Winching - Reverse Auto Tow
John Spargo
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
F.L. Whiteley
"John Spargo" <ssp...@iafrica.com> wrote in message
news:3fa54...@news1.mweb.co.za...
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_pages/ground_launching/reverse_pulley/default.htm
Both systems were used on paved surfaces.
Frank Whiteley
Colorado
Chris Nicholas
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.
Martin Gregorie
<REMOVE_TO_REP...@yahoo.co.uk> wrote:
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?
--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :
Chris Nicholas
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.
Bill Gribble
>I've stowed some images of that here.
>http://www.soarcsa.org/thinking_pages/ground_launching/reverse_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 |
\----------------------------------/
F.L. Whiteley
learned to soar) operates a winch out of Wormingford. When at Whatfield,
two tow planes were used.
Frank Whiteley
"F.L. Whiteley" <gre...@greeleynet.com> wrote in message
news:3fa5f578$0$202$7586...@news.frii.net...
F.L. Whiteley
Believed there were two complete systems and were replaced when the pickup
trucks finally wore out. Those were elegant in design, operation, and
simplicity and very inexpensive to operate. Only limitation is available
space. Put them on a 10K runway and wow!
Frank
"Bill Gribble" <Bi...@scapegoatsanon.SPAM-ME-NOT.demon.co.uk> wrote in
message news:yWnVhzFeSlp$Ew...@scapegoatsanon.demon.co.uk...
F.L. Whiteley
"Chris Nicholas" <REMOVE_TO_REP...@yahoo.co.uk> wrote in message
news:bo5gc9$187v2l$1...@ID-49798.news.uni-berlin.de...
> 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
Robin Birch
>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.
>
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
Robert Ehrlich
There is a limitation in the initial acceleration that is intrinsic
to this launch method, due to the limitation of tyre grip. As solid
friction coefficient (i.e. ratio of tangential to normal force)
barely exceeds 1, the tow vehicle can't deliver much more force than its
own weight. This would result in 1g for the tow vehicle alone, with
a glider with a weight about 1/2 the weight of the the tow vehicle you
get .66g. If R is the ratio of glider weight to tow vehicle weight.
you are limited to 1/(1+R) g. You can get as close to 1g as you want by
increasing the weight and power of the tow vehicle, but efficiency would be
bad, since most of the power would be used to accelerate the tow
vehicle rather than the glider.
One may argue that the initial acceleration is not the most important thing,
but I think it is an element of security that it is sufficently quick that
the glider has no time for dropping a wing before being airborne.
Maybe this is the reason why Costwold preferred a winch.
Chris Nicholas
pulley or direct) than with winching. At both North Weald and Aston Down
there was more than one runway, so most launches were broadly into-wind.
Such cross wind as there was could be handled. The initial ground run
was a phase of flight in its own right - the pilot had to learn to
balance on the wheel and taxi straight until flying speed was achieved.
Wingdrop was not normally a problem, but training people to taxi was a
feature. The same considerations apply when landing, in any case, so
they got two lots of taxi training in one flight.
On tarmac or concrete the F250 trucks had adequate power and grip. F100'
s were not bad, but we didn't have such heavy gliders in those days.
Aston Down tried a variety of tow vehicles over the years, including
some home-built diesel dragsters, but I believe they ended up with
factory-built trucks, as we did, and as Lasham (using straight autotow
at one time) also did. I worked for Ford then, and helped to get some
advantageous prices for imported US-built vehicles for two if not all
three clubs IIRC - Ford used gliders at North Weald as background for
some advertisements, and did us a favour in return.
My club used LPG rather than petrol/gasoline, which made it a comparable
fuel cost to diesel winching, per launch/cable-retrieve. Total
depreciation/financing cost was probably about comparable, but needed
less cash flow up front. Trucks were cheaper capital cost than new
winches, though not as durable - ours lasted for about 50,000 launches
each and were not fully worn out - we recycled one old powertrain into a
winch when we had to adopt that method for our Ridgewell site.
