Introduction: Cartouche: Wooden Heart Locket

Picture of Cartouche: Wooden Heart Locket

Introduction

The intention of this project is to design and build wooden locket similar to the one shown in the film The Illusionist.

The film's main character: Eisenheim (Played by Edward Norton) describes the wooden locket as a Cartouche which is derived from Egyptian hieroglyphs, roughly meaning an oval with a line at one end.

As you can see from the embedded video, the locket incorporates a double hinge system in order to twist in half, before the lid can then be opened.

Research

I had researched several different methods of achieving the locket hinge including these other instructables:

  1. The Illusionist's heart
  2. Illusionist Heart Locket

  3. Illusionist locket: A how to.


Abstract

Wanting to achieve a true double hinged locket as per the film, I set about designing the locket in a similar style as research item #3 the 'Illusionist locket: A how to.' by nazdreg2007, whilst also bringing in a few touches from the work of others.

I designed a tailored a logo onto the front which would then transform into the first letter of my wife's name once the locket was twisted into heart configuration. However due to a miss assumption made by myself, half of the logo inscription was unfortunately on the wrong side. I highlight the error, so that you can avoid my misfortune.

Once the locket had been designed, using AutoCAD I created a PDF of my design the work in vector format (a good guide can be found here ) in order for the manufacturer to laser cut work-pieces from 1.5mm walnut using a CNC machine. Once the parts were then returned to me, I manufactured the hinges (one 'split pin' and one 'bent pin' hinge), and performed the final assembly.

I found that creating the Cartouche locket is a very rewarding project, however there are a couple of very fiddly, time consuming sections that can easily be done wrong and require rework.

I recommend that if you are attempting this project, you:

  • Like me, double up on all work-pieces in case of breakage.
  • Have lots of patience
  • Unlike me, model all of your work-pieces using 3D CAD system to ensure correct design.
  • Look into making each layer thicker than 1mm. This would make the locket stronger, and enable easier addition of the magnets. (Magnets help to maintain the stiffness of the locket.)
  • If possible to source a small enough double ended barbell, it would be a more suitable hinge than the 'bent pin'
  • double up on the laser cut pieces. (it will probably cost you no more to have two of each piece laser cut. you pay for the size of wood used, so if you have spare space, have duplicates made. This is particularly important for the more delicate middle layers.)

Step 1: Equipment

Picture of Equipment

I required:

Mechanical Equipment

  • Fine Cut Razor Saw (Important - £12.99)
  • Vernier Caliper (digital versions also suitable - £15.00 upwards)
  • Drill (£ Various)
  • Spirit level (if you have a lathe that would replace the need for both the drill and the spirit level - £ Various)
  • Small circular neodymium magnets, (used to ensure both halves of the split pin hinge remain in contact during transition - £5.00)
  • Fold out work bench (woodworking vice would have been more suitable, but I don't have one. - £25.00)
  • Wood-glue (£4.50)
  • Various grades of sandpaper
  • woodworking file (£15.00)
  • G clamp (or vice - £10.00)
  • Laser cutter (or send your design out for manufacture.) 4D are brilliant.

Design equipment

  • Computer (you probably have one of these.)
  • AutoCAD (or similar design software, Solidworks, or Creo etc..)

Materials

Step 2: Design

Picture of Design

The most important aspect of the design for me was ensuring that the locket was personalised.

As the locket was going to be a gift to my wife, I first focused on how the locket would appear in heart formation. As her name begins with M, I designed an M onto the heart shape. The next step was to decide what relevant image i wanted in standard formation, that could then be translated into an M.

Recognising that the spit line was effectively a mirror in heart formation, I set about finding a shape or embalm which has the top (or right hand side, similar to an M).

After playing around using a sketchpad, I chose a 'Quaver' over a 'Dove', and moved onto the CAD stage.

Using a similar design concept to Nazdreg2007 as previously mentioned, I drew up my own design ideas on AutoCAD. Warning - This is where I made two mistakes.


