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Principal
of Operation
These are definitely the most common
type winch available. The winch comprises a high torque electric motor, coupled
to a gearbox, and the gearbox drives a rotating drum.
These winches are very reliable if maintained properly, water ingress and faulty
or dirty electrical connections will leave you stranded.
Electric winches come in a wide range of shapes and power ratings.
Pros and
Cons
It is important to know that you use
the winch mainly on battery reserve power and not on alternator power, this
means that you can winch for as long as your batteries can supply, and a bit
more as the alternator assists to a certain extent. Generally your winch draws
from 300 up to 1000 Amps and the alternator is only rated at around 80
amps.
Electric and hand powered winches are the only types that will get you out of
the mud if your engine is dead - care must be taken not to winch your batteries
flat to get out of the mud and then not be strong enough to start the engine.
Electric winches get very hot if used continuously, this excessive heating will
damage the motor, and the current draw may damage the batteries if allowed to
run down flat too often.
The high power consumption and low duty cycle are the electric winches only
disadvantages.
Principal
of Operation
The power steering system of the vehicle consists of a high pressure hydraulic
(oil) pump, connected to the steering box. The steering box has a biasing valve
and a hydraulic motor in. When the biasing valve senses a pressure differential
(When you turn the wheels), the high pressure from the pump drives the hydraulic
motor, which turns the steering mechanism and ultimately, the wheels.
In the winch application, this high
pressure oil from the pump is tee'd off from the main power steering line and
fed via a 2 way valve to a hydraulic motor inside the winch casing (Where the
electric motor would be), When either valve is opened, the motor is driven and
the winch operates.
Pros and
Cons
The advantages of this type of winch
are that the winch draws practically no electrical power thus excluding the need
for a powerful alternator and multiple battery system.
Power is obtained directly from the engine in a more efficient way, enabling the
winch to run at full load constantly all day without fear of damage to any
component - power steering fluid temperature must be monitored if the winch is used heavily
for long periods.
The winch is exceedingly strong and is rated at around 11500Lbs ( divide by 2.2
to get Kilograms = 5227Kg)
The disadvantages are that the
engine must be running when winching, and the power steering system must be
checked for compatibility before fitting - see the Mile Marker Story below.
History -
The Mile Marker
Story
The power steering powered hydraulic winches came onto the market with a big
bang with high performance and equally high expectations.
Sadly for the man in the street, the release of these winches onto the South
African market was badly researched.
The problems started when the
winches where not able to perform as specified - this quickly spread and gave
the winches a bad name.
The problem is that the winches
where designed for the American market, no different to our local market except
for the vehicles. The American vehicles had very large heavy duty power steering
pumps which produced double the oil flow and a higher pressure than the pumps
used on locally available vehicles.
As a result, the winches where not receiving their full design pressure and
could therefore not perform to specification.
The way to fix the problem is to fit
a heavy duty high volume power steering pump to the vehicle.
 Principal of operation
The transfer box is placed in neutral, and 3rd
gear is engaged, the hydraulic pump is selected for operation by a gear lever in
the cab which engages the pump with PTO gear on the end of the gearbox main
shaft. The pump supplies pressurized oil to the valve body which is also mounted
with a control lever in the cab. The lever has a 3 positions - idle, cable in
and cable out. The vehicle can either winch itself out as above or with the
transfer box in low range and any gear selected, it can operate both the winch
and drive the wheels.
Pros and Cons
It is a very reliable, strong winch where the
cable speed can be varied from very fast down to painfully slow because the
engine speed can be varied and the gear in the gearbox can be selected and
finally, the valve block lever can be operated only partially - This gives
extreme control of the entire system - especially for hoisting operations.
The winch uses a worm and roller drive mechanism which is a fail safe system
compared to the planetary drives of other winches, enabling it to be used for
hoisting operations.
The system only fits Series vehicles, fittings
can be made for newer vehicles but besides that the 25L oil tank does tend to
take up a lot of space. The system is also very heavy and bulky - it will appeal
to hardened purists and those that like agricultural type fittings.
History
This rather rare winch is a combination of two original Land
Rover components - As fitted to vehicles from the 1960's onwards.
The first part is a Dowty 3000 Psi hydraulic pump which is fitted to the PTO
(Power Take Off) port of the gearbox. This is fed by a 25 litre oil tank fitted
to the chassis of the vehicle behind the rear left wheel.
This unit is used to drive anything from a fire water pump or a jackhammer to
the jaws of life and a winch. The winch is driven by a virtually identical Dowty motor unit on a huge brass
worm drive mechanism.
The drum & cable winch which was originally fitted to the front of Series Land
Rovers, and to the middle, underneath of SANDF Series 2A and 2B Forward Controls.
Principal of operation
The actual winch unit is similar to the hydraulic unit above except it is driven
from a coupling to the engines crank shaft.
Pros and Cons
The winch is operated by the engine directly, so it gets quite complicated and
hazardous.
Since the unit is driven from the engines crankshaft, it only has the capacity
to winch in, winching out is by means of a freewheel. This limitation can cause
the winch to lockup in some situations.
History
As a result of the winch limitations it was not that popular and it was soon
replaced by the next version...
Principal of operation
This winch takes it's drive from the PTO on the gearbox main shaft via a dog
clutch. The drive is fed to the front mounted winch by a thin prop shaft. The
actual winch unit is identical to the one mentioned above.
Pros and Cons
Since the drive for this winch comes from the PTO port on the gearbox, Both the
speed and direction of the winch can be controlled, making it almost as
versatile as the hydraulic unit.
Principal of operation
The capstan winch operation is the same as those used in sea going vessels. It
consists of a tapered bollard fixed to a brass wheel, the wheel is driven by a
worm roller connected via a dog clutch to the engines crank shaft.
When engaged the bollard rotates very slowly in one direction. Then, a thick,
20mm Marlow Braid or braided Polypropylene, rope is rapped around the bollard 3
times. When the loose end of the rope is pulled it causes the rope to tighten on
the bollard. The shape and surface of the bollard makes the rope ride upwards
towards the thinner end thus tightening the rope automatically. The load can be
winched in at a variable speed, or, if the loose side of the rope is released,
the load can be relaxed very controllably.
Pros and Cons
The winch, like all mechanical winches, is very strong and ultra reliable. With
only the force exerted by one person on the loose end of the rope, a force
significantly greater than many an electric winch can be exerted. The winch can
operate at full load forever...the operator is the one who will get tired !
Since the rope is rolled on and then off the bollard, the pulling force is
always constant and does not decrease as the recovered object comes closer to
the winch as in all drum winches.
Your rope length can be as short or as long as you like, there are no limitations.
Being engine driven it cannot be operated if the engine has failed, it does
however,
have a crank handle attachment and can be operated by hand.
The winch takes a bit of getting used to, but once mastered, it is great to use.
They are very scarce and take up some bumper space on Defender vehicles - on
series vehicles they fit in very neatly.
History
They are available for both Series and Defender vehicles - in the UK. They are
also available in South Africa, somewhere on the second hand market - expect to
pay dearly. |
