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Winching - Reverse Auto Tow



 
 
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  #1  
Old November 2nd 03, 06:49 PM
John Spargo
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Posts: n/a
Default Winching - Reverse Auto Tow



Can anyone direct me to Clubs / Web sites using this method of launching -
Interested in finding out more about this method, particularly from clubs
that operate from gravel/dirt strips

Thank you


John Spargo


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  #2  
Old November 3rd 03, 06:27 AM
F.L. Whiteley
external usenet poster
 
Posts: n/a
Default


"John Spargo" wrote in message
...


Can anyone direct me to Clubs / Web sites using this method of launching -
Interested in finding out more about this method, particularly from clubs
that operate from gravel/dirt strips

Thank you


John Spargo


Over the years Cotswold GC and Essex & Suffok GC in the UK used this method.
Cotswold abandoned it 2-3 years ago in favor of a winch. Not sure about E &
S. Differently designed between sites. E & S was over engineered in my
opinion. Cotswold's system was elegant in it's simplicity. I've stowed
some images of that here.
http://www.soarcsa.org/thinking_page...ey/default.htm

Both systems were used on paved surfaces.

Frank Whiteley
Colorado


  #3  
Old November 3rd 03, 12:06 PM
Chris Nicholas
external usenet poster
 
Posts: n/a
Default

It was Essex GC (UK - and the club I belong to), not Essex & Suffolk,
that also did pulley launching. We stopped several years ago because
the Council, who own North Weald Airfield where we operated the system,
banned it when they allowed more and more powered aircraft there. Cables
dropping and rotating propellors are a bad mix. Cotswold stopped when
they decided winching was better (dunno why - we would have continued
pulley launching if we could.) The two clubs developed the method in
parallel, sometimes copying each other amd sometimes going separate
ways. Both copied the idea from a club in Ireland - but I never heard if
they continued, and the English clubs did their own detailed engineering
and development without much learning from the Irish, I believe.

When we operated at North Weald with reverse pulley (and before that
with straight autotow) we acheived up to 100 launches a day, and could
have done more. Max rate was about 20+ in an hour with reverse pulley.
There is far too much to it than possible to write here, but some points
are as follows.

We used Ford F250 trucks with 7.5 litre engines for our most successful
power units. (In earlier days we used F100's.) Important to have the
auto trans and heavy duty oil cooler option. You could start with just
a big car, but trucks are better for durability.

Tyre grip is important. It worked on good concrete/tarmac surfaces
(which we have at N Weald). Dirt or gravel sound challenging, but I
guess you can try. To enhance grip, we mounted the tow hitch on the
truck behind the cab, about 5 feet above ground. When towing, this
exerts more pressure on the (rear) driving wheels. The tow hook was a
glider nose hook (Tost) mounted horizontally, with a release cable thru
the back wall of the cab.

The driving technique is to take up the slack slowly of course, then
accelerate until the glider is seen to leave the ground, note the truck
speed, and go on to 5 mph faster than that. As the glider rotates into
the climb, cable tension increases, and slows the truck. The driver
balances the tension with throttle. The truck has to progressively
reduce speed as the glider gets higher. At the top of the launch, back
off the power, even brake if necessary to relieve the cable tension. As
soon as the cable comes away from the glider, accelerate to about 50 mph
to stop the cable falling in a heap. Slow down and stop before you hit
the next glider at the launch point. Aim to go past it if there is room.

We mostly operated without any cable tension gauge. Cotswold had a
gauge at least part of the time they used the system. You can rig up a
pivoting arm and a brake cylinder to a pressure gauge. Actual units
don't matter, it gets calibrated by finding the optimum pull required
for 1-seat, 2-seat gliders etc. and marking the scale with an indicator
point. We just found it too much trouble to keep the hydraulics free of
air, and it was not too difficult for drivers to learn how much
speed/throttle to use.

We used 11 gauge piano wire (had used 13 gauge but it broke too often).
It had to be unrolled from its reel by a special unrolling device, to
avoid laying it in spiral twists. We towed a new length round the
pulley system a few times with a tractor tyre on the other end, to help
straighten it. Spirals rub the ground in one place and result in breaks
too soon.

You need to join it after breaks, unless you throw the cable away after
the first. We eventually joined broken ends copying Cotswold club's
method - a machine was made to twist the two ends together, overlapping
about 18 inches. Alternatively you can do a spiral knot, or use
ferrules. Whatever, it has to go thru the guide mechanism, fairly
smoothly onto the pulley, and be flexible enough to go round the pulley
rim without breaking thru fatigue. We got about 200+ launches per
cable. Cotswold got more - up to 600-700, IIRC. The knot machine makes a
lot of difference - ours was not very good.

