titanium's cost often consigns it to the skies rather than the shop floor. But the design engineers at Ingersoll-Rand's Productivity Solutions Group recently found that titanium can actually provide a lot of value to air tools.
When they sat down to design the new IR2135Ti ½ Ultra-Duty impact wrench, they were charged with creating a lightweight tool that didn't scrimp on power. Ingersoll-Rand's air tools already boast plenty of power, but the design team did make some refinements to the wrench's air motor. The resulting wrench delivers 700 ft-lb of traditional torque output and can, in six seconds, loosen a 1¼-inch nut tightened to 1,000 ft-lb. "It's the most powerful tool in its class," reports Michael McCalley, Ingersoll-Rand's Worldwide Product Manager for Vehicle Service Solutions.
Taking the weight out proved a far more difficult task. "We broke our existing wrench design down into systems and evaluated each one for potential weight savings," recalls Mike Loomis, senior project manager for the new wrench. And at first, that potential appeared dim. The hammer mechanism, one of the beefiest systems, actually needs its mass in order to generate the wrench's force. "It was off limits," says Pat Livingston, engineering manager for impact products. And much of the tool's housing had already made as much use of lightweight composite materials as possible. "They were as lightweight as they could be," he says.
With these other chunks of the tool off the table, the design team turned to its hammer case. This substantial component houses the hammer mechanism and must bear the brunt of a 6-ft drop test on concrete. After evaluating other lightweight materials—including aluminum and reinforced plastics—IR opted to change the case from a deep-drawn steel to a cast titanium alloy (3-2.5). In so doing, they trimmed more than a half-pound from the new wrench, which now weighs in at 3.95 lb.
Weight savings can really matter to the weary professional mechanics who use air tools all day long. "Our customers initially dismissed titanium as being too expensive," says Loomis, "until we told them about the weight savings." In fact, Loomis argues that weight reduction does more for ergonomics than just about every other design strategy. "Our focus on ergonomics increases every year," he says, pointing out that the new wrench has hand-friendly features such as the patterned grips. But given the inherent heft of professional-grade air tools, nothing matters as much as weight. "Air tools are so heavy that subtle changes in the grip or controls can't overcome the weight issue," Loomis says.
Weight savings is the key driver behind the switch to titanium, but the high-performance material produced other benefits too.
Smaller and lighter
Titanium helped the design team decrease the volume of the tool's hammer case—and thus its nose—by roughly 9%. Much of this size reduction came from a process change. Livingston explains that the drawn steel parts could only achieve radii of roughly 2.5 x wall thickness. "There was lots of wasted space in the housing because of the gentle radii," he says. Casting, with its capability for far sharper radii, allowed a more space-efficient design, Livingston continues. This size reduction won't matter much when the wrench tackles lug nuts on an exposed wheel, but it can make a big difference for jobs under the hood and up in the suspension.
Titanium didn't just take weight out of the tool; it took the weight out of the right part of the tool. "Another ergonomic advantage of titanium was that it let us tune the balance of the tool," says Scott Price, global design manager, who explains that previous tools were heavier in the front end than this new model.
Don't dismiss the "coolness factor," also says McCalley. "Our customers already had titanium ingrained in their minds as a high-tech material," he says, citing the aerospace products and even golf equipment as the source for that mindset.
Not too often you see those words in the same sentence. But titanium can be used more sparingly in the efficient cast housing design, offsetting at least some of steel's price advantage. And it turns out that titanium really didn't cost much more than the alternative lightweight materials either. Loomis reports that both aluminum and composites fell short in the strength-to-weight department and would have needed steel structural reinforcements not required by the titanium part. The material and fabrication, and assembly cost of these reinforcements made titanium a cost effective choice, Loomis explains.
Titanium may still cost several times more than steel on a per-lb basis, but it's a good value in this application. Considering the weight and size savings, the coolness factor, and the ergonomic advantages, McCalley expects that the new wrench will command about a 20% price premium over previous models. The first production tools were scheduled for release last month and have seen "record bookings since January," McCalley says.
For more information on Ingersoll-Rand's impact tools, go to the website www.irtools.com/industrial/i_tools.html.