11th August 2006.



My father spent his whole life working in the auto industry. He was a coach builder and was part of the team that built the
Sunbeam World Land Speed record car in 1927. He ended his career working for Jensen Motors.

One of the projects they developed was the Jensen FF (Ferguson Formula) four wheel drive car that was later adopted by
a number of Formula 1 teams until 4wd was banned.

At one point in time, an experimental car was produced that took the 440 CI Chrysler engine and transmission and hooked it
up to a hydraulic pump, which then sent hydraulic fluid to a motor at each wheel, so that full power could be applied to any
wheel at any time.

But of course, without the benefit of computer control, the driver needed to be as skilled as a fighter pilot to get much of the
4wd advantage out of it.

So was born, apparently, the first fully hybrid hydraulic car.

In the engineering world, almost nothing is ever uniquely new, it's almost always been done somewhere else at some other time.
My father, I well remember said that the "bloody thing could climb the side of a house" if only you could keep the hydraulic fluid
where it belonged - leakage was a major problem.

Now comes along a modern version of this concept. The hydraulic hybrid is conceptually similar to battery-electric hybrids
It has an internal combustion engine, and its design makes it possible to store power for a while before sending it to the wheels.

When the driver presses the brake pedal, the storage system may engage, slowing the vehicle by capturing the energy of its
forward motion rather than using the brakes. This design, known as regenerative braking, is more efficient than conventional
friction brakes which simply convert the vehicle's momentum into wasted heat.

The captured energy can be stored and returned to the wheels when the traffic light turns green.

A hydraulic hybrid has several advantages. One is that it can accept and deliver huge amounts of energy quickly, which batteries
cannot. And its' storage ability does not degrade over time, which is a fact of life with batteries available today.

Generally speaking, though, hydraulic systems do not store as much total energy as an electrical battery does, because the
storage tanks are bulky.

Some commercial systems have four "accumulator tanks" of 22 gallons each which can be pressurized to as much as 5,000 psi.

(A leak from such a system would happily amputate any limb that got in its' way.)

When fully charged, the system can deliver 33 horsepower for a full minute.

When the truck is in operation, its diesel engine runs a pump to fill the storage tanks with fluid. The tanks contain nitrogen gas.
When the driver presses on the accelerator, pressurized fluid is released from the high pressure tank and routed to the pump.
The pressurized fluid pushes a piston down in its cylinder, recycling some of the energy to turn the vehicles' wheels.

A prototype truck has a 6-liter V-8 diesel engine but  with the hybrid system it could use a much smaller engine and still get the
same performance.

Hydraulic hybrids use technology that has been in service for decades, and unlike a computer-controlled Prius, they might not
require a technician with an engineering degree to do repairs.

There is also a related technology, a "hybrid launch assist," which could possibly be retrofitted on existing vehicles.
It would capture braking energy and deliver it to the wheels again when it was time to accelerate.