We eventually developed a two-pulley system, pivoting every which way to
ensure the cable ran true from truck to pulleys to glider. Between the
two pulleys (about 30 inches dia each) there was a short straight run,
past the horizontal pivot. the pivot was hollow, had a chisel with a
motor cyle spring thru its centre, and could guillotine the cable
against a short anvil mounted between the pulleys.

Cotswold developed a much larger "pulley" - about 4+ feet dia - but it
was really a collection of small dia rollers mounted round the edge of a
circular frame. I don't know if they had a guillotine.

Both systems had large V-shaped guides to keep the cable in the right
part of the pulley. The pulley system has to mounted onto something,
usually a fairly heavy truck - it must not move, or be pulled off the
ground, when the launch takes place.

We had a safety person in the tow truck cab with the driver - to look
out forward when the driver was looking over his shoulder at the glider
high up the launch and by then behind him. We also had a safety person
in the pulley truck, to operate the guillotine if necessary.

When really busy, we used two tow trucks. The second one followed the
glider being launched. Two thirds along the runway, the launch finishes,
the glider pulls off, the first tow truck proceeds to the launch point
to deliver its end of the cable for the next glider, and the second tow
truck proceeds to the pulley to do the next launch. The cable is double
ended, with the usual rings, strop, weak link, drogue, swivels etc. at
each end. The pulley safety person hooks the cable onto the second tow
truck and the system is ready to do the next launch. It is as fast as
any way of doing successive launches, because the cable is retrieved at
the same time as the launch is happening. (The only rival is the Long
Mynd winch system, with a retrieve winch - only suitable for non-tarmac,
I believe, and where you don't care about damage to the ground when the
metal triangle/sled joining the two cables and the glider strop all meet
as it falls to earth.) In less busy times, a single tow truck can be
used - it has to go back to the pulley ready to do the next launch,
which takes another 1-2 minutes per launch.

I don't know of any photographs or engineering drawings - tho some
people surely took some pics in its day. I could do some sketches, but
the detailed engineering would have to be done again to replicate it.

We sold our equipment to the Connell Gliding Club (Scotland, UK) but
they have no website and I don't know if it is still used there.

Chris N.





  #4  
Old November 3rd 03, 01:07 PM
Martin Gregorie
external usenet poster
 
Posts: n/a
Default

On 3 Nov 2003 12:06:33 GMT, Chris Nicholas
wrote:

It was Essex GC (UK - and the club I belong to), not Essex & Suffolk,
that also did pulley launching. We stopped several years ago because
the Council, who own North Weald Airfield where we operated the system,
banned it when they allowed more and more powered aircraft there. Cables
dropping and rotating propellors are a bad mix. Cotswold stopped when
they decided winching was better (dunno why - we would have continued
pulley launching if we could.) The two clubs developed the method in
parallel, sometimes copying each other amd sometimes going separate
ways. Both copied the idea from a club in Ireland - but I never heard if
they continued, and the English clubs did their own detailed engineering
and development without much learning from the Irish, I believe.

When we operated at North Weald with reverse pulley (and before that
with straight autotow) we acheived up to 100 launches a day, and could
have done more. Max rate was about 20+ in an hour with reverse pulley.
There is far too much to it than possible to write here, but some points
are as follows.

We used Ford F250 trucks with 7.5 litre engines for our most successful
power units. (In earlier days we used F100's.) Important to have the
auto trans and heavy duty oil cooler option. You could start with just
a big car, but trucks are better for durability.

Tyre grip is important. It worked on good concrete/tarmac surfaces
(which we have at N Weald). Dirt or gravel sound challenging, but I
guess you can try. To enhance grip, we mounted the tow hitch on the
truck behind the cab, about 5 feet above ground. When towing, this
exerts more pressure on the (rear) driving wheels. The tow hook was a
glider nose hook (Tost) mounted horizontally, with a release cable thru
the back wall of the cab.

The driving technique is to take up the slack slowly of course, then
accelerate until the glider is seen to leave the ground, note the truck
speed, and go on to 5 mph faster than that. As the glider rotates into
the climb, cable tension increases, and slows the truck. The driver
balances the tension with throttle. The truck has to progressively
reduce speed as the glider gets higher. At the top of the launch, back
off the power, even brake if necessary to relieve the cable tension. As
soon as the cable comes away from the glider, accelerate to about 50 mph
to stop the cable falling in a heap. Slow down and stop before you hit
the next glider at the launch point. Aim to go past it if there is room.

