But first, a demo! Click the image to see the full-size (potato-quality) clip:
Winter is coming. I normally visit my club’s 3D archery range either early in the morning before work, or in the evening after, but with the lengthening dark it’s getting harder and harder to spot my arrows in the targets1. Lighted nocks to the rescue!
Component-wise, a lighted nock is just an LED and a battery inserted in an ordinary transparent nock, but the trick is getting the LED to turn on only upon release, so that you don’t walk through the forest looking like a Christmas tree, but also to conserve batteries.
Before we move on to the step-by-step, the usual disclaimers apply. Messing with your nocks can compromise their structural integrity. If a nock shatters on release, your bow will dry-fire, and that can destroy its limbs. If the shaft cracks too, that can destroy your limbs. You are responsible for your own safety. I am merely showing you how I build my lighted nocks.
Components (per nock)
CR435/BR435 lithium battery.
Some way of attaching the LED to the battery. Soldering works great if you’re handy with a soldering iron, but I’m not, so I use a 26-24 AWG butt connector.
18-20 cm of 30 AWG (0.25 mm) solid steel wire2. It doesn’t have to be precisely 30 gauge, 28 AWG probably works just fine, but it must be steel. Any softer material will get severed after not too many shots.
Nock collar/shaft protector. Must not be painted or anodized, because we want it to conduct electricity well. *You might not need the collar, read the note below.
Electrical insulation. Plain electrical tape will do fine, but I also like to use some shrink tubing and insulation stripped off of 24 AWG wire.
Permanent glue. I use plain super glue (cyanoacrylate), but I’ve also tested some Bohning Fletch-Tite Platinum and that worked too.
A note on carbon and current
Carbon shafts are made of carbon fibers (graphite) and epoxy resin. The good news is that graphite conducts electricity. The bad news is that epoxy doesn’t. So, depending on the layup of the carbon fibers and the construction of your shafts, the inside surface of the shaft may or may not conduct electricity. Mine doesn’t (Gold Tip Traditional shafts), or at least not easily, which is why I need the nock collar. I use collars anyway so it’s not a problem for me, but if you don’t and your shafts conduct electricity, you can skip the collar and adapt the design so that you connect the battery straight to the inside of the shaft, which means you’ll also need to make a single hole in your nock rather than two.
Start by insulating the negative terminal of the LED (short leg). Leave a bit uninsulated at the end to fit into the butt connector:
Trim the plastic ends of the connector, and crimp it over the exposed part of the LED’s negative terminal and the battery’s negative terminal (the pin at the top). I use a crimping tool, but needle-nose pliers should work too:
Make two very small holes on opposite sides of the nock, right up against the nock’s “shoulder”. I prefer to melt the holes by heating the end of a paper clip and pushing it through the plastic. You can also drill them with a small drill bit, but these nocks are made of brittle polycarbonate and I’m afraid a drill bit might cause tiny micro-fractures around the edges which might spread in time, whereas melting the holes smooths out and solidifies the edges. Clean up the exterior of the holes with a sharp blade so the hole is level with the nock body and the nock can slide freely into the shaft.
Thread your wire through the holes in the nock:
Bend the ends of the wire to form tiny loops, leaving a small tag end on each side and trimming the rest. The one in the photo below is a bit long, I trimmed it some more after I photographed it:
Center the nock on the wire and pull the wire from the inside of the nock using a paperclip bent into a small hook. Push the tag-ends of the small loops inside the holes, so you end up with two “ears” on each side of the nock:
Cut the wire in the middle and insert the LED+battery assembly into the nock. Make sure you push the LED all the way up past the two wires:
Slide a piece of insulation or thin shrink tubing up one of the wires until it reaches the hole on the inside of the nock. The insulation should be long enough so that the wire doesn’t touch any other component inside the nock, but short enough so that we have enough wire to wrap around the battery in the next step:
Wrap the end of the insulated wire around the battery body (which is also its positive terminal) and the uninsulated wire against the remaining LED leg (also positive terminal), then trim both wires:
Glue the components to the inside of the nock. Do not overlook this step, even though it seems the nock works without it. Otherwise, the two tiny wire ears support the weight of the entire internal assembly, and when the arrow impacts the target the inertial force will rip them out through the holes and slide the entire assembly down the shaft.
I found that the best way to apply the glue is with one of those thin micro-tips that slides onto the end of the tube. They’re very handy to have around the house anyway, so I recommend you buy some.
Allow the glue to cure, then wrap the outer components tightly in electrical tape. I like to prettify mine with a bit of shrink tubing as well at this stage, but it’s not mandatory.
Voilà, the nock is done! The ambient light kinda made it look like the LED is lit in this next photo, but it’s really not. If yours is, you have accidentally connected the wires inside the nock.
It should go without saying, but if you’re using shrink tubing, be careful with heat around a lithium battery.
Push the nock into the arrow shaft until it sits as close as possible to the collar without making contact:
When the arrow is shot, the string will push the nock fully in, touching the wire ends to the collar, completing the circuit, and lighting the nock:
The final cost of the complete nock comes to around €2 here in Austria. At around €1.4, the battery is the most expensive component.
A lighted nock will add some weight to the end of the shaft (around 30 grains extra compared to a regular nock), which will slightly increase the dynamic spine of the arrow. If you want to have perfect consistency in your arrows, you should add the difference in weight to your other nocks as well. I found that an old bicycle spoke cut into sections and glued into the nock works nicely, but to be honest I don’t really bother with it.
A popular alternative design uses a fishing bobber light, which is a complete LED+battery assembly. That design is easier to assemble and makes for a neater final nock, so you should definitely give it a watch and see if you prefer it, but I believe it comes with its own set of problems, so I prefer mine.
That said, I’m pretty sure my design can be improved. If you have any ideas for improvements, I would be very happy to hear them!