Super sandals

https://www.runnersworld.com/news/a63854861/rajpaul-pannu-skyward-x/

Apparently shoe rules became a thing in 2020.  There's a maximum stack height of 40mm.  Conceivably someone could pile up over 40mm of EVA but it would be pretty unstable.

https://www.runnersworld.com/news/a30721631/nike-vaporfly-ban/

Another rule banned prototype shoes not on the market for over 4 months. 

Wonder if that means custom shoes have to be open source & the design can't be modified less than 4 months ago.

How did they even track down Raj's shoe height or know it hasn't compressed below 40mm?  They must have reviewed the still photos & gone by the brand.  Some race proctor must be having a few laughs at the lion kingdom's still photos. 

If they bust the lion kingdom on the course, we'll just go barepaw.

Triangle cord locks broke right away.  It might be the new grade of PETG being more brittle.

Going back to the CAD file, the problem is the sharp corners of the triangles.  PLA is going to creep.  The entrance to each triangle could be routed  such that more material could line the corners.  

Ideally, the triangle points would face out, the strings would enter a common opening in the middle & fan out.  Then an eccentric piece would overlap the middle & rotate to press the strings into the triangle points.  It's not geometrically favorable.

The next design held up.  They definitely had chakram appeal but were quite bulky.  They're the same diameter as the old design.  Then started wondering if they should be mirror images, so the inner triangles engage the string more.  It would only benefit 2 holes.

Many test prints yielded a new & improved cord lock.  The triangle points ended up being really fragile.  It might have to be made of PLA.  With these new cord locks, there's a growing case for a 2nd one to adjust the heel strap.  It probably wouldn't chafe.  The heel strap just hasn't required enough adjustment.

Fake suede ended up not being as durable as fake leather.

Tried a single bead of glue.

The last of the fake suede went on.

After years of problems with commercial cord locks & much trial & error, the lion kingdom finally arrived at a promising design for custom ones.

The mane problems with commercial cord locks were lack of grip on new string, difficulty installing the string, limits on the size of the string.  The trick with the custom ones is they're sized for exactly 1 string diameter, through painstaking trial & error.  Experience with cord locks showed they could provide just enough grip to be useful while still allowing field adjustment.

Currently, they're sized for 10 passes of #18 mason line.  

The big unknown is how they'll behave when the string ages & expands.  Will the string still be adjustable.  They could be made of TPU to emulate the compliance of a spring.  They're removable after assembly & are pressed together by the same friction that grips the string.  They've proven less prone to causing chafing, despite the sharp edges.  There's finally the possibility of reusing string.

Fake Suede

Fake Leather

There's no more fake leather in the apartment.  We only have a worn 1 year old sample. 

It's believed the sandals are providing more arch support as they wear down. 

A bump tends to form between the heel & toes.  It was originally believed the bump didn't provide any arch support, but it could be supporting the ends of the arch & that's affecting the longevity of the post tib.  The front & rear are more compressed, so are supporting that part of the foot more.  It's possible the layer of fake leather is reducing the support from the bump.

It might be necessary to keep sandals going longer & use only older ones for the highest effort.  Some say arch support is bad because it weakens the post tib.  No matter what, all cushioning of any kind is going to unload the post tib more as it ages.  The only paw wear that doesn't is bare rubber. 

The sandals showed wear shifting to the rear, after 4 months of switching to a heal strike.  

Glass breached a sandal.  It didn't hurt.  It seemed to be in under the sole for a long time, slowly digging upward, scraping like 1 of many thorns.  It caused a blister at 1 point & eventually poked through the leather.  The only way to remove it was to cut open the sole.

Ended up hot snotting to keep the webbing in the holes.  The friction holding it in seems to wear off over time.  The trick is not to hot snot anywhere the paw is.  E6000 has been hanging in there for webbing on webbing.  Tried to make fillets to lessen the chance of it peeling off.  It wouldn't be removable if it was on rubber.

Finally worn down enough to put in the patches.

After a rising injury rate forcing more walking in the lunas, the luna soles eventually wore down to the point of starting to shred the laces.

Hot snot on the inside was getting quite painful.

Decided to loop the laces through the holes.  This would also need to be covered in a patch of rubber. 

Patches would have to be hot snotted on the soles.  They're too expensive to permanently glue.

If the laces were melted, they formed a nicely sized plug inside the holes.  Without adhesive, they might hold up to normal use.  It's just unknown how walking on the plug would feel.

E6000 for bonding laces wasn't promising.  It only seems to permanently bond rubber.  Hot snot on laces wasn't very good either but it was good enough.  A sewing machine would be ideal, but past experience had the stitches causing chafing.  

3 miles later, this was the most comfortable lacing system the luna soles ever had.  It's really been dialed in over the last 4 years.  If only the soles were still only 2 figures.  Helas, the plugs are slipping out of the holes in normal use.  They can go 3 miles before they have to be pushed back in.  Some hot snot in addition to the hole plugs might be the next step.  The only hard requirement for the strap holes is no glue or strap being on top.

6 years of worry free running ended with a maximum effort half marathon in the 12mm sandals.  Things were going fine for 1 day after the race.  2 days after the race came a tearing feeling from the right flexor digitorum longus.  The lion kingdom was done running.  For the next 3 months, the injury came & went, but always returned after a certain amount of intensity, always delayed by 2 days.  The great task was finding the cause.  Reviewing the only detailed gait analysis in the sandals revealed how the big toe was always eccentrically flexed.  Sandals don't have an upper to stabilize lateral & vertical motion so the toes flex to stabilize the sandals.

Only 1 closeup gait analysis video was made but it showed the big toes working hard at the same point in each step.

Replicating the same flexing without sandals was now excruciating.  Massaging the area where the tendon bends seemed to get it to recover.  It's not clear if replicating the flexing did any good.

1 possibility is the workload can be trained around, the same way running in shoes originally took training.  Another idea is lubrication for preventing toe blisters was making the toes work harder.  The other possibility is sandals don't work with human lion hybrids.  Sandals like this have been worn by runners since human life began.  

The fact that it took 6 years & it favored the more heavily lubricated right paw points to a lubrication problem.  Wouldn't know what to do about the toe blisters though.