We mostly operated without any cable tension gauge. Cotswold had a
gauge at least part of the time they used the system. You can rig up a
pivoting arm and a brake cylinder to a pressure gauge. Actual units
don't matter, it gets calibrated by finding the optimum pull required
for 1-seat, 2-seat gliders etc. and marking the scale with an indicator
point. We just found it too much trouble to keep the hydraulics free of
air, and it was not too difficult for drivers to learn how much
speed/throttle to use.

We used 11 gauge piano wire (had used 13 gauge but it broke too often).
It had to be unrolled from its reel by a special unrolling device, to
avoid laying it in spiral twists. We towed a new length round the
pulley system a few times with a tractor tyre on the other end, to help
straighten it. Spirals rub the ground in one place and result in breaks
too soon.

You need to join it after breaks, unless you throw the cable away after
the first. We eventually joined broken ends copying Cotswold club's
method - a machine was made to twist the two ends together, overlapping
about 18 inches. Alternatively you can do a spiral knot, or use
ferrules. Whatever, it has to go thru the guide mechanism, fairly
smoothly onto the pulley, and be flexible enough to go round the pulley
rim without breaking thru fatigue. We got about 200+ launches per
cable. Cotswold got more - up to 600-700, IIRC. The knot machine makes a
lot of difference - ours was not very good.

We eventually developed a two-pulley system, pivoting every which way to
ensure the cable ran true from truck to pulleys to glider. Between the
two pulleys (about 30 inches dia each) there was a short straight run,
past the horizontal pivot. the pivot was hollow, had a chisel with a
motor cyle spring thru its centre, and could guillotine the cable
against a short anvil mounted between the pulleys.

Cotswold developed a much larger "pulley" - about 4+ feet dia - but it
was really a collection of small dia rollers mounted round the edge of a
circular frame. I don't know if they had a guillotine.

Both systems had large V-shaped guides to keep the cable in the right
part of the pulley. The pulley system has to mounted onto something,
usually a fairly heavy truck - it must not move, or be pulled off the
ground, when the launch takes place.

We had a safety person in the tow truck cab with the driver - to look
out forward when the driver was looking over his shoulder at the glider
high up the launch and by then behind him. We also had a safety person
in the pulley truck, to operate the guillotine if necessary.

When really busy, we used two tow trucks. The second one followed the
glider being launched. Two thirds along the runway, the launch finishes,
the glider pulls off, the first tow truck proceeds to the launch point
to deliver its end of the cable for the next glider, and the second tow
truck proceeds to the pulley to do the next launch. The cable is double
ended, with the usual rings, strop, weak link, drogue, swivels etc. at
each end. The pulley safety person hooks the cable onto the second tow
truck and the system is ready to do the next launch. It is as fast as
any way of doing successive launches, because the cable is retrieved at
the same time as the launch is happening. (The only rival is the Long
Mynd winch system, with a retrieve winch - only suitable for non-tarmac,
I believe, and where you don't care about damage to the ground when the
metal triangle/sled joining the two cables and the glider strop all meet
as it falls to earth.) In less busy times, a single tow truck can be
used - it has to go back to the pulley ready to do the next launch,
which takes another 1-2 minutes per launch.

I don't know of any photographs or engineering drawings - tho some
people surely took some pics in its day. I could do some sketches, but
the detailed engineering would have to be done again to replicate it.

We sold our equipment to the Connell Gliding Club (Scotland, UK) but
they have no website and I don't know if it is still used there.

Chris N.

Good description, Chris. I saw launches back in '91 when I commuted
past North Weald, but never realised it was an auto-tow system. I've
only one question: what did you do about swapping weak links? Were
both ends swapped to suit the glider?


--
[email protected] : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :

  #5  
Old November 3rd 03, 01:14 PM
Bill Gribble
external usenet poster
 
Posts: n/a
Default

F.L. Whiteley writes
I've stowed some images of that here.
http://www.soarcsa.org/thinking_page...erse_pulley/de
fault.htm


Heh. I noticed this truck hidden behind the Butts on Saturday, rusting
away quietly with brambles growing over it. Realised it was a now
disused winch system. Didn't realise it was the one they used to use for
auto-tows, though in hind sight should've guessed. Having said that, I
hadn't realised the club discontinued auto-tows as recently as the turn
of the millennium (I only joined at the beginning of last month).

Nice to see pictures of the thing in all its old glory. Thank-you.

