The Retrieval Winch

Dave Broyles 2006

 

 The big problem of using a stationary winch is that the tow-line is pulled in as the glider is towed and must be pulled out again to do the next tow. Radio controlled sailplanes have been towed with stationary winches for many years, and the ingenious people who do this have the same problem. Their solution to this problem was to create a second winch to tow the tow-line back out for the next tow. Always being willing copy a good idea, we devised a retrieval winch for scooter tow. To make this work most easily, we found that the retrieval winch should be right next to the tow winch. So, we adopted another innovation from RC sailplanes. In RC sailplane towing, the winch operator is also the sailplane pilot, and also the sailplane launcher. Since the winch is thus stationed right next to the pilot, an extra item of hardware, the turn-around pulley, is required. The pulley is subjected to twice the force of the tow rope tension, so needs to be very strong. It also must be designed to prevent rope jams and tangles. After some research, we found that a lineman's pulley, the Western Power Products Model 303, fit the bill. This pulley is built with two large ball bearings. It is a snatch block, which means that the top opens up so that the rope can be put into the pulley. The real value of the snatch block is that it allows the pulley to be put on the 5000 ft rope at the middle of the rope rather than just at one end.

For use with the retrieval winch, the rope is run through the turn-around pulley. The turn-around pulley is usually attached to a 3 ft long earth anchor or a car bumper stationed 2500' away from the winch.

The pulley and the rope should be protected from rope recoil by wrapping duct tape around the top of the pulley so that there is nothing for the rope to catch on. The top of the pulley includes the pin to open the snatch block, the swivel and the opening in the hook. It is also possible to replace the snatch block, swivel and hook with a triangular aluminum 3/8" plate with a hole for a carabiner to reduce the chance of the rope snagging on the pulley. There have been a number of instances of Spectra rope damaging the pulley if this is not done, which also tears up the tow rope, so this action is essential.

 

 

 

The retrieval winch has a number of special features. It is based on a 6 or 12 volt Ford long shaft starter. The 6 volt starter has more torque but the 12 volt starter runs the battery down more slowly. The endplates of the stock starter has plain bearings which wear out  at a high rate of speed, usually wearing out the shaft on the armature as well. They were replaced by "Real Balls" aluminum endplates with ball bearings which last much longer in this winch application, but are hard to get since they are out of production. A recommended solution to this problem is a ball-bearing winch motor such as that for a Ramsey winch. The winch drum is adapted from a radio control sailplane winch. The side plates were 1/8" but were replaced with 1/4" plates after it was found that wrapping nylon retrieval string on the drum at 50 lb or more of tension blew the stock side plates off.

 

 

Normally the drum would mount directly on the starter shaft, but at the speed the starter turned, it instantly broke the retrieval line, so a jack  shaft was mounted with a chain reduction of about 4 to 1. In addition, a low RPM centrifugal clutch was added to keep the motor from turning when the line was being paid out.

 

 

A brake was added to stop the drum from spinning wildly when the payout stopped.

 

 

The only thing cheap about this winch is the string, which is the best #18 nylon twine available. (Avoid braided string. Twisted string is much stronger. Braided #18 string lasts for hours and twisted #18 string lasts for months. Also avoid cheap imported string. The best American made string lasts much longer.) This winch works very well if the string used is high quality and is replaced when it starts wearing out.

 

Various people have suggested a more elegant lever for the anti-backlash brake than a piece of 1/4" steel with a hole in the bent end. They worry that the steel will wear out the string. We should point out that the string goes through a hole  in the end that started out 1/8" in diameter, but is now about 3/8". The string wore the steel out... so we don't worry about about the string. The original battery fit in the box with the winch motor. It was an Optima deep cycle. It was always dead before the end and required being jumped from a truck. to finish the day Now we use a really serious battery. This Interstate Batteries 4DM is a deep cycle marine battery and the biggest battery of this type I could find. It usually lasts for a full day of instruction if it is fully charged before going out. This battery is not your grandmother's battery and needs more than your grandmother's charger.

 

 

Here is a picture of a tow with the retrieval winch in action. The retrieval winch  provides a really short turn-around between tows.

 

We found that it would have been nice to have a level wind, but the level wind would have doubled the cost of the winch. The person winding the winch uses a piece of aluminum tubing to level wind the string. If not, the string piles in the middle and then tangles. If anyone knows of an inexpensive level wind adaptable to this application, we are interested.

 

 

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For more information, call 972-390-9090 or email to d.broyles@comcast.net Dave Broyles.