LIGHTING A FLY PORSCHE 917K
Lighted slot cars look kewl, even if you don't race in the dark. It's gratifying to outfit a special car with a special feature (thus destroying its value as a collectible), and I think it would be effin wunnerful if the Porsche's fan were powered... but you've gotta draw the line somewhere. Even though lights aren't a performance tweak, as near as I can tell the addition of a few grams of weight doesn't hurt performance, and might possibly improve it.
Installing lights in slot cars is a fun challenge, since one size does not fit all. Some cars have lots of room to mount electronic "guts", while others have very little. Fly's Porsche 917K is not an easy car to light, mainly due to the limited area available to mount the lights. But I like challenges, and what better car to demonstrate a show-offy technique than the ostentatious Marqués de Riscal? (Not to be confused with its sister fancycar, the Duque du Hazard.)
The most obvious way to give a 917K working headlights is to install them in the lower position. From a cursory examination, there doesn't seem to be enough tire clearance to install them in the upper position. However, if you're willing to do a little drilling and roto-tooling (a.k.a. "Dremeling"), and are willing to dabble with some fairly close tolerances, it can be done. Most of the info outlined here can also be used to light the lower headlights, assuming that you're already familiar with the basic issues of lighting cars. I'll leave it up to you to figure out the finer points of mounting the circuit board or diodes and resistors, and run the wiring (there's a pic below). I've used a Ninco lighting circuit since it was cheap and compact, but replaced the LEDs and wiring. I've also trimmed the circuitboard to make it slightly smaller since the fully detailed cockpit takes a lot of interior space and doesn't leave many mounting options.
HEADLIGHTS The good news is that the 917's headlight housing assembly is easily removed. It's not even glued into place. This makes it very easy to drill holes, fit parts, and test the final assembled fit. The bad news has already been mentioned: There's not very much clearance between the headlight housing and the tire. The LED and wiring has to fit within that space, which is no larger than the distance taken up by the melted plastic that secures the upper headlights to the removeable headlight housing assembly, plus a small gap of air. If that doesn't scare you off...
The first step is to prep your LEDs. The 3 mm kind work well for this application and don't look odd when the lights are unlit. The goal is to grind away as much of the excess resin material as possible, without cutting into the vital innards and destroying the LED. You should test the LED each time after you remove material, so that you don't waste time working on a destroyed LED. A 3-volt watch battery is very convenient for quickly testing an LED.
The LEDs need to be shortened so that they'll fit into the short cavity between the wheel well and the headlight lamp cover (which you have to drill). You can safely grind off the dome of most LEDs, and go a little beyond that, using the embedded LED "guts" as a visual guide. Bear in mind that the LED's dome acts as a magnifier/diffuser, and grinding it off will make the LED seem less bright-- it isn't actually dimmer; it's just concentrated at the center, where the LED's guts are. After grinding, the LED lens will have a rough appearance (which probably doesn't make much difference); you can polish this with a felt polishing bit and some plastic polish. You can also give the light a slight yellowish tint with Tamiya's clear paint if you want the headlights to look more like the incandescent type found on most cars.
Grind off the lip from the LED's base to make a tube-like shape; it doesn't have to be perfectly round since it won't be visible. This will let you shove the LED as far into the housing as possible, since every fraction of wheel clearance is valuable.
Drilling the hole through to the headlight can be a bit tricky. The first step is to grind off the melted plastic which secures the upper headlight to the housing. This will let you remove the headlight, and grind off whatever remains of the retaining pin. Once the headlight is removed, you're faced with a decision: You can try to remove the headlight lens and hope that you can get it to fit back in securely, or drill the hole and live with whatever marring you might inflict on the inside of the lens. Although it's preferable to drill the hole without the lens on, in my experience, some lenses don't come off easily except when you don't want them to (after you've drilled the hole), and that the lens marring isn't very noticible. In my experience, the upper lenses are easier to remove than the lower ones-- if any of the lens edge is showing, grip it with an Exacto blade edge and work the lens out. If it's stubborn and doesn't want to come out, don't try to force it.