--
Bill Gribble

/----------------------------------\
| http://www.cotswoldgliding.co.uk |
| http://members.aol.com/annsweb |
| http://www.shatteredkingdoms.org |
\----------------------------------/
  #6  
Old November 3rd 03, 04:10 PM
Chris Nicholas
external usenet poster
 
Posts: n/a
Default

We used Mity or Tost weak links at each end of the cable, on
quick-release links, and changed them to suit whichever glider was next
to be launched. On high throughput evenings, when we had two K13's
doing perhaps 30 air experience flights, there was no need to change
them of course. For the tow, the truck had the main cable hooked on by a
separate towing link, to avoid the stress going through the weak link,
drogue, etc. at the truck end of the cable, so only the glider end weak
link was operative. The drogue etc. at the truck end were all left
connected, and loaded into the back of the tow truck to deliver them
back to the launch point..

Chris N.






  #7  
Old November 3rd 03, 05:51 PM
F.L. Whiteley
external usenet poster
 
Posts: n/a
Default

Sorry that's Essex GC. Essex & Suffolk GC (my first club BTW, where I
learned to soar) operates a winch out of Wormingford. When at Whatfield,
two tow planes were used.

Frank Whiteley

"F.L. Whiteley" wrote in message
...

"John Spargo" wrote in message
...


Can anyone direct me to Clubs / Web sites using this method of

launching -
Interested in finding out more about this method, particularly from

clubs
that operate from gravel/dirt strips

Thank you


John Spargo


Over the years Cotswold GC and Essex & Suffok GC in the UK used this

method.
Cotswold abandoned it 2-3 years ago in favor of a winch. Not sure about E

&
S. Differently designed between sites. E & S was over engineered in my
opinion. Cotswold's system was elegant in it's simplicity. I've stowed
some images of that here.

http://www.soarcsa.org/thinking_page...ey/default.htm

Both systems were used on paved surfaces.

Frank Whiteley
Colorado




  #8  
Old November 3rd 03, 05:54 PM
F.L. Whiteley
external usenet poster
 
Posts: n/a
Default

Peter Skelly was the designer, builder, maintainer as far as I know.
Believed there were two complete systems and were replaced when the pickup
trucks finally wore out. Those were elegant in design, operation, and
simplicity and very inexpensive to operate. Only limitation is available
space. Put them on a 10K runway and wow!

Frank

"Bill Gribble" wrote in
message .. .
F.L. Whiteley writes
I've stowed some images of that here.
http://www.soarcsa.org/thinking_page...erse_pulley/de
fault.htm


Heh. I noticed this truck hidden behind the Butts on Saturday, rusting
away quietly with brambles growing over it. Realised it was a now
disused winch system. Didn't realise it was the one they used to use for
auto-tows, though in hind sight should've guessed. Having said that, I
hadn't realised the club discontinued auto-tows as recently as the turn
of the millennium (I only joined at the beginning of last month).

Nice to see pictures of the thing in all its old glory. Thank-you.

--
Bill Gribble

/----------------------------------\
| http://www.cotswoldgliding.co.uk |
| http://members.aol.com/annsweb |
| http://www.shatteredkingdoms.org |
\----------------------------------/



  #9  
Old November 3rd 03, 06:06 PM
F.L. Whiteley
external usenet poster
 
Posts: n/a
Default


"Chris Nicholas" wrote in message
...
It was Essex GC (UK - and the club I belong to), not Essex & Suffolk,
that also did pulley launching. We stopped several years ago because


Chris, of course it was Essex GC, not my first club Essex & Suffolk GC.

My first launches at checking out on the reverse pulley were a bit alarming
as the pickup truck was down for some reason and I was launched in the K-13
by a small displacement Vauxhall with a manual transmission. Each gear
shift was accompanied by the drogue chute ballooning on-to the nose. In
think we got 600ft and gave it up as dangerous. I later flew there with the
SHK as a day member.

The Cotswold system had no guillotine, but the small wheels had no energy.
The larger wheels of the Essex system were more likely to snarl in the event
of a wire break.

Piano wire was about 1/10 the cost of 7/7 wire rope IIRC.

Frank Whiteley


  #10  
Old November 3rd 03, 06:37 PM
Robin Birch
external usenet poster
 
Posts: n/a
Default

dropping and rotating propellors are a bad mix. Cotswold stopped when
they decided winching was better (dunno why - we would have continued
pulley launching if we could.) The two clubs developed the method in
parallel, sometimes copying each other amd sometimes going separate
ways. Both copied the idea from a club in Ireland - but I never heard if
they continued, and the English clubs did their own detailed engineering
and development without much learning from the Irish, I believe.

