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Cycling - DIY headlight project

In a hot climate it can be hard to get out and enjoy a bike ride, especially if you're a night owl and regard 8am as the crack of dawn. Personally I love riding late at night when the roads are empty, the temperature drops and there's no chance of frying in the hot sun.

Riding at night involves certain preparation: a reflective vest is good, as are reflective ankle and wrist bracelets. I wear sunglasses with clear lenses, to prevent insects flying straight into my eyes. A red flashing light on the back of the bike is important, but most important is seeing where you're going.

What is the ideal cycling light? To me, something very bright, low cost, and which uses cheap batteries which seem to last forever. Until now this was an impossible dream, but I've managed to bodge together several readily-available components into a massively bright headlight ... and the total cost is under $15!

Items required:
"76 LED Bicycle Bike Light Torch" (about $8 new plus postage) - Search ebay for it
6v lantern battery (el cheapo ones are $3 or so)
Approx 2 metres/6 foot of cheap speaker cable (two wire)
Two crocodile clips or spade lugs, preferably one red/one black
Soldering iron and solder
Pair of scissors or snips
Drill or small flat-bladed screwdriver.

Now, you can just buy the bike torch, fit it to your bike and go merrily on your way, but four AA batteries will only last a few rides. (Plus the battery contact is intermittent, which can be dangerous.) To really make this project work you have to bypass the four-AA-battery holder and provide juice from the 6v lantern battery instead. The lantern battery will fit into a drink bottle cage on your bike, and I get a year out of a battery whilst riding 2-3 one-hour rides per week.

First things first - remove the battery cap from the light and take out the battery holder (black plastic with springs). It has two silver terminals, and it will only go into the light one way. Fit four AA batteries into the holder and note which of the terminals is positive, and which is negative. Look into the battery compartment of the torch, and you'll see two matching lugs deep inside. By checking the battery holder, the batteries and the lugs, you should be able to work out which lug is positive and which is negative. (If you can't do that, I wouldn't go any further with this project.)

Look inside the battery compartment and you'll notice the lugs are actually long metal strips which start near the opening and travel down a pair of plastic channels, before bending at right angles to make contact with the battery holder. We COULD solder to the lugs at the far end, but it's much easier to solder the wires right near the opening ... after you trim away some of the plastic channel. Using the scissors, snips or screwdriver, cut away 5-10mm (1/4 to 1/2 inch) of the plastic channel near the opening of the battery compartment, exposing the full width of the shiny metal strips.

Next, separate and strip 5mm / quarter inch from each end of the speaker cable then twist and tin the four bare wires. One wire of the two will have a coloured line on it - this is your negative cable. Solder one end to the silver strip you identified as negative. Solder the unmarked cable to the other strip. (Try and do this fairly quickly. If you get the strip too hot, the thin wires already soldered to the back of it will come off. You'll need to unscrew the front of the torch, expose the innards and solder them back on again.)

Now tie a knot in the wire about 10cm/3 inches from the solder joint. Make two small holes in the battery cap and pass the free end of the wires through these holes.

Solder the black crocodile clip/spade lug to the negative (marked) wire, and the red clip/lug to positive. Check your work carefully, especially the -ve and +ve inside the battery compartment. Then connect the blue lug/clip to negative on the battery, and the red wire to positive. Cross your fingers, and switch the torch on.

I've made seven of these lights so far, and they're great. I put the light on the handlebars, then place the battery in the nearest bottle cage and feed all the spare wire inside the light.

By the way, the handlebar clip which comes with the torch is useless. It will break after you remove it from your handlebars a couple of times, but all is not lost. Drill a small hole through the broken clip (right through the part where the torch fits on to it) and use a large zip tie to secure it to your bars. You can also fit the thing upside-down to unclutter the top of your handlebars, and because the light isn't full of heavy batteries it's not subject to much stress.

One refinement is to stick a rubber pad on the back of the light, and run velcro through slots cut in the (now unused) battery compartment. This makes it very easy to move the light from one bike to another. Alternatively, use one of those silicon bike bandages (like a big rubber band) to secure the light.

Enjoy your night rides, and remember your hi-vis vest and reflective tape!

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