Introduction: High-heel, Clipless Bike Shoes
I was inspired to make these shoes on my ride home one evening when I witnessed a beautiful woman riding in high-heels along Market Street in San Francisco. True to form, I will acknowledge that I noticed the sexy handmade bike before the woman, and what was (perhaps, unfortunately) most noteworthy to me was how awkward the connection was between the pedals and the shoes.
Having recently built up a bike for my beloved, I was immediately taken with idea of making high-heels with a clipless cleat. I had been keen to build a pair shoes for a while and the curves of a high-heel shoe seemed like an inviting challenge.
Indeed, it was a challenge. The project spanned about 18 months, and sadly, outlived my relationship. However, don’t let this dissuade you – if I had worked straight though on the project, it would have only taken a few months, and if you can make these shoes, you are probably capable of not loosing the relationship with a wonderful girl.
Step 1: Find a Benchmark
I surreptitiously looked through her collection of heels until I found a pair that looked most suitable for riding – if any are – and well worn. I then photographed these shoes and used photoshop to extract the base curves. I then pulled these curves into Solidworks and began lofting the sole
Step 2: Drawing the Sole
This was a little more interesting than expected. I tried many combinations of extrusions and lofting before finally giving up and lofting the entire thing.
The challenge in lofting the entire shoe is, as usual, building a nice set of guide and profile curves. I made a spine curve down the center of the shoe from the top view. I then projected that across the side profile of the top and bottom outline of the shoe. This formed outline guide curves for the front of the shoe.
Once I had the top and bottom spine curves, I created a set of planes perpendicular to these spine curves and set about making the profiles.
The final trick was to separate the forward loft from the heel and loft the heel separately.
I also recessed a section in the top surface of the sole to allow space for a leather insert. I modeled this surface as a sheet metal loft so that I could unwrap it to create the pattern for the leather insert.
The final Solidworks file is attached. This is modeled as a size 6 shoe.
Step 3: Realizing the Sole
Material: I found a nice chunk of Zebra wood at Macbeath Hardwoods in Berkeley (Macbeath was super helpful and has a huge selection!). I am not sure that I would use Zebra wood again since there seems to be so much sensitivity on machining in a direction which is commensurate with the grain.
Pre-processing: Rather than trying to get the toolpath perfect, I did a quick lofted path with a ½” ball endmill and planned on a lot of finish work. In retrospect, a more subtle approach would have been less work in the long run.
Machining: I trued up the block with a large shell mill so that when I flipped the part, I would be able to find the center again. In total, it was about 5 hours of machining (Zebra wood is incredibly dense – it would have been easier to machine aluminum). Obviously, wood is not great for machine tools, so actively cleaning as you go is a good idea.
Step 4: Finishing
Finishing was lengthy. Since I was insensitive to the grain while planning my toolpath, there were chunks of wood that had been pulled out by the cutter in the machining process (it remains unclear to me whether climb or conventional milling is better). I filled these with epoxy.
For the sanding, I started with a pneumatic angle die grinder which is an amazing tool for finishing almost anything – it is lightweight and powerful. Following this, there was a lot of manual sanding. Still more sanding and ever more sanding.
Finally, when things looked reasonably smooth, I propped the shoe up on the tips of drywall screws and painted on a thin layer of epoxy. I made a mistake here and added some mico-ballons to the epoxy to increase the viscosity for filling voids in the wood. This has the undesirable effect of replacing the voids with small white dots… ugg.
After more vigorous sanding of the epoxy layer, we sprayed the shoes with a layer of Polyurethane which made them beautiful… do not skip this step.
Step 5: Design the Straps
The straps were an enlightening adventure unto themselves. I was surprised to find that straps on heels are commonly symmetrical left to right across the foot. However, all feet that I have seen are far from symmetric, and hence, it seemed like an asymmetric design would be far nicer.
I experimented with modeling her foot from memory and creating developable lofted surfaces (sheet metal parts in Solidworks). This was useless, and since the surprise was … well, over (see step 4) … it was a lot easier to do the typical dress making approach and cut to fit.
Using some of the basic curves I had developed in Solidworks, I cut out a set of paper templates and fit them to her foot. After about 7 iterations, I found something that liked.
Step 6: Build the Straps
I went to Britex in San Francisco and bought some nice, supple blue leather. I then added seam allowance (4 mm) to the paper pattern in Solidworks and cut the straps out with a laser cutter. Leather cuts very nicely with a laser.
I then attempted on a number of occasions to sew the straps. After failing on all attempts, I capitulated and hired a friend who is a pro, Bree Hylkema, to finish the straps. She did a wonderful job. Sorry, I don’t have any pictures of this – imagine a very skilled woman sewing with intimidating precision.
In finishing the straps, Bree added some stiff canvas into the center of the layers of leather to prevent the leather from stretching.
Step 7: Final Assembly
The final assembly was straightforward. I attached the straps with 3 mm machine screws. Machine screws in wood are awesome – pre-drill with the standard tap drill size and add the screw. For the back of the strap, I had to remove material to hide the strap thickness under the sole leather.
Some of the leather for the sole had been misshapen during the sewing process. I found it easy to bring it back into shape with an iron and a light misting of water.
Step 8: Make a Box
It seemed like they needed a box...