Introduction: 12-sided Dice Lampshade
Moving into my new apartment, there were a few things I needed – a lampshade was one of them. Why buy one and settle for what’s available when you can build one? A non-cubic dice (popularised by role playing games such as Dungeons & Dragons) came to mind. These dice are synonymous to gaming culture and is a cool accessory for anyone, even if you don’t get the “I roll 20s” joke.
Step 1: Design
I decided to go with a 12-sided dice. This is a regular dodecahedron which consists of 12 regular pentagonal faces. The mathematical nature of these shapes makes it easy to scale this project up or down depending on your needs. [For the rest of this project I’ll just refer to the dodecahedron as the dice – it’s easier to type.]
To determine the size of the pentagons I measured from the base of my lightbulb to the distance I want the top face to be. I used this as the diameter of the dice’s inscribed circle, Di. This relates to the side length of each pentagon, L, by the following approximate formula: L=0.45*Di. From this a side length of 120mm was chosen.
The structure is built from bamboo skewers and covered with paper. No covering is added to the bottom pentagon as the lamp screws on there. Also, a lid was added to the top of the dice to enable access to the lamp.
For the base of the lampshade, the fitting of an old lamp shade was used.
Step 2: Materials
- Bamboo skewers
- Epoxy glue (clear); any clear, hard-drying glue should work fine.
- Adhesive tape (thin, clear); using clear tape is important as it doesn’t show up against the light. Darker hues might. Rather test your tape against the light before using it.
- Prestik / Clay
- Paper for covering (type dependant on preference)
- Side cutter
- 2x cable ties
- Old lampshade fitting; for this project I’m modifying an old one. If one is not available it can easily be constructed from some wire.
The lampshade is constructed from rather inexpensive materials. I had all of the tools so only the skewers needed to be bought.
Step 3: Preparing for the Pentagons
Pick out the best looking skewers and cut them into 120mm lengths. As each pentagon is built individually you’ll need (12x5=) 60 sticks.
Print out a page with a circle, the diameter (Do) can be calculated with the formula for the outscribed circle of a pentagon: Do=1.7L. For 120mm side length you need a 204mm diameter circle. Lay out the pentagon so that the circle inscribes it, mark the location of the corners on the circumference of the circle. Make another 2 pages like this.
Step 4: Building the Pentagons
Place blobs of Prestik/clay (about 5-10mm high) on each of the marked spots on the circle circumferences. The Prestik/clay allows for re-use of the guides, holding of the sticks and helps to avoid gluing the pentagons to the paper.
Build the pentagons on top of these blobs. Epoxy the corners of the pentagons together, letting the epoxy flow to the inside. Allow time for the glue to settle and then remove the pentagons (along with the Prestik) from the paper and leave to dry.
Repeat using the same guides until you have made 12 pentagons.
Step 5: Building the Base
Remove everything off the old lampshade so that only the support frame remains. Cut off excessive metal and use the pliers to flatten the structure. Draw a pentagon on the guide and use this to align the spokes of the frame with 3 of the sides. Choose a pentagon to use as the base (one should be dry enough by now), place it on the frame and mark the edge crossings. Bend the spokes to cradle the pentagon, ensuring it fits snugly. Cut the uprights just after the bend (2-5mm up) – your frame should cradle the pentagon but not stick out above the pentagon when viewed from the side. Finally, epoxy the frame to the pentagon.
Step 6: Choose the Covering
- The darkness of the paper colour will determine the amount of light let through
- Type of bulb used and heat resistance of the paperI used normal white A4 paper with black numbers printed on them. Choose a font you like, exclude your least favourite number from 1 to 12 (the bottom has no number), centre a number on each page, increase font size to taste (300pt works well for these pentagons) and print the 11 pages. Alternatively you can paint, draw, cut, burn, whatever the numbers on the paper.
Step 7: Pause and Plan
Before covering the pentagons, take a moment to plan. The dice is essentially made up of two flower-like 6-pentagon patterns – one for the top and one for the bottom. Map out the numbers that you want to put on each face taking note that if you want all the numbers to be upright when finished, you need to change your orientation when covering 5 of the pentagons. Thus, 5 pentagons will have a flat edge below the number, 5 pentagons will have a corner below the number and the orientation of the last pentagon (the top one) doesn’t really matter.
Step 8: Cover the Pentagons
To account for minor shape variations between pentagons, cover them fully one at a time.
Place a pentagon on the back of the covering paper. Mark the corners (keep tightly to the pentagon). Use a ruler to crease the paper from corner to corner to the inside. Cut along the creases and remove the paper not adjacent to the edges. Cut a little lip (5-10mm depending on the thickness of the skewers) around the edges of the pentagon shaped paper – just enough to fold around an edge.
Place the pentagon on the paper, fold the lips back over the edges and stick with the clear tape. Wrap the paper as tightly as possible to the pentagon, just make sure you don’t warp or break the shape.
Step 9: Assemble the Dice
Unless you can work with machine-like accuracy, you should start noticing the small inaccuracies during this step. Some pentagons will fit better with other, move them around a bit to find a happy place. Also, make ample use of the Prestik during the assembly phase to keep things in place while you motivate your pentagons to fit where you want.
Start with the bottom section of the dice. Use clear tape to stick the edges of the bottom 5 numbers in a semi-circular pattern. Fold the pattern up when sticking the last two edges. Place the pattern on the bottom pentagon and epoxy the 5 bottom corners (3 pentagons meet at each one), as well as the 5 upright indented corners (2 pentagons meet at each of these).
Make the same semi-circular pattern for the top 5 numbers. This pattern then fits on top of the bottom half. You may need to rotate it a bit to find the best fit. Using a spare skewer for access, epoxy the 10 corners where the bottom and top sections meet. Turn over the dice and epoxy the base of the top section.
Step 10: Check for Leaks
At this point it is possible to check for any light exiting from the corners or edges of the dice. Identify them and remedy:
- Tightening the connecting edges with clear tape fixes most minor leaks.
- For big leaks, sticking think strips of paper on the edges inside the dice helps. Be careful when working on the inside of the dice from the outside – it’s easy to tear the paper or break away parts from the dice.
Step 11: Add the Lid
To allow access to the lightbulb and the inside of the dice, the top pentagon is not epoxied to the rest of the dice.
Make two small slits in the paper of an inner edge of the top pentagon. Do the same for the connecting upper pentagon on the dice, making sure the slits are aligned. Feed the cable ties between the paper and the stick of both pentagons. Make sure the cable tie closes on the inside. Tighten the cable tie as much as possible whilst still allowing the lid to open freely. Cut off the cable tie excess.
This step can be skipped if there's no chance of the top piece being bumped off and provided it fits on top without falling in. You can then simply place the top on the dice.
Step 12: And There Was Light
Screw the lampshade onto the lamp, put in the bulb, close the lid, switch on and enjoy.