AutoCAD design

As the design is complex and tricky to visualise in 2D, I should have modelled it in 3D including the pivot and the split pin, prior to converting to a 2D dxf for the laser cutter to use. As I didn't, I made an assumption that previous design works were 100% correct. In particular the pivot pin, was situated on the incorrect side of the part.

I also misplace the left hand side of the M. It appeared on the underside of the lid.

At this point you want to familiarise yourself with the dxf file if possible.

In spite of these two aforementioned mistakes the CAD design steps are as follows:

  1. Select a suitable size for the locket - I chose 40mm x 20mm and drew out four outlines. (Notice that I actually made eight, this is because I doubled up on all pieces in-case of later mishap.)
  2. Cut and bend the dress makers pin (use wire cutters). - I wanted a short pin with a 90 degree bend in one end. I found it very tricky to get the bent pin to the dimensions I wanted, so I changed the dimensions to meet that of the already bent pin. (I have since decided that a simple miniature barbell would be more suitable than a bent dress makers pin.)
  3. Sand down the spherical end of the dress makers pin - This is a tedious task. You want the ball to be small enough so that it wont poke through too much of each layer. Use sandpaper, and keep at it! use the Vernier caliper to measure the finished pin, and add the suitable size diameter into your drawing.
  4. Add remaining detail to the CAD model - This included the images, and the internal cut-outs.
  5. Check that your line weights, colours and etching depths are correct - choose a suitable manufacturer, (if you don't have your own laser cutter) and check their drawing requirements and meet them!
  6. Add a scale

Drawing advice:

  • The manufacturer / your laser cutter, will not be able to meet tight tolerances on depth.
  • Don't design your pieces too close together, the laser may burn your wood.
  • Don't be tempted to make pieces very narrow. - These pieces are delicate.
  • Avoid sharp corners. - Stress raisers will make your work-pieces more likely to break.

Step 3: Glue the Middle Layers Together

The locket has four layers in total. This section focuses on gluing together the middle two layers

  1. The first part of the assembly is to create the wire attachment for the locket.
  2. I simply made a loop of wire, and then wound one end around my needle nose pliers three times (to make an attachment loop). I then then twisted the other end around the wire several times, completing the whole loop.
  3. Insert the loop into the cut out U-shape slot in the middle layer, and seal it in place with some wood-glue.
  4. Now place the bent dress makers pin into the dedicated wooden slot, and check it fits snugly into the groove.
  5. Place the other wooden middle piece over the top, and check that the pin can rotate freely. If not sand down the pin head more, and/or carefully carve out more wood from the groove using a knife.
  6. Once the pin head end is rotating freely, check the bent end fits snugly between the two layers on the other side.
  7. Once you are happy with both ends of the pin, and the middle layers of wood. glue them together using wood glue. Be careful not to get glue anywhere near the rotating end of the pin (with the head).
  8. Clamp the layers of wood together carefully using a G-clamp or similar, and leave to dry for a few hours.

Step 4: The Split-pin - Part 1

Picture of The Split-pin - Part 1

The split pin is a very delicate and important part of the assembly. If your locket will not operate correctly, it is likely to be down to the split pin.

The Split-pin is a stepped-dowel that is sawn in half. It enables the lid to rotate in the heart configuration. However it must be split in half for the locket configuration.

To make the spit-pin

(you will notice from the DXF file or the to scale drawing, that the larger section of the split-pin dowel has a diameter of 5mm, with the inner 3.5mm.)

