Airspeed control during ground launch?

Bill Daniels wrote:
Actually, John, I've done better than that. I have several cable tension
traces from a Skylaunch made with a tensiometer load cell at the glider.
The data shows horrific tension surges as the transmission shifts up and
down during the launch. These surges were violent enough to break weak
links and the cable. Surges such as these would be unacceptable in a $200
junkyard winch. Given the price of the Skylaunch, we should expect MUCH
better.

I stand by exactly what I wrote. It's extremely foolish to allow a winch
transmission to shift - particularly when it's easy to prevent it. Just
because big American V8's and automatic transmissions are dirt cheap is no
reason to use them without the needed modifications.

BTW, I do like the Skylaunch paint job.

Bill Daniels


"John Galloway" wrote in message
...

Bill,

If you were to stand beside a Skylaunch winch (which
has a big American petrol/LPG V8 and a fully functioning
3 speed auto box) you would notice that the box is
in 3rd gear by the time that the glider is leaving
the ground and the rest of the launch is normally carried
out in 3rd gear.

John Galloway


At 17:36 30 March 2007, Bill Daniels wrote:

'toad' wrote in message
egroups.com...

Ok, thanks. That's the physics as I understood it.

With a modern winch, I won't have to worry about reverse
control. But
with an old technology ground launch, I do.

Todd


Actually, it's neither difficult nor expensive to eliminate
the worst
problems with an automatic transmission.

Replacing the stock valve body in the transmission
with a 'manual valve
body' allows the winch driver to lock out 1st and 2nd
gears. (Google 'manual
valve body'). These gadgets replace the stock 'PRND2L'
shift pattern with
'RN321' which can be further restricted to 'N3' with
a simple shift gate.
This results in the transmission starting in 3rd and
remaining there
throughout the launch.

For a bit more money and little more effort, the stock
1800 RPM stall torque
converter can be replaced with a 'high stall' TC that
lets the transmission
slip up to say 2800 RPM during power up for a softer
but still energetic
launch. It also prevents a heavy glider in strong
wind conditions from
bogging down the winch engine. Don't do this without
adding an effective
transmission cooler.

It won't be perfect, but it's FAR better than the stock
setup.

Bill Daniels







Hi Bill

I don't understand the mechanics well enough, but this is what we have.

Our little red monster - which looks scrappy but has served well for nearly 30
years consists of:

1x Ford 352 V8 Windsor in stock condition - (Removed from a galaxie I believe.)
1x Standard manual transmission
1x Ford Ranchero one ton truck axle with the differential and one axle locked.

The Single drum is driven from the other hub.

I presume we have the 1,800 RPM stall torque converter as I have not seen any
modifications, and the transmission acts locked from around 2000RPM.

Shifter is 'RN321' manual override.
We launch in 2nd gear - to prevent the engine bogging down. Typically RPM is in
the 3,500 - 3,800 range with a 55-65kt launch in the glider. We only shift to
third manually when needed to retrieve the cable fast. First is locked out.

Am I right in assuming the locked differential and axle are changing the gearing
on the axle. (I think it is a nominal 3.59:1 ratio)

By the way - this setup is nearing the end of it's life at around 50,000 launches.
There is now runout on axle bearings, and oil weeping from the transmission, the
guide rollers are worn beyond machining and the drum rim is deformed. The winch
driver thus gets exposed to quite a lot of vibration, although the cable appears
to absorb most of the vibrations as they are not noticeable in the glider. The
engine is still running well, although it goes through fuel pumps with
distressing frequency (about every 4,000 launches.)

The "capital" cost per launch is tiny.
Fuel is around one litre per launch - less than 1US$.
Maintenance cost is negligible. Filters and batteries mainly.

Now we have to build a replacement - and I wonder where we will find components
as robust.

"Bruce Greef" wrote in message
...
Bill Daniels wrote:
Actually, John, I've done better than that. I have several cable tension
traces from a Skylaunch made with a tensiometer load cell at the glider.
The data shows horrific tension surges as the transmission shifts up and
down during the launch. These surges were violent enough to break weak
links and the cable. Surges such as these would be unacceptable in a
$200 junkyard winch. Given the price of the Skylaunch, we should expect
MUCH better.

I stand by exactly what I wrote. It's extremely foolish to allow a winch
transmission to shift - particularly when it's easy to prevent it. Just
because big American V8's and automatic transmissions are dirt cheap is
no reason to use them without the needed modifications.

BTW, I do like the Skylaunch paint job.

Bill Daniels


"John Galloway" wrote in message
...

