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#21
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"Chris Nicholas" wrote in message ... Frank Whiteley wrote [snip] " 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." 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. It was repaired with steel pipe of a suitable diameter and thickness by the 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 |
#22
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"W.J. \(Bill\) Dean \(U.K.\)." wrote in message ...
The initial acceleration for a car or reverse pulley launch is no worse than 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" wrote in message ... Initial acceleration is certainly much slower with autotow (whether 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. 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 |
#23
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Winching - Reverse Auto Tow
Has anyone had experience with a reverse pulley system on asphalt runways and using a rope, rather than piano wire or cable? I am considering the feasibility of 1/4" Dacron rope on an 8,000' runway in Hobbs, NM. My concern is that the rope will wear out too fast, being drug at launch speeds (45-55 mph) down the runway. We do straight auto tow now with steel wire, but there are power lines in the area, and we couldn't risk 4,000+ feet of conductive cable being in the air in case of a break, or even a decent crosswind.
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 |
#24
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Winching - Reverse Auto Tow
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.
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#25
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Winching - Reverse Auto Tow
On Tuesday, July 19, 2016 at 2:11:46 AM UTC+12, Gen Shib wrote:
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. Yeah but on a regular winch launch the cable is off the ground along its entire length pretty quickly. There won't be anywhere near enough tension with a reverse pulley system to keep the cable between the pulley and the car off the ground, especially as the length of cable increases as the glider gets higher and the tension becomes less. Interesting pics he http://www.coloradosoaring.org/think...ey/default.htm |
#26
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Winching - Reverse Auto Tow
Suggest you consider a 2:1 pulley launch. Gets the rope up off the concrete during the launch very quickly.
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. |
#27
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Winching - Reverse Auto Tow
On Monday, July 18, 2016 at 1:06:39 PM UTC-6, Tony wrote:
Suggest you consider a 2:1 pulley launch. Gets the rope up off the concrete during the launch very quickly. 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. 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 |
#28
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Winching - Reverse Auto Tow
On Tuesday, July 19, 2016 at 8:22:07 AM UTC-7, wrote:
On Monday, July 18, 2016 at 1:06:39 PM UTC-6, Tony wrote: Suggest you consider a 2:1 pulley launch. Gets the rope up off the concrete during the launch very quickly. 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. 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 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 |
#29
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Winching - Reverse Auto Tow
On Tuesday, July 19, 2016 at 10:22:07 AM UTC-5, wrote:
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 End of rope is anchored to the ground. Rope goes around pulley on the launch car, then back to the glider. Car travels half the speed of the glider (2:1 system). The only rope moving relative to the ground during the launch is the rope between the pulley and the glider. And similar to a winch launch, all that rope becomes airborne pretty quickly. Steve Leonard |
#30
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Winching - Reverse Auto Tow
On Tuesday, July 19, 2016 at 11:07:40 AM UTC-5, JS wrote:
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 Hobbs, NM, Jim. There is no grass alongside their runway! :-) Steve Leonard |
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