  1. Insert the wooden 6mm dowel into a lathe (I used a drill mounted onto the workbench, then ensured the dowel was level using a spirit level).
  2. Spin the drill, and reduce a wide section of the visible dowelusing sandpaper.
  3. Using the Vernier Calliper make the diameter just below 5mm (4.8 will do), along a length of around 30mm.
  4. Sketch a straight line around the circumference of the dowel. (This indicates where you will further reduce the diameter down to 3.5mm)
  5. Using a wood file, Vernier calliper and a steady hand, carefully reduce the diameter of the dowel to 3.5mm for a 10-15mm length. (This piece shall now be known as the stepped dowel)
  6. Check that your dowel slides nicely through the first layer of the locket (in heart shape), and stops neatly at the dowels change in diameter.
  7. Mark a centre line around the length of the dowel (symmetrically halving the stepped dowel)
  8. Using the vice or workbench secure the piece,
  9. Begin splitting the stepped dowel in half using the razor saw.
  10. Just before you get halfway down the pin, repeat the process from the other end.
  11. Again, just before half way, you want to cut the sides. (using your all ready cut lines as a guide for the saw.)
  12. Once you have completely split the stepped dowel, lightly sand the inner sides to ensure they fit together smoothly.

Step 5: The Split-Pin - Part 2

Picture of The Split-Pin - Part 2

Inserting magnets

I put magnets in each half of the split pin. This helped to ensure the pins stayed together whilst the heart lid on the locket rotates. It's up to you whether you use the magnets, the pins will still work without them.

Warning: If you do use magnets, be sure to keep them away from young children.

Note: Be mindful of magnet polarity

  1. Using a 1.5mm drill bit, make a small hole (deep enough so that the magnet will be completely flush with the dowel) In the split pins near the step (change in thickness) of the dowel.
  2. Ensure that the magnet it is in the same location on both sides of the pin.
  3. Use wood glue to fix the magnet in the dowel and leave it to dry.

Cutting down the split-pin

Both ends of the split pin(s) need shortening now. On the narrower end a square tab needs cutting into the split pin, which will fit into a groove on the underside of the lid, and be glued in place.

The opposite (wider) end of the split pin(s), the length needs reducing to less than the thickness of one of your wood pieces (mine were 1.5mm).

Suggestion: Cut the narrower end first.

"It is always best to measure twice, and cut once."
  1. Cut straight vertical lines down through the length of the dowel from either side, (leaving a square or rectangular section through the middle.
  2. Cut a groove the same shape in the underside of the lid-piece using a sharp knife (or similar). Note: If you have got the design/laser-cut stage correct, you could have had this notch laser cut out.
  3. Shorten the square end of the split-pin, using a combination of the saw and sand paper. Ensure there is enough excess, to fit inside the notch on the underside of the lid. (you can use the Vernier callipers again to make sure the length is perfect.)
  4. Once the square end is the right length, saw off the wider end of the split pin. Ensure that the end is recessed within the middle layer hole when assembled, (no part of the dowel is sitting proud of the middle layer) otherwise it will grate on the rear of the locket and not turn.
  5. Check everything fits together, and then affix the two rear pieces onto the locket using wood glue. (Be careful to keep the pin away from any glue.) - If you want you can make this the last step of the whole locket assembly, but found it fine to do it now.

Step 6: Glue the Small Split-pins Into the Lids

Picture of Glue the Small Split-pins Into the Lids

Use wood glue to fix the pins into the lids.

Suggestions:

  • Ensure the pins are vertical.
  • Give this part 24 hours to dry. (I didn't at first, and wished I had.)

Once dry, carefully slide the lids with split pins into the locket. (This is easiest with the locket at 90 degrees angle).

Congratulations!

Step 7: One More Thing...

Picture of One More Thing...

Add a hidden message into the secret compartment of the locket!

You don't get to see what it says I'm afraid :P.

Comments

stechi (author)2015-01-11

Hi, I like this project, might try it! Does your message get cut in half when you rotate the two halves? Not sure I quite understand it yet!

forerunneruk (author)stechi2015-01-11

Hi Stechi

Thanks for your comment.

Yes you do cut the message/image in half, although you have the opportunity to either make a new message/image, or show the same message again if you are clever. see here:

That's a unique way to show a message.

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Bio: Design Engineer
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