Super sandals

Finally had a confluence of ideas & an old enough pair to try adding lugs.

Grip would be provided by some conventional patches over the worn out parts & some 1/2" squares of 2mm thick common rubber where the soles were most worn.  The battle with grip has always been not making the soles too heavy.  

Another new discovery was that black EVA is harder than white EVA, on account of the pigment.  The last of the white EVA would have to be used up 1st.

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A test run up & down the mountain showed the lugs to be very effective compared to the last run on smooth soles.  Their weight wasn't a problem.

Helas, still bailed on the same 2 downhill trouble spots as last time.  The last descent on those sections was in 2018 with hokas.  The problem with those sections might not be the sandals but the lion.  If these sandals with lugs couldn't do it, no-one else would be doing it.  It's a lot faster to do that downhill section on the paved road, even though it's longer.

Would continue using 16mm soles with the lugs, to defeat the rocks.  Would add lugs to the sections with the repair patches.  That might improve confidence in the downhills.  They might replace the patches.

The previous attempt was documented thus: https://hackaday.io/project/88623/log/204326-mountain-test-1

Managed to beat it by a few minutes.

Common rubber wears down so fast, they wouldn't make daily drivers.  Wouldn't go thinner than 2mm.

Right rear had the most wear.  Applying a dab of E6000 might buy them some time.  Found bending the lugs before gluing them on can keep them from curling up.  Might make the lugs smaller to reduce the curling in the corners & make them lighter.

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.