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This idea is specifically for heat engines which are capable of self starting -- they produce enough torque at zero rpm that they can spin themselves up to speed. This includes Sterling engines, positive displacement steam engines, and most types of positive displacement hot air engines.
The engine
would drive a variable angle swashplate hydraulic pump. When the driver's foot is off the accellerator, the swashplate is at it's maximum angle, so that it produces a minimum conversion of engine torque to hydraulic pressure. When the accellerator pedal is pushed all the way down, the swashplate is at it's minimum angle (not quite zero degrees, but close to it), producing the maximum conversion of torque to hydraulic pressure.
The driveshaft would be driven by a variable angle swashplate hydraulic motor. When the driver's foot is off the accellerator, the swashplate angle is at zero degrees, allowing the driveshaft to spin freely, without torque being applied to it, and without allowing any hydraulic fluid to flow through the motor. When the accellerator is pressed to the floor, the swashplate angle increases to it's maximum, producing the maximum conversion of hydraulic pressure to driveshaft torque.
Hydraulic CVT
http://www.artemisi...pli_auto_transm.htm
[Twizz, Apr 17 2009]
[link]
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What you describe is a hydraulic CVT. These exist (I recently worked on one) and the modern version of the swashplate is digital displacement which has the capacity to run to almost infinite gear ratios.
Whether the engine can run to stall or not is incidental. When driving a motor vehicle, there is almost zero time during which the engine is not driving the wheels or the wheels driving the engine. |
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I suspect that the inefficiency of the hydrostatic drive is the real barrier here. Consider the waste heat of a planetary automatic and multiply that by about three for a given output. Sound about right Twizz? |
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I know hydraulic CVTs are baked. (Although this is idea is about a full IVT, not a mere CVT) |
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Really, the important part of the idea is about being able to go all the way from 0:1 gear ratio up to 1:0 ratio. |
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Whether this is done hydraulically, or using variable diameter pulleys, or some other form of CVT or IVT isn't what's important. |
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A quick look at the Artemis system shows that it can indeed go from zero to infinite ratios, which pulleys cannot. |
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Baked, filled with butter & jam and now half eaten. |
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WcW, your estimate of losses from hydrostatic drives are probably about right for conventional systems. Much of the ineffeciency comes from redundant pumping of fluid under pressure. The point of digital displacement is that it only pumps when power is required. |
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