The key features for us at North Weald were that on hard runways we had
to use piano wire (single strand steel cable), not stranded, to avoid
too much wear and cable cost, and pulley/autotow lends itself to that
better, with pulley giving also the benefit of fast launch rate when
well organised. We did about 9,000 launches a year, and added
considerably to our cash flow, when we had optimised the system.
Chris N.
W.J. (Bill) Dean (U.K.).
for an aerotow; it is flown in the same way. There is of course no tug
slipstream to contend with.
A car launch starts like an aerotow, and turns into a winch launch when you
are airborne.
W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.
>
> "Chris Nicholas" <REMOVE_TO_REP...@yahoo.co.uk> wrote in
> message news:bo8ku6$1bn8o0$1...@ID-49798.news.uni-berlin.de...
F.L. Whiteley
shunned by most BGA types.
There's still a story out there somewhere. Maybe someone will ask around
this winter.
Frank Whiteley
Chris Nicholas
It was diesel, not steam, but made from a converted combine harvester.
The saga of Freddie's club is fairly complicated, but he was far more
tolerated by the BGA and quite a lot of BGA types until he made it
impossible to be allowed to carry on in BGA membership.
His achievements in starting a club from scratch, converting a rough
field at Ridgewell into a useable gliding site, backing it with his own
money, and carrying on until illness intervened, were prodigious. We
all recognized those things, and perhaps let him get away with other
foibles for too long. My club has since benefited from his pioneering
efforts, having bought the site in 1991 when it looked like we would
lose the use of North Weald.
Before starting his own club, Freddie acquired a PPL and a Silver C
elsewhere. He went on an instructors course, and failed to qualify.
When his own club had mustered the enough equipment to start, he
appointed himself Chief Flying Instructor (CFI).
In establishing the club, he sought help from, and was given it by, the
BGA, free gratis. He did not join straight away, but did after a while.
The BGA tolerated his lack of qualifications and tried to get him up to
standard, but he was unable to reach the level needed. The BGA tried to
get him to accept a qualified instructor from elsewhere as CFI, but he
refused. He then claimed to be operating in two ways. When there was
no BGA-qualified instructor on the site, he said he had a soaring group
and he was carrying passengers and letting them try the controls. When
his passengers had reached solo standard as he thought, he then called
in a visiting instructor from elsewhere, called it a gliding club that
day, and got the visitor to check out his students so they could have a
BGA A and B certificate. The BGA let this go on for some years, all the
time trying to get him either up to scratch himself or persuade him to
accept outside help. I was on the BGA Executive Committee at the time,
and took an active part in trying to help - to no avail.
During this time, there were various events which brought interest from
outside authorities. One was a tug accident, Fred towing and IIRC
hitting his own mechanical shovel. After one of these, he was again
assessed by the BGA, and a second opinion sought when he refused to
accept the first. Both thought he was not up to instructing. There
were also concerns about the airworthiness of his fleet.
Eventually the BGA delivered an ultimatum. He was in breach of a prime
regulation - not having a CFI with qualifications, and himself
instructing while unqualified. I went personally to try to persuade him
to accept another CFI, and at one time I thought I had succeeded. But
he then dug in and refused to accept it. The BGA put it to a General
meeting and it was resolved, with only his vote against, to discontinue
his club's BGA membership. What would any responsible regulatory body
do?
Sadly, he fell ill and died not long after. His club went moribund.
After his death, several of my friends and colleagues helped to set up
his club again. My club's deputy CFI went to help, and promptly
declared all their gliders unserviceable through neglect. Eight of us
bought them a K7 2-seater to start again. (I have just sold it for
virtually nothing, so lost 1000 sterling on it.) One of my friends
became their CFI and technical officer. I persuaded the BGA to let them
back in without paying a subscription for a year.
