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#1
09-26-2008, 01:12 PM
 ricksmol Member Join Date: Jul 2008 Location: Hacienda Heights Ca. Posts: 40
OK, let's talk compressed air cars

I was reading another thread that sort of drifted into compressed air (CA). Somebody hinted that a new thread should be started dealing specifically with this subject. So here it goes.

Now, I understand that there are cars already running on this technology. Tata the Indian car builder is very much involved as well. I read quite a bit about the capabilities and range of these vehicles. Increasing the temperature of the compressed medium increases its range as well .

The heating of this stored air could come from the heat generated by the vehicle as it stops, which under most circumstances it would help increase the range.

We all know that cars as they travel do not only go forward (x direction). There are other movements at work. There is an up and down movement caused by irregularities on the road. Shock absorbers are there to dampen and smooth this movement. Shock absorber pistons do travel a certain amount in the "y" direction. Now, imagine each shock is appended with a small air pump. As it travels up and down it could compress air. The weight of the vehicle would assure that that pressure would be rather high. I have no concept but just let us say 1000lbs per shock. That would be at least 4 pumps replenishing the amount of air stored in the car. More shocks or pumps could be added. Air is free, at least till last week. The weight of the car is already there. Roads are not perfectly smooth.

I do not have the capability of calculating how much travel in the "y" direction an average car traverses, but I am sure it could be calculated as well as the amount of air that could be pumped into the tank.

Now this is by no means a"perpetual motion" deal. But my intuition tells me that if it is technically possible it would add quite a bit to the range of the tank.

Let me know why my thinking is "wishful". I hope it is not.

Rick
#2
09-27-2008, 07:41 AM
 elevatorguy Senior Member Join Date: Jul 2007 Location: indianapolis, Indiana Posts: 402
Re: OK, let's talk compressed air cars

In theory it would seem a good idea but I am not sure how you could possibly generate enough compression in the shocks to get the pressure required.
From the little I have read, the air source is in the 4500 to 5000 psi range,
I think that you would have to jump a heavy car to even approach that range.
Just my thoughts, I am not a mechanical or pneumatic engineer
#3
09-27-2008, 09:50 AM
 gottdi Guest Posts: n/a
Re: OK, let's talk compressed air cars

You could add a smaller lower pressure tank just for that purpose and use that to supplement the larger high pressure tank. It may not give lots of range but may help recapture some lost energy that can then be used for when you start from a stop. Air Regen. No reason you could not implement this idea. You may want to implement the idea into a standard automobile first and if the results are promising then install it into an air car. Or design and sell a retro kit for those who have air cars.

Pete : )
#4
09-27-2008, 12:59 PM
 Astronomer Senior Member Join Date: Aug 2008 Location: North Texas Posts: 189
Re: OK, let's talk compressed air cars

Quote:
 Originally Posted by elevatorguy From the little I have read, the air source is in the 4500 to 5000 psi range, I think that you would have to jump a heavy car to even approach that range.
Or simply reduce the diameter of the piston in each pump. But, as with any other mechanical energy conversion device, it's a trade-off. The higher the PSI, the lower the volume of air added to the tank.

For a 3000 pound car, each wheel would have (on average) 750 pounds of static weight. (The dynamic weight would be significantly greater, but I have no way of estimating dynamic weight at the moment.) So to achieve 5000 PSI, the pump piston would have to have an area of 0.15 square inches, or a diameter of 0.437 inches.

( 750 lb / 5000 lb/sqin = 0.15 sqin )
( 2 * SQROOT(0.15 sqin / Pi) = 0.437 in diameter )

If the average travel is 3 inches per bounce (purely a guess), then the volume of air (at 1 atm) added per bounce is 0.45 cubic inches. Multiply that by four (since this is for each wheel), and you get 1.8 cubic inches of air (at 1 atm) per bounce.

I don't know the CA engine efficiencies, but this doesn't sound insignificant to me. I think it would be worth exploring.

Does anyone have an estimate on how much a car "bounces" per mile?
__________________
-Brian
Conversions: 0
Electrons Bullied into Submission for Future Conversions: 3.6 * 10^19
#5
09-27-2008, 01:52 PM
 ricksmol Member Join Date: Jul 2008 Location: Hacienda Heights Ca. Posts: 40
Re: OK, let's talk compressed air cars

The bounces per mile would definitely vary according to the topography of the terrain. Freeway driving, I would assume, would likely result in higher rate of bounces (frequency), but at a smaller amplitude. While street or uneven roads might lower the frequency and increase the amplitude. This is beginning to sound interesting. What for example if the air compressed could be used not to drive an air car, but to power a generator that would charge batteries on an EV?
I think that what this concept would add is the ability to partially use the existing force of gravity in a gratuitous way. In other words using the same force that costs you energy to overcome in the first place to provide energy once in movement.
Rick

Last edited by ricksmol; 09-27-2008 at 01:55 PM.
#6
09-27-2008, 02:26 PM
 gottdi Guest Posts: n/a
Re: OK, let's talk compressed air cars

Might be asking a bit much of this minimal system but any ability to regain some power without taking away from the original would be helpful. It takes quite a bit of energy to generate a substantial amount of electricity and it would have to produce at or better than your battery pack for the battery pack to be charged.

Quote:
 but to power a generator that would charge batteries on an EV?
#7
09-27-2008, 03:24 PM
 Astronomer Senior Member Join Date: Aug 2008 Location: North Texas Posts: 189
Re: OK, let's talk compressed air cars

Quote:
 Originally Posted by ricksmol What for example if the air compressed could be used not to drive an air car, but to power a generator that would charge batteries on an EV?
If that's your goal, then I would dispense with the air compressor piston thingy and replace it with a linear motor/generator that produces electricity directly. It would be more efficient, but I don't know if it would extend your range to a worthwhile extent.
__________________
-Brian
Conversions: 0
Electrons Bullied into Submission for Future Conversions: 3.6 * 10^19

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