Compressed Air Bike Frame

I have an 8 mile commute and like many people, drive it alone in a 3000lb vehicle burning more gas than really necessary, so I should just ride my bike to work. The reason I don't is threefold: safety, lack of carrying capacity and cleanliness/weather. I have to think there are a lot of people who are in similar situations or who could use a vehicle like this for basic transportation.

The basic solution I usually come to is the velomobile (link). It solves two of the three issues, but fails due to cost and safety. The small amount of safety afforded a bicyclist is in their ability to avoid danger, i.e. hopping to a sidewalk, keeping out of normal traffic, etc. These options are not available to a velomobile and due to weight restraints most velomobiles would probably fair badly if even tapped by a small car. Also cost. You can easily purchase a small car or motorcycle cheaper than getting any velomobile. This situation certainly adds to the cost as no one has the volume to reach economies of scale which would lower prices.

So my idea is for a scalable frame design which incorporates safety, scalable carrying capacity and options for enclosability to keep occupants insulated from road dirt and weather. Add to that the option for a small auxiliary power source like gas/electric hybrid or electric and batteries and I think this could be the solution for lots of people’s transportation needs. To do that we need to create a spot for the driver inside a strong cage that can then be wrapped with an aerodynamic external shell and because people are weak, as the average human being can only produce about .1 HP continuously (link), the whole structure needs to be light and suffer from as little drag as possible. Normal trikes are built on steel or aluminum frames. Velomobiles have been made with aluminum and steel subframes, aluminum monocoque, fiberglass over foam and even carbon fiber monocoque in the case of the Go-One (link).

The core concept of this frame design can be easily visualized by anyone who has held a plastic bottle of carbonated soda. The bottle alone is very weak, but when pressurized it can support large loads. Now imagine a long tube with the diameter of a 2 liter PET soda bottle wrapped by fiberglass and pressured to a multiple of the normal soda bottle pressure and you get the idea. To protect the driver and provide a basically aerodynamic form the PET tube will not be straight, but formed in a tear drop shape though tapered and open (like a U bent to almost touch) at the pointy end. This will then get wrapped by alternate layers of rosin soaked fiberglass tapes running axially then radially. The radial wraps will eventually resist hoop stress caused by the air pressure and the axial tapes will resist both longitudinal stress from the air pressure and torsional stresses imposed externally on the frame. This frame member will be placed at bumper height as the central spine of the vehicle. To it will be attached two similarly constructed secondary rib members of about half the diameter tapered at the back where they are bound to the main member and with spherical ends at the front where they all attach to the main member. They each run from the front down to the floor level at each side and then connect to the main member at the back. There is one similarly constructed circular tube, located just behind the driver and inside all the longitudinal ribs. The structure is then enclosed in shrinkwrap plastic and windows added where desirable. Each tube is connected to a central system for inflation and monitoring, but also has an overpressure blow out valve vented to a muffler in the back.

Into this cage arrangement a standard mesh recumbent style seat and petals are installed, plus twin external front wheels and single rear wheel that attaches to and rides between the tips of the main drop shaped member. The whole structure should be light and very stiff. In an accident the tubes would become overpressurized at which point the gas would be vented to absorb the energy. The rollcage would protect the driver though would probably be destroyed in the crash though the driver and the expensive drive chain would be preserved to be moved to a new vehicle. The PET liners could then be recycled to make new PET liners.

When I want to ride my bike, I always have to check the air pressure in the tires, in this case I'd have to check the air pressure in the tires AND the frame. I'd have to get a large volume foot pump and then just pump it till the overpressure valves squeaked.

My greatest worry is having a structural blowout near my ear and loosing hearing, so maybe having a thin shell around the drivers head or on driver facing surfaces might be a nice add-on, but not necessary as long as quality control and necessary extra material is used to far exceed design stresses are used.

I think these could be HUGE sellers in China. Add in a stand for the front or a hook in the back and you could store them vertically to save space when not in use.