Then they lost the use of their site, and went into hibernation again
until we bought it a few years later. Several of their members joined
us - several more were members of both clubs anyway, having helped in
their regeneration.
I think Freddie's family held me personally responsible for the rift,
when in fact I had done all I could, and more than most, to try to help.
I could say more, but that covers the essential part of a strange story.
Somebody else can write up the saga of the combine harvester winches (I
think there were two in succession).
Chris N.
F.L. Whiteley
Thank you very much. That fills in a lot of details.
For sure, our club CFI and Chairman told us to steer well clear.
Frank Whiteley
"Chris Nicholas" <REMOVE_TO_REP...@yahoo.co.uk> wrote in message
news:bo9h9g$1bcbl3$1...@ID-49798.news.uni-berlin.de...
Alistair Wright
"Chris Nicholas"
|Hi Chris,
Remember me? I was an instructor at North Weald from 1972 till
1978 when I went to the LGC (a bad move) and gave up gliding
when they refused to ratify my instructor's ticket (I only had
1000 launches instructing and about 20 solo pilots to my
credit).
However the winch story is interesting. When I was at the
Staffordshire Club in the late 60s I designed(!!) and built a
diesel winch which consisted of two old artic tractors , one
mounted on the top of the other (looked like a particularly
nasty copulation). The lower lorry was for transport and the
upper had its wheels replaced by large drums with brakes. You
braked one drum and the other ran at twice prop shaft speed
using the diff as a gear (didn't half heat up the oil). Worked
a treat and was very economical. I never saw anyone else try
this method. The SGC called it the 'Winchosaurus' as it
certainly looked primeval!
Alistair Wright
long retired glider pilot
Chris Nicholas
after North Weald.
I have seen a recent posting which suggested that using the diff as the
drive for a winch drum on the axle and doubling the speed is not a
recipe for long life. As others have pointed out, a better long term
solution seems to be a proper rightangle drive (the crown wheel and
pinion seem fine for that) and dog clutches for the drum, one at a time
and at crown wheel speed.
I did not see your winchosaurus, but I believe that there have been an
amazing variety of winches over the years. The most eccentric I know of
were Freddie Wiseman's 1977 converted combine harvester at one end of
the scale, and a totally portable, demountable, device to bolt onto the
hub of a Rover car at the other extreme. The latter was a commercial
offering, again in the 1970's.
When we lost the use of wire launching at North Weald but had bought
Ridgewell and needed to acquire one or more winches, we tried a
converted bus. That had two axles, one above the other, rather than the
whole second chassis. It had one drive shaft which had to be
disconnected from the lower axle after driving the bus to the winch
point, and reconnecting it to the higher, drum, axle. IIRC it had dog
clutches. We didn't buy it because it was unreasonable expensive and
looked as though it was not a sufficiently long term solution for us.
I had seen a similar arrangement in 1970 when Essex's original winch was
an old truck with that idea. I had my first instructional launch from
it, one cold March morning when there was too much ice to autotow. Got
300 feet and a free second go, which was not much better.
Now, we have ended up with 4 ex-ATC winches bought at auction, getting
two reasonable ones from them plus a lot of spares, and replacing their
powertrains. One had a total cab transplant too, professionally built;
the other is in the course of having a lower cost replacement cab, made
by some of our members.
Regards - Chris.
Alistair Wright
> Alistair, Hi! I certainly remember you. Didn't know where you went
> after North Weald.
>
> I have seen a recent posting which suggested that using the diff as the
> drive for a winch drum on the axle and doubling the speed is not a
> recipe for long life
Quite true as we found out. We had a source of free lorry back axles at the
time and we went through a fair number till we altered the lubricating
system to thinner oil with a pump and cooler. I left SGC about that time so
have no data on the subsequent fate of that winch. Considering it replaced
our original S/H ex Derby and Lancs one (Ford V8) which was on its last legs
when we bought it , it did pretty well.
