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# Help Needed on Compressed Air Vehicle

03/30/2017 2:12 PM

I am making a compressed air vehicle as my project. I am stuck with the calculation part. Please somebody tell me how to calculate the power, torque and other critical aspects of a compressed air engine. Also is there any effect of the hoses that i use to direct compressed air from compressor to the double acting cylinder, if yes then what. please do help me.

Pathfinder Tags: Compressed air vehicle
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#1

### Re: Help Needed on Compressed air Vehicle

03/30/2017 2:19 PM

Try here.

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#2

### Re: Help Needed on Compressed air Vehicle

03/30/2017 5:09 PM

This should help, and some good ref at bottom of pdf page...

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#3

### Re: Help Needed on Compressed air Vehicle

03/30/2017 5:31 PM

One of the faults of the compressed air driven cars (Tata) was the fact that as compressed air expands it causes a cooling effect which made the engine very cold and hard to lubricate as the oil would not flow thru the engine. I believe they even tried a small propane heater that would heat up the engine but eventually junked the project.

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#4

### Re: Help Needed on Compressed air Vehicle

03/30/2017 8:18 PM

You find a physics or thermodynamics book. You'll see work is just W=∫PdV, that's just the product of Pressure and the difference of volume. For air, generally you can use PV^n=constant, where n is process dependent(eg. isothermal, isentropic etc.)

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#5

### Re: Help Needed on Compressed air Vehicle

03/30/2017 11:44 PM

A bad idea with many problems and very inefficient. Also very dangerous driving a high pressure tank around that could rupture in an accident.

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#6

### Re: Help Needed on Compressed air Vehicle

03/31/2017 7:25 AM

Nor any difference from driving around a car full of batteries that occasionally go on fire. The tank would need to pass a pressure vessel test before being certified for safe use and usually would require a rupture valve in case of an impact. Transformer have the same rupture valve installed.

There are a number of available motors on the market and a Spanish company has built several air power vehicles.

It also depends on what type of motor the lad is suggesting using, which he has not disclosed.

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#11

### Re: Help Needed on Compressed air Vehicle

03/31/2017 3:28 PM

He did state opposing piston.

I think he needs an air pre-heater, and a minimal ICE to power this thing. That way, he can get rid of that silly extension cord.

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#7

### Re: Help Needed on Compressed air Vehicle

03/31/2017 7:58 AM
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#8

### Re: Help Needed on Compressed Air Vehicle

03/31/2017 11:56 AM

My best tip for you is "DON'T".

High pressure air is REALLY dangerous stuff. Its killed a whole lot of people over the years....plus there are a lot more still alive but missing body parts...

Dangers-of-compressed-air

The hoses and other parts needed are horrendously expensive IF they are properly sized for the pressures you need to make anything that goes for more than a mile or two.

See here:-

Compressed_air_car

Where you can read the following:-

Energy density

Compressed air has relatively low energy density. Air at 30 MPa (4,500 psi) contains about 50 Wh of energy per liter (and normally weighs 372g per liter).

For comparison, a lead–acid battery contains 60-75 Wh/l. A lithium-ion battery contains about 250-620 Wh/l. The EPA estimates that a gallon of gasoline is equal to 33.7 kWh; however, a typical gasoline engine with 18% efficiency can only recover the equivalent of 1694 Wh/l. The energy density of a compressed air system can be more than doubled if the air is heated prior to expansion.

In order to increase energy density, some systems may use gases that can be liquefied or solidified. "CO2 offers far greater compressibility than air when it transitions from gaseous to super critical form."

I sincerely believe your work would be put to better use in another direction/idea.

Sorry to be so negative. Do have a great day and don't let me stop you, I am only making you "aware"....

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#12

### Re: Help Needed on Compressed Air Vehicle

04/01/2017 2:40 AM

Exaclty,

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#13

### Re: Help Needed on Compressed Air Vehicle

04/01/2017 3:22 AM

Great informative video! Thanks for sharing! The pressures in Truck tyres are NOTHING in comparison to what the OP will need for his vehicle.....

I wonder just how many of those involved are now deaf forever? Or worse.....

The only thing that I know of (not that I am an expert!) that is even worse, is high pressure oxygen!! That is truly the "Dynamite" of all gases, as far as I am aware....

See here:-

Oxygen and oil or grease!

These are ONLY a burnable gas cylinders, propane for example, probably ONLY the driver got roasted, no oxygen explosions as far as I could see:-

This is a "tiny" Oxygen accident, that may have killed the welder!:-

I worked with 4000 lbs per square inch air on Naval gun "Recuperators" (spelling questionable) in the RN many years ago....they were the "springs" that partially damped recoil and also returned the barrel back to the firing position.

With a lot of really good training/common sense, I personally was never involved in any accidents. Nor saw any on the ships I served on either.

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#9

### Re: Help Needed on Compressed Air Vehicle

03/31/2017 1:42 PM

http://engineair.com.au/

http://engineair.com.au/index.php?option=com_content&view=category&layout=blog&id=2&Itemid=11

Air tank can simply be some scuba tanks. Nothing wrong in using them besides added weight. But some folks, as in the above link, have done a neat job in making it operable.

Its all about having the right motor.

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#10

### Re: Help Needed on Compressed Air Vehicle

03/31/2017 3:26 PM

So how long is the extension cord on that compressor?

You need to de-rate based on resistance-length, rather resistivity-length product.

Try this: W = PV, where work is W, P is pressure, and V is volume.

That is the entire system capacity. Power is the time derivative of work. Now get to work.

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