If you live somewhere that's dark and difficult to reverse out of at night,
this light's for you. So many cars have got lousy reversing lights - sometimes
apparently put there only for legal reasons - that it's a lucky dip what you hit
and what you get past. But while you might want to upgrade the reversing lights,
not too many people want the visual impact of a single large driving light
mounted on the back of the car!
But this quartz halogen light is so small that you can tuck it under the rear
bumper, out of sight to all who don't get down on their hands and knees. It's
also cheap and easy to make.
The Parts
You'll only need a few parts to make the light. First up, the black thing is
an ordinary towball cover. The light (with inbuilt reflector) is a 12V halogen
downlight of the sort used in commercial and domestic lighting - they're
available from everywhere that sells light bulbs. The other item is a small
magnifying glass, which is used to make the beam more even and protect the bulb.
(Alternatively, you can buy a bulb which comes with a clear glass cover built
in.)
This particular towball cover came with an internal metal spring strip, but
it's easily removed. A metal towball cover would be even better, but they're
hard to source.
The 12V lights come in different wattages and beam shapes. A 20W unit is best
- despite being less powerful than a 50W bulb, by the time the voltage drop of
the larger current draw is taken into account, a 50W lamp can be no brighter
than a 20W one! The 20W bulb also saves the reversing switch having to work
too hard. Wider beam spreads are usually more useful than narrow ones - though
it depends a bit on if you are going to use a proper lens.
We decided to use a convex lens (ie one like a magnifying glass) that had
been salvaged from a slide projector. A small glass magnifier could also be used
- or you could use nothing at all and select a halogen bulb with a 'lens' built
in.
Building It
If the pins are cleaned-up with a file, the cable can be directly soldered to
the lamp. Connectors are available for the bulbs, but they can double the cost
of the project!
Place a knot on the cord (so it can't be pulled out) and then feed the cord
through a hole drilled in the back of the cup.
A little experimentation with the bulb and the convex lens showed that a
good, even spread of light was obtained if the front edges of the bulb reflector
were right up against the lens. (Some other combinations might need the
reflector spaced back a bit from the lens.) The cup was then stuffed with some
acrylic quit wadding that was handy (any springy relatively non-inflammable
substance could be used) so that when the lens was inserted, the bulb would be
pushed up against it.
The lens - which was sized to be a push fit inside the plastic cup - was then
glued into place and the light tested. If the lens is undersize, use black
silicone sealant to glue it into place. (This also applies if you are using bulb
that comes with a glass cover.)
Wiring of the light is easy - just find the pair of wires that run to the
reversing lights and connect to those. The connections were made here with
plastic crimp connectors. (The extra two are for the centre high mount brake
light that was previously added.) Note that a 20W extra reversing light
shouldn't cause any problems, but if the fuse for the reversing lights keeps on
blowing, just upgrade its current rating a little.
The light could then be mounted under the bumper with a small bracket.
|
Heat!
This light is not designed to be run
for long periods! As a reversing light - where it's on for less than a
minute at a time - it's fine, but if left on continuously, the plastic towball
cover will melt! If you want to follow the same general approach but run the
light continuously, source a metal towball cover and use a high temperature
silicone adhesive to hold both the reflector and lens in place.
|
|
Too Dim?
If you find that the new reversing light is much dimmer when installed than
when you were testing it, it's probable that a voltage drop is occurring through
the thin factory wiring. A normal automotive relay can be used to overcome this
problem, installed as shown in this circuit diagram.
|
|