Neils, this is really VERY, VERY clever. Actually it's elegant.

We have now heard of 300+ launches a day with one winch and launches to 5200
feet AGL with another.

Lets say your only tug is doing 4 - 5 launches an hour at $75 each and
you're #6 in the aero tow queue. The winch across the field is making a
2500 foot launch every 3 minutes for $10. (You're #6 because you failed to
notice a solo student catch a thermal off a winch launch at 10:30 so
everybody else got in front of you.) The tug will need a fuel stop every 5
or so launches but the winch will run all day on one tank. It's going to be
2PM before you get an aero tow. What do you do?

What's not to like about winches.?

Bill Daniels


"Niels Erik Danielsen" wrote in message
...

"Marc Ramsey" wrote in message
...
Niels Erik Danielsen wrote:
In our Club in Herning Denmark we have a 25 year old Diesel Electrical
winch, controled by an industrial controller.

http://www.herningsvaeveflyveklub.dk/jordmateriel.shtml

Prior to launch the maximum wire tension is preset according to aircraft
type, and the rest of the launch is basically automatic.

It looks to be quite an interesting design. Does the generator drive AC
traction motors directly through the controller, or are there batteries
or some other form of buffer in the system?

There is no buffer, all power is generated by the generator when needed.

The frame consist of a late 60' SCANIA VARBIS tractor trailer,
combined with two traction motors (used as winch motors)and generator from
a diesel DC
electric locomotive.

The engine has been replaced with a newer more powerful turbo
charged SCANIA engine. (This engine is used for both road driving, and
winch.)

The generator is mounted as a part of the drive shaft between the
gearbox and the differential.(Rotating when in gear)
The differential had two gears controlled by air pressure, one for
normal road speed and another for reduced speed.
As the pinion for the 'normal road speed' has been removed, it has
become a `neural' allowing the generator to run without driving (moving)
the
winch.
When the winch is moved the generator is still rotating, but not
magnetized.

The winch drums are mounted directly on the traction motors drive
shafts.

The first 'computer' was analog, and consists of a custom made
circuit board filled with operational amplifiers, and passive
components.

This computer controls:
Parking brake/Differential interlocking
Throttle actuator for engine.
Contactors for drum selection.
Contactor for wire retrieve-braking dump load.
Torque by excitation of the windings in the generator

The systems measures:
Engine RPM
Engine Actuator position
Generator speed.
Wire speed.
Torque derived from DC current, no tensiometer needed.
DC Voltage.
Wind speed.
Wind direction component.
Position of spring loaded torque/speed command handle.
Calculation of power based on Current and Voltage.

In the late 90' the analog controller was replaced with an
industrial micro controller, but the functions as seen from the
operator is essentially unchanged.
Except for the possibility of connecting a PC via. a serial cable,
and record a time track of the launch parameters.

The max speed and max force is set on two dials.
For an ASK21 the force is set at 550daN, and max speed is set to 125
km/h,

Max. force is approx the weight of the glider, and max. speed is a
speed approx. halfway between normal launch speed and max speed
allowed in winch launch for type of glider.
Then one of the drums are selected by pressing the Left or Right
push button, this starts excitation of the generator and set the
engine in high idle (ca. 1200 RPM)

The spring loaded command handle has a manual control range for
taking up the slack and at the end of launch bring down the chute.
When the handle is full forward against it's stop a 'kick-down button'
is activating the automatic sequence.

During the launch the diesel engine RPM is controlled to ensure
enough power (Max RPM used is about 1800 RPM)

The set point for the speed/torque servo is ramped up (Ramp time
approx 2 sec.) to the values given by the dials. (Power peaks at
about 160KW for a heavy two seater)

After acceleration, during the initial climb the speed set point is
automatic ramped down to
approx 70% since the glider now have a speed composant tangential to
the winch.
The decision on when to start speed ramp down is based on time
calculated from the wind composant in launch direction. (My feeling
is rampdown is done 4 to 10 secs into the launch)

Later during the launch the max force (torque) is also ramped down,
this is also based on time.

When the glider is at an angle of approx. 75° the command handle is
eased a little backward and the glider hook back releases.