I got a little carried away with my son's Pinewood Derby car this year. We decided to buy another car that he could build himself but I decided to finish the first car. I based the design on the hot rod from Woodcarving Illustrated's Special pinewood derby edition.
I've also seen Pinewood Derby cars with LED headlights and taillights and thought this was a great idea, but I've never anything using the vintage headlight buckets that fit the 32 Ford Roadster.
(2) Yellow or white LEDs - Yellow for a more vintage look. Smaller LED's are easier to fit.
(2) Red LEDs - Mine had chrome rings already attached.
(2) Sharpie Markers or another brand with the correct shape.
2 part epoxy cement or clear casting epoxy
Sandpaper - Assorted grit from 320 to 2000
Pinewood Derby Kit
Coin Battery holder (I used holder and 2032 battery from an old motherboard)
(4) lengths of 2 different color wires - I used red and blue.
Hot glue gun
Soldering Iron and solder
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Step 1: Create the Headlight Bucket
I don't have a wood lathe. I do have a box of dried Sharpie markers from the office. Cut the marker in half and remove the felt. Save the back barrel. Cut about 1/2" from the back of the pen, leaving about 1/16 more than the final intended length. An exacto saw and miter box works great for this. Clean the stringers, especially from the inside of the cut.
Drill a hole through the back of the bucket just large enough for both leads of your LED to fit through. If the hole is too small it will bend the leads together and risk a short. The markers I used had some ribs inside that interfered with seating the LED. These needed to be opened up. Drilling didn't work; the drill grabbed the ribs and made it hard to hold and deformed the bucket. Running the dill backwards seemed to push the ribs out of the way enough that the LED would seat in the bucket. A dremel might work too.
Step 2: Modify the LED
Test fit the LED. Smaller LEDs may fit without much modification. The ones I used were too big; you want the end of the LED to be about 1/16 behind the final edge of your bucket. I chucked the LED backwards in a drill and sanded the lip from the base. Using a sheet of 320 grit sandpaper I also sanded the tip of the LED down flat, testing as I went (I didn't know how much I could remove without damaging the LED). Don't worry about polishing the LED; the frosted surface diffuses the light for a more realistic look.
Step 3: Mount the LED
Insert the LED body into the bucket. Hold the LED to center it in the bucket and add a little hot glue to the base from the outside. The glue must hold the LED in the desired position but more importantly it must seal any gaps in the hole so the epoxy that we're about to pour in there doesn't leak out. I use a piece of polystyrene foam and stick the leads in the foam to hold them for pouring.
Step 4: Pour the Epoxy
I've done this two ways...First was a syringe-type 2-part epoxy cement with a yellowish tint. This worked OK but was a little thick to pour. I've also used two part casting epoxy that mixes a little thinner. I mixed equal part of each resin and hardener in a plastic cup. Your ratio may be different; read your directions. It only takes a couple of teaspoons to fill two buckets. If your hot glue sealed properly you can simply fill each bucket with the mixed resin. Give it a couple of minutes to settle and add more if necessary. I found that any resin that drips down the marker body doesn't stick very well, so don't worry too much about drips. The first time I tried to clean these off before the epoxy cured and ruined a part. They find a nice warm spot for the resin to cure. Don't rush this--the resin must be fully cured before the next step.
Step 5: Complete the Lens
My resin required 72 hours for full cure. With a sharp exacto blade, carefully trim the excess hot glue from the base of the bucket. Starting with 220 grit sandpaper on a hard flat surface, begin sanding the lens flat. Check often that the surface of the lens is perpendicular to the centerline of the bucket. Progress through 320, 400, 600 grit sandpaper. I continued through 1000 and 2000 grit paper.
To paint your bucket, place the lens down on a piece of masking tape. protect the leads with a little tape or vaseline, and spray the bucket your color of choice.
At this point you can polish your lenses or coat with clear nail polish.
Step 6: Mount and Wire the Headlights
I used the leads from the LED as the headlight bracket. When insulated with a little hot glue they are srtong enough to hold the headlights in position.
I realized the buckets were a little big to fit between the hood sides and the tires. I decided to thin the wheels, since I wasn't racing and didn't need to follow all the rules. The big n little look fit well with this car anyway.
Taillights for this car were purchased as-is at Radio Shack for a couple bucks each. They already had the chrome trim ring on them and fit perfectly. Measure the diameter of the shaft and drill a hole to fit.
I know I'll get some criticism for recommending this but here goes--the pinewood derby only lasts a few hours and you don't really need resistors. The LEDs will last longer than needed. We'll be running 4 LED's with a single 3V coin battery. If you really want to add resistors there are plenty of 'ables showing how.
Solder a thin red wire to the long leg of each LED. Use a clip for a heatsink between the solder joint and the LED to protect against excessive heat. Solder a blue wire to each short leg. Route the wires through the body through holes to the battery holder. Twist each bundle and solder the black wires to the positive terminal on the battery holder and the bundle of white wires to the negative. I used a big puddle of hot glue to fasten the battery holder to the bottom of the car.
If I made the battery cavity larger I could have made all the connections with a small perfboard for a cleaner job. Sorry I don't have pics of the underside - I'll try to add them when I get a new camera.
Place the battery in the holder and the lights should fire right away. My on/off switch is a strip of plastic from the battery packaging slipped between the battery and the clip.
Thanks and good luck!!