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ZF Introduces New Reverse/Reduction Gear To North American Market

ZF Industries has now introduced to the North American marine markets its BW-751 reverse and reduction marine transmission for continuous-duty, single- or twin-screw propulsion applications. The new transmission is a deep ratio version of the company's popular BW-750 family, a design that makes it well suited for workboats and fishboats, large yachts and merchant vessels. Like other transmissions in the ZF series, the BW-751 meets ABS and NATO AQAP-1 quality assurance program standards.

Six gear ratios from 4:1 to 6.83:1 are offered standard with this transmission, and according to Richard Graff, application manager, marine, at ZF's headquarters in Vernon Hills, 111., up to 2,368 hp can be transmitted continuously at a maximum input speed of 1,800 rpm.

Also, the transmissions provide equal power ahead or astern, and reportedly are easily adapted for non-standard, counter-rotating engines. This is achieved by a 180-degree rotation of the main oil pump mounted externally on the back side of the transmission housing. This pump is gear driven via the engine driven input shaft.

To meet the rigorous demands of continuous duty service, the Model BW-751 has an extremely torsion-resistant cast iron housing. The transmission has three shafts with multi- disc clutch packs fitted to the input and reverse shafts. In the event of service requirements, the main components, including the clutch packs, are accessible through openings in the housing of the transmission.

All load carrying bearings are of the anti-friction type. The output shaft flange is designed for use with standard bolts, and this in turn permits installation of custom-built prop shaft flanges, if required, in place of the standard prop shaft flange. The transmission is available with an optional trailing pump which is prop shaft driven and fully operational at all times. The model BW-751 offers four different PTO options for SAE standard hydraulic pump drives. Also available is a wide range of torsional couplings; a customer-specified coupling can readily be installed.

Optional for application with ZF's complete family of BW-750 transmissions is the company's Autotroll system. The electronically-controlled trolling system allows the operator to make use of an infinitely-variable propeller speed range beneath the vessel's engine idling speed. This system can be used without restrictions for both ahead and astern travel, enabling low-speed maneuvering in narrow waterways, docking, position holding, and similar requirements. The first BW-751s are now in service in the U.S. via a retrofit installation aboard the 91-ft. (27.7-m) push tug Southern Kraft-16. Owned and operated by International Paper Co., headquartered in Memphis, Tenn., the push tug normally operates on the Southern waterways with eight loaded barges in tow, averaging 9,200 tons of wood products. The ZF transmissions are matched to a pair of counter-rotating 3512 TA turbocharged and intercooled diesels installed during repowering in 1990. Each are rated 1,060 hp at 1,200 rpm.

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