My next club was the Coventry GC at Husbands Bosworth where very little
winching took place -- I only had about 4 in as many years - it was all
aero-towing at HB.
>
> I did not see your winchosaurus,
You were lucky then! It wasn't a pretty sight I can tell you. I have a
model of it somewhere.
> When we lost the use of wire launching at North Weald but had bought
> Ridgewell and needed to acquire one or more winches, we tried a
> converted bus.
I used to think NW's auto towing was magic. On a good day you could get
twenty launches an hour. Didn't half use up Ford Zephyrs though!!
>
> Now, we have ended up with 4 ex-ATC winches bought at auction, getting
> two reasonable ones from them plus a lot of spares, and replacing their
> powertrains. One had a total cab transplant too, professionally built;
> the other is in the course of having a lower cost replacement cab, made
> by some of our members.
Good idea. The ATC jobs were very well built and designed to launch T21s.
A winch that could hoist one of those to 1000ft would launch anything.
Best wishes
Alistair
All the best to any others in the EGC who remember me.
F.L. Whiteley
"Alistair Wright" <lms...@netcomuk.co.uk> wrote in message
news:boeg1h$4p9$1...@taliesin2.netcom.net.uk...
275hp XJ-6 Jag we got some pretty solid launches. After a time we developed
a vibration and thought one of the pillow blocks on the drum had given up,
but this wasn't the case. The vibration got worse, so we pulled all of the
wire from the drum and found it to be collapsing inward under the strain of
launching the Twin Astir and L-13 under more power than the winch had been
designed for.
Frank Whiteley
Chris Nicholas
wire from the drum and found it to be collapsing inward under the strain
of
launching the Twin Astir and L-13 under more power than the winch had
been
designed for."
This happened to another club, and I am concerned it might to us too.
What did you do do to fix it - could the ATC-type drum be suitably
reinforced to prevent it, or did it need a new drum which would no doubt
be of heavier material or with added stiffeners inside?
Chris N.
F.L. Whiteley
late Robyn Pierce-Boby and Larry Green(e?). Since Enstone GC is defunct, I
have no idea how to contact Larry. Someone like Ken Sparkes may be able to
help with contacting Larry. I don't have the specific details, but the pipe
was cut to a suitable length and split into two halves and clamshelled
around the existing drums. Once welded into place, it was turned true and
balanced. Seemed to do the trick though I originally thought it inelegant
and perhaps trickier than just making new drums.
Frank Whiteley
Frank Dobbs
It was the Dublin Gliding Club which used reverse pulley launching in
Ireland up to the early 1970s.
I flew there, from Baldonnel airfield. The pulley was about 3feet in
diameter and very simple with hardly any fairing. It was mounted on
the back of a large Chrysler car which had a tow-beam coming out of
the front with a heavy metal spike at right angles that was embedded
in the ground to anchor it. The mount for the pulley allowed it to
rotate to any angle to follow the line of the cable. The cable was
single strand piano wire. The concrete runways would have worn out
stranded cable too quickly.
The tow car, a large American automatic transmission car, had a
standard cable release mechanism welded to a lever which compressed a
small plastic football filled with water connected to a clear plastic
tube leading in to the top of the dashboard. The water rose in the
tube as the tension in the cable increased. Marks indicated the right
pressure for single seaters and two seaters (we flew K7, K13, K8, K6
mainly). The launch driver technique was very simple. Accelerate
rapidly to the correct tension once the glider was established in
climb. Slow down or speed up to keep the tension on the mark. I don't
remember ever having to signal too slow or too fast from the glider.
When the wind was strong, it was possible to reverse down the runway,
paying out the cable, as the glider kited upwards. My highest launch
was 4500 feet using this approach.
Cable breaks took rather a long time to disentangle as the cable
sprang back and tied itself in knots. Good heavy gloves were useful.
Splices were carried out by two people standing opposite each other
and winding the free ends back over the wire by hand.
