MarineDrives
Marine Drives
AAmpere (amp), SI unit of electrical current standard marine drive system consists of an engine, reduction gear, propeller shaft and bearings, and a propeller. Alternate drives consist of an engine, hydraulic pump or alternator, shaft motor (hydraulic or electric), propeller shaft and bearings, and a propeller.
Mechanical Drives
Hard Mounts
In a standard mechanical-drive system, the engine is hard mounted to the engine bed because the propeller thrusts the engine A reduction-gear transmission such as ZF reduces the engine rpmRevolutions per minute to the rpm required by the propeller. The propeller shaft is fixed, and great care is taken to align the shaft with the engine. Periodic re-alignment may be necessary.
The advantages are simplicity, low cost, reliability, ease of repair, and maximum mechanical efficiency of around 95%percent.
The disadvantages are increased noise and vibration, central engine-room placement, and stress on the engine. Noise and vibration are transmitted directly through the hull. To get the right angle on the propeller shaft, the engine room usually has to be placed amid-ships. Finally, the thrust of the propeller pushes directly against the engine.
Constant Velocity
In a constant-velocity (CVConstant velocity) anti-vibration system such as the AquaDrive®,[1] there is a propeller shaft and a separate drive shaft, coupled with a CV joint. The propeller shaft ends in a thrust bearing mounted to the hull.
This bearing takes the end-thrust from the propeller and transmits it to the hull to move it through the water. The drive shaft has a CV joint at both ends, and is splined inside so that its length is adjustable. This allows the engine to be mounted on flexible rubber mounts.
The advantages are reduced noise and vibration, slightly more flexibility in the placement of the engine, and no stress on the engine.
The disadvantages are higher cost, higher maintenance due to the CV joints, and increased complexity of repair. But don’t take this too much to heart. CV joints are in most cars, trucks, buses, tractors and racecars.
Other noise-reducing systems include the Centaflex AGMAbsorption glass mat[2] and Rubber Design.[3]References
- ↑ AquaDrive, http://www.aquadriveusa.com/advantage/advantage.htm
- ↑ CENTA, http://www.centa-uk.co.uk/
- ↑ Rubber Design, http://www.rubberdesign.nl/
