Introduction: Laser Cut Clock Escapement and Pendulum
After several prototypes and failed attempts, I managed to create a consistent clock escapement as part of a larger kinetic sculpture. This model is based on a variation of the deadbeat escapement. Escapements in general work by limiting how fast potential energy is released. Since the escapement ensures a consistent time between swings of the pendulum (adding a small amount of energy back to the pendulum as it swings) we rely on the escapement in order to tell accurate time in mechanical clocks. These directions tell you how to create the functioning pendulum and escapement set, but it will not run without adding a spool and weights to the end of the rod connected to the escapement gear (shown on top).
I purchased the majority of my parts through McMaster Carr, but you may find alternatives elsewhere.
You will need:
10 1/4" shaft collars (single set screw)
10 1/4"-20 hex nuts
Approximately 16" of 1/4"-20 steel threaded rod, cut into two 4" pieces and one 6" piece
5" of 1/4" steel smooth rod
One roller bearing with interior diameter of a 1/4". The outdoor diameter is flexible as long as you change it in the laser cutter
2 1/4" sleeve bearings. Flanged or regular both work (I use one of each in this instructable)
Set of Laser Cut parts which include two identical frame pieces, an escapement gear, and a pendulum with the pair of necessary
(if you wish to change your escapement type, I recommend Clock and Watch Escapement Mechanics by Mark V. Headrick)
Allen wrench (same size as your set screw)
Gorilla glue or epoxy
Step 1: Pieces and Affixing Bearings
If you haven't done so already, create or procure a set of the 4 pieces from the attached design files (available both in dxf and adobe illustrator cs6). This should include 2 identical frame pieces, one escapement gear, and the pendulum with attached escapement pallets. If your bearing has a larger profile than the one suggested, be sure to increase the size of the hole at the top of the pendulum (near the pallet teeth, where it branches out into a claw shape). I cut my pieces using Acrylic due to the slipperiness (coefficient of friction) that the Acrylic has for the escapement to release on each swing. I imagine that there are other possible materials to use.
With a ton of caution, apply epoxy or gorilla glue to the outside of your bearing and place it inside of the pendulum (nearest the pallet head).
DO NOT GET ANY GLUE/EPOXY ON THE BEARING FACES (or in between any cracks). This will cause your bearing to not function well at all.
Also glue your sleeve bearings into the top section of the frame (the side with one hole in the middle of the rectangle, the bottom has two holes on the edges). Do not get glue inside of your sleeve bearings for it will also change the friction and make it harder to use.
Step 2: Assemble Pendulum
Once the bearing glue has dried, you need to attach the steel smooth rod as an axle.
First, place the steel rod through the inside of the bearing, and while holding the rod place a shaft collar onto one side of the pendulum/bearing. This first shaft collar should leave an edge about 2," but right this moment exact placement is not necessary since we will later go back and adjust the shaft collar and nut positions.
Tighten the set screw on your shaft collar down again the rod so that you can not budge it.
Place the other shaft collar on the opposite side of the pendulum. This one needs to be tight enough against the bearing to prevent any horizontal wobble, but not so tight as to prevent the bearing from moving. Once you are satisfied with its placement, tighten it into place.
Step 3: Assemble Gear
Now we will perform a few similar steps to attach the longest threaded rod piece as the axle to our escapement gear.
Place the threaded rod inside of the to gear. Screw one 1/4" hex nut against the gear so that the amount of space left outside of the nut (towards the end of the rod) is approximately the same as the pendulum arm, about 2" or so.
NOTE: The Pendulum and gear have a correct orientation. If later it is found they are backwards to each other, you can just come back to step 2 or 3 and flip one of the pieces.
On the opposite side, screw another 1/4" rod against the first one so that the gear is unable to spin freely around the threaded rod. Be careful not to over-tighten and crack the acrylic.
Outside of this second hex nut slide a shaft collar against the nut and tighten it down. If you have an extra shaft collar, do the same on the first side as well. This prevents the nuts from loosening as the gear spins. Alternatively you can glue the nuts to the gear and the shaft itself (super glue or gorilla glue work best for this).
Step 4: Adding the Frame
Now we need to add the frame. The frame is designed so that the distance between the pendulum and the gear is ideal which makes the impact of the pallet teeth onto the gear teeth the most efficient.
Place a shaft collar on both the gear axle and the pendulum axle at least 3/4" from the long end. Tighten both shaft collars so that they don't move, then insert both axles into one side of the frame. The gear goes onto and should pass through one of your sleeve bearings.
Place an additional shaft collar on the outside of the frame. In the case of the escapement gear, the second shaft collar should allow for the axle to rotate inside of the sleeve bearing without wobbling. The pendulum axle should be tightly affixed to the frame.
Place and tighten another shaft collar on the opposite side of the gear. Do the same with the pendulum. Both of these new shaft collars should be at approximately the same distance from the end as each other. Stand the first frame piece up on the table, and slide the second frame piece onto the opposite side of the pendulum / gear set. Place an outside shaft collar on the pendulum axle and the gear axle. As before, the gear should be loose to turn inside the sleeve bearing, and the pendulum axle should be affixed. Turn the frame sideway to ensure that the gear and pendulum are aligned horizontally within the frame.
Test that when your gear is facing the right direction. To do this, place your finger on top of the top most tooth and put weight towards the backside of the tooth (the side which is closer to 90 degrees). If you have placed both parts in the correct orientation, pulling down should cause the pendulum to swing back and forth freely. If it appears to be binding (stopping motion) or otherwise giving inconsistent results return to early in the step and reverse the gear (each end should now be in the opposite frame side).
Step 5: Stabilizing the Frame
The frame should stand on its own, but it has an uncomfortable amount of wobble in it at this point. Grab one of the remaining 1/4"-20 threaded rod pieces and insert it through one of the holes on the bottom of one of the frame pieces. Screw two 1/4"-20 hex nuts inside of the frame far enough down that the threaded rod can then be pushed into the other frame side (see image 3). Place a hex nut on the outside of each frame side. Tighten them so that the frame maintains a consistent distance apart from top to bottom (ie that it is still perpendicular to a flat table).
Repeat the first set of steps with the opposite side of the frame. The nuts on both this new rod and the original rod should align, but it doesn't matter if there is some extra threaded rod outside of the frame.
Step 6: Finishing the Piece
TADA! You now have a working self-supporting escapement mechanism.
If you attach a spool with rope / string and a weight to the gear axle, the weight will unwind trying to spin the gear freely. However, the escapement pallets on the pendulum will block this action, and will force the pendulum to swing back and forth releasing one tooth at a time.
With the enclosed pieces, the pendulum length ( ~9.8inches) makes a pendulum period of approximately 1 second (or 1/2 a second per side). The pendulum has holes on the bottom so that you can attach a weight (which will stabilize the swings a little bit) and also since the distance to the center of mass is what determines the period, you can adjust the mass up or down to reach 1 second.
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