A modern Gas Bag car
 

Look here http://krisdedecker.typepad.com/.a/6...3c14970b-500wi

And to: http://www.aerocivic.com/imgs/aerocivic-top-2.jpg

Low-tech Magazine: Gas Bag Vehicles
Natural Gas Bus in Zigong, Sichuan

"Fish tail" would be sufficient to store 0.7 to one cubic metre of gas by visual calculations. Or to one liter of gasoline equivalent. Should any one check this on real example ? If fish tail is useable for 60++ mpg, storing methane in it should give 10-20 miles "free" miles.

For skeptics - if adding batteries for toyota prius to get 10-20 ev miles is good, this mod could cheaper and more efficient.

They use inner tubes in India for hand-tractors. Allows you to store at a higher pressure without spending too much on it.

I think the problem with the gas bag is, since it's unpressurized, it relies on the bag being on top of the car to work. The inner tube's natural tendency to squeeze its contents out through the filler nozzle would probably suffice, and give you more range.

I've found this concept intriguing... you could essentially create a backyard digester, fill a tube, and use it to run a carburetor-equipped engine.

Inner tire could be an option, but it is not made to hold any bigger pressure. And its shape is not aero at all. But plastic bag with rubber strips for deflating could be made to work, event for diesel engine.

Also - http://c1gas2org.wpengine.netdna-cdn...3/dolphin1.jpg

With such a shape of car and high efficient you could store enough gas for 100 miles.

The Dolphin ^^^ has 200 miles worth of *lead* acid* batteries, that weigh 1,984 pounds. Can you imagine how many miles it could go on say 700-900 pounds of modern lithium cells?

Which cost 5000 to 10000 usd. Or more, depends on technology.

You don't take the point. We could take a toyota prius, add to it plug-in kit with 2 to 4 kwh of energy which will add 100++ pound of weight, or we could add a bag in empty trunk of ~400 litres of capacity to hold 1.36 kw/h energy. Or make a boot tail to hold 1000 litres of gas to hold 3.4 kw/h of energy. Pure methane will give close to 10 kw/h per cubic metre, assuming engine conversion ratio of 31% it will give 3.4 kw/h of energy at the whells.

Why not just compress the methane and put it in a standard DOT propane/NG tank ??

You can't do it at back-yard.

When driving through Wyoming, I think the side winds would rip the bag off the roof.

Just wondering if you filled the bag from your house natural gas line, what would be the equivelent energy costs compared to CNG or gasoline at the pump?

A simple sketch.

http://i40.tinypic.com/205avbb.jpg

Just like plug in hybrid without cost and weight of batteries.

Mike can modulate his range thru the gas pedal of the aerocivic.
Driving a tad slower will instantly increase his range ;)

Storing CNG at near-atmospheric pressures in easily damaged tubes is ridiculous - and dangerous.

As for the first pic, that bag on the roof instantly doubles the aerodynamic drag.

These were desperate desperate solutions in desperate times, resulting in minimal range.