If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
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 |
#2
|
|||
|
|||
"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
|
|||
|
|||
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
|
|||
|
|||
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? -- martin@ : Martin Gregorie gregorie : Harlow, UK demon : co : Zappa fan & glider pilot uk : |
#5
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
"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
|
|||
|
|||
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 |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
vortex ring state at any point during an auto?? | Greg Johnson | Rotorcraft | 18 | August 30th 04 09:12 PM |
Auto Fuel Residue | Stu Gotts | Restoration | 4 | May 12th 04 08:52 PM |
Auto conversions & gear boxes | Dave Covert | Home Built | 56 | April 1st 04 06:19 PM |
Arrow auto gear extension oddness | Roy Smith | Owning | 10 | March 8th 04 02:27 AM |
VOR & Reverse Sensing | mrwallace | Piloting | 1 | August 21st 03 03:08 AM |