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1.4 The Ultimate Homebrew Bike Light: IV. Construction


This article is from the Misc Bicycles FAQs, by various authors.

1.4 The Ultimate Homebrew Bike Light: IV. Construction

This assumes that you have some basic tools at your disposal. If not,
buy a commercially made bike light. Otherwise, read on.

1. Cut the PVC pipe into 6 sections as follows:

1- Two pieces - ~ 3" long
2- Four pieces - ~ 1/2 to 3/4 " long

I used a radial arm saw to cut mine so the ends came out smooth and
square. If you use a hand saw, like a hack saw or coping saw, you'll
need to do some finish work with sandpaper or a file, or both, in
order to get a smooth, flat end. One technique that works well is to
put some medium sandpaper ( 100 grit ) on a flat surface and sand the
pipe edges on that.

Don't buy the thick wall pvc pipe that is most common in hardware stores.
Schedule 200 has a wall thickness of about 1/8", rather than 1/4", which
is the more common size. The lamps will fit inside of the schedule 200
pipe, but the thick wall pipe will need to be machined out. Also, its
lighter and stays cooler than the thicker material.

2. Cut a section of about 3/4" in length out of each of the 4 PVC rings.

This will allow you collapse the diameter of these rings and slip them
inside of the the 3" long pieces. These split rings will become the lamp
support and will form an internal shoulder for the aluminum disk which
will form the rear of the lamp housing.

The hardest part of this project is making the back of the lamp. This
is how I did it. If you have a better way, let me know!.

3. Mark two circles, about 2-1/8" diameter on the aluminum plate.

4. Drill a 3/8" hole in the center of each circle.

5. Rough cut each circle using a sabre saw with a metal cutting blade.
Be sure to stay outside of the marked circumference of the circles.

6. Insert a 3/8" bolt through the two disks and locked them together with
a nut. Place a washers on either side of the disks help to hold them
securely in place.

7. Put the body of the bolt in a 3/8" drill and clamped the drill in
a vise ( a drill press would be even better ). With the disks spinning,
files the rough circumference until the disks were round, smooth, and
just small enough to fit inside of the 3" PVC pipe.

Don't get carried away here. It is quite easy to remove too much material
from the disks.

8. Carefully locate a point on the radius to drill a hole to mount the
on/off switches. They take about a 1/4" hole. The hole should be about
1-1/4 from the center of the disk.

You will need to locate the hole far enough out to clear the mounting
hardware but not too far to interfere with the PVC ring that will form
the rear lip to hold the back of the lamp enclosure ( the aluminum
disks ) on.

9. Drill the holes.

10. Sand the inside of the PVC pipes near the rear, sand the outside
of two of the PVC split rings and sand the edges of the aluminum disk.

11. Wipe all the pieces clean ( or wipe with alcohol ). Mix a batch of
epoxy and spread it around the inside of one of the pipes, at the end.
Also spread some epoxy on the outside of one of the split rings.

12. Compress the split ring and insert it into the pipe.

Try to avoid pushing all the glue into the pipe, this glue is needed to
hold the split ring to the pipe.

13. Recess the split ring about 1/16" into the pipe. Be sure there is ample
glue around the lip that you just formed and place the aluminum disk
into this gooey mess. Press down, forcing glue around the disk and
further recessing the split ring until the aluminum plate is flush with
the rear of the pipe.

14. Wipe up the excess glue and set aside to dry. Repeat for the second
pipe and disk.

15. After the back is firmly attached, glue the remaining slip rings
to the front of the pipes. Recess them about 1/4" .

These rings will hold the bulbs. Before the glue sets check that the
ring is not cocked in the pipe. It should measure the same distance
into pipe around the circumference.

16. When the glue is completely dry, sand the outside surface of the
pipe and the aluminum disks.

17. Wipe them clean and then paint with two coats of spray primer. Only
paint the outside of the holder and the 1/4" recess where the lamp will

18. Paint with gloss black spray enamel. When dry, your lamp holders are


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