This project is a candleholder with three gears and parallel action arms which move the candles up and down at different rates.It is made from aluminum plate and uses tea lights or small floating candles. The design and the variable gearing make it a playful device.
Step 1: Marking and Cutting the Gears
I make gears basically by drilling holes in a circle, and then cutting away excess material so that the holes become the "valleys" between teeth. The diameter of the circle that passes through the center of each tooth (the Pitch Circle), is calculated by the formula shown below.
Also note the additional holes marked "#25". These are mounting holes for the connecting rods that join to the parallel arms. They need to be drilled with a #25 drill bit, and then tapped with a 10-24 tap to accept the shoulder bolts that act as pivots for the connecting arms.
Step 2: Cutting the Chassis Plates
The front and back plates of the chassis are cut from 1/4" aluminum plate. Use the chart below to mark out the back plate, then use the back plate to mark up the front plate (remember the front plate does not have holes for the gears, so it can be much smaller and simpler.
Step 3: The Feet and Knob
The feet are cut from 7/8" diameter aluminum rod. I cut slots in the rods to fit the front and back plates of the chassis into. During final assembly, you will epoxy the feet in place.
The knob can be any shape, but I made it in a similar shape as the gears. It needs a center hole, 1/4" dia., and a 1/4" shaft collar joined to the knob with a tension pin (see photos).
Step 4: Arms and Candle Brackets
The arms are cut from 1/8"x1/2" aluminum flatbar. See chart below. You will also need to cut spacers for the arms so that they don't collide with each other or with the protruding bolts that hold the gears to the chassis. The candle brackets are made from two pieces of the same material, plus a disc cut from some other plate (I used 3/16" aluminum plate). The discs are drilled and the bracket pieces cut so that they form tenons which can be staked to the disc. Finally, a glass drip ring (these are also called bobeches) is epoxied to the disc to hold the candle in place.
Step 5: Assembly and Finish
I brushed everything with scotchbrite pads to leave an even finish. I used wave washers to add tension to the mechanism so that the candles wouldn't just flop down. I also added blue threadlocker to the joints so that they would not come undone accidentally.