If you drill with the lenses on, you have no choice but to drill from the backside. Using your smallest bit, either with a pin vise or with bare fingers, start a pilot hole as close to dead center as you possibly can. The small bit will make centering the hole easier since it will drift less than a bigger bit. You can switch to a bigger bit once the center hole has been started. It's probably a good idea to gradually work up in bit sizes, instead of doing it all at once. Drill the hole very carefully and gradually-- I use my fingers to twist the bit, and watch the inside of the headlight for the telltale bump that forms when you're almost there. The interior of the headlamp body has a thin electroformed layer, which makes it look mirrored. There's a very tiny air gap between it and the lens. Unfortunately, the foil protrudes before it's drilled through, so it's very difficult to drill a hole through it before you've hit inside surface of the lens. It's just a tiny blemish though, and hardly noticible.
Once the initial hole has been drilled through, you can work on enlarging it with bigger bits, to match the diameter of your LED. Subsequent drillings should stop just short of the lens. Once the hole is big enough, you can use an Exacto blade to very carefully slice through the thin layer of plastic and foil, making a clean, circular edge. Chances are, this is when the lens scribing will occur-- unless you're very, very careful, the blade will scribe a neat little circle on the inside of the lens. Not to worry though-- once the LED's in place, you won't notice it at all.
After the holes are drilled, the headlamps will probably be filled with all kinds of unsightly plastic drill dust. A blast of pressurized air is usually all it takes to clear this out (warning-- it may blow out the formerly-stubborn lens).
Hopefully, the LED can now be slipped through the housing (you figured out that you'd need to drill that, right?) and into the headlight. If you've selected your drill bits wisely, the headlight will be held in place to the housing by the LED, which takes the place of the shaft you grinded off. If it's a loose fit, you can glue the back of the headlight to the housing.
When installing LEDs in the upper headlights, it's very important that the LED's leads protrude as little as possible into the wheel well. That's why it's been important to make the LEDs as short as possible, and to grind their ends so that they can be inserted into the housing as far as possible. The LED's leads should be bent as tightly as possible at a right angle to the LED, heading inward-- you probably won't be able to get a perfectly square 90-degree bend, so that's why every fraction of clearance counts. The point is to create as low a profile as possible in the wheel well until they're past the point where they might rub against the tire. To reduce the profile, the leads won't have any insulation in that area; the natural stiffness of the lead wire near the LED should ensure that they don't short out. Once they're past that area, you can add shrink-wrap tubing, hot glue, or whatever else you want to protect the wiring and keep it from shifting.
TAILLIGHTS If you thought mounting the headlights was challenging, get ready to kick it up a notch! Well, it's a different kind of challenge... The challenge of lighting the 917K's taillights comes from the fact that the rear-end is open, with the thin-profile taillights connected to tubing which hangs below the enclosed area. If you're not too fussy, the installation of working 3 mm taillights wouldn't be too difficult, but if you want the installation to look suave, you'll need to use something other than those humongous bullet-shaped 3 mm LED.
Fortunately, LEDs are manufactured in a tiny, tiny surface-mount package, which are designed to be used in the production of compact electronics devices. You can see examples of these in Scalextric's P4 330 Ferrari-- the LEDs look like a rectangular hump on the circuit board.
Basically, these things were meant to be handled by robots, not humans. Like most active electronic components, LEDs can't take heat for very long, and that's true of even larger LEDs-- if you solder too close to the package without a heat sink to draw away some of the heat, the LED will boil. With this installation, both LEDs must survive the soldering of two tiny wires on the tiny copper pads. Since I fired my robot, I had no choice but to do the job myself.
There's another challenge that I hadn't even anticipated: Upon liberating the first one from its packaging, the bent-back packaging plastic slipped and propelled the chip into oblivion, before I even got to see what the chip looked like! Number 2 escaped from my tweezers into oblivion just as it was approaching the soldering pencil. If you work in a carpeted area, you can save yourself lots of time by calling off the search before it's even begun-- with Optivisors and a flashlight I found all sorts of robot dander, but no chips.
