Winch Launch Extreme 5200 ft

"Andreas Maurer" wrote in message
...
Hi Bill,

On Mon, 30 Oct 2006 06:48:05 -0700, "Bill Daniels"
bildan@comcast-dot-net wrote:
addition, modern winches are constant tension with computer controlls that
prevents the winch from applying enough force to break the weak link.

Interesting facts - does such a winch actually exist?
I have to admit that I haven't seen any winch with such a computer
control yet.
Bye Andreas


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.

The Pilots controls the airspeed via. pitch.



I would assume the winch has accumulated something like 100000 starts.



Niels Erik Danielsen

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 are clearly tension controlled winches in use at a number of
sites, but so far all seem to be have electric or hydraulic drive. Does
anyone know of a true tension controlled winch using an internal
combustion engine engine driving the drums through a conventional
automatic transmission or torque converter?

Marc

Andy wrote:

With a traditional winch of adequate power,

There's an oxymoron. Traditional winches (new and old) pretty much
define themselves by their inadequate power.

pitching up increases
airspeed. How do these modern winches result in the reverse effect?
Does the reversal only happen once the line tension limit has been
reached?

I must have only flown off traditional winches. My experience is the
same as Bill Daniels. What over-powered monster do you fly off?

GC

Andy

Marc Ramsey schrieb:

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 are clearly tension controlled winches in use at a number of
sites, but so far all seem to be have electric or hydraulic drive. Does
anyone know of a true tension controlled winch using an internal
combustion engine engine driving the drums through a conventional
automatic transmission or torque converter?

Marc

Ours is tension controlled. The glider type information and tension
reading is processed by the winch driver who then applies the correct
power settings. Basically shouldn't be a major problem to replace the
human with a computer.

http://www.cumulus-segelflug.ch/index.php?id=14

Regards
Marcel Duenner

Eric Greenwell wrote:
Surely the cable tension must be greater to provide a 3500 fpm launch
instead of a 1000 fpm launch? I'm curious about the amount of tension

No, I don't think so. And I think the climb rate is not related to the
cable length, IOW, you get the same 3500 fpm with, say, a 3000ft cable.

-Gerhard
--
Gerhard Wesp / Holderenweg 2 / CH-8134 Adliswil
+41 (0)76 505 1149 (mobile) / +41 (0)44 668 1878 (office)
+41 (0)44 668 1818 (fax)
http://gwesp.tx0.org/

Hi Eric,

On Mon, 30 Oct 2006 22:00:06 GMT, Eric Greenwell
wrote:


Surely the cable tension must be greater to provide a 3500 fpm launch
instead of a 1000 fpm launch? I'm curious about the amount of tension
needed to provide a 1000 pound glider that 3500 fpm climb.

The strongest available weak link is about 2.000 lbs which is
obviously the maximum possible tension on the cable.
A single seater's maximum allowed weak link is usually in the 1.200
lbs range.

BTW: The standard climb rate in a winch launch is usually about 3.000
ft/min, independent of glider type.



Bye
Andreas

Graeme Cant wrote:

I must have only flown off traditional winches. My experience is the
same as Bill Daniels. What over-powered monster do you fly off?

I have flown off winches at 5 UK sites and 5 US sites (9 different
winches). I don't think any of them were over-powered monsters but
most had enough power to see this effect.

Please refer to "Gliding" by Derek Piggott, which was the standard UK
text when I started flying gliders. Page 80 of fourth edition -
"Unless the winch is seriously underpowered, steepening the climb will
result in an increase in launching speed".

Andy

Eric Greenwell wrote:
Bill Daniels wrote:

Good show!

Dyneema/Spectra winch cable allows for launches to approximately 50%
of the original cable length. Calculations show that there is really
no upper limit to the amount of Dyneema that can be used.

90 seconds to 5200 feet AGL on a winch beats the hell out of 20
minutes on aero tow. That's especially true when the typical cost is
$10 for the launch.


That sounds a bit frightening - 3500 fpm! What are the stresses on the
glider to get that kind of climb rate? How far away is disaster if the
pilot twitches a bit on the controls or hits some wind shear or a thermal?

Hi Eric

I would expect that the aircraft were flown within their maximum winch speeds,
which limits the lifting load on the wings to ~2G (this is with a high bending
moment at the root because there is no relief on the wing)

The limiting structural element on most airframes on winch launch is the
elevator down load.

The 3500fpm comes from flying with a very steep angle to the ground - the
aircraft maintains a 12 to 14 degree AOA, but as vertical speed builds it
rotates relative to the ground to maintain the AOA. Do the trigonometry. The
aircraft is never at extreme speed, G load or angle of attack. It is a common
misconception that normal winch launches involve dangerous loads on the
airframe. When the airspeed exceeds the design speed, it is probable that the
loads on some part of the airframe can exceed design limits. This is
particularly true on the "top" of the launch.

The wind shear part is a possible cause for concern, which is why one uses the
specified weak link.

For what it is worth my personal best is 2300" off a 2km wire solo in a low wing
loading twin seater (Bergfalke III) into a 25 - 30 km/h wind. The winch driver
was almost at idle for the top part of the launch. The key to a high launch in
these conditions is a winch driver who knows to keep the power down once the
glider has rotated. (of course a tension controlled winch does this automatically)

A long field like this has no part of the launch where a cable / weak link break
would make it unsafe to land ahead, or execute some form of circuit. It is
generally the "no good options" window on short runways that is cause for
concern on a winch launch.

Never heard of this one...

"Bruce Greef" wrote in message news:ei7o8q$po7
The limiting structural element on most airframes on winch launch is the
elevator down load.

"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.