Pneumatic pusher and brake regeneration

[oldtamiyaphile]

Originally Posted by Old Mechanic

Most gas-electric hybrids can not recuperate any more than one third of the energy in regeneration, while the hydraulic configurations developed 10 years ago were at 78%, using a bent axes pump that was spinning at prop shaft speeds which forced the pump to sping at 3.5 times the speed of the wheels. The solution was to move the drive pump to the wheels where rotational speeds seldom exceed 1000 RPM and pump efficiencies easily stay above 90%, compared to 75% at speeds above 3000 RPM.

I'm guessing there must have been some issues or we'd have production versions now? I'm really interested in doing something like this for my VW, connected to an AWD rear subframe.

[master_of_disaster]

Wow! I'm surprised at all the comments that came in over the weekend.
Some very encouraging especially from Old Mechanic about it being implemented before.
Now that somebody has brought up the issue of safety, if ever I do implement this, I probably should just make it a push button type of feature.
When I'm about 1/4 mile away to a stop in a straight smooth road, I can press the pbrake (pneumatic brake) button which will lower the 5th weel/tire. The arm will lower the 5th wheel similar to the rear wheels but be also suspended or have suspension like the rear wheels so the rear weight of the vehicle is evenly distributed between the 2 rear wheels and the fifth wheel. Maybe then the fifth tire will add some lateral stability since its another tire that prevents side to side motion of the rear. The fifth wheel will turn and start driving the compressor to pressurize the air tank. The resistance might be not as smooth so I need to find a way to automatically vary the resistance offered by the compressor either thru electronics or pnuematics.
As I get closer to the stop, I start to use my regular brakes while still pressing the pbrake button until I come to a full stop. I release the pbrake button and the arm goes up.
When I'm about to accelerate, I let go of the regular brake and press the passist (pneumatic assist) button without stepping on gas yet or step on gas and press the passist button at the same time.
This will lower the arm for the fifth wheel and make the air motor drive the fifth wheel and the car forward. This might also need some automatic speed variance via electronics and/or pneumatics.
The air tank will keep running the air motor until the minimum pressure is reached and a light will show that the air tank is depleted and will raise the arm.
Now its back to regular driving.
So the safety precautions will come from making it only active when the driver thinks its pretty benign and not in emergency or uncontrolled situation. There should probably be a max speed cutoff switch.
I plan to put the pbrake button, passist button and air pressure light on the steering wheel just like the volume up and down buttons in newer vehicles.
This project is kinda low on my to do list but if I get more encouraged, and more discouraged with my current job haha, I might really do it.
It really helps to get some negative comments too so I know what I'm up against and find out if this idea is not really viable after all.

[master_of_disaster]

As far as connecting the pneumatic (or maybe hydraulic) recapture from the engine compartment, I think won't capture the energy from the momentum of the vehicle as much as an extra wheel. If the compressor needs to be driven at the same time as the engine is driven then the resistance from the engine (engine brake) will steal from the compressor and will stop the vehicle too quickly.

If the pneumatic compressor/motor is attached to the transmission or rear axle it will be a more elegant solution although a more complicated and more expensive approach.

I want something that is simple, not so expensive and can easily be added to an existing vehicle so I can sell it as an accessory/add-on and maybe have a small business.

Hopefully it can add an additional 5 miles per gallon so if it costs $500 with installation it might be worth it.
If you drive 12,000 miles a year / avg 23 mpg (without device) = 521 gallons X $3.70 /gallon = $1927 total gas cost per year...... 5 additional mpg / 23 avg mpg = .21 (21%) ...
$1927 * .21 = $404 savings per year !

If it just adds 2.5 mpg its still worth it since you save $202 a year...recoup the cost in 2.3 yrs.

It might also lower brake pad replacement cost.

[Frank Lee]

Not personally excited about using compressed air as it is known for very low energy transfer efficiencies, mainly due to heat loss.