One of the things that inevitably happens as new technologies are adopted and explored is that some inventors and designers will use the new technology to mimic previous applications while others will start completely fresh.
There are advantages to each approach, and in the case of electric outboard motors, there are examples of each. The outboards of Elco, Stealth, LGM and others have taken the first route: the battery is separate from the motor, just as the gas tank is in a gas-powered machine, and the electric powerhead sits under the cowling and attaches to the drive shaft in the same way that the fossil fuel motors do.
Others, like Torqeedo and ePropulsion, have taken one of the unique aspects of electric motors – the ability to put them under the water (try that with an ICE outboard!) – and created a new and different “only-possible-with-electric” configuration with an integrated battery pack that sits where the powerhead is on an ICE motor.
Swiss engineer and designer Charles Baumberger has another take on the optimum way for an electric motor to be applied to the task of marine propulsion, and he is putting it to work in the Navigaflex retractable, rotating motor that can be used as an inboard, outboard or pod motor.
The first thing that strikes you about the motor is that it is simply two cylinders stacked on top of each other, the larger of the two on top.
The big difference not apparent from the outside is that the electric motor – at the top of the assembly as in an ICE outboard – sits on its side, spinning vertically. So instead of requiring a gear assembly to transfer the direction of the power and make the propeller spin, there is a carbon belt, similar to the fan belt in a gas car engine, that turns the propeller shaft directly. The diagram above gives a simple portrayal. In reality there are two belts with an intermediate axle to enable ‘gearing’ for different propeller speeds. It also isolates the motor from the water.
Navigaflex started with a blank sheet of paper
M. Baumberger arrived at the Navigaflex motor because he started with no preconceptions about how a motor should be configured. His approach was to look at what he saw as the needs and wants of different sailors/boaters with the goal of a universal motor design that could address and satisfy all of them.
The process is outlined on the Navigaflex website:
- Sailor: prefers a silent and discreet use of the motor. It has to be reliable and strong enough to perform critical manoeuvres.
- Motorboat Owner: looks for power to get to a desired place in a fast way.
- Fisher: often has two motors, one to get around and one to fish.
- Workboat: Needs to adapt quickly and easily to different water depths and be highly manouevreable
The task to be addressed was:
“Design a motor that suits all these navigators.”
The idea of ‘one motor fits all’ is probably not absolutely achievable, but there is no doubt that the Navigaflex solution can be applied to many different uses without significant modification.
At its simplest, the same motor with identical dimensions can be attached to the stern of a boat or set midship. (The illustration shows both motors on the same hull only for demonstration purposes). The retractable mechanism is the same, and in fact only 5% of the parts are different. The main difference is the hull covering above and below the propeller on the inboard. One covering seals tight with the hull when the Navigaflex is retracted, the other when it is extended.
There are obvious advantages to thinking about and designing a motor this way. The production process is simplified and costs reduced, and this carries over into being able to the controllers and auxiliary technologies like remote steering.
Lots of options within the standard form
That is not to say that there is only one Navigaflex motors On the contrary, there are numerous options available within the dimensional framework.
The standard motor is 4kW, but the shell can hold motors of 6, 8, 10 and 15 kiloWatts. There are options for assisted steering, GPS, smartphone and remote diagnosis and, as trifling as the appearance of a motor might seem – it is an easy task to supply the cylindrical stack in a variety of colours to please the most picky.
The other thing that should be added is that the motor can also function as a battery regenerator when a boat is operating under sail power.
Currently the Navigaflex is available only in Switzerland and neighbouring countries, but the company is actively seeking distributors to build a larger international licensing and sales network.
You can find out more on the Navigaflex website