Concept

This instructable will walk through the creation of a yoke prop, similar to that used by horses or oxen to pull heavy loads, out of packing foam. I created this prop for a cosplay (Big Macintosh of My Little Pony: Friendship is Magic, photos:http://tinyurl.com/kqpudrd), but the steps outlined could be used to create a variety of inexpensive foam based props for a variety of costumes.

(This is my first instructable, so please feel free to leave critiques and suggestions in the comments.)

Materials

The materials used in this project consist ideally of free or cheap scraps, but will allow you to create a reasonably nice prop.

The materials I used are the following:
(Optional materials are preceded by a '*'.)
(Yoke specific materials are preceded by a '†'.)

Packing foam
(Any sort of packing foam will work here as long as it can be cut into layers and glued together!)
Two Bottles of Glue
(Cheap craft glue)
Bread Knife
(This tool is to cut the styrofoam, longer, serrated blades are good)
* Vacuum
(To pick up foam particulate)
Scissors
(To cut out your paper pattern)
Paint/Fabric
(Whatever you plan to coat you foam form in- I wrapped mine in fabric)
Printer Paper
(You will use this to draw the pattern of the desired finished product)
Clear Tape
(This will be used to attach multiple sheets of printer paper together for large patterns)
*† A Bowl that fits nicely over your head
(Optional, but very handy for tracing to make sure the yoke fits over your head!)
A handful of Paperclips or Sewing Pins
(These are used to attach the pattern to the foam)
Drawing Utensils
(Pencil & Marker
* Duct Tap
Needle and Thread (*Curved Needle)
(To sew a cloth wrapping on to the foam form
† Handsaw
(To cut dowels)
† .5" Dowel ~12in [30cm]
(To form the metal protrusions of the yoke)
† Coat Hanger
(To form the metal protrusions of the yoke)
† Drill & Bit
(Drill Bit sized to match hanger)

Step 1: Prepping the Block

Prepping the Block
(Requires: Foam, Glue, paper) (Optional: Books)

To create a three dimensional object, we'd like to start with a large cube of foam, which we will carve into our desired shape. Now unfortunately, few of us have large, handy blocks of foam sitting around, so it is up to us to create the blank form.

This can be achieved several ways depending on the materials you have available. The foam I had came in many flat panels, so I stacked them to the depth I wanted. If you have rectangular pieces of any sort you should be able to use a similar stacking method to create the large block. If your foam takes more irregular forms, my advice would be to carve them into flat panels or another rectangular shape, then follow the steps I've outlined.

If the shape you want to create is larger than the pieces of foam you are using, fret not! Simply combine several pieces to create each layer. Be careful, however, not to place the pieces in the same pattern on each layer, or the gaps between the pieces will form large cracks in the final block.

Glue it all Together

Before beginning, cover your work area with paper to protect it from spilled glue. Keeping in mind the guidelines from above, lay the first layer of foam. Be sure the first layer is large enough for the object you are creating. Continue adding layers, applying glue generously between each, until the pile is taller than the desired object.

If you'd like, cover the top in a layer of paper and place some weight on it, perhaps a couple of textbooks. This may help the layer bind together better.

When you have completed your block of foam, move on to Step 2 as it dries. (Let your block dry overnight.)

Step 2: Creating the Pattern

Creating the Pattern
(Requires: Paper, Clear Tape, Pencil) (Optional: Bowl)

Now that you have a block of foam, it is time to create the pattern which will allow you to easily cut out the shape you desire.

Gaining Perspective

I recommend sketching the item you are trying to create from a variety of perspectives. Ideally you should have a good grasp of what it looks like from the top, front, and side. (For cosplays, find many reference images of the object from various images to get a clear view of it and its 3D shape. The shape may need to be modified, especially if it changes based on the vagaries of 2D animation, or is designed to be used by a non-humanoid, etc.)

Keep your sketches- they will come in handy in step 5!

Because I was creating a yoke, the top-down perspective most clearly defined the overall shape, so I used the top-down perspective to draw my pattern. Depending on your shape, a side-on or front-on view may best define your shape. Pick the perspective which gives you the clearest picture of the form you want to end up with.

(I will use top-down terminology for the rest of the guide, because it will match the example images.)

Note that drawing skills are handy, but not necessary for this step. The final pattern just needs to be vaguely the right shape and size. We will be touching up the shape in later steps.

Drawing to Scale

Once you have determined the appropriate perspective, tape together several sheet of paper until you have a sheet the size of the top of your block. Begin sketching the pattern on this sheet, remembering to size it appropriately for its desired use.

