Pneumatic pusher and brake regeneration
 

Hi ecomodders,
I just had a car improvement idea that would be an appropriate thing to post here for comments.
I'm thinking of recapturing the braking energy from a car by utilizing a small wheel in the rear that goes down to touch the ground and rotate as the car rolls along. The additional rear wheel will drive a compressor which then stores the pressurized air to an air tank. The rear wheel will go down either by the press of a button or activated when the brake lights go off, and will be a supplemental braking system to the standard brakes. The rear wheel connected to a compressor will provide enough resistance to recapture maybe 50% of the braking energy that would have been lost to heat in the brake pads.
When its time to accelerate, the same rear wheel will also go down to touch the ground, but this time, the compressor will act as an air motor via switching of the in/out valves and will rotate using the pressurized air from the air tank. This can be activated via a button or via the pressing of the accelerator pedal. The torque/speed of the rear wheel should be higher than the engine driven wheel so as to not be a drag to the acceleration of the car.
Once the pressure in the air tank goes down a certain level, the rear wheel goes back up.
This mod will make any car into a gasoline-compressed air hybrid.
It should be a doable mod with moderate complexity and cost.
Thanks.
Eric

You are going to use 1 wheel and tire to offset 50% of the braking effort of the original 4 on a vehicle? :eek:

I have a feeling that there won't be enough weight on the wheel and or traction for it to do anything as far as acceration goes. chances are the added weight of the entire mechanism and the air tank will actually decrease gas mileage.

Good points!

@Cobb -The extra wheel will not really replace the braking capacity of 4 wheels...its just trying to recapture the remaining momentum of the vehicle when you are about to stop, probably starting a quarter mile before you need to stop, and not provide sudden stopping force.

@Backpacker3 - the assembly will definitely add weight but it should be just a smallish tank..some valves/electronics, piping, an arm, aluminum pneumatice actuator to bring the wheel up or down, an air compressor/motor and a wheel with chains connecting the wheel to the motor. Maybe total 50 lbs. The actuator will force the wheel down but there will be a stopper so the car is not raised from the ground, so I think the weight of the vehicle divided by the no. of wheels on ground is on the extra wheel which would help in the acceleration.

I think it would work better to use an air compressor/motor on the accessory drive as its likely the engine will always be spinning. You could cut the clutch on when the brake petal is pressed and load up the tank.

Another good idea Cobb.
Although, your idea recaptures lost energy from engine idling and not the lost energy from braking.

Do you have an idea of the wheel/tire you'll be using?

The issue is that without sufficient weight on the wheel there won't be enough traction to keep it from slipping and just spinning around doing nothing however to get sufficient pressure on the wheel you'll have to use the weight of the vehicle and to do that requires the arm to slightly lift the car. Not enough to take the tires off the ground enough though to actually put weight on the wheel (think about jacking your car up you have a good amount of travel before the wheel leaves the ground) the problem then becomes that under an emergency or hard breaking that tiny bit of lift could be enough to get the back end of the car to want to fishtail or at least make it pretty squirrelly.

If you were going to do this you'll need to either make sure it won't activate above certain speeds or have a switch you can easily get at to instantly deactivate it in an emergency scenario.

If you're in gear, it will do both, and have the potential to capture a lot more energy from two wheels with the vehicles weight on them than from a 5th wheel arrangement.

You could possibly run a two stage system one that operates at neutral/idle, and a higher rate during over run/braking.

In a RWD, it would be fairly easy to add a compressor to the axle housing/ driveshaft.

I'd like to know how much energy is lost from compressing air to then reusing it. My daily is a FWD but there was a AWD option, so fitting the rear drive system off a AWD and adding a small motor to drive it all would be pretty simple.

I was assuming an automatic or engine braking if stick shift.

Finding a pneumatic motor would be another story unless they make a compressor/motor?

In essence you are using the same system f1 is using - capturing energy by using an alternative method to slow the vehicle down. In your case, it's using a separate wheel, but it could just as easily be done using the existing wheels already on the ground.

It has been suggested that you use something attached to the engine, which is connected to the drivetrain, which is connected to something already in touch with the road surface - and in essence would do the same thing you are proposing, just without the additional hardware.

Just keep in mind that you would be changing the brake bias no matter what system you use, and that could result in a dangerous skid. be careful and think this all the way through.