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

  • Chris Brandow

    Higher pressure tanks are available and could double or triple stores energy at same volume pretty safely. Fairly routine for labs. Though I don’t drive my lab on dirt tracks.

  • Cameron C

    It is great to see this kind of creativity. It will be interesting to see where it goes. Hopefully a video surfaces soon.

  • Chris, do you know what bar/psi they go up to?

  • Jon

  • steve

    From Wikipedia on dive tanks…
    United States Department of Transportation rules presently prohibit the transport of metal scuba cylinders on public roads with pressures above about 230 bar, even if the cylinders and air delivery systems have been rated for these pressures by the American agencies which oversee cylinder testing and equipment compatibility for SCUBA (Occupational Safety and Health Administration and Compressed Gas Association).

  • RJ

    The whole point in all these new style of machines is that it is beginning to become painfully obvious how idiotic our insistance with ICE engines really is…

    There are so many viable alternatives that it’s not even funny….

  • This is pretty awesome. Nice work, Dean.

  • buellracerx

    pretty cool concept, but he essentially designed a chassis around existing components…good work, show me FEA & ride/handling test results; then I’ll be impressed.

    Oh, & I might be wrong, but what I took from the vid was that the 140km/hr figure was measured at the back wheel (essentially sitting on the stand, spinning up the wheel) I’d be surprised if you could go over 110km/hr in real world.

    overall, congrats on creativity, a pretty sound-looking chassis, and an obviously unlimited proto budget

  • Interesting to say the least. But ICE engines so far are the most efficient. They set a very high bar for alternative power sources to aim for. Coincidently I was just watching TV and a VW commerical came on the air. They have a running prototype, real world 4 passenger car that uses less than 1 liter of fuel for every 100 kmh. Not many motorcycles achieve that level of efficiency.

  • Ken C.

    You still have to consider the electricity used to run the air compressors uses to fill the tanks and the energy used to produce that electricity, which most likely comes from coal. Not to mention the energy used to mine the coal. Etc. etc. It’s really that clean, when you think of it.

    That said, it’s a fascinating concept. Probably fun, like a BB gun. :)

  • dan

    What you didn’t mention was that compressed air can be refueled in seconds/minutes rather than hours – the present limitation of pure electric systems.

    The DiPietro motor is also pretty amazing, it can operate on 1 bar of pressure cos it has really low starting inertia.

    Air might not be a real alternative for long range touring but for inner city commuting it could be ideal. As for ICE of course they are more efficient, they’ve had over 100 years of intensive development by the entire automotive industry, who knows what will be propelling the transport of the future, bring on fission powered Deloreans I say!

  • pat walker

    With the range limits why not just ride a bicycle?
    Where is all the energy to run the air compressors going to come from


  • RJ

    Dan is 100% correct. The 100+ years of development ICE powertrains have enjoyed far exceeds any sort of advantage any of these new alternative powerplants have. But the point is there is still an entire complex, expensive, and polluting infrastructure in place to support these types of machines. Fuel doesn’t just “come out of the ground” you know.

    Therefore knowing this it is plainly obvious to see that when comparing on a strict efficiency level, ICE engines become clearly the least efficient. People are used to thinking modern ICE powertrains are efficient cause they’ve been watching propaganda from manufactures stating how their ICE products are getting more efficient everyday. Yes, more efficient compared to the previous versions of themselves, which in the broad spectrum of power sources isn’t that efficient at all…

  • Richard Gozinya

    @Jimbosidecar Actually ICE’s are about the least efficient motors in existence. Their one saving grace is the very high energy density of gasoline and diesel, as opposed to say, batteries. A gas engine, optimized for efficiency has what, 25-30% efficiency, max? Compare that with the 90%+ of an electric motor.

    Again, it’s not the motors that make ICEs better, it’s the energy source.

  • Mark

    Here’s an idea to greatly increase energy density and power. Just squirt a little bit of gas into the motor and light it off at just the right time!!
    I would hardly call this new technology, this isn’t any better than a steam engine from 100 years ago.