For the yoke, I first found a bowl whose rim fit over my head and ears. I traced this to form the center hole of the yoke. This made sure I didn't design the center hole too small to fit my head through. Once the center hole was in place, I drew the outer edge to match.

Once you have sketched your pattern, cut it out with your scissors and head to the next step!

Step 3: Attaching the Pattern

Attaching the Pattern
(Requires: Pins/Paperclips, Pattern, Foam Block)

After cutting out your pattern, attach it to the top of your block. Sewing pins would be ideal for this. Unfortunately I didn't have any on hand, so I used paperclips. (See the second image for how I folded them.) Use your pins/paperclips to pin the pattern to the foam securely. Focus on the areas that will not be cut away, but instead will form the object.

Step 4: Cutting

Cutting
(Requires: Knife, Foam Block) (Optional: Vacuum)

Once your pattern is attached, begin to cut along the edge. As you cut, be sure to keep the knife vertical.

Choosing a Blade

I used a bread knife because it was both long and serrated. A long blade was useful for me because my starting block was very thick, and the serration is useful because 'sawing' at the foam is far more effective than trying to use the sharpness of the edge.

I use a steak knife later for smaller areas because it is also serrated. Choose a knife that works for your shape, and remember to cut away from your body. (Rather than pulling the knife towards you.)

Tips and Tricks

If your layers begin to separate as you cut, attempt to hold them together till you finish the cut and add glue as needed to re-bind the layers.
As you cut, occasionally cut in from the edges of the block to allow excess material to fall off (see the second image). This removal of material will make it easier for you as you continue to cut.
As you cut, use a handheld vacuum to suck up the foam particulate to expedite the cleanup process.

Step 5: Shaping

Shaping
(Requires: Foam Form, Knife, Sketches)

Now that you have the rough stencil of the object you want, it's time to refer back to those top/side/front sketches you made in step 2.

Your shape is currently the top-down profile of you final product- we need to also include the front/side information to get the 3D product we want!

Looking from the Side
(Images 1-5)

Refer back to your side sketch while looking at your shape side-on. Note the shape from the side and compare it to the shape you currently have.

In my case, the biggest feature of the side view is the concavities for my shoulders. I started by using a sharpie to draw the shape I wanted to cut out on both sides of the foam. I ended up removing far more material from the shoulder areas than I anticipated based on how it felt to wear. (See the tip regarding wearable props below.)

Looking from the Front

Repeat that step with your front-on sketch. Note the differences that are most apparent from the front.

In my case the front-on sketch was not very helpful, and I relied on my other sketches throughout the rest of the process.

Tips and Tricks

If you are creating a wearable prop, try it on several times as you work, noting areas that don't fit well and marking them. I used a sharpie to mark where the yoke fit oddly, or where I wanted to remove material. This process will help make your prop fit well and be more comfortable in the end.
Feel free to draw all over your shape at this point, you will be covering the marks with cloth (or paint) later!

Step 6: Smoothing

Smoothing
(Requires: Foam Form, Knife, Sketches)

Once you have roughed out the shape you want, begin smoothing the edges.

I wanted a smoothed form factor, so I spent time rounding edges and smoothing areas where different angles interacted.

Details

If your final product contains a lot of details, this would be the time to carve those details into your foam.

Note that some foam is not suitable for fine details due to the large size of the granules it is composed of.

When you have your form the way you want it, move on to step 7.

Step 7: Wrapping (Part 1)

Wrapping (Part 1)
(Requires: Tape)

At this point in the instructable, I choose to cover my prop with fabric. I made this choice because it would be aesthetically pleasing, simple, and comfortable to wear. You may want to paint your prop instead, if so, please see the note at the bottom of this step.

To cover the prop with fabric, we will first create anchor points to which we can fasten the end of the fabric. To do this I wrapped three portions of the yoke in duct tape. This allowed me to sew the end of a strip of fabric to these anchors and wrap from that spot. I only covered three spots because I ran out of duct tape (hence the mix of colours), you may want to coat the full prop for easy anchoring at any point.

Wrap the duct tape around the object at intervals to provide spots to later anchor strips of fabric. If your shape is complex, give yourself many anchor points, especially near corners and in the center of large flat areas.

This process will also strengthen your prop and prevent layer separation during use. When you have finished, move on to step 7 (part 2)!

