Rammers have come a long way from their original design which consisted of a heavy post which was manually pounded into the ground to consolidate cohesive soils. Today's rammers use advanced technology to achieve maximum impact force along with ease of use and operator comfort.
Over the past 10 to 15 years, there has been active debate over the best type of engine for rammers. The original design used a two-cycle engine, but there were drawbacks including the necessity of mixing gasoline and oil. As a result, a four-cycle engine for rammers was developed which required only straight gasoline. The problem with original four-cycle rammer engines was that they were limited to a 20-degree angle of operation and they could not be laid on their side for transport.
Many advancements have since been made to both the two-cycle and four-cycle rammer engines. Fortunately for equipment owners, gone are the days of tedious fuel mixtures and transport issues with rammers. Whether it uses two-cycle or four-cycle power, today's rammers are light years ahead of where they were even a decade ago and are continuing to improve.
So while the engine is still a primary point of differentiation among brands of rammers, there are numerous features to consider that enhance performance, ergonomics, maintenance and more.
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Due to increasingly stringent environmental regulations in the late 90s, most rammer manufacturers had to switch to four-cycle engines which have lower environmental emissions. The exception is Wacker Neuson, which still manufactures its own two-cycle engine specifically for its rammers.
"Wacker Neuson offers two-cycle, four-cycle and diesel rammers in order to satisfy the needs of our global markets," says Rebekah Gallert, product manager, compaction products at Wacker Neuson. "[We] are the only manufacturer that has met and will continue to meet EPA emissions regulations with our own two-cycle rammer. The two-cycle has the highest shoe stroke in the market, which is important for operation in high lifts. Two-cycle engines by nature are simpler than four-cycle engines with fewer moving parts and a more robust design."
For the two-cycle and four-cycle rammers, Wacker Neuson has its own engine models that have been designed specifically for the tough conditions a rammer operates in.
"The WM80 is Wacker Neuson's two-cycle engine that we build in the same factory as the rammer," Gallert says. "The WM90 is our four-cycle engine with proprietary features and enhancements."
Gallert explains that Wacker Neuson chose to build its own two-cycle engine because of the company's belief that it offers them a unique competitive advantage. "Through our design and engineering analyses, [we] realized that an off-the-shelf engine could not offer the features, performance or robustness necessary to meet our tough testing criteria; therefore, we have enhanced and built our own engine specifically for rammer applications."
At Bomag Americas Inc., four-cycle engines are the state of the art in rammers, or tampers, as they are referred to in the Bomag product line.
"The introduction of a four-cycle tamper/engine has been the greatest development regarding tampers in many years," says Peter Price, light equipment product manager. "Many engineering obstacles related to high forces and the jumping action of a tamper had to be overcome - it's not as simple as bolting on an engine. Today, the technology is by far the most durable and environmentally friendly technology available for tamper applications."
According to Price, Bomag worked directly with Honda in the development of the GX100 engine used on many rammers today. This engine was designed specifically for rammer applications where an engine will work at sharp angles and will often be laid on its side during transportation.
Prior to the introduction of the GX100, laying a four-cycle engine on its side caused starting problems, which made two-cycle engines preferable. "Compared to older sump-lubrication four-cycle engines, the GX100 is easier to start, uses less fuel, is quieter, lighter and has higher torque and horsepower," Price says.