GardenBanter.co.uk - View Single Post

13-09-2004, 05:11 PM

(Roy) wrote:

Just because your in the dark on how a
hydrostatic tranny works as compared to mechanical drive trannys and
too cheap to have one, why knock em...........hydro
drive.........hands down its the better , no, BEST way to go.....Has
all the power at low speeds as well as high all with just pushing the
pedal down...........simple enough for even you to operate......I

Garden tractors 101:

First, all power created on gas garden tractors is created by 2 things:
1) change in elevation such as going up or down hills
2) the gasoline engine

Second, the gasoline engines are designed to operate at constant speeds
determined by two things:
1) the governor on the engine
2) the tension the throttle lever applies to the governor-spring.

Third, three things determine the speed of a tractor:
1) the speed of the engine
2) the gear ratio of the transaxle
3) the drive tire diameter

Fourth, there are two types of transaxles:
1) mechanical
2) hydrostatic

Either type of transaxle just ratios of the number of revolutions of the
engine to the number of revolutions of the rear wheels, nothing more and
nothing less. However, in doing so the torque available to the rear
wheels is changed, but all power comes from the engine and the torque is
determined by the ratio and not the type of unit. Hydrostatic units
have more power loss due to more heat generation.

The advantage of the mechanical is that the ratios are predetermined by
the gears and are reproducible.

The advantage of the hydrostatic is that the ratio is infinitely
variable.

They hydrostatic usually costs more and is sometimes called automatic,
but it isn't automatic. It usually has forward and reverse pedals and
usually a cruise lever. The mechanical transmission has a clutch and a
shift lever.

People who use automatic transmissions usually like the fact the
hydrostatic transaxles don't have a clutch.

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