Painting

Should you desire to paint your prop, please be aware of the following:

Normal spray paint will literally melt styrofoam, you must coat it or use styrofoam specific paint!
Things to coat your foam with include: plaster of paris, 'foam finish', or Mod Pod
This article has a few details about painting Styrofoam:
http://www.thriftyfun.com/tf66117542.tip.html

Step 8: Wrapping (Part 2)

Wrapping (Part 2)
(Requires: Needle, Thread, Cloth, Scissors) (Optional: Curved Needle)

To wrap your new prop in fabric, begin by cutting your desire fabric into strips.

Fabric Colour

I chose two shades of brown for a bit a variation on my yoke. Often a single colour will be the best choice.

Fabric Width

For a shape of similar complexity to the yoke I made, cut strips that are about 4in [10cm] wide. For a more complex shape you will probably want to cut thinner strip to make the wrapping easier.

Anchoring

To start a strip, lay the end of a strip of a duct-taped anchor area and use needle and thread to sew the cloth to the anchor. I originally purchased a set of curved needles to facilitate this process, but found that straight needles were actually easier to work with.

Wrap the strip around the prop tightly until you come to the end of the strip. Remember to overlap the edges of the strips generously- a thorough 'coating' is important. The more overlap you have, the less thoroughly you have to sew each wrap down to prevent exposed styrofoam during use.

At the end of a strip, either sew it to an anchor, or sew the end of the current strip to the beginning of a new strip. You may want to trim the end of a strip such that it ends in an inconspicuous location so the seam is hidden. (For example, all the seams on the yoke are inside, next to my neck.) The photos illustrate how I chained strips until I reached the next anchor to which I could attach an end.

For extra strength, you could sew the edges of each adjacent strip together so no layer could slide and reveal the inner foam. I chose not to do this, but instead rely upon the tightness of my wrapping to hold all the strips in place.

Once you have completed the fabric outer layer of your prop, congratulations you now own your very own fabric-covered-foam-prop! ^.^

If you are constructing a yoke like me, proceed to step 8 to attach 'metal' prongs to your yoke.

Step 9: Adding the 'Metal' Pegs

Adding the 'Metal' Pegs
(Requires: Foam Remnants, Knife, Dowel, Coat Hanger, Drill, Drill Bit sized to hanger)

Big Macintosh's yoke has two metal protrusions on the back which seem like aesthetic derivatives of the upper part of an oxbow. (Based on a few minutes of wiki searching for what to call them... Heh) Regardless I am sure they are handy for tying ropes to.

The Rods

To recreate these utilitarian hunks of metal we will first fashion the rods from wooden dowels. Cut two approximately 6in[15cm] lengths of dowel.

Take the drill and, using a drill bit just a tad narrower than the coat hanger to have selected, drill an deep hole in one end of both dowels.

The Balls

Next we will fashion the spheres at the end of the rods. To do this we will use a method similar to how we constructed the yoke. Cut several layers of foam larger than the orbs, and stack them. Use your knife to bore a hole through the stack and thread them on to the end of your dowel (opposite the end with the hole). You should now have a rod with a block of foam at the end. Use your knife to trim off the corners of this block repeatedly until you smooth it down to a sphere.

Repeat this process with the second dowel, attempting to achieve a similar sized sphere.

Wrapping the dowels in silver cloth is probably the best choice here. I had no silver cloth, so I opted to wrap both pegs in silver duct tape to hold them tight and colour them. Now you have two silver pegs ready to be mounted on your yoke!

Mounting the Pegs

To mount the pegs, begin by untwisting your coat hanger until it is straight. Then fold it in the fashion depicted in the fourth image. The length highlighted in red should be long enough to pierce the back of the yoke and extend about 3/4in [2cm], in other words, just long enough to pass through the yoke and into the dowels. The fifth image shows a side-on cross-section view.

After bending the wire, stab both ends through the fabric and foam to come out where you desire your pegs to attach. If they don't end up just where you want them on the first try, fear not! Simply remove and aim the wire again, the foam is forgiving.

Once your wire is in place, press the dowels firmly on to the bare ends of wire. They should fit snugly. If your holes are simply too small to allow the wire, select the next larger bit and re-drill them. A bead of glue in the holes will result in a permanent bond, though if your clearances are similar to mine, you may not need glue for them to be firmly attached!

Step 10: Finished!

Finished!
(...Profit!)

If you have completed the previous steps you should now be in possession of your very own yoke!

Congratulations!

If you have ideas to improve the design please comment and I will add them to the appropriate section. :)

(Photos of me wearing this costume: http://tinyurl.com/kqpudrd)

Introduction: Cheap Foam (Yoke) Prop