The Release-Cord Collar: Let the Dog Go Without Reaching Its Neck

"This invention relates to an improved dog collar and leash by which a dog may be firmly held but instantly released when desired by unlocking the collar from the handle end of the leash". "When it is desired to release the dog for returning the bird or other game or for any other purpose, the releasing-cord e² is pulled back by the finger, which is readily accomplished, as the pull of the dog on the leash holds the cord taut, so that when the line is pulled back the latch b⁴ releases the hook b′ and produces the instant unlocking of the lock and the release of the collar from the neck of the dog."

**Collar.** Cut nylon webbing to the dog's neck size plus 12 cm and seal the cut ends with a lighter. Fold each end back 5 cm and sew it down with a saddle stitch in nylon thread, leaving a loop just wide enough for a 6 mm pin. Sew a short webbing loop beside one end for the leash to clip to. **Pin.** Cut 6 cm of hardwood dowel, round one end, and drill a 2 mm hole across the other end. Lay the two loops one on top of the other so their openings line up, push the dowel through both, and tie paracord through its hole. **Leash.** Sew a snap hook to one end of 1.5 m of webbing and a hand loop at the other. Sew 5 small webbing guide loops along it and pass the cord through them, ending in a finger loop tied beside the hand loop. **Measure.** Close the collar round a broom handle held in the vice, clip on the leash and hang a bucket from the hand loop. Load it with 5 kg of sand, pull the cord with the spring scale and write down the reading when the pin slides out. Repeat at 10 kg. Divide each reading by the load's weight to get μ.

**Carl Detmar Stahlknecht** of Bremen filed US 794,563 on 29 March 1905; it is dated 11 July 1905. The leash and cord were carried "in the pocket or hunting-bag until required for use" and snapped to the collar. **Honest limits.** Our lock is a pin in two loops, not Stahlknecht's hook and spring latch, so it needs more pull. The notebook treats the friction as the same on both loops. A wooden pin is for the bench; your measured μ is the result.