Saturday, Jan 10, 2004 at 18:15
"Doesnt the torque multiplication occur thru the application of the gearing, i.e 300Nm at the flywheel via a 1:10 gearing gives 3000Nm at the back of the gear box, if 5th gear is at the back of the gear box then it'd get a lot of that extra torque. I ony use low range to 4th gear also due to the "straightthruness" of the gearset".
Yes it does, but through each succesive gearset. For example consider a gearbox with 1st gear of 3:1, 4th gear 1:1, and a transfer case high of 1:1 and low of 2.5: 1, and consider points A input to gearbox, B output of gearbox/input of tcase , and C output of tcase.
With 200 Nm at point A:
In 1st high there would be 600 Nm at point B and point C,
In 4th high there would be 200 Nm at point B and point C.
In 1st low there would be 600 Nm at point B and 1500 Nm at point C,
In 4th Low there would be 200 Nm at point B and 500 Nm at point C.
"... but 4H still turns all the wheels and is easier on the whole vehicle...".
Not really.
From looking at the above example it is clear that in 1st high both the gearbox and tcase are stressed to 600 Nm, wheras in the 4th low example, the gearbox only has 200 Nm going through it and the tcase has 500Nm (roughly equal in reality due to friction losses). The tcase is designed for continuous running in low ratio whears the gearbox is designed with a definite duty cycle to get to 4th gear (ie not "live" in 1st, 2nd or, 3rd).
I think there is also a little bit of confusion about "...the back of the gearbox...". This refers to the output shaft and not to the physical location (most 5th gearset are located physically at the rear but in mechanical reality are driven by the same shaft that drives all the other gears). The 5th gearset will recieve the same 200 Nm (in my example) input toque as any of the other gearset would, but it would produce LESS torque output ie. 160 Nm with a 20% overdrive at our point B.
Not criticism, just education......... :-))
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