A Candelabrum for Halloween

This candelabrum represents a simplified model of the skeleton of the human hand (a left one) which raises from the table in a relaxed posture while carrying lights on the points of its fingers. A skeletal hand that raises from a table or another flat surface is a unique phenomenon proper to Halloween, and you could reproduce it by following the indications presented in this Instructable.

(Reference

https://en.wikipedia.org/wiki/Hand#/media/File:Handskelett.png

https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/anatomy-of-the-hand

Supplies:

Materials

bamboo sticks with the diameter of 8 mm (approximately)

wooden beads with the diameter of 10 mm

glue gun sticks with the diameter of 7 mm

plywood 20 mm thick

plywood 8 mm thick (for the templates)

plywood 4 mm thick

black paint

white paint

epoxy glue

Components

five flickering amber LEDs (to play the role of candles)

current limiter

power adapter 110/220V to 12 V

jack

on-off switch

wires

LEDs, current limiter and switch were bought at http://lighthouseleds.com.

Tools

saw

fretsaw

drill with drilling bits

wire cutters

exacto knife

file

soldering iron with solder

sandpaper

brush

Teacher Notes

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Step 1: Fingers

The fingers are made of bamboo sticks (fig.1), and the joints - of wooden beads. Through holes with the diameter of 4 mm should be made in the sticks, and the central holes in all beads should be enlarged by drilling to 4 mm of diameter. The holes in the sticks should be countersunk to the diameter of around 7 mm on the ends where the stick will be glued to the bead, see fig. 2, it’s necessary to increase the contact surface between the stick and its corresponding joint, see fig. 7. The holes in the beads should be countersunk to the diameter of 6 mm (see fig. 3) where the bead will contact the stick, to provide enough space for the wires which will pass through the fingers.

The sticks and the beads are joined according to the diagram in Intro section; a template shown in fig. 4 is necessary for this operation. The first two ‘phalanges’ (counting from the end of the ‘finger’) of a ‘finger’ are assembled by using this template.

All three phalanges of the middle finger and the thumb lie in the same plane, that’s why these fingers could be assembled as shown in fig. 5. On the contrary, the phalanges of the other three fingers lie in slightly different planes, therefore, the template shown in fig. 6 should be used to join the 3rd element (scientifically - the metacarpal bone) of these fingers to the first two phalanges.

You observe that the ends of the fingers are not perpendicular to the vertical; however, the flame of a candle should be essentially vertical. Figs. 8 and 9 show how I modified the ends of the fingers to ensure that the LEDs, and, consequently, the ‘flames’, be vertical. (In fact, they are not exactly vertical, but let’s imagine that there’s a draught in the room). This modification should be made after the fingers are installed to the wrist, when the fingers’ tilt is well defined.

Step 2: Base

The bottom part of the base is made of 20 mm thick plywood, it’s a 100 x 100 mm square having a central hole with the diameter of 80 mm; the wiring would be placed in this hole. There’s a groove to place the jack and the switch; the size of the groove depends on the size of these components.

The top part of the base is made of 4 mm thick plywood, it has two holes with the diameter of 10 mm to install the assembled hand.

The base is painted in black.

Step 3: Wrist

The wrist consists of the top and the bottom parts, both being made of 20 mm thick plywood. Fig. 1 and 2 show the top part; figs. 3 and 4 show how the joints of the fingers are glued to the wrist.

The bottom part is shown in figs. 5 and 6. Both parts have a groove to accommodate the wiring which passes through the wrist.

Fig 7 shows the ‘big bones’ (scientifically - the radius and the ulna) inserted into the bottom part of the wrist. The diameter of the ‘bones’ is 10 mm, theirs length is 100 mm.

Step 4: Wiring

I made it with rigid wires used in phone cables; if you use soft wire, you might consider passing a thick fishing line through the assembled fingers - it would to facilitate the passage of wires. Fig. 1 shows the wiring passing through the ‘fingers’ and the ‘big bones’.

Fig 2 shows the jack and the switch installed in their respective groove in the base; fig 3 shows the final wiring in the base; the current limiter is identified in the picture. The function of this component is to limit the current in the circuit to 20 mA even when the input voltage is bigger than strictly necessary to power the LEDs.

For example, 5 amber LEDs need 10.5 volts (see the link

https://www.hobby-hour.com/electronics/ledcalc.php); however, I power the circuit with the standard 12 volts.

Step 5: Technology

The ‘flames’ are made of glue gun sticks; I proceeded as follows:

hold an end of a stick over the flame of a candle

when plastic begins to melt and flow, remove the stick from fire

wait until the plastic solidifies; you might need to cut periodically the ‘thread’ which is being formed to avoid that the ‘end of the flame’ becomes too thick

cut the piece of the stick

drill a 5 mm diameter* hole, 8 mm deep in the bottom of the piece; this is the place for the LED

make a chamfer around the rims of the hole in the bottom of the piece to make it look more similar to a small ‘flame’

The figure explains the proceeding.

I began drilling with a 2 mm bit to ensure that the hole is well positioned in the centre of the stick; then I continued drilling with 3.5 mm and 5 mm bits. However, the elastic walls of the piece ‘make way’ to the 5 mm bit, so it doesn’t cut enough material to produce a 5 mm hole; I repeated the drilling with a 5.5 mm bit and managed to get a slightly tight fit of the ‘flame’ on the LED. The ‘flame’ should be installed easily on the LED.

Step 6: Assembly

The starting point was that all fingers were assembled, and the base was assembled and painted.

Then, I proceeded as follows:

glue the fingers to the top part of the wrist (the modification of the fingers’ ends should be made at this stage)

insert and glue the ‘big bones’ into the bottom part of the wrist

install the switch and the jack in their respective groove in the base

pass the wires through the fingers and both parts of the wrist

connect the LEDs to the wires

glue together both parts of the wrist

paint the hand in white

install the hand on the base

make the final wiring in the base

put the ‘flames’ onto the LEDs

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