Geared Candleholder

The gears are made by drilling holes around a circle, and then cutting material away so that the spaces between the holes become the teeth.

Download patterns for the gears and all other project parts from the Documents section above. To calculate the radius of each gear’s pitch circle, which runs through the center of the teeth, I used the formula: r = s * n where s is the tooth size and n is the number of teeth. I used a 1/4” drill, giving a 1/4” tooth size, so for my 8-, 15-, and 24-tooth gears, I got pitch radii of 0.637”, 1.194”, and 1.910”, respectively.

Center-punch the center of each gear on the 1/4” aluminum plate and use a protractor and scribe to mark the angle position of each tooth gap. The 8-tooth gear needs a mark every 45∘, the 15-tooth gear every 24∘, and the 24-tooth gear every 15∘.

For each gear, use a straightedge to scribe lines radiating from the center out to the angle marks. Set a drafting divider to the pitch radius (I did this with a caliper) and scribe the pitch circle. Similarly mark the outer circles. On the 2 larger gears, mark lines to position the connecting arm holes, at 0.687” radius for the 15-tooth gear and 1.125” for the 24-tooth.

Wherever the pitch circle crosses the radiating lines, punch and drill a 1/4” hole. Also drill the center with the 1/4” bit. The connecting arm holes need to be tapped for 10-24 threads,so punch then drill these with a #25 drill bit.

Cut the gear out as much as you can on a band saw.

CAUTION: Aluminum dust is very harmful. Wear a respirator and work in a well-ventilated space.

Finish the teeth by filing them until they are semicircular and even-looking.

Test-mount the gears onto a wood board using 1/4” bolts or rod. Leave a tiny bit of room, or “slop”, between the gears to decrease the chance of binding. Turn them, and mark any problem areas for more filing.

To tap the holes for the connecting arms, clamp the gear so the hole location is off the edge of a table. Secure the 10-24 tap into the handle, put a couple drops of tapping oil on the tap, and screw it slowly into the hole. Apply light pressure, and turn back every quarter turn to break off the curls of metal. Go all the way through the hole before backing the tap out. Clean the hole, and screw in one of the 10-24 shoulder bolts to test the threads.

These gears are not precise, so you need to lay them out and adjust their relative distances before you machine the body pieces that they mount to. However, the distances to the arm pivot points are fixed and must be accurate. Follow the vertical and diagonal measurements on the pattern at makezine.com/21/candleholder, and within these constraints tweak the gears’ relative horizontal positions so that they mesh effectively. Center-punch your marks, but hold off on drilling yet.

Tip: Use a combination square and a divider to mark vertical lines and distances from the bottom edge of the plate.

Follow the pattern to outline the body. Use your center marks to create the outline, scribing circles and connecting them with “necks”. I used an oval drafting template to make smooth curves.

For the 2 feet, mark two 7/8”-diameter half-circles at the bottom. In the upper corners, mark 7/8”-radiuscircles (1-3/4” diameter) that encompass both arm pivot holes. Make the central circles small enough to show off the mechanism inside. The resulting outline will be fun and reminiscent of old machines.

Roughly cut the back panel of the body on a band saw and drill the holes. The 11/64” holes in the corners are for 8-32 machine screws that hold 1-1/2” threaded standoffs between the 2 panels.

Use the back panel as a template to mark the front panel. To improve visibility of the gears, make the middle area of the front panel a little smaller. Clamp the panels together and redrill the 1/4” holes for the pinion (the smallest gear) and the 11/64” arm holes through the back and front panel together. These are the only holes in the front panel.

Tap the holes for the larger gears on the back panel the same way you tapped the gears in Step 3.

For the pinion axle, which will connect to the knob, cut a 1” piece of 1/4” steel rod. Put one end through the center of the pinion and slip a clamp-on shaft collar on top. To join the collar and pinion, drill a 1/16” hole down through both, off to one side, and use a small hammer to drive in a 1/16” tension pin.

Make the knob the same way you made the gears, as a 5-tooth gear with 1/2” teeth (pitch radius = 0.796”, marks every 72∘). Drill and attach the knob to a shaft collar with a tension pin, the way you did the pinion above.

For the feet, cut two 4” lengths of 7/8” aluminum rod. They need 2 slots cut halfway through them, 1/4” wide and 1-1/2” apart. Put the feet in a vise and use a hacksaw to cut each side of the slot, and then saw diagonally across both to clear out material in between. Finish clearing out the slots with a coarse file until the body panels fit in them. You’ll attach these feet with epoxy later.

Each of the larger gears drives an arm that moves 2 parallel levers up and down. The other ends of these levers hold the candle bracket, forming a 4-bar parallelogram linkage that keeps the candle upright. All the holes need to be placed accurately for the movement to work.

Cut the arms. Refer to the connecting arms pattern under Documents. All measurements are based on the centers of the holes, so add some extra length for the ends, and grind or file the corners round.

Drill the holes. Some need to be 1/4” while others are 13/64”. The connecting arms attach to the gears with 1/4”-diameter shoulder bolts and the parallel arms pivot on 1/4” threaded standoffs. The arm parts attach to each other and to the candle brackets using 13/64” binding posts.

Cut the spacers. Ten spacers of varying lengths hold the arms and gears at the correct distances between the front and back panels. Referring to the spacer plan online, cut the 2” unthreaded aluminum spacers down to the lengths needed with a hacksaw. Cut them a bit long and then file them down to a hair short, to allow for free movement.