Quote:
Originally Posted by img
You sure shaft speed is in the physics equation for a gear's mechanical efficiency? I don't think it is. But if you're talking about the inertia of the wheels, then yes you lose more the faster you spin.
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Inertia has an impact and so do the shear forces of the oil in the transmission and diff. Power to overcome drag is proportional to the cube of speed...
Quote:
Originally Posted by img
Think you can find a picture to post of one of those types of trannies? Maybe post cut-away picture, or even a make/model number? That would be pretty sick if one could be built that way and I'd love to see how that could be done.
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This is the best illustration I could find quickly
. The concept is actually quite commonly used... this is a big reason why we often see 1:1 ratios in gearboxes as it eliminates the need for a set of gears.
In this example, for gears 1,2 and 3 the power is transmitted from the input shaft to the lay shaft through the set of fixed pinion gears (left most gears in the illustration); then from the lay shaft to the output shaft through the selected gears. The gears are free to spin on the output shaft unless they are connected to it by the dog collar when a gear is selected.
In fourth gear, the dog collar directly connects the input shaft to the output shaft. The fixed pinion gears will still spin the lay shaft and all the other gears, but since none of the other gears are connected to the output shaft, no power is transmitted through the them.
In reverse, the power is routed through an additional idler gear to reverse the rotation.
Typically a 3 shaft design is used on RWD cars to keep the input and output shafts on the same axis, while FWD may use a 2 shaft design.