The wire should be as thin as possible so that it fits and doesn't look too out of place. I used wire from a computer ribbon cable since it was very thin for an insulated wire. Although the single, thin conductor wire keeps the diameter down, it's less durable than a stranded wire. That means that the wire shouldn't be subjected to repeated bending or metal fatigue will cause an open circuit.
To solder the LED to the wire, the wire should be pre-tinned. The soldering action should be as brief as possible: if the solder from the wire doesn't flow instantly, back off the soldering pencil, give everything a moment to cool and try again. Eventually, when you've succeeded, test the LED to make sure it works, and treat it very gingerly.
Onto the installation... It's very convenient that some body decorations are press fitted over pins, and therefore easy to remove. To fit the LED unobtrusively, I grinded out small depressions in the back of the lenses (to recess the face of the LEDs) then threaded the wires behind the posts into grooves I'd cut through the black platforms. There's probably enough room in the platforms to wire the 100 ohm resistors, but I thought that it would be easier to install them in the body, farther from the LEDs.
The hardest part of this step is getting all the wire bends in the right place, while keeping the practically zero-mass LEDs in place (without breaking anything). I attempted to hot glue them in place, and succeeded to some extent, but it's a very messy adhesive that's not really appropriate for fine, controlled work. I spent most of my time cursing, removing glue spiderwebs and poorly placed globs from the framework. On the other hand, it's a really quick adhesive solution, and when you're this close to completion, that's an appealing quality.
After the taillight assembly is completed, it's a relatively simple matter to route the wiring to the circuit board with inline resistors. As I said, there isn't much extra room inside after it's all sandwiched together. In retrospect, I should have used the thinner wire for the headlights since every bit of space savings is welcome. The circuitboard is placed off-center since the (blue) gold cap has to clear the magnet pocket when it's assembled (even though I run it without a magnet, I hate to cut unless it's necessary). Note that the stub axles have been replaced with brass tubing-- this removes slop and makes the wheels less likely to rub.
Performance-wise, it's faster than my other 917Ks, with a current best average lap speed of 185 scale MPH-- the others range from 180 to 182. I don't know if this is because of the extra weight or because I unconsciously try harder with this car. Likewise, my lighted Duque de Veragua is the fastest of my Ferrari 512S Coda Lungas. (Reminder to self: Position camera above, not in path of oncoming car!)
Watching the movie Le Mans may inspire you to add lights to Porsche #20 and Ferrari #8. It's hard to see in the photo, but the Porsche's lights are lightly tinted yellow to subdue the blue-ish hue of white LEDs. Despite the slight greenish cast (which comes from mixing blue with yellow), I think it make them look more like incandescent lamps. I didn't like the intense orange hue of amber LEDs, so I tried blending in a slight red tint-- but that made the LEDs stand out too much when the lights weren't on, and looked funky. Unfortunately, Fly left off some interesting details that you notice in the movie, like the side vents and the tiny lights on the side. The Ferrari's next... --04/30/06
This shows the difference between "Xenon" headlights and the tinted ones. Balancing the tint between the headlights takes a bit of trial and error, since you can't tell until they're glowing.--05/02/06
|FUTURELIGHTS Thanks to the info at Brent Carlson's website, I hope to become a cheapskate and roll my own. Admittedly, it seems a little silly to fret over the cost of Ninco's light kits considering the amount of money I've blown on out-of-production slot cars. Ninco's kits aren't that expensive, perform well, and are very compact, with commercial quality production. Given the size of the LM7805 voltage regulator alone, I'm thinking of constructing this sans circuit board (the way they did in the really old days) so that I can distribute the parts according to the car's interior space. Won't that look lovely? Still, it's a fun challenge, with considerable dollar savings when you make a bunch (I've got parts for 20)-- it just costs more time. --05/12/06|