This is an OpenSCAD application producing a print file for a 3D-printable spikes bracket, fitting your personal hiking shoe (or your kids').
The enclosed .stl files are for illustration only and will most probably not fit your shoe or your Velcro or your nails (see below). But you will be able to easily amend the dimensions. Therefore I call my contribution a "factory". Read on.
Update 13 March 2022:
Today I tested the strengthened design in nature on the same route as the initial design on 6 March. Snow having melted away slowly there was a significant higher percentage of my trail on gravel (> 50%), stressing the hard PLA much more than snow or ice. I did not treat the brackets with care under these circumstances because they are still prototypes and I wanted to test their strength.
The new design withstood the challenge and remained intact. I will therefore stick with the current bottom and wall thicknesses. I sliced for three top- and bottom- and four perimeter-layers, 50% infill and 0.3 mm layer height.
The cover slab's mounting is fiddly and needs improvement.
During transport the protruding nail pins may damage the backpack. My idea is to design a mount which holds the brackets underside-to-underside with the nails inserted into holes of each other bracket.
If you print it for four spikes but mount less spikes you will have to fill the empty mounting holes with spacers in order to avoid crushing the bottom under the empty mounting holes (e.g. while walking on pointed gravel). I may provide a printable solution for this.
Update 9 March 2022:
I designed, printed in PLA and uploaded a much stronger design (see option (1) according to the list in my 6 March update below) with carefuly rounded inner and outer edges, but have not tested it in mother nature yet.
You may now choose between 2, 3 or 4 spikes in the parameter section of the source file. Less spikes (i.e. 2) is advantageous on ice because you will exert more pressure per mm2. More spikes (i.e. 4) may be advantageous on hard snow because more spikes will have to move more snow before you start to slip. The cover and the spikes are easily removable: You may even print for 4 spikes and install only as many as required by the circumstances of the day's hike.
The tabs of the cover are still a bit hard to insert into the slots and require some grinding of the corners.
I added grooves to improve grip on soft snow. May be they should be deeper.
I added a gauge to cut the nails to size. Put the gauge onto the nail shaft and move it up to the head, insert the end of the nail shaft into a vise and cut it with the hacksaw parallel to the gauge.
Update 6 March 2022:
Today I tested the spikes brackets while hiking in the mountains. The grip was surprisingly good uphill and downhill on ice and hard snow (as e.g. on crowded hiking trails). Of course it was important to walk uphill "heels first".
It was a bit less performant uphill on soft snow and it failed on glass-like hard ice very steeply uphill or downhill. For soft snow the underside should bear a profile imprinting into the snow. For the steep-angled ice the nails should have a smaller diameter to better penetrate into it under my weight. I also walked on concrete and gravel.
After an hour I took them off and only then I noticed that both brackets were broken. But they had not yet failed to fulfill their function. The current construction and dimensioning in combination with the very hard material (PLA) could not sustain the mechanical loads on uneven hard ground (e.g. uneven ice, gravel).
The weak spots were the 90 degree angle between wall and bottom of the main part, and the bottom itself. The Velcro attachment region was ok.
There are basically three ways to improve:
(1) Make it stronger (thicker bottom, reinforcings, rounding of sharp edges, ...).
(2) Make it more flexible (e.g. TPU, Polyamide or a new segmented design while still using PLA).
(3) Make it stronger as above and attach a piece of rubber to the underside in order to distribute loads more evenly.
For the time being I will have to keep the "Work in Progress" banner.
The workflow is as follows: You will have to measure the heel width of your hiking shoe before adapting at least this parameter (and possibly several more) in the enclosed OpenSCAD source file, render it and export a file for slicing and printing.
Bill of materials (apart from your 3D printing environment):
- Two samples of Velcro tape, each around 2.5 cm wide and around 75 cm long, preferably with a buckle.
- Six steel nails with oversize heads as e.g. used to mount soft insulating slabs to a wall. I use nails with a 3.1 mm shaft and a 20 mm diameter head obtained from a local DIY shop.
- A hacksaw to cut the nail shaft to a suitable length.
If the width of your Velcro tape or the dimensions of your nails differ from mine you will have to amend the respective parameters at the top of the OpenSCAD source file.
Proceed as follows:
- Download and install OpenSCAD from https://www.openscad.org
- Launch OpenSCAD and open the enclosed OpenSCAD source file (/File/Open).
- Amend the parameters at the top of the file.
- Save your changes (/File/Save).
- Render the design (/Design/Render). This may take a minute or so, depending on your PC. Observe the progress bar.
- Export the rendered design e.g. as a .stl file (/File/Export/Export as STL).
- Slice and print.
- While printing, cut the nails' shafts to size with the hacksaw.
- When printing completed: Insert the nails into the 3D-printed main part. Mount the 3D-printed cover on top of them by bending it while inserting the three tabs into the slots of the main part. The idea of the cover is to keep the nails in place when not wearing the spike bracket.