O2 Pursuit – An Air-Powered Dirt Bike

12/15/2011 @ 2:42 pm, by Jensen Beeler27 COMMENTS

It doesn’t really matter whether electric motorcycles are the next thing in two-wheeled transportation/recreation, because the door has been opened for an honest debate about the permanence of internal combustion engines (ICE) in our future motorcycles. One of the bi-products of this rare “think outside the box” moments in motorcycling is the idea that compressed air could be a viable energy source to replace gasoline. I have to admit as PADI certified diver, the idea has always seemed extremely far-fetched to me whenever I’ve heard it brought up.

I have played with small-scale compressed-air cars before, and even at a larger scale there would appear to be issues of energy density, efficiency, storage safety, and of course refueling that crop up as potential deal-breakers. That being said, the concept still has some legs as there are ways to work around these many of these constraints. It’s that potential that surely was propelling (oh, god) Dean Benstead, a design student at Australia’s venerable RMIT.

Given a DiPietro air engine by the folks at Engineair, Benstead was tasked with making a viable two-wheeler that would be use a standard scuba tank as an energy storage device. Getting some help from Yamaha Australia, who donated a Yamaha WR250R to the cause, the 02 Pursuit concept is very compelling with its 140 km/h top speed, though knowing the math involved, we’re not sure if it will replace your petrol bike anytime soon.

My immediate mathematical concerns go to the limited “fuel” storage possible on a motorcycle’s form factor, and the potential energy density issues that accompany a compressed-air power system as a source for locomotion. Relatively speaking, a standard scuba tank holds at a maximum of .675 kWh of energy (300 bars of pressure in a 18 liter tank). When you consider that a bike like the BRD RedShift SM has 5.2 kWh of battery power on-board, a motorcycle with less than 1kWh seems less intriguing, especially with the highly-efficient systems used by electrics.

I’ll admit I’m not as well-versed on air engines, but I can’t imagine that they run at the same efficiency levels as electric motors (typically 90+% efficient), and even if they do, having 1/5th of the on-board power is going to be extremely limiting on range. Of course larger tanks can be made, and denser air pressures can be achieved with better tanks designs. Getting to a suitable energy factor for urban use however, is going to take some serious work.

At 18 liters, the 02 Pursuit is already equivalent to the tank size of modern ICE motorcycles, and realistically it will be very challenging to even just double the volume of air stored on such a design. This means in order to achieve figures ideal for real-world use, the gains will have to come from increased air pressure. While scuba tanks are extremely safe, when we start talking about 2x, 3x, on up to 5x the air pressure currently used for diving, the design requirements are going to be extremely challenging.

I’ve clearly digressed from Benstead’s 02 Pursuit at this point, which is shame because the motorcycle is very well thought out design-wise. The purpose of this build was to explore the idea of air-powered motorcycles, and it does very convincingly. Perhaps the perfect pit bike at a track day, we’d ride one for sure. But as a replacement for an ICE dirt bike? I’m not convinced (though I’d ride one in a heartbeat). A bevy of build and design images are below, enjoy.

Source: 02 Pursuit Blog via Two Wheels Blog