We, I fly from Cotswold and was there at the time that the decision was
made to switch, changed for a number of reasons. The first was that
spares for suitable trucks were getting hard to come by and we were
beginning to wear everything out. The second was that winch launching
offered a more reliable and easier to use system. Those who have done
auto tow will know that a good launch is totally dependant on the skill
of the truck driver. Whilst a winch launch, especially with today's
winches such as the Skylaunch that we have is much more "by numbers".

There are plenty of horror stories from the older members of when we had
lower powered trucks and ending up with gliders passing the truck when
still on the runways.

When we operated at North Weald with reverse pulley (and before that
with straight autotow) we acheived up to 100 launches a day, and could
have done more. Max rate was about 20+ in an hour with reverse pulley.
There is far too much to it than possible to write here, but some points
are as follows.

The launch rate can be very high. However, to attain this you need two
trucks, possibly three and a person at the pulley handling the hooking
on to the truck. It also requires a lot of launch point co-ordination.
This is attainable on open days or comps but not on normal club days.
On a normal day the rate usually fell to sub 10.

Important to have the
auto trans and heavy duty oil cooler option. You could start with just
a big car, but trucks are better for durability.

Yes
Tyre grip is important. It worked on good concrete/tarmac surfaces
(which we have at N Weald). Dirt or gravel sound challenging, but I
guess you can try. To enhance grip, we mounted the tow hitch on the
truck behind the cab, about 5 feet above ground. When towing, this
exerts more pressure on the (rear) driving wheels. The tow hook was a
glider nose hook (Tost) mounted horizontally, with a release cable thru
the back wall of the cab.

Same as ours but with the pressure sensor mentioned later. We also had
a release lever but no guillotine.

The driving technique is to take up the slack slowly of course, then
accelerate until the glider is seen to leave the ground, note the truck
speed, and go on to 5 mph faster than that. As the glider rotates into
the climb, cable tension increases, and slows the truck. The driver
balances the tension with throttle. The truck has to progressively
reduce speed as the glider gets higher. At the top of the launch, back
off the power, even brake if necessary to relieve the cable tension. As
soon as the cable comes away from the glider, accelerate to about 50 mph
to stop the cable falling in a heap. Slow down and stop before you hit
the next glider at the launch point. Aim to go past it if there is room.

This is the same as we used. On a good day (decent wind) you could be
almost stationary as a light glider, Ka8 or 6, was nearing the top of
the wire. Also easy to "kite" . As we have a long runway (just over a
mile) the glider was off by the time you got about two thirds of the way
along the runway unless it was a horrible heavy one. Really big birds
(ASH25 for instance) launched with their motor deployed.

We mostly operated without any cable tension gauge. Cotswold had a
gauge at least part of the time they used the system. You can rig up a
pivoting arm and a brake cylinder to a pressure gauge. Actual units
don't matter, it gets calibrated by finding the optimum pull required
for 1-seat, 2-seat gliders etc. and marking the scale with an indicator
point. We just found it too much trouble to keep the hydraulics free of
air, and it was not too difficult for drivers to learn how much
speed/throttle to use.

Ours was marked in link colour



You need to join it after breaks, unless you throw the cable away after
the first. We eventually joined broken ends copying Cotswold club's
method - a machine was made to twist the two ends together, overlapping
about 18 inches. A

Well, I never saw that, in the two years I used the system we always
tied reef knots in the system. We had a couple of bars with pegs that
you could use to wrap the wire round the main wire.

We cut the knots out and replaced them at the beginning of each day and
regularly got cable breaks during the day. Although the winch system is
incapable of doing the high launch rates that the reverse auto two is
the cable hardly breaks so you gain in the time it takes to tie knots.

Cotswold developed a much larger "pulley" - about 4+ feet dia - but it
was really a collection of small dia rollers mounted round the edge of a
circular frame. I don't know if they had a guillotine.

No
Both systems had large V-shaped guides to keep the cable in the right
part of the pulley. The pulley system has to mounted onto something,
usually a fairly heavy truck - it must not move, or be pulled off the
ground, when the launch takes place.

Yes, ours was an old 3 ton bread van, or something like that.

We had a safety person in the tow truck cab with the driver - to look
out forward when the driver was looking over his shoulder at the glider
high up the launch and by then behind him. We also had a safety person
in the pulley truck, to operate the guillotine if necessary.

Due to the length of the runway we usually got rid of the gliders when
they were overhead so a safety person wasn't used.

We saved the trucks and use them to pull out the cables for the
Skylaunch, the rest of the kit is mouldering in quiet parts of the field
:-)

Cheers

Robin


--
Robin Birch
 




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