Candela, the Swedish boat builder, just unveiled its revolutionary new electric C-Pod drive unit with two motors, each one driving a counterrotating propeller. The company says this electric drive will have “an almost unlimited life.” In this story, Electrek says the drive is “an engineering work of art.” Read about it here:
Swedish electric boat manufacturer Candela has just unveiled a revolutionary new electric drive unit known as the C-Pod for its premium electric boats, and it’s an engineering work of art.
Candela claims that these are the highest-efficiency and longest-lasting boat motors ever.
The company’s patented C-Pod consists of two electric motors. Each drives a counterrotating propeller to provide a combined power of 50 kW (67 hp) per pod.
That high power comes despite the drive pod having an ultra-compact, torpedo-shaped design and weighing just 50 kg (110 lb).
Additionally, the C-Pod was designed to have an “almost unlimited lifetime,” thanks to the design’s long maintenance interval of 3,000 hours and lack of oil changes or other major upkeep. For a typical recreational user, that results in years of use without maintenance. Or as Candela CEO Gustav Hasselskog put it:
For the average leisure boat user, this means you can just use the motor and forget about the usual hassle with service and winterization. The C-Pod will outlast you and probably your kids as well.
Candela didn’t just design the C-Pod to be an improvement over gasoline and diesel-powered outboard motors – the company also designed it to leapfrog traditional electric-powered outboard motors.
Fossil-fuel-powered boat motors are notoriously loud, but even electric outboard motors have an audible gear whine that comes from linkage transferring power to a submerged propeller. Candela’s C-Pod is essentially silent because it lacks gearing or other linkage and the entire unit is submerged under the water.
To create the new design, Candela’s engineers had to first solve several design challenges.
The first major problem was creating enough power from a slim, torpedo-shaped pod. Electric motor power isn’t directly related to the diameter of a motor. Instead, that’s largely a function of torque. Power = torque x RPM, and so to maintain high power, the designers reduced the torque with a narrower motor but made up for it with higher RPM.
That led to another problem: cavitation. When a propeller spins too fast, it actually creates air pockets in the water formed by drawing a vacuum, and in effect, boiling the water locally. This kills efficiency and damages the propeller over time, and so the team avoided it by using two smaller counterrotating propellers. The pair of smaller diameter propellers greatly improved efficiency and allowed higher RPMs to be used.
