Custom Ski Boots

Hi, I'm Le Chiffre and I'm from Argentina. I'm an Electronic Engineering student at my last year in the University of Buenos Aires. I've been following RepRap for a year and a half, but I still don't have the time or space (and I suspect, the skills) to start building my own RepRap. But I think that in the next few months I will finish all my final tests, and I will get some free time, and start experimenting with this project that, I belive, has the potential to become a disruptive technology.
Anyway, during this year and a half, I had accumuleted a lot of question, so let's start with the most trivial one:

I like skiing, but the equipment is so expensive, specially in the third world. And the prospect of having custom made equipment design especially for me, it's very exciting. After the success of the plastic sandals, do you think that the RepRap could build custom-made ski boots? I know that the overhang could be a problem, but maybe there are some workarounds. I don't know which kind of plastics uses this boots, but it probably needs to be water-proof, and not very weak.
So, what do you think? It's possibly right now (or in the next months o year )to print a ski boot with Darwin? Or it will take some more time to be able to print things like that? What about the quality of the final product?
Best whishes

le chiffre

THere may be a strength issue. Idont know what plastic they are made from, but it would need a good low temperature performance. I have heard of a (older) boot line that would shatter. Of course, this is the last thing you want at speed (where loads are high) or in the back country where exposure kills.

I totally broke my ACL knee ligament in a high speed incident - the binding didnt release but I had them tested with my boots the same day and they where fine. Just the way I fell I suppose but I wont be taking unnescescary risks with my knees again. The boot is a critical part of the skiing process.

Mind you, If the plastics can be processed by reprap and are proven to laminate strongly, I would be interested in experimenting.

I wanted the surgeon who fixed my knee to build in some strain guages while he was in there - I could build a binding that released when it sensed ligament overload directly, not based on some spring ay my boot toe.

Ski boots! Fascinating idea!

Very fascinating. I googled some stuff - up popped a ski forum posting by a chap I know who is a ski boot guru. I must drop him an email.

Edt; On the internet he's known as 'smallzookeper' for esoteric reasons I never quite got to the bottom of.

Edited 1 time(s). Last edit at 07/12/2008 03:09PM by Richard Benjamin.

Ive just got my ski boots out of their bag and had a look - the main shell is marked as .

Has anyone tried to extrude thermoplastic polyurethane ? It is available in welding cord form @3mm from a quick google.

Is this stuff anything special? What is a non-thermoplastic polurethane - a 2 part mix&cure?

I'm glad that others find ski boots extrusion interesting! In fact, now I'm thinking that a lot of ski and sports equipments are made of plastic. I play football (soccer), studs and shin guards could also be interesting customizable items.
I think that a potential problem is that ski boots usually have one continuous, large body. I don't know if currently Darwin can "resume" printings (that is, stop extruding half a piece, and some time later conclude the printing), without affecting the quality of the print.
Richard, thank you for your little research.

The idea that I could scan my foot and make a boot to fit is an interesting idea.

You could scan your shin for perfect shin pads.

'personalised' cricket boxes anyone ?

Current state of the art with Darwin would probably need some artful dodges to printout ski boots or anything else like that which needed a support material to support arches etc.

Options printout ski boots in sections and weld/glue them together ??

I remmeber seeing some work done by the Fab@Home folk who made a ball by printing out a half mould and then printing the ball into the half mold and the other half directly on top.

Add this to Nopheads work he has been doing with making seperable layers ie printing objects ontop of just printed rafts to get around base board issues and there may be the germ of an idea for a method in there.

The problem is the internal void of the boot. Rather than the curve of the top side (The ball method could possibly work for this)

I can't see how you would get around that without doing something like printing the boot in two parts ie upper + outer sole plus sole infil that could be welded/glued into the the base after printing.

All in all some experimentation to be done for someone with a machine.....

aka47

BTW. Put the strain gauges in the boot not the knee. Strain gauges are notoriously prone to trauma induced failure. ie they are pants with sudden shocks. Putting them in the boots is far less invasive than trying to repair/replace them in the knee.

