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Old 07-30-2008, 07:05 PM   #1
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Imagine this

A car that winds up a hydraulic "spring" and recovers 90% of braking energy (normally lost) and reapplies it for aceleration using infinitely variable transmissions that are located in the wheels themselves and replace the brake components with no net gain in unsprung weight.

Every time you want to slow down you are storing the energy it takes to accelerate, insted of wasting it in braking heat.

This is the basic advantage of hybrids, but without the cost. In fact the system I am describing actually eliminates the sum total of powertrain components.

Using hydraulic accumulators, this vehicle has its own internal catapult that does not use engine power directly. Instead it uses stored energy to initiate acceleration, while the engine cycles between not running and running at its highest BSFC to recharge the storage component, even when cruising at higher speeds.

Acceleration is solely the function of storage, the same storage that recovers deceleration forces. The linear inertai of the vehicle can be exchanged for hundreds of horsepower seconds of force to be reapplied when normal acceleration uses the most fuel consumed dueing any instant in time.

Like tossing two giant bungee cords out and hooking them to two telephone poles to stop your car, then moving the ploes in front of you and using the same energy to accelerate at rates that would be in the range of 0-60 in 5 seconds, WITH THE ENGINE NOT RUNNING.

Separate engine function from the accelerator pedal, which now serves to adjust the displacement of the pumps in response to acceleration demands.

You only need to store a single accleerative event. Once you have achieved cruising speeds, with no engine power necessary, you can resize the engine to cover average demands with an ample reserve for sustained hill climbing events.

The core of the concept is to make the vehicle hypermile itself, transferring that operational tactic to the vehicle instead of the driver. At 50 MPH the engine runs about 20% of the time to recharge the accumulator as it gradually looses its reserve of energy.

The engine never idles
It never runs at WOT

Instead it operates at the highest load and speed range determined by the BSFC maps.

The five states of vehicle operation are
Idling-total waste
Coasting-wasted fuel unless you turn the engine off
Acceleration-best efficiency but highest consumption
Cruising-wrong part of BSFC map-inefficient
Deceleration- losses due to friction braking or unnecessary engine drag

On page 64 of the August issue of the magazine of the American Society of Mechanical Engineers there is a one page article about exactly such a design. An infinitely variable transmission that is placed in each wheel of the vehicle and drives that wheel directly without any rube goldberg arrangement of gears, shafts, bearings, axles, clutches, torque converters, bearings or universal joints, or brake system components.

The dispalcement (and effective "gear ratio") of the in wheel drives is infinitely variable, and relies only on hydraulic pressure to create acceleration. If the accumulator is fully charged the vehicle could accelerate to 80 MPH with no engine whatsoever.

Use any engine or motor you desire, its only function is to replensih the accumulator pressure when it drops to a certain predetermined minimum, probably a range of 1500-5000 PSI.

The heavier the vehicle the greater the accumulator size and regenerative storage. The accumulator is fully charged at startup, so you can begine driving without the engine running initially.

Hypermilers understand the tactic is effective. This design concept moves the hypermiling responsibility from the driver to the vehicle and makes it the most basic design parameter of the vehicle.

Virginia Tech has committed the resources to build the prototype of this design. The efficiency needs to be at least 82% from wheel to accumulator back to wheel. I am hoping to reach 90%. Accumulators are 98% efficient so the wheel motors need to approach 95% for the overall efficiency to reach 90%.

The world market is 3.6 billion wheel pump modules, which is only passenger vehicles. The applications range from ships to planes, as well as hydroelectric and electric storage.


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Old 07-30-2008, 07:26 PM   #2
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Interesting idea. I always thought is would be interesting to use a flywheel based braking system that would spin up a flywheel during braking. Of course that wouldn't help us hypermilers that refuse to use our brakes.

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Old 07-30-2008, 08:47 PM   #3
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Sounds like kind of a logical extension of what Tucker originally wanted to do on his car. But I don't think he had an accumulator on there.

Really neat idea. Kinda like having an electric car, but instead of a battery, using a really big-*** capacitor. One question comes to many p.s.i. in the hydraulic lines? High pressure hydraulic fluid could become really nasty really quick if a line burst in an accident, or in a 30 year old jalopy...
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