  • Richard, you say “in existance”. In existance I still stand by the ICE engine, as the most efficient engine right now. Electric motors get their energy from either coal, oil, or nuclear power generation, but the most inefficient part has to be the manufacture of the batteries. One day when we can manufacture clean high power batteries, I’ll change my mind but looking at the manufacture and disposal, not to mention the resources used in manufacturing batteries, I just don’t see anything remotely as efficient “in existance”

  • mxs

    For some reason I like this idea much better than any electric solution I have seen.

    The simplicity of the bike and the simplicity of the refueling stations makes it very likeable solution to me. Compressed air vs. expensive and heavy batteries. I will take that on any idea.

  • Mark L.

    Anyone know what happens when you experience a sudden loss in air pressure?

    It is accompanied by an equally sudden drop in temperature. Basic physics.

    The problem will be getting the air out of the tank in sufficient volume and pressure without condensation freezing everything in sight solid.

    Nice concept though.

    Mark L. – Engineer

  • Bob

    Air has weight. Ever weigh a wheel before and after filling the tire with air? Easy to add 3-4 pounds of weight at 36 psi. How heavy would a large high pressure cylinder weigh fully filled?

  • Bob

    Richard and Jimbo,

    I agree that ICEs are the most inefficient motors around. They have about 30% efficiency. 70% is lost to heat, mechanical losses and vibration. But they are only 30% efficient when you think of them as a motor. By definition, a motor has an external power source. An engine has an internal power source (the combustion process for instance).

    The fact is, the ICE is an engine but is essentially a power plant. It is a motor, power source and fuel storage combined and they travel together.

    The electric motors are a true motor and the battery is its power source which travel together. But in order to charge the battery, you need another power source and it happens to be external, along with it’s external fuel storage. Now if you were to carry that power plant with you (ICE, coal fired, NG), you would then have a hybrid. Now, try accounting for the energy production for charging the batteries. Now you’re comparing apples to apples.

    I have no doubt that the “electric vehicle” is still more efficient overall. But it definitely does not have the high efficiency rating most everyone thinks it does.

    Essentially electric vehicles are hybrids that just don’t carry the power plant with them. That’s why the range is crap. But since I can not carry my own power plant around with me, I prefer the ICE solution. I factor time into the efficiency equation and ICE wins in the refueling contest.

    Personally, I’d rather have a true hybrid than a pure electric vehicle. Toyota’s Synegy drive is really pretty nice. If they could put that into a 2 wheeled chassis, we’d all more likely buy into it. I would. Just think of the instant torque, power capbilities and superior mpgs.

  • mitch middleton

    why not have a air intake on the front so when moving at speed the air tank gets refilled

  • mitch middleton

    how much are they going to be?

  • CB77

    I suppose you have also been seeing some info and pictures of Honda’s electric
    concept bike, the RC-E. Perhaps I am showing my age…but I am having a really
    tough time getting excited about electric motorcycles. For me, an awfully large
    emotional-component of my pleasure of M/C riding, is the interaction with an
    internal combustion engine: The exhaust note, use of the transmission, etc.

    Riding a bike and hearing only the whine of an electric motor would not be
    satisfying to me…regardless of its speed capability.

    Seemingly, the main reason for an electric-powered (or hybrid) vehicle is to
    lessen (or totally avoid) the expense caused by a gasoline or diesel engine that
    consumes large amounts of fuel.

    Since a motorcycle does not really consume large amounts of fuel (and in the
    U.S. they are 99.5% used for pleasure riding…not utility) it seems to remove
    all the need for an electric version. Maybe they need to be kept on the back
    burner, though, for when we do start to actually run out of gasoline and diesel.
    I doubt that I will still be around when that happens. But if I am…I guess I
    would take an electric bike over no bike.

  • JTH

    Do I detect an error – wasn’t this to be embargoed until April 1 ?

  • CB77
  • Miguel Speed

    Curious if they think this could do motorcross. Consider a hard or fast crash…. What happens to all that condensed O2 and the valve breaks on impact. Would that cylinder become a missle? I’ve scuba dived before, those tanks are heavy. Dont think this, in its current state, could be a realistic option for todays riding. Cool technology though.

  • jason

    how many calories are in a single drop of gasoline?