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Fleenor Mfg. Inc. has developed a new tub grinder platform using a new patented flywheel technology for reducing diesel fuel consumption in tub grinders. The goal of the project was to reduce the diesel fuel consumption by 20% as measured by diesel fuel cost per ton of material processed. The field research data collection and prototype development was funded by the National Science Foundation Small Business Innovation Research (SBIR) program.
The theory of operation is that the flywheel supplements the diesel engine duty cycle by supplying the short duration, high-horsepower spike demand that occurs in every tub grinder operation. The general trend in the industry has been to just throw more horsepower at grinders. While the productivity may go up with more horsepower, the upfront cost goes up as well as the diesel fuel consumption. In some cases the capital equipment then required to feed the machine as well as labor cost can double resulting in an actual decrease in business profitability. When comparing two equal engines side-by-side, the one with an additional flywheel will on average grind more material for the same diesel fuel consumed. The net effect is a lower cost per ton of material processed for the machine that utilizes a flywheel.
The prototype tub grinder platform developed is an 11-ft inside tub diameter size class powered by a Tier 2 Caterpillar C27 engine rated at 950 HP @ 1800 rpm. The drive train starts with a PT Tech HPTO wt clutch with integrated pump drives for the hydraulics. Drivelines connect the PT Tech wet clutch to a 1.5 to 1 speed reduction gearbox for a final output speed of 1200 rpm. A driveline connects the output of the gearbox to a torque limiting hub mounted directly onto the hammer mill shaft. The flywheel is then mounted onto the torque limiter such that one can take advantage of the large shaft diameter to both carry the load of the flywheel as well as transfer the inertial torque of the flywheel.
We also designed some unique features into the hammer mill system to allow the flexibility to optimize productivity in both primary grinding and re-grinding operations. If you regrind for mulch, we have designed some very cool flexible features into this system to increase the productivity significantly. In regrind operations we are targeting a 20 to 25% increase in productivity.
If you own and operate tub grinders in your business, and if you are in the market to replace or buy a new tub grinder in the near future, we have a new tub grinder platform that you will want to investigate further. Give us a call. We would like to talk to you about your operations, your diesel fuel bills, and how we can help.

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