APRIL 24, 2020
Two speed gears were introduced commercially in the early 2000s and, although having a relatively small range of application, made a world of difference when used in the right place. The best applications are for very high speed recreational craft, which benefit from the deeper gear to get on the plane, as well as vessels that take advantage of the deeper gear to apply lots of power at low vessel speeds, and oddly enough, waterjet-powered fire boats.
An example of this is the two fast attack fireboats designed by DLBA for the Portland, OR Fire Department, where the deeper gear ratio was used during pumping operations. By reducing the shaft speed of the waterjet, the thrust developed at the engine speed required for pumping is reduced, and it was then much easier to balance the thrust between the waterjet in use and the fire nozzle reactions. A secondary benefit is less wake and disturbance in the water, meaning less seagrass, sand, and silt through the intakes, helping to keep the fire system cleaner.
Take a look at this technical paper to better understand how a two speed marine transmission works, and the benefits your next project could reap from its inclusion.
In case you would like to receive more information or discuss about this subject, please contact Jeffrey Bowles
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