Robin Subaru makes noise with silent series gen-sets

Diesel Progress North American Edition, May, 2004 by Mike Brezonick

Despite the din of the average jobsite, reducing the noise generated by equipment has become a key design target for OEMs of every type. In some cases, it's a matter of shielding or the addition of sound-attenuating materials into cowlings, hoods and panels. But in other equipment segments, manufacturers have gone further, looking at the more fundamental aspects of noise generation and designing their machines accordingly.

A good example is Robin Subaru, which has developed a new range of low-noise portable generators targeted toward a variety of applications in construction, contractor and rental markets. The Silent Series generators span a rated output of 1.4 to 3.8 kW--with peak outputs from 1.65 to 4.3 kW--and are available in North America through Robin America Inc., Wood Dale, Ill.

"These are the quietest gen-sets we've ever offered and people who have heard them are just amazed at how quiet they are," said Brad Murphy, vice president, sales and marketing at Robin America. "Noise is really an issue in Japan and Europe and it's becoming more and more important in the U.S. These generators rely put us in a very strong position."

The Silent Series gen-sets consist of three models, the R.1700i, the RG3200iS and the RG4300iS. All three are powered by Robin air-cooled, four-cycle gasoline engines--the P,.1700i by the EH09-2 OHV series engine while the larger machines are powered by the EX21 and EX27 OHC engines. But perhaps the most significant feature is the use of an electronic inverter unit that works with a multiphase alternator that brings several benefits in terms of both noise generation and fuel economy the company said. The multipole rotor mad stator are smaller than standard two pole alternators with their large stators. This design, working with the inverter, allows the engine to generate usable power at less than rated speed, resulting in reduced engine noise and fuel usage in low-load situations. As the power demand increases, a microprocessor controller allows the engine to ramp up to meet the requirements of the load.

"Most of the generators you see out there have to be running at 3600 rpm to generate power," said Murphy. "With the inverter technology, we're able to generate power at lower speeds, which means less noise, and still have a short-term power surge capability that gives them good motor starting ability."

Noise is also reduced by two other design features, a "reverse cooling" airflow design and the use of sound-attenuating poly-resin panels and enclosures. In the reverse cooling configuration, the air is drawn into the unit by a fan on the generator end and directed over the generator and engine, exhausting through louvers on the front of the unit. This is different from maW generators, in which air is drawn in from the engine side and conducted back across the engine and generator.

The smallest R1700i generator, including 1.1 gal. fuel tank, is completely enclosed in a poly-resin case that has a carry handle molded into the top. The complete unit is 19.3 in. long, 11.6 in. wide and 17.5 in. high--roughly the size of a small suitcase--and has a dry weight of just 42.5 lb. The larger RG3200iS and RG4300iS gen-sets incorporate poly-resin panels on each side, with the fuel tank (3.7 gal. and 4.2 gal., respectively) positioned on top of the machine.

Robin cited noise levels at rated output at 7 meters of 59 dB(A) for the R1700i, 58 dB(A) for the RG3200iS and 62 dB(A) for the RG4300iS. "If you're any distance away from them," noted Murphy, "you really can't hear them very well."

Dimensions of the RG3200iS gen-set are 21 in. long, 18.9 in. wide and 22.9 in. high, while the RG4300iS measures 22.8 in, long, 20.7 in. wide and 24.3 in. high. Dry weight is 130 and 163 lb., respectively.

All of the units incorporate electronic circuit breakers for overcurrent protection and automatic idle control that allows the engine to idle in no-or low-load conditions.

The R1700i gen-set has a recoil starter, while the larger gen-sets have both recoil and electric starters. The two largest machines also incorporate Robin's Multi-Monitor system, which integrates an ac voltmeter, frequency meter, hourmeter, idle control and electric oil level sensor into a single unit. Each function can be displayed on a five-character LED, selectable by push button. All of the units also have a one-touch control system that allows all engine functions to be controlled with the turn of a dial. When the dial is turned to the shutdown position, along with shutting down the engine, it also disengages the fuel supply, preventing fuel leakage during transport.

The Silent Series gen-sets are built by Robin Subaru's parent company, Fuji Heavy Industries, at its Saitama, Japan, facilities.

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