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.
Start me up
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.
Other manufacturers, like Multiquip, for example, agree on the benefits of Honda's technology. In addition to Honda, Multiquip offers Robin gasoline engines, as well as Yanmar for its diesel models. "Honda, with its profound reputation for excellent performance, made the ideal engine for rammer applications," says Jonathan Cuppett, manager of product & training for Multiquip.
Gallert states that Wacker Neuson's two-cycle engine has made significant advancements as well, noting in particular its lower carbon monoxide and two-cycle engine smoke.
Wacker Neuson's two-cycle engine is designed for the high accelerations that rammers must endure during operation and the difficult conditions found both on the jobsite and in transportation, Gallert says. She notes that their technology features a patented advanced oil injection system that eliminates spark plug fouling and carbon buildup. "We also run a very lean gas/oil mixture of 120:1, which eliminates the smell of oil and doesn't affect the environment," Gallert states.
"Both the [Wacker Neuson] four-stroke and two-stroke have smaller profiles than our competitors that make them better machines for trenches and compaction near a structure," she says, adding that two-stroke technology offers superior performance. "The advantage of the two-stroke engine technology is that it provides the best compaction force, long shoe stroke, more blows per minute and best balance. All of this results in high productivity on the jobsite."
Ease and comfort
Manufacturers are working hard to improve the operator's experience when using a rammer. Price at Bomag says, "Reduction in hand-arm vibration values, reduction in noise levels and reduction in emission values are some of the areas where we have improved our tampers and will continue to do so. Also, using stronger, lighter materials will reduce weight and make them easier to transport."
Gallert notes that Wacker Neuson continues to work at making two-stroke technology more user friendly. "We have an advanced oil-injection system that takes operator inconsistency out of the mixture and ensures a perfect mix of 120:1 fuel/oil. Because of this lean fuel/oil ratio, operators will get 65 hours run time on a single tank of oil," she says. "This also eliminates the need for another fuel on the jobsite. Straight gasoline can be used in the fuel tank."
In addition to designing rammers to be easier to operate, manufacturers are working to also make their machines simpler to maintain. This is most apparent in the lubrication and air filtration systems.
"The four-cycle engines are lubricated through the crankcase instead of through the fuel; this feature eliminates oil burning in the cylinders," explains Cuppett at Multiquip. "It also reduces buildup and minimizes gumming problems."
Cuppett notes that Multiquip MTX Series rammers also feature heavy-duty PVC protective cover guards to protect electronic components.
Wacker Neuson's multi-stage air filtration system significantly removes dust from the intake air, says Gallert. "The filter is easy to access and clean out with no potential for the dust to fall back into the system. Our in-tank fuel filter eliminates the need to replace and dispose of inline filters, which is great for the environment. The tank just needs to be flushed with gasoline periodically," she says.
For its part, Price says Bomag features a nitrated spring cylinder which has "profoundly reduced wear on the bottom end of the tampers, as well as virtually indestructible springs."
Furthermore, Price notes that Bomag is currently developing components and technology that increase service life and reduce maintenance intervals.
Up and coming
While rammer technology has come a very long way over the past several years, the progress is ongoing with new features and models being introduced all the time.
For example, both Bomag tampers and Wacker Neuson four-stroke rammers currently offer a standard oil alert system that prevents the operator from starting the machine if the oil level is below recommended minimum levels. "Traditional oil alerts, which shut the engine down during operation when oil levels fall too low, are not possible in tampers due to the 'jumping' effect," Price states.
Wacker Neuson has introduced a new carburetor with a purge bulb for all two-stroke rammers in 2008, Gallert says, noting that "this feature allows users to purge all air from the fuel lines, making the rammer easier to start, especially in high altitude and cold conditions."
On its latest models, Cuppett says Multiquip features an hour meter/tachometer that allows accurate tracking of usage and maintenance intervals and the new Cyclone Air Filtration system that triples the amount of clean air to lengthen the life of the rammer with less maintenance than before. It also offers a unique throttle control feature which consists of a single lever that controls the throttle, start/stop and fuel shut-off functions. A new recoil guard protects the recoil from impact, eliminating costly repairs and downtime.
Cuppett adds that Multiquip uses its AVS Anti-Vibration System on its handles for improved ergonomics. Also, Multiquip rammers feature a "duck bill" fuel cap that allows the fuel tank to breathe while preventing fuel leaks and spills.
As for new features coming down the pike, Gallert says Wacker Neuson will introduce technology for Europe later this year that further reduces emissions and maintains EPA-compliancy on its two-cycle engine beyond 2010.
Price notes that Bomag is continually finding ways to increase performance and reduce harmful effects to operators such as noise levels and hand-arm vibrations. "We, along with the engine manufacturer, are looking for ways of reducing the machines' impact on the environment through reduced noise and polluting emissions and reducing waste oil," he says, adding, "Bomag does have some interesting concepts on the drawing board regarding the next generation of tampers, but we need to complete in-depth development and testing of these new ideas before we can comment on them. It's safe to say that the tamper compaction process will continue to become much easier and efficient."
Despite their differences, manufacturers sourced for this article agree that designing user-friendly rammers that provide optimum performance with reduced emissions is the ultimate goal. And while there is some degree of disagreement over which type of engine is best, the market has room for them all.