I got interested in high powered flashlights through a friend who had discovered them. All I could do was dream of the bright light, until, while surfing the Internet I came across the Candlepower forums. Candlepowerforums.com is where they talk flashlights and make-over flashlight projects. The projects range from changing the bulb out to rewiring and adding logic circuits. After plenty of reading I came away with a plan to get started and build this simple but very bright flashlight.
This flashlight has most of the guts of a $200 model. I like this flashlight better than the $200 models because it is much lighter weight and if it gets lost, I won't feel too bad about the cost. This one is much brighter than anything you can get under $100 and almost as bright as the really expensive ones. I made mine in an hour.
What makes a $200 flashlight worth the money? First of all their major customer is the Federal Government. The US Army, Marines, FBI, and all the police departments around the country use these lights. So supply and demand is what keeps the cost high.
What makes a tactical flashlight so nice? As the Surefire advertising says...
SureFire, the tactical technology company developed Special Operations Lights for law enforcement and military applications where intensely bright light is used to startle, disorient, and control anyone on the receiving end, and where hard use in tough environments is expected. Featuring optically coated and tempered Pyrex lenses and Mil-Spec Type III hard-anodized finishes, these flashlights also have an internal shock isolation system to cushion the lamp assembly against impact, plus double O-ring seals for redundant moisture protection.
How does mine compare? Well, it has an intensely bright light which will startle, disorient, and control anyone on the receiving end (and you can see what varmint is making all the noise in the dark). Mine is not for use in tough environment, does not have shock absorbers, O-rings, Pyrex lens or an anodized finish. Basically all it has is that intensely bright light thing going for it, oh, and mine is intensely inexpensive.
Mine has a very bright spot, good projection, no visual "artifact," batteries last a decent time, and it will clip right onto your rifle. Actually mine won't clip to your rifle, but is very light weight, will hang from a tree, and did I mention inexpensive. In fact this one is made from one of the cheapest lights I could find, so it is not going to attract the attention of someone looking to steal your very cool high powered beam.
In order to make this light, you need a cheap flashlight body, new bulb, new batteries, and a custom made battery holder.
Step 1: Parts list
1 KPR118, 7.2-volt, incandescent, flashlight bulb
3 CR123A lithium photo flash batteries
1 4-inch long piece of 3/4-inch, cold water, schedule 40 PVC
1 3/4-inch long #8 bolt
4 #8 by 1-inch diameter fender washers (from the parts bins at Lowe's)
4 #8 hex nuts
Why these parts?
The flashlight body:
This particular flashlight body is important because it has a "prismatic" reflector. This is the key element to eliminating the artifacts from the projected beam. Have you ever noticed that when you project a smooth reflectored beam onto a wall you see a dark spot in the middle along with shadows and streaks in the beam? What you are seeing is the magnified and projected inner guts of the bulb itself. These "impurities" in the light beam are called artifacts.
The "prisms' in the reflector on this model of RayOVac flashlight blend the bulb reflections together and average out the light with the dark. The result is you see only a pure beam with a slight halo. Even if you don't do anything to this flashlight, it will give you a much nicer projected beam than a smooth reflector will. I also like this body because it is bright yellow (easy to find) and it is very light weight. And I like it because it has room in the head behind the reflector to do other mods later.
If you try to run 9 volts through a 3-volt flashlight bulb, it will blow before you can see it. It's hard to find a 9-volt bulb, but the folks at Radio Shack will tell you the KPR118 bulb will work. It does, but it does not last forever.
These are 3.0 volts each and last a pretty long time. When you use three in series, you get 9 volts in a smaller and MUCH lighter package than D-cells. These are the heart of the flashlight. Once you decide you like these batteries, you can buy them online for about a dollar each.
The PVC pipe:
This is needed to keep the batteries in the center of the flashlight body. The cold water pipe fits perfectly inside the D-cell flashlight and the batteries fit nicely inside the pipe.
The bolt, washers, and nuts:
Notice that the three CR123A batteries are about 3/4 inch shorter than the two D-cells. The spacer made from these parts makes up that difference.
E6000 is a hobbiest's glue. I got mine at Michael's. Any hobby shop that carries artificial flowers should have this glue. You could use caulk, Gorilla Glue, or any sturdy glue. I have even used white glue, but that is very temporary.
Step 2: Assemble the parts
1. Unscrew the head of the flashlight, discard the existing bulb, and replace it with the new bulb. Screw the head of the flashlight back on.
2. Run one fender washer up against the head of the bolt. Follow the washer with a nut and tighten it firmly. Run another washer and another nut. Continue with washers and nuts until you are out of room on the bolt.
3. Cut the pipe to 4 inches long. If you think you want to make a lot of these, invest in a pipe cutting tool. The tool looks like gardening clippers and will cut through the pipe like a cold knife through cold butter - still faster and easier than a hacksaw.
3. Glue the spacer to one end of the PVC pipe. The spacer will fill the gap between the shorter batteries and the inside space of the flashlight body. It also provides the electrical connection for the positive side of the batteries. The spacer needs to be glued in place to the pipe so it remains centered inside the body. Let the glue dry for a day.
Step 3: Assemble the flashlight
1. Unscrew the end of the flashlight.
2. Drop the battery holder inside with the spacer first.
3. Drop the batteries in, positive end first.
4. Screw the end back on the flashlight.
Step 4: Using the flashlight
Don't look into the beam in the dark and don't shine it in someone's face unless you intend to hurt them or temporarily blind them. In fact when you shine this straight down at a black street and look directly at the bright spot, you'll notice your eyes starting to throb.
One of the interesting things about these batteries is that they lose a little bit of power after an hour, and then they hold their brightness for at least another couple hours before suddenly going dim and out.
I was worried about the light heating up and softening the plastic. I turned it on and left it running for 45 minutes and it didn't seem to get any warmer than it was after just a minute of running.
UPDATE May 16, 2007:
I'm attaching a beamshot of my flashlights. The one in the lower left is the stock Ray-o-vac that I started with. Diagonally across from it is the mod from this Instructable.
Step 5: Comments and troubleshooting
I hope you enjoy your new flashlight. My daughter took it with her on Halloween. I could tell she was coming back when she was 3 blocks away. I usually walk my dog after the late night news. There is usually enough light pollution to make a flashlight unnecessary, but sometimes we get clear nights and it's darned dark out there. I'll take this flashlight to make sure there are no boogie men hiding in the dark streets.
If you already have a 2C flashlight, you can replace the bulb with the KPR118, use a battery holder made of 3/4-inch hot water PVC, 4-inches long, and the three CR123A batteries. You don't need the spacer with a 2C flashlight. If you don't yet have a 2C flashlight and want to use that, look for one with stippled or prismatic reflector.
At Christmas time you can get pretty good deals on flashlights. I bought a case of 2C Maglites last year, customized them, and gave them to my manly men friends as presents.
If you turn on your flashlight and it does not work, use the following checklist in order.
1. Open the battery compartment and make sure the batteries are installed (these batteries are so light you can't always tell when they are installed). While you have the back off, drop the entire battery holder out and make sure the spacer is connected to the pipe. Make sure the batteries are all facing the right direction (positive end in first). When you reinstall the batteries make sure the spring is aligned with the bottom of the batteries as you tighten the back.
2. If it is still not working, try a different bulb. Make sure the bulb is the KPR118 model. Lower voltage bulbs are instantaneous flash bulbs with this much battery power.
3. If it is still not working, try fresh batteries.
4. If it is still not working, you probably have a defective flashlight body.