The end came when the Army Air Corps installed VASI instrument landing
lights at the ends of the runways. The runway lights had been
expensive to replace if hit by flying rings, but the VASI lights were
£20,000 each and would have meant bankruptcy.
The Dublin Gliding Club still launches by (straight) car tow from
beaches in County Kerry each year on their wave safaris, using parafil
cable.
Frank Dobbs
Ulster Gliding Club, Northern Ireland
texastec...@gmail.com
Spectra rope makes more sense, but I would like to use Dacron to prove the concept without as much investment. If it works, Spectra would likely make more sense for performance and longevity.
Stephen Layton
Hobbs, NM
Gen Shib
Bruce Hoult
> I have about 2,000 winch flights. Most damage to rope/cable is done after glider release when rope hits ground and being reeled in fast at the same time, not launch. Synthetic materials are great because they are light and impact themselves less on ground.
Interesting pics here:
http://www.coloradosoaring.org/thinking_pages/ground_launching/reverse_pulley/default.htm
Tony
We've done 10 or so at Sunflower. 4000 feet of rope on a 7000 ft runway. Easy 1500 ft launches in our nose hook equipped 2-33.
Only time the rope drags on the runway is when (very slowly) resetting the rope after the launch.
texastec...@gmail.com
Stephen
JS
Jim
Steve Leonard
> I'm not sure I see much advantage of a 2:1 system (assuming you mean the reverse-driving vehicle has a pulley as well). Wouldn't you still be dragging 4,000 ft of rope behind the tow vehicle (from the fixed pulley)? It hardly seems worth the extra rigging trouble...but I've never done it either. My primary concern is rope wear, and I'm not seeing much improvement with that. Please let me know what I am missing.
>
> Stephen
Steve Leonard
Steve Leonard
> Stephen, if runway markers allow and you have the luxury of grass, park the pulley in the grass at the side of the runway and drive on the grass.
> Jim
Steve Leonard
texastec...@gmail.com
Doug C
Frank Whiteley
http://linearcomposites.net/media/parafil_case_study_13.pdf
Used 500m lengths of this for autotow and got 1500ft launches with L-13 and G-103. Doesn't like pulleys I'm told. Another poster said they had frequent breaks. Wasn't my experience. Rather heavy.
Frank Whiteley
Peter Higgs
launch car, then back to the glider. Car travels half the speed of the
The amount of rope between the glider and the car is shortening all the
time, and the pilot is alive at the start of the tow ?
Bruce Hoult
Except in this case the winch is moving.
Martin Gregorie
effective rope gets shorter during the launch.
- with a winch you get roughly 1/3 the height of the rope length
in calm conditions, so 2/3 of the cable has been wound in at
release, and a lot more if there's wind to help the glider kite
while the winch slows down.
- on a 2:1 factor auto tow the height:rope length ratio must depend
on where the anchor peg is along the runway. If its at the launch
point the height gain will be poor, but if its half-way down the
run, the worst case would be launching to 1/2 the height of the
rope length and, like the winch, a lot higher with wind to help.
The main disadvantages compared with a two drum winch is that the launch
rate will be lower (cable must be retrieved after every launch vs after
every two launches) and each retrieve will be slower because the tow car
needs to:
- detach from the cable
- find the end
- tow that back to the launch point
- go back up the field and put the cable back on his pulley
compared with:
- drive the cable truck to the winch (or follow the first launch down)
- hook both cables on
- drive back to the launch point
Did I miss anything?
--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |
Peter Higgs
>> There may be a snag to that....
>>
>> The amount of rope between the glider and the car is shortening all the
>> time, and the pilot is alive at the start of the tow ?
>
>That looks similar to the winch situation to me: in both cases the
>effective rope gets shorter during the launch.
of rope between winch and glider.
With the Car, you can only start with half that distance from car to
glider.
Peter Higgs
>> There may be a snag to that....
>>
>> The amount of rope between the glider and the car is shortening all the
>> time, and the pilot is alive at the start of the tow ?