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Necessity hopefully becomes the absentee parent of successfully invented children.

Hi Andy,

... remember the first posts in this thread: [forums.reprap.org] - this could be made with thicker and more complex shapes too ...

Viktor

Quite right I had forgotten that one.

Been too long looking at wooden Darwin Parts.

I guess given current state of art though someone needs to do further work on using a Darwin to mill.

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.

I've created a page in the objects library for the project:
[objects.reprap.org]

It's a wiki, so edit away.

*waves*

Anyways, just to assist you on the concept of ski-boots...

1) The "custom" part isn't really at all that custom--I have a pair that had its soles heat treated to mold around my own two feet while they were in the boots themselves. So, going from that, you should understand that rental boots don't really have that kind of (minimal) luxury built-in. I'll let you research termal-set foam soles on your own.

2) With that custom part out of the way, boots do come in standard sizes. Mine is around a 10ish--I'd have to check--but generally they all have a standard size "void" that your foot goes into. I'm gonna point to 1/2 inch as a rough estimate of padding between the shell and the foot, but again, research.

3) Following that line of thought, roughly 2/3rds of the boot itself is padding. This is primarily some sort of composite foam with a fabric covering; this is pratically an internal boot (without a sole) within the shell itself. The padding should do two things: pad the foot between the shell and body; and insulate the foot (as by default you're gonna wear only a thick sock, and that's no protection against the elements. I would recommend a soft to semi-soft plastic exterior (with a rigid tongue where the shell primarily contracts around it), then foam, and finally interlayered fabrics of choice for comfort and insulation. Research.

4) The shell itself is actually several layers of plastic; this varies from manufacturer to manufacturer. You've probably heard of "clamshell" boots--this is the most common type as the lower half and back are mostly one solid peice, with a hinge for the shin/tongue part and the buckles go across the top of the foot and with straps along the outer side of the boot. Others are a split-front type, like mine, where it's all one single shell and all the buckles go down the front of the boot over where the boot itself is "split" and folded over on itself. Regardless, all boots have the folded-over mechanism over the top of the foot. I can't tell what plastic is used, but I do know it's fairly rigid but with generous give when you bend it.

The sole itself is pretty much tough rubber; can't say much about it.

5) The internal mechanism are fairly unique from boot model to boot model, but all have a heel adjustment on the back. It's basically a big screw and a molded heel plate that helps adjust the inner boot against your foot so it stays on your feet better. The buckles themselves are always metal; I haven't seen plastic ones before, but I do know how much strain is placed on them--so that's right off the slope. Hinges, the same. The "belt" is pretty much there to keep the tongue against your calf to assist in buckling up and down--it does help in skiing, so I leave it on tight. Anything else should be researched--I've heard of strain gauges in the sole, but that's hearsay on my half.

I hope that helps!

Lampbus Wrote:
> I totally broke my ACL knee ligament in a high
> speed incident - the binding didnt release but I
> had them tested with my boots the same day and
> they where fine. Just the way I fell I suppose but
> I wont be taking unnescescary risks with my knees
> again. The boot is a critical part of the skiing
> process.

Somewhat off topic but...

There are situations where the forces in a fall are indistinguishable from the bindings point of view to normal skiing - unfortunately these are generally the ACL tearing types of fall. I've seen a boot (can't remember the brand) that claims to cope with this situation by releasing the back of the boot but I've no idea how well it works. Best solution is to take up snowboarding ;-)

Slightly more on topic - creating custom footbeds would seem to be an ideal application for a scanner / printer combo. The loads are primarily compression and high strength is not required. Physical scanning could be quite tickly though :-)

Hi Mark,

look at David-Lserscanner ( [www.david-laserscanner.com] ) for a simple 3D-scanning method - with better optics and a projected black line in a beamer-focus it could be more precise than with a line-laser, but as simple as the basic concept too ...

Viktor

Edited 2 time(s). Last edit at 11/07/2008 04:24AM by Viktor.

Wow thats come on a long way from when i last looked at it.

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Necessity hopefully becomes the absentee parent of successfully invented children.