The ham in me really wanted to put this in GD, but as much as I am stumped, I do not actually believe that this will be the physics debate of the decade. So here I am for a factual answer.
My retractable dog leash is possessed by twist-happy gremlins. If we can figure out how to harness their magical gremlin powers, we could potentially provide free and clean energy to the world.
I have a “wide web” variety of a leash similar to these.
Note the pivoting clip that can freely rotate 360 degrees on it’s axis, and the flat webbing that feeds through a narrow slit into the (spring loaded?) winding mechanism/case/handle.
Observe my assurance that I usually walk with the leash unlocked, with my dog usually 5-10 ft in front of me, such that the retracting action of the leash unspools and retracts accordingly (through the aforementioned narrow slit) in response to the swinging motion of my arm in such a way that the tension on the leash remains relatively constant.
Ponder my testimony that the pivoting clip is attached to a standard choke chain that is in turn attached to the neck of my dog.
Now tell me, HOW in the FSCKING HELL are twists somehow introduced periodically (and annoyingly every 5-10 minutes) into this system such that the perfectly flat, twist-free, and coiled leash gets jammed because of twists that have somehow already migrated up past the narrow slit, into the coiled leash held within the plastic handle casing, causing the retractable action to freeze, thereby making the system unable to maintain the constant tension on the lease between my hand and the dog, which drives me completely FSCKING NUTS and requires me to repeatedly stop and manually untwist the leash by extending it all the way out and pushing all of the twists towards the dog and then spinning the base of the pivoting clip until all of the twists are released???
No, I am certainly the caboose in our little gang. Mrs. WeHaveCookies and her dog are up front, with her pom-poo zig-zaging like a maniac, though not ever pulling ahead of her. My dog plods along next in the middle, steady and in a straight line, and then there’s me. I’ve actually encouraged the behavior as she is very well behaved on the leash and it keeps her out from under my feet and allows me my full range of normal walking motion.
As for greasing the clip…
That was my first thought too, a design flaw in that too much force is required to spin the base of the clip. But if that is the case, I still don’t clearly grasp how the twists are introduced in the first place. Are they coming from the clip as it sometimes rotates as it rolls along the neck/shoulder of my dog as she walks? Does her choke collar do some sort of undulating roll as she walks?
Probably. I would guess that some aspect of your dog-walking is making the clip act as a ratchet, like angle-dependent slip-stick friction. You know the toy with the little pecking birdy that slides down a rod? That’s slip-stick friction, stopping and starting as the bird oscillates on its spring.
There could be some very subtle dynamics going on. The strap is under tension but it will still sag under its own weight, even if the sag isn’t visible. The centre of mass of the strap may be oscillating around the axis with a circular motion, maybe in time with your footsteps. So the tension on the clip will be fluctuating slightly, the tension angle will be fluctuating, and the clip will receive a periodic rotational impulse.
As to how the twists are propagating into the mechanism beyond the entry slit, you got me! Time to get one with a transparent case, and wear a video camera strapped to your hat when you walk the dog.
Construct a large copper coil at your house with the axis vertical and an open end at the top.
Install a hook in the ceiling above it.
When you get home from walkies, attach a powerful magnet to Rover’s tail. Fasten one end of the leash to the hook such that the hound is suspended inside the copper coil, and release.
With a long enough walk and sufficient RPM, enough power should be generated to supply your domestic needs for a substantial part of the day.
Best to put newspaper down under the coil - the energy may not be totally “clean”…
I know you want a scientific answer but since I don’t know science, but I know dog leashes, might I suggest switching to a retractable leash that isn’t “all belt” and is instead a cord that ends in a belt, such as this? The cord is just a round nylon rope, and the belt part doesn’t go inside the mechanism at all (but it’s there so you can grab the leash - the cord isn’t so grab-able). Since the cord is round and the hole in the mechanism is round, the cord can twist freely.
I had one like that previously, but it broke, probably because it wasn’t the right weight capacity. This one was the replacement that I just grabbed off the shelf not realizing it was different.
The slip-stick friction makes the most sense, and if it is the actual cause, I could prevent the twists by preventing the clip from pivoting at all. Right?
Tomorrow night is the next scheduled familial walk along the cliffs of Santa Cruz. I shall be performing a series of extremely sloppy and unstandardized experiments involving duct tape and other assorted things that I have not yet concocted. It is not going to be as sexy as a transparent case and a LeashCam, but I will be sure to report back any findings.
I’ve had it for at least a year (I have just been suffering silently) and we bought it in another state, and I don’t remember which pet store chain we were in. Ignoring this particular problem, there are features that I enjoy about this variety compared to others. Plus now it is just a geeky vendetta to best the gremlins.