>
>That looks similar to the winch situation to me: in both cases the
>effective rope gets shorter during the launch.
Dave Nadler
> That is quite true, except with the winch you have the full runway length
> of rope between winch and glider.
> With the Car, you can only start with half that distance from car to
> glider.
With a payout winch, its possible to drive around the corners
of the huge triangular airfield and keep climbing.
Don't know if anybody that does so with a glider, but I did that
with a hang-glider back when Curt Graham had a hang-glider
operation at Hobbs (kinda weird flying around the corner
on a ground launch).
Payout winch keeps line almost always off the ground,
uses more of available space - anybody doing glider (sailplane)
payout launches these days???
Martin Gregorie
> That is quite true, except with the winch you have the full runway
> length of rope between winch and glider.
>
> With the Car, you can only start with half that distance from car to
> glider.
>
looks like a worst case scenario. If the anchor is somewhere along the
runway, in theory at least, you can do a lot better. Putting the anchor
at the midpoint with the car starting at the 3/4 mark should launch to a
height of half the rope length. However, this is all theoretical because
I've never done an auto-tow or seen it done: most of my flying is done
from a winch.
So, here are some questions for those who have used the 2:1 auto-tow
system. I'd enjoy seeing the answers as they'd help me get my head around
how the system works in practise:
- where is the stationary end of the rope anchored along the runway?
- what ratio of launch height:rope length is usual on a calm day?
- on a windy day?
- does the glider ever tend to lift the rear of the tow vehicle,
allowing wheel spin, etc?
Bruce Hoult
> On Thu, 21 Jul 2016 10:30:00 +0000, Peter Higgs wrote:
>
> > That is quite true, except with the winch you have the full runway
> > length of rope between winch and glider.
> >
> > With the Car, you can only start with half that distance from car to
> > glider.
> >
> That assumes the end of the rope is anchored at the launch point, which
> looks like a worst case scenario. If the anchor is somewhere along the
> runway, in theory at least, you can do a lot better. Putting the anchor
> at the midpoint with the car starting at the 3/4 mark should launch to a
> height of half the rope length.
If you want to be able to reel in (nearly) the entire length of rope after glider release, as is commonly done with a winch, then you're limited to the car starting at most half way along the runway so that the rope is fully retrieved as the car nears the far end of the runway.
It's hard to figure out what release height you might get.
Assuming a standard winch launch gets 33.33% of the runway length in height, and assuming the glider averages the same climb angle with a 2:1 auto launch with the car starting from the runway mid point, then release will occur with the car about 75% of the way down the runway, and the glider at a height 25% of the runway length.
Martin Gregorie
> On Thursday, July 21, 2016 at 3:18:23 PM UTC+3, Martin Gregorie wrote:
>> That assumes the end of the rope is anchored at the launch point, which
>> looks like a worst case scenario. If the anchor is somewhere along the
>> runway, in theory at least, you can do a lot better. Putting the anchor
>> at the midpoint with the car starting at the 3/4 mark should launch to
>> a height of half the rope length.
>
> That doesn't make sense. The anchor point can be anywhere at all at or
> behind where the car starts from, including next to the glider, or
> behind it. It's only dead (unused, wasted) rope length from the car to
> the anchor point.
>
Lets assume a 4000 ft run and 4000 ft of rope.
With the rope anchored at the launch point, the car will start at the
midway mark because that is when the slack will be out of the rope. Its
equally sure that when the car has driven 1000 ft from there, the glider
will be 1000 ft from the car and so cannot be higher than 25% if the rope
length.
With the rope anchored at the 2000 ft mark, the car has to be 3000 ft
from the launch point for all 4000 ft of rope to be tight. If the car
then drives the 1000 ft to the end of the run, the glider still has 2000
ft of rope between it and the car, so in theory could be at 2000 ft.
As you say, calculating what happens with other anchor points is hard.
