SAFE Winch Launching

Unless Bill has invented a perpetual motion machine, you can't get more
power out of a mechanical device (such as an automatic gearbox) than you
put in. You can gear that power down to get more torque, but the Skylaunch
winch depends on supplying the right amount of power (related to throttle
setting) for the given glider type and headwind component. The automatic
gearbox is only useful to provide some extra torque at low revs to get the
glider moving at the start of the ground run without stalling the engine.

Derek Copeland

At 22:45 12 July 2009, bildan wrote:
On Jul 12, 3:30=A0pm, David Chapman
wrote:

But other nonsense posted here . please help me, =A0...

A standard car auto gearbox has some magic power to automatically
adjust
the torque to the car wheels on reaching a hill, without changing
gear,
road speed or engine setting? What magic is that?


That 'magic' is called a torque converter which begins to slip and
multiply torque under increasing load. Stock units can double torque
to the wheels.

Modern transmissions use a torque converter locking clutch allowing an
even greater torque multipication factor after the clutch disengages
under load. The effect can be 4:1 or greater.

For basic info, see: http://en.wikipedia.org/wiki/Torque_converter

In addition, automobile engine torque curves have peak torque lower
than cruise RPM. As the vehicle encounters a load such as a hill, the
torque output actually increases as the RPM is pulled down by the
increasing load. The typical V8 used in glider winches has a torque
peak at about 1800 RPM.

The engine/transmission combination acts in exact opposition to what
is needed in a glider winch.

On Jul 13, 6:30*am, Del C wrote:
Unless Bill has invented a perpetual motion machine, you can't get more
power out of a mechanical device (such as an automatic gearbox) than you
put in. You can gear that power down to get more torque, but the Skylaunch
winch depends on supplying the right amount of power (related to throttle
setting) for the given glider type and headwind component. The automatic
gearbox is only useful to provide some extra torque at low revs to get the
glider moving at the start of the ground run without stalling the engine.

Derek Copeland

At 22:45 12 July 2009, bildan wrote:

On Jul 12, 3:30=A0pm, David Chapman
wrote:

But other nonsense posted here . please help me, =A0...

A standard car auto gearbox has some magic power to automatically
adjust
the torque to the car wheels on reaching a hill, without changing
gear,
road speed or engine setting? What magic is that?

That 'magic' is called a torque converter which begins to slip and
multiply torque under increasing load. *Stock units can double torque
to the wheels.

Modern transmissions use a torque converter locking clutch allowing an
even greater torque multipication factor after the clutch disengages
under load. *The effect can be 4:1 or greater.

For basic info, see:http://en.wikipedia.org/wiki/Torque_converter

In addition, automobile engine torque curves have peak torque lower
than cruise RPM. *As the vehicle encounters a load such as a hill, the
torque output actually increases as the RPM is pulled down by the
increasing load. *The typical V8 used in glider winches has a torque
peak at about 1800 RPM.

The engine/transmission combination acts in exact opposition to what
is needed in a glider winch.

In fact, with an automatic transmission in the drive line, it's
impossible to ever get the rope tension exactly right - certainly not
with something as simple minded as a throttle stop.

Most of what an automatic actually does in a glider winch is either
unnecessary or detrimental. Only the auto-clutch action at idle is
useful and there are far better ways to do that. The only
justification for using an automatic in a winch is that it's cheap and
comes with the engine.

The idea that low starting gears are necessary with a glider winch is
absurd. Tost gutted their automatics - even while saying automatics
were dangerous - to eliminate everything but the torque converter
leaving the box in it's straight through 1:1 ratio. Simple torque
calculations show that 3rd gear is capable of breaking the strongest
weak link during acceleration. Stepping through 1st and 2nd gears
only makes it more difficult to achieve accurate acceleration.

When our Tost winches were fitted with 'one speed' (fixed in top)
automatic gearboxes, the ground run acceleration for the heavier two
seater was somewhat ponderous, although they could still rocket launch
lightweight K8 single seaters. They also tended to overheat the gearbox
oil, despite being fitted with big oil coolers with electric fans.

This was also why you had to apply full throttle to get the gliders moving
and then back off as the gliders entered the full climb, to avoid a huge
overspeed. From a winch driver's point of view, it was hard to get this
right, which was probably the cause of some of the awful launches we used
to have to endure in that era.

Derek Copeland


At 14:49 13 July 2009, bildan wrote:
On Jul 13, 6:30=A0am, Del C wrote:
Unless Bill has invented a perpetual motion machine, you can't get
more
power out of a mechanical device (such as an automatic gearbox) than
you
put in. You can gear that power down to get more torque, but the
Skylaunc=
h
winch depends on supplying the right amount of power (related to
throttle
setting) for the given glider type and headwind component. The
automatic
gearbox is only useful to provide some extra torque at low revs to get
th=
e
glider moving at the start of the ground run without stalling the
engine.

Derek Copeland

At 22:45 12 July 2009, bildan wrote:

On Jul 12, 3:30=3DA0pm, David Chapman
wrote:

But other nonsense posted here . please help me, =3DA0...

A standard car auto gearbox has some magic power to automatically
adjust
the torque to the car wheels on reaching a hill, without changing
gear,
road speed or engine setting? What magic is that?

That 'magic' is called a torque converter which begins to slip and
multiply torque under increasing load. =A0Stock units can double
torque
to the wheels.

Modern transmissions use a torque converter locking clutch allowing
an
even greater torque multipication factor after the clutch disengages
under load. =A0The effect can be 4:1 or greater.

For basic info, see:http://en.wikipedia.org/wiki/Torque_converter

In addition, automobile engine torque curves have peak torque lower
than cruise RPM. =A0As the vehicle encounters a load such as a hill,
the
torque output actually increases as the RPM is pulled down by the
increasing load. =A0The typical V8 used in glider winches has a
torque
peak at about 1800 RPM.

The engine/transmission combination acts in exact opposition to what
is needed in a glider winch.

In fact, with an automatic transmission in the drive line, it's
impossible to ever get the rope tension exactly right - certainly not
with something as simple minded as a throttle stop.

Most of what an automatic actually does in a glider winch is either
unnecessary or detrimental. Only the auto-clutch action at idle is
useful and there are far better ways to do that. The only
justification for using an automatic in a winch is that it's cheap and
comes with the engine.

The idea that low starting gears are necessary with a glider winch is
absurd. Tost gutted their automatics - even while saying automatics
were dangerous - to eliminate everything but the torque converter
leaving the box in it's straight through 1:1 ratio. Simple torque
calculations show that 3rd gear is capable of breaking the strongest
weak link during acceleration. Stepping through 1st and 2nd gears
only makes it more difficult to achieve accurate acceleration.

Yeah... well, my point exactly. Over and out.

Bob Lacovara