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On Mon, 2 Apr 2007 13:29:20 -0600, "Bill Daniels"
bildan@comcast-dot-net wrote: Actually, if you think about it, the diesel winch with a Vioth Turbokuppling is very close to a tension controlled winch. Diesels have a very flat torque curve and torque increases linearly with throttle. The Voith coupling just passes that torque to the drum at a 1:1 ratio. If the winch driver makes a reasonable guess as to throttle setting based on the glider to be launched and the wind, the result will be pretty good. Forget all that high-tech stuff - much too complex for an average gliding club. Hard to design, hard to build, hard to maintain, hard to debug, hard to repair. ![]() Here in good ole' Europe usually a standard truck clutch is used (with a big engine this clutch is either actuated by hydraulics or pneumatics) to connect the engine to a standard truck rear axle. Initial acceleration is made by moving the throttle smoothly forward until a certain RPM is reached which depends upon glider type wind. During the launche the throttle is slowly brought back to keep the gliders' speed halfways constant - a couple of RPMs more or less doesn't matter. Even in Germany, however, it's likely that the average tension will be 50% to 70% of the weak link breaking load. Increasing this to 70% to 90% will significantly increase release heights. 80% - 90% would be even better but that will likely be more precision than the average human winch driver can manage. Automated tension control systems can shave it as close as you like. I don't think so. A striong winch is easily able to enable toe glider to exceed its particular winch-launch Vne. Usually the speed is kept about 10-15 kts below the Vne. Release altitudes on a standard 3.300 ft rope length are usually sufficient to thermal (1.000-1.500 ft) or fly a 7 minute no-thermal traffic circuit. Completely satisfying for me - and apparently for the other 30.000 glider pilots here... ![]() In the US for the last 50 years or so, 'simple' has meant a V8 engine and automatic transmission from a wrecked car. The engine will not produce anything like a flat torque curve and transmission will run wild shifting whenever it pleases. Combine this with gliders without CG hooks and the results are very inconsistent leading to absurd 'rules' like "raise nose to increase speed". I can imagine that. Until about 15 years ago the German standard winch also consisted of an old V8 engine, coupled to a manual gear that was usually locked in the 2nd gear. When these engines became unavailable (and the gliders heavier) we switched to Diesel engines. In the US, a little intellegence built into the winch will be a big help to a fledgling winch operation. I'm not so sure, Bill. Intelligence is always a good thing - but what happens if the system fails or does something unexpected? The more simple the design, the easier it is for a small club to build and maintain a winch - and to fix it. I guess on any airfield in the US there's at least one mechanic who can repair a Lycoming engine... for if your winch (a new technology for most clubs) depends on complex closed circuits, you'll probably get a problem sooner or later - and revert to the trusty Pawnee. BTW: Have you tried this to get a winch operation running? Put an advertisement in the German gliding magazine "Segelfliegen" or the "aerokurier", offer half a year of free board and lodging, mention 15.000 ft cloud base, and I'm sure you'll immediately find a dozen enthusiasts who will build a usable winch for you for less than $25.000 and provide all the training. It would certainly help if you could offer more than an 1-26 for their leisure flights. ![]() This is even more so when it's important to achieve the highest launch possible to compete with aero tow. Automating cable tension control allows higher tensions to be used with safety and thus higher launches. Nah... forget about the 10 percent height advantage an optimized winch system can bring. In 95 percent of the cases a winch launch is completely sufficient to catch a thermal (...maybe not for a 2-33...). Key factor for a winch operation are cost savings - and the lower costs for a winch launch (compared to an aerotow) ought to convince even the most stubborn club members, don't you think? You know the deal from your club - nothing better than being able to offer some highschool kid flying lessons for less than $3 per launch, don't you agree? If someone really needs 3.000 ft release altitude, he can still take the Pawnee. Bye Andreas |
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