Planetary drives deliver more profit on mobile shredder plant22 March 2013

Whitham Mills Engineering is reporting reduced eight and improved profitability since specifying a Brevini Power Transmission planetary drive for its latest commercial mobile shredder.

The firm manufactures equipment for the recycling industry – including mobile paper shredders, fixed to commercial vehicle so that users can shred paper on-site. That means payload is a key to profitability, and hence Whitham Mills' requirement for lighter weight, more compact drives.

Malcolm Moon, technical sales manager for Whitham Mills Engineering, explains that the shredders require three gearboxes: two to drive the shredder shafts, and a further one to drive the auger screw that compacts the paper and transfers it to the storage compartment at the back of the truck.

The original drive for the shredder shafts used two heavy shaft-mounted, right angled helical bevel gearboxes, each driven by an electric motor. The units needed to be large to transfer the torque and keep the blades turning while up to four tonnes of paper per hour was processed – so limiting the capacity of the shredding vehicle.

"We were looking for a solution that would allow us to reduce the weight of the shredding machinery and therefore increase the profitability of the shredding vehicle," states Moon.

"The original gearboxes were not particularly efficient, which meant that we also needed larger motors to drive them than was ideal. So the decision was made to approach Brevini, which already supplies gearboxes for some of our static products."

Brevini suggested one of its high-efficiency planetary gearbox, each stage of which uses three planetary gears located inside a toothed outer ring, meaning that the load is spread among many contact points. This not only leads to less pressure and up to 98% efficiency per stage, but also means smaller units can transfer higher torque.

To replace the shredder shaft gearboxes Brevini specified two stage planetary gearboxes with a reduction ratio of 14.28:1 and a female splined output shaft to connect with the shredders. Each gearbox connected to a shredder shaft: the first transmitting 5,306Nm at 27rpm and the second transmitting 4,621Nm at 28.5rpm.

A two stage planetary gearbox was also supplied to drive the auger screw with a 12.5:1 reduction ration. Each gearbox was driven by a compact Samhydraulik hydraulic motor, which was supplied by sister company Brevini Fluid Power.

"The mobile shredder is in use for up to eight hours a day 350 days a year so reliability is key. Thanks to the planetary gearbox design, and Brevini's ability to produce detailed design life calculations, the correct drives were selected and have been proven to be very reliable," comments Moon.

Brian Tinham

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Brevini UK Ltd

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