Getting optimum performance out of a smaller package requires a careful balancing act. "How the motor spins; how the connecting rod and piston interface with the striker pin and the tool holder; the machining tolerances of all these pieces; where the holes are in the tubes, which allow air pressure in and out - all this has been balanced over time to produce a mechanism that provides the power with minimal loss of energy," Burdick states. "All these different parts are working in unison to minimize the energy loss and maximize that impact energy."
In some cases, this may actually mean increasing the size/volume of certain components, while reducing the size/volume of others. For example, DEWALT and Milwaukee Electric both incorporate larger rams in their hammer mechanism.
"We incorporate large rams so that as they move forward, they translate a lot of that energy to the striker and into the bit," Fernandes explains. "If you make the ram another gram heavier, or increase the velocity with which the piston moves, it can also affect the impact energy. So we can optimize the way the system is working together."
The result of such optimized system interaction is more efficient delivery of power to the bit. "The hammer mechanisms are much more efficient than they used to be in the past five or 10 years," Goebel asserts. "In other words, if a tool is rated at 2.5 ft.-lbs. of impact energy... they're actually able to generate 2.5 ft.-lbs. every time the hammer mechanism works, or every beat that a hammer generates."
Built to last
Durability is a major concern with rotary hammers. "On a commercial jobsite, the tools can, unfortunately, get abused, either on the job or when they're stored and moved around," says Fernandes. "So durability is key."
The use of lighter weight, yet stronger materials is facilitating added uptime. "Through the use of glass-filled nylon [and other] materials like that, you can make them lighter and more efficient," says Burdick, "but you still maintain the best durability possible."
Internal components of the hammer are perhaps the most prone to damage. "Rotary hammers are, by their very nature, very destructive tools internally," says Fernandes.
By boosting the size/volume of select components, manufacturers are adding toughness internally, as well. For example, DEWALT incorporates both a larger piston and ram in its hammer mechanisms. "Not only are they larger, but the components are more durable," Goebel states.
Seals to keep out dust also reduce component wear and tear. "All of these hammers are used in environments where they're very susceptible to dust and debris getting into the internal components of the tool - specifically, the hammer mechanism - and wreaking havoc," says Goebel. "We use three major dust seals to keep all of that dust and contamination out."
Even features intended to optimize drilling performance can serve a dual purpose by reducing wear and tear. For example, improved speed control can reduce the risk of the hammer beating itself apart.
"If you have a compact hammer that beats at, say, 7,000 bpm, it's beating very fast in rapid succession. That really compromises the durability of the hammer mechanism," says Goebel. "Our approach has been to slow down those bpms, because we know the wear that it puts on the ram and the piston of the hammer mechanism."
Rather than beating more often, the hammer puts more force behind every blow. "That's how we've been able to achieve optimum drilling performance," says Goebel.
Comfort's role in productivity
Productivity isn't limited to hammer performance. It also depends on how comfortable the user is running the tool over the course of the day.
"Users are looking for a lightweight tool that hits hard and is easy to control," says Fernandes. "What I mean by that is they can hold the tool comfortably in multiple different orientations."
This is largely dependent on balance between the weight, size and shape of the hammer. "If you can get it a little bit smaller, a little bit lighter... it all translates into better user comfort over time," says Burdick. "The key is to make them as compact as possible so that the weight of the tool is more evenly distributed, and is more comfortable to the user when he's working all day."
Handle design has a big influence on user comfort. Many handles found on today's rotary hammers incorporate comfort features such as soft grips, ergonomic shapes and adjustable placement. Consequently, the design emphasis is now shifting to vibration control.