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MAX Update No. 64: Glowing With Pride

12/3/2010 5:53:33 PM

Tags: MAX, 100 mpg, headlight, Jack McCornack

MU64aMU64bI discovered an interesting problem on my way to Rally Green. It was my first trip in the dark with MAX's new body and...well here, take a look under the front fender and see how I mounted the headlight.

I'd followed Bill Bushholz' advice and made plywood mounts for the headlight bulbs, and they worked pretty slick. I'd bought a pair of high intensity headlight bulbs from my local NAPA, and they had a feature I'd never seen on a headlight bulb before: the mirroring stopped a little above and below the filaments.

My guess is, this feature reduces the amount of light that gets projected at the stars and the ground, by letting the light come straight through the glass in the back. Pretty clever, but MAX has white gel-coated nose and fenders, they're translucent, and when it got dark and I turned the headlights on, MAX lit up like a Jack-o'-Lantern. I didn't think there was a law against that, but it was pretty distracting, and it would have only been a matter of time before I'd be talking to the police about it (“Do you know why I pulled you over?” “Uh...because my car is glowing?”). I needed to make some headlight covers; opaque, cheap, light weight, and hopefully easy. Fortunately they didn't have to be attractive, since nobody'd be looking under there.

Lucky me; I had some scraps of the perfect material left over from another project, 0.050” thick black ABS plastic. It's opaque, lightweight, cheap, and unattractive, and it's a thermoplastic so it's easy to work with.

Thermoplastics get soft when heated, you can then stretch and bend them, and when they get cold again, they harden back up and keep whatever new shape you gave them. Most plastic bottles are thermoformed-pop bottles, water bottles, milk jugs-they start out as a plastic tube which is heated, inflated in a mold, cooled, and they pop out as an exact reproduction of the inside of the mold. I didn't need to get that fancy.

MU64cI measured the back of the headlight bulb, including the electrical fastener that plugged into it, and scouted around the shop for an appropriately shaped object to be my mold. I found this can of cement, it said “All Purpose” on the label so I figured it had to be just the thing. Then I cut a headlight-sized hole in a scrap of particle board (formerly a bookshelf) to be my template.

MU64dI stapled a square of ABS to the particle board template, shined a heat lamp through the hole for about five minutes (poking the ABS with a pencil now and then to gauge its softness) and when it seemed just about right (soft enough to stay dented when I pushed it, plus a little softer) I smooshed it straight down over the glue can. I held it down with one hand and one foot while I took this picture, and once it was cool enough to touch, I pulled out the can, pried out the staples, and trimmed the base of the ABS to shape with some heavy duty scissors.  

MU64eAnd there you have it. I set the new part over the headlight bulb, put four woodscrews through it to hold it to the plywood headlight frame, and Bob's your uncle. It was a nice change of pace for me, having something work perfectly the first time-as you loyal blog readers know, I haven't experienced a lot of that of late.

As well as putting an end to the otherworldly light show, and thus reducing the number of UFO reports ("The alien spacecraft was hovering right over the freeway, there was some sort of radiation coming from its hull...but the strangest thing, it sounded more like a backhoe than a spaceship."), it also gives the headlight bulbs protection from those little rocks that get flung around by tire tread. These covers would have been worth making even without the light leak, and if they were just going to be rock deflectors, I probably could have cut the plastic I needed out of a milk jug. 

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7/11/2011 8:56:17 PM
Wouldn't the lack of mirroring near the center of the reflector be more likely to minimise the blinding effect of being right in front of the bulb? That way you'd only get the direct light from the front of the bulb rather than reinforcing that with a reflection from the back of the bulb.

12/11/2010 8:48:34 AM
I would think the glowing body would be a great addition to the safety and viability issue all cars have at night!

Jack McCornack
12/10/2010 5:01:16 PM
Jeff, it probably depends on how big a town you live in; in Eugene Oregon I can find "Plastics--Rods, Tubes, Sheets Etc" in the yellow pages but you might want to check "Plastics--Fabricating" or sign shops, which might have small bits of thermoplastics left over. George, good idea. I didn't think of that, and if I didn't already have the other stuff I needed I would have had to think more. Abbey, I didn't paint it black because previous experience had taught me that light bulbs get very hot if painted. Also I think the rock protection was important, since having hunks of broken headlight fall right in front of the tire could be bad news. But as with my response to George, I'm used to using thermoplastics to make things (doesn't sound very MENish of me, does it, but I do recycle the stuff) and as my grandmother used to say, Give a boy a hammer and everything looks like a nail.

Abbey Bend
12/10/2010 10:23:46 AM
Looks good and needing a rock deflector makes sense but would not a can of black paint applied to the back of the bulb have done the same thing in just a few seconds? Just asking.

12/7/2010 2:14:40 AM
Jack, I'm just curious, but wouldn't a pair of those aluminum clamp lamp reflectors have worked? They would deflect rocks quite well, be very lightweight, and able to withstand the bulb's heat. George

jeff dean
12/6/2010 8:37:41 PM
jack, Very nice! Looks great! Where did you get the plastic?

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