Q A vehicle . fitted with a Gardner engine, has a speed
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range of say, 1000 rpm; to 2000 rpm at the engine crankshaft, .feeding into the gearbox.
With the standard David Brown gearbox (six-speed), could you tell me what the rpm would be, out of the gearbox. on the propshaft, for each of the six .forward speeds?
I require these speeds on the propshaft and not on the rear axle.
A It is not known what gearbox ratios you will specify but an easy formula to determine the propshaft speeds for yourself is propshaft speed equals engine speed divided by gear ratio.
Let us assume that you wish to know 'the propshaft speed while the engine is turning over at 1300rpm and that 3rd gear, having a 2.5 to I ratio, is selected. Then a propshaft speed of 1300 divided by 2.5 gives 520 rpm.