Never having seen one of these launches I don't know if that happens or
how far back and lower the glider would be in reality, but I bet the F3J
radio glider boys know all about optimising a single moving pulley launch
because some of them do it all the time, typically with the line anchored
at the launch point (an F3J requirement IIRC) and with two fit guys
pulling on the pulley to fire the model off as high as they can get it.
> Assuming a standard winch launch gets 33.33% of the runway length in
> height, and assuming the glider averages the same climb angle with a 2:1
> auto launch with the car starting from the runway mid point, then
> release will occur with the car about 75% of the way down the runway,
> and the glider at a height 25% of the runway length.
>
car will be at the 3/4 point when the slack is out and 3/4 of the line is
still between the car and glider, but what I don't know is how far up the
glider will be when the car gets to the end of the run.
There has to be an optimum anchor point, but, guessing wildly, I suspect
its less than half-way down the run from the glider.
Frank Whiteley
Bruce Hoult
> On Thu, 21 Jul 2016 06:18:46 -0700, Bruce Hoult wrote:
>
> > On Thursday, July 21, 2016 at 3:18:23 PM UTC+3, Martin Gregorie wrote:
> >> That assumes the end of the rope is anchored at the launch point, which
> >> looks like a worst case scenario. If the anchor is somewhere along the
> >> runway, in theory at least, you can do a lot better. Putting the anchor
> >> at the midpoint with the car starting at the 3/4 mark should launch to
> >> a height of half the rope length.
> >
> > That doesn't make sense. The anchor point can be anywhere at all at or
> > behind where the car starts from, including next to the glider, or
> > behind it. It's only dead (unused, wasted) rope length from the car to
> > the anchor point.
> >
> Draw a diagram: I had to before I could work out what was what.
>
> Lets assume a 4000 ft run and 4000 ft of rope.
>
> With the rope anchored at the launch point, the car will start at the
> midway mark because that is when the slack will be out of the rope. Its
> equally sure that when the car has driven 1000 ft from there, the glider
> will be 1000 ft from the car and so cannot be higher than 25% if the rope
> length.
Draw a diagram.
> With the rope anchored at the 2000 ft mark, the car has to be 3000 ft
> from the launch point for all 4000 ft of rope to be tight. If the car
> then drives the 1000 ft to the end of the run, the glider still has 2000
> ft of rope between it and the car, so in theory could be at 2000 ft.
Once again: The anchor point can be anywhere at all at or behind where the car starts from, including next to the glider, or behind it. It's only dead (unused, wasted) rope length from the car to the anchor point.
What counts is the length of rope from the glider to the car at the start, and the distance the car has available to drive from there.
The length of rope from the car starting point back to the anchor is absolutely irrelevant to anything .. it just lays there and does not affect the launch in any way.
> > Assuming a standard winch launch gets 33.33% of the runway length in
> > height, and assuming the glider averages the same climb angle with a 2:1
> > auto launch with the car starting from the runway mid point, then
> > release will occur with the car about 75% of the way down the runway,
> > and the glider at a height 25% of the runway length.
> >
> Exactly so - and if you move the anchor point halfway down the run, the
> car will be at the 3/4 point when the slack is out and 3/4 of the line is
> still between the car and glider
> There has to be an optimum anchor point, but, guessing wildly, I suspect
> its less than half-way down the run from the glider.
Doug C
> 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
Bruce: I can give you some quantitative numbers. In 1966-67 I made ~70 car-pulley tows in a 1:26 at Dansville using an asphalt runway that is almost 4000ft in length. The average tow was to 1300ft with some tows to 1500ft when the wind was optimum. For comparison, in 2009 I gave many instruction winch flights in either a Blanik L13 or a ASK21 using the same runway at Dansville. The average tow again was 1300ft and 1500ft when the wind was favourable. Thus under similar circumstances car pulley and winch give essentially the same height. Winch tows can utilize the full length of the airfield whereas car pulley tows are limited to the length of the paved surface because of the damage caused driving on the grass. Also winch tows are less intrusive than car pulley if the airport has mixed power and glider activity.
