Basic PTO Power Transmission Components
PTO implements are powered by the truck or tractor's engine and this power is
provided through the drive train. The basic drive train consists of five parts
which includes the transmission (gearbox), clutch, differential, power take off
or PTO, and the drive shaft. All of these components come together to drive your
particular piece of PTO equipment.
The Gearbox
The Gearbox allows you to achieve a certain fixed speed, while just as in a
manual automobile, it allows you to progress from a low gear to a high gear to
effectively accelerate the equipment from a dead stop. Every implement will have
a certain speed rating with which it will work most effectively, and you will
need to verify that the speed of your gearbox most effectively corresponds to
your chosen tool. Most implements are designed to operate at the standard fixed
speeds required by most power take off transmissions of 540 and 1100 rpm.
Many owners opt for a tractor with a range of gearbox speeds in order to make
full use of the variety of PTO tools available in the marketplace. While some
people are willing to spend the money to purchase a clutchless power
transmission, most opt for the simpler gearbox that operates with a manual
clutch. These most often consist of two boxes, with one gearbox containing the
speed ranges (usually low, medium and high or low and high) and the other main
gearbox containing the customary 3 forward and 1 reverse gear setup.
Gearboxes are often termed a 12 x 3, which means that it has 12 gears, 3 of
which are reverse gears. Or a 16 x4, where of the 16 gears, 4 are reverse and
the other 12 are forward.
The Clutch
The clutch of the tractor works just like that of the standard automobile in
that it disengages the engine from the gearbox to allow for gear shifts.
Tractors often utilize a dual clutch so that the tractor can change speeds and
operate independently of the PTO.
The Differential
The differential of the drive train allows sends the power to the wheels and
allows them to operated at different speeds to make up for slip or cornering. On a
four wheel drive tractor, a separate differential sends power to the front
wheels which are often operated at a slightly faster speed than the rear wheels
to account for slippage. While this is beneficial for agricultural use, it can
quickly degrade the tires if the tractor is driven on roads while in four wheel
drive.
PTO or Power Take Off and Drive Shafts
The power take off comes directly off of the engine from the clutch. The PTO
speed of most tractors is 540 rpm, but in some small and most large tractors,
1100 rpm is available. Various drive shafts can be purchased to correctly match
the available speed, size and spline arrangement of the tractor PTO to the
driven equipment. Drive shafts are additionally used to connect the gearbox the
differential.
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