Bill,

If you were to stand beside a Skylaunch winch (which
has a big American petrol/LPG V8 and a fully functioning
3 speed auto box) you would notice that the box is
in 3rd gear by the time that the glider is leaving
the ground and the rest of the launch is normally carried
out in 3rd gear.

John Galloway


At 17:36 30 March 2007, Bill Daniels wrote:

'toad' wrote in message
legroups.com...

Ok, thanks. That's the physics as I understood it.

With a modern winch, I won't have to worry about reverse
control. But
with an old technology ground launch, I do.

Todd


Actually, it's neither difficult nor expensive to eliminate
the worst
problems with an automatic transmission.

Replacing the stock valve body in the transmission
with a 'manual valve
body' allows the winch driver to lock out 1st and 2nd
gears. (Google 'manual
valve body'). These gadgets replace the stock 'PRND2L'
shift pattern with
'RN321' which can be further restricted to 'N3' with
a simple shift gate.
This results in the transmission starting in 3rd and
remaining there
throughout the launch.

For a bit more money and little more effort, the stock
1800 RPM stall torque
converter can be replaced with a 'high stall' TC that
lets the transmission
slip up to say 2800 RPM during power up for a softer
but still energetic
launch. It also prevents a heavy glider in strong
wind conditions from
bogging down the winch engine. Don't do this without
adding an effective
transmission cooler.

It won't be perfect, but it's FAR better than the stock
setup.

Bill Daniels







Hi Bill

I don't understand the mechanics well enough, but this is what we have.

Our little red monster - which looks scrappy but has served well for
nearly 30 years consists of:

1x Ford 352 V8 Windsor in stock condition - (Removed from a galaxie I
believe.)
1x Standard manual transmission
1x Ford Ranchero one ton truck axle with the differential and one axle
locked.

The Single drum is driven from the other hub.

I presume we have the 1,800 RPM stall torque converter as I have not seen
any modifications, and the transmission acts locked from around 2000RPM.

Shifter is 'RN321' manual override.
We launch in 2nd gear - to prevent the engine bogging down. Typically RPM
is in the 3,500 - 3,800 range with a 55-65kt launch in the glider. We only
shift to third manually when needed to retrieve the cable fast. First is
locked out.

Am I right in assuming the locked differential and axle are changing the
gearing on the axle. (I think it is a nominal 3.59:1 ratio)

By the way - this setup is nearing the end of it's life at around 50,000
launches.
There is now runout on axle bearings, and oil weeping from the
transmission, the guide rollers are worn beyond machining and the drum rim
is deformed. The winch driver thus gets exposed to quite a lot of
vibration, although the cable appears to absorb most of the vibrations as
they are not noticeable in the glider. The engine is still running well,
although it goes through fuel pumps with distressing frequency (about
every 4,000 launches.)

The "capital" cost per launch is tiny.
Fuel is around one litre per launch - less than 1US$.
Maintenance cost is negligible. Filters and batteries mainly.

Now we have to build a replacement - and I wonder where we will find
components as robust.

Bruce, It sounds as if the builders of your 'little red monster' got it
right 30 years ago to the standards of that day. If I understand correctly,
your transmission has a manual valve body allowing you to over ride any
automatic shifting. The axle undoubtedly has the differential gears welded
to eliminate their action and make the axle act as a simple right angle
drive. Your simple machine has returned the original investment many
thousands of times over. It deserves an honored retirement. Some current
winch builders could benefit from studying your winch.

When you build your new machine thee are a lot of new ideas to consider.
Electronically controlled, common rail diesels are available either new or
used at reasonable prices. I just located a brand new 425HP Mercedes Benz
14.2 liter diesel for $10,000 USD. These engines produce constant, massive
torque from just above idle to redline. They are very well matched to the
job of launching heavy modern 2-seaters. These engines should last forever
in winch duty. If desired, they can be fueled with biodiesel.

Hydrostatic transmissions and hydrostatic drive systems are now available in
many configurations. They allow absolutely precise control of cable tension
and speed under all conditions.

Since both engines and tranmissions are now electronically controlled, this
makes near full automation both possible and highly desirable. This means
the pilot can expect absolutely smooth, high performance launches every time
regardless of wind, turbulence, thermals, glider type, even rough pilot
technique and inexperienced winch drivers.

There seems to be a trend toward fully enclosed cabs with climate control to
make the winch drivers day more pleasant.

New synthetic cable materials like Dyneema and Spectra have eliminated
virtually all cable related problems. With them, winch builders can make
their creations far more user friendly.

Bill Daniels