Doug C
Frank Whiteley
chris_gr...@dsl.pipex.com
We started with piano wire but moved to Parafil after the RAF resurfaced the main runway with a very abrasive surface that wore out piano wire very rapidly - in 8 launches on one occasion.
We tried reverse pulley but it wasn't successful. Our inexperience meant that it was difficult to know when the glider was at the top of the launch and stop and if the pilot hung on the cable would break. From what I've read here we were probably trying too hard and should have backed off a lot earlier.
With auto tow on one runway we would turn to go along the peri track to extend the run. This was fun because the glider was now pulling at an angle and the heavier two seaters would lift the back of the truck and move it sideways - it was a bit like driving a wheelbarrow.
Chris Rowland
texastec...@gmail.com
Peter Whitehead
> Does anyone have particularly bad experiences with pulleys used like this. I am talking about the pulleys themselves. Has someone found a particular diameter that is too small. Obviously larger is better for both bearing speed and rope bending, but there are limitations on cost and availability...particular for the trial run I'm thinking about. I am considering a trial run with a swiveling pulley on the receiver hitch of a pickup, no guides, just the pulley, with around 8,000' of 1/4" poly hollow braid, flying a 1-26. That should prove the launch height, assuming the rope doesn't break on the first launch. I'm not sure what to expect at the pulley end, and don't want the rope jumping out of the sheave, catching and breaking. I doubt it will, but have no experience to back it up.
Steve Leonard
If you are anchoring the pulley (say, to a parked car), still no need for a swivel. Keep your life simple!
Just my two cents worth.
Steve Leonard
texastec...@gmail.com
texastec...@gmail.com
Bruce Hoult
https://www.youtube.com/channel/UC_GpPGZVYWaGdMMduefDVAg
Dan Marotta
On 7/26/2016 9:28 AM, texastec...@gmail.com wrote:
> <Snip> If you could send me an electronic copy of your article, I would love to read it.
Or post it on Dropbox or similar so we can all read it!
--
Dan, 5J
John Foster
https://www.youtube.com/watch?v=Q0rv1zOmyWg
Frank Whiteley
Frank Whiteley
Frank Whiteley
IMVHO,
Frank Whiteley
moshe....@gmail.com
WB
WB
Karl Striedieck
Initially, launching a K-8, a 1965 V-6 Jeep was enough. A 300 ci Olds V-8 engine was installed when glass ships with ballast came along. Later, something with more muscle was needed to launch a ballasted Duo Discus so the vehicle used now is a supercharged 454 ci Chevy Suburban.
Traction has been a problem from day one, especially on early morning launches on wet grass. The jeep was equipped with chains on all four wheels which was still marginal during the soft ground in spring. To harness the 600 hp of the '99 Suburban a 350 foot paved strip was added, and this "launch pad" does the trick. Catapults to 150 feet altitude (all we need on the ridge top) take seven seconds for a 15M ship and 10 seconds for the Duo.
With the 2 to 1 reduction in required vehicle speed due to the pulley on the Suburban there is no need for the transmission to shift gears, so we use first gear, high range, 4wd. The glider releases from tow just as the Suburban reaches the end of the pavement. The throttle is floored until the glider calls "3,2,1,release" at which point the throttle is cut back.
Tow cable used is 3/16th galvanized. It lives outdoors. The pulley is a MG B trailing arm suspension welded to a 2 in coupling ball with the 13" steel wheel serving as the pulley. Totally indestructible, it has giving flawless service for 52 years.
Karl Striedieck
markm...@gmail.com
Apparently, you have figured out the solution for your operation. I can only offer one suggestion:
Bluetooth.
According to Dr. Sheldon Cooper on the "Big Bang Theory." everything is better with Bluetooth.