Marine Motor Expertise

High-performance materials – and the expertise to utilize them – are key to successful marine propulsion projects.

electric boat with cutaway

Originally published in Electric & Hybrid Marine Technology.

Today’s boat engines, gallon for gallon, emit more pollutants than vehicles on the road. As a result, the US Environmental Protection Agency introduced requirements for catalytic converters on inboard and stern-drive boats beginning in 2011. Many manufactures of personal watercraft initially switched to outboard propulsion and are now looking to electric motors as the next step.

Converting a boat from gasoline to electric is not as straightforward as dropping in a battery and motor from a car, though. Since boat drag increases with speed, the energy to move a boat through water is far greater than that required for an equivalent electric vehicle.

Arnold offers Arnon silicon steel, laminated magnets and carbon-fiber windings for electric motors that require higher efficiencies. Arnold’s non-grain oriented electrical steel (NGOES) is optimized by thickness and finish. Arnon silicon steel is frequently used for laminations in high speed, high-efficiency motors and generators. Whereas common laminations use thicknesses between 0.356mm and 0.813mm, Arnon 5 and Arnon 7 are thinner – at 0.127mm and 0.178mm respectively.

Arnon electrical steel has been shown to be particularly advantageous for higher-frequency motors and generators above 400Hz. In these designs, the thinner material offsets the less efficient effects of increased eddy currents and subsequent heat build-up. Using thin laminations of Arnon produces a more efficient unit and frees up design constraints by making it possible to fully enclose the motor without external cooling, for example.

Arnold’s Wraptite composite sleeves offer a superior design alternative to metallic solutions, particularly in applications that require high rotational speed or the containment of high centrifugal forces – such as high-speed motors and generators. Wraptite has a low density and high strength-to-weight ratio, as well as greater containment stresses for sleeves of the same thickness, leading to increased rotor speeds. Reduction or elimination of eddy currents in the containment sleeves reduces hear generation and improves efficiency.

Wraptite composite materials include carbon fiber, Zylon fiber and glass fiber composites using a range of epoxy cyanate ester and BMI-based (bismaleimide) resin systems. The material can operate at temperatures up to 170° C.

When entering a partnership, the first step is to decide what the end goal is, and how best to accomplish it. Perhaps a world-class supplier is struggling with pricing, quality or delivery from its existing supply chain. In that case, Arnold can be an alternative source for either an individual motor component or the complete motor system, having complete control over the supply chain. For example, Arnold sources SmCo (samarium cobalt) magnets from its plant in Switzerland, where all pressing and sintering is done in-house, coupled with a partnership with a rare earth mine to ensure the supply of quality raw materials.

Developing a marine electric motor takes specialized expertise in electric motor design. Arnold can collaborate at whatever step of the process makes the most sense. It offers everything from specialist information on permanent magnet technology, to sources components from an extensive selection of Arnold-operated global resources, all the way up to a complete motor design. Arnold provides quick-turn design, rapid prototyping and testing, using one of its technology centers around the world.

About Arnold Magnetic Technologies

Based in Rochester, NY with an operating history of more than 125 years, Arnold is a leading global manufacturer of engineered solutions for a wide range of specialty applications and end-markets, including aerospace and defense, general industrial, motorsport, oil and gas, medical, and energy. From its Technology Center and manufacturing facilities located in the United States, the United Kingdom, Switzerland, and China, the company produces engineered magnetic assemblies in addition to high-performance permanent magnets, precision foil products, and highly loaded composites that are mission critical in motors, generators, sensors, and other systems and components. Based on its long-term relationships, the company has built a diverse and blue-chip customer base totaling more than 2,000 clients worldwide. For more information on Arnold, visit   

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