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We love our bike lights, but they shine such a small, intense light. We have expanded the visiblity of a rear bike light. We use the translucent material of a milk bottle to diffuse light across a wider space. We've checked to make sure it does project enough brightness at a distance to keep a rider safe. Better yet, the design is surprisingly fun and seems to put all road users in a friendly mood :)

Step 1: Materials

You will need:

  • A translucent bottle. We used a plastic milk bottle.
  • A marker
  • A cutting blade
  • A red bike light. A tube-shaped bike light with ridges is best.
  • Old nylon stockings or cable ties.
  • A bicycle with a rear rack.

Step 2: Insert the Bike Light Into the Bottle Lid

  1. Rest the bright end of the bike light against the top of the lid. Trace around the light with the marker.
  2. Using your cutting knife, cut a hole at least 5mm smaller than the circle you just traced. You want the bike light to fit snugly in the hole, so it's best to start small.
  3. Test inserting the bright end of the bike light into the top of the lid. Enlarge the hole as needed. It's easier to get the bike light to sit snugly if the light has ridges along it's body.
  4. When the bike light is secure, screw the bottle lid onto the bottle.

Step 3: Position the Diffuser on Your Bike

  1. Hold the bottle horizontally along your bike's rear rack.
  2. Note where the vertical bars of the rack meet the horizontal tray of the rack. These bars will help straps from sliding along the rack.
  3. Mark points on the bottle for straps to wrap under the rack, using the bars as anchors.

Step 4: Optional: Make Nylon Straps

If you are using old nylon stockings as straps, cut the stockings into 1 inch strips. Combine strips as needed to make the length of strap you need. Remember to account for the stretch in the stockings!

To combine the strips:

  1. Place two strips down, one overlapping the other
  2. Take the part of the strip that is being overlapped, and fold it in half lengthways (out towards the other end of that strip, over the overlapping strip)
  3. Continuing to hold the strip, slide it under the opposite end of the same strip.
  4. Pull both 'ends' until the knot in the middle is snug

Step 5: Attach Straps

  1. Cut small holes where you marked them on the body of the bottle.
  2. Thread nylon straps or cable ties through the holes.

Step 6: Attach the Diffuser to Your Bike

  1. Lay the bottle horizontally along your bike rack.
  2. Wrap the straps under the rack.
  3. Tie the staps off to the side (so the ends don't interfere with your bike wheel).
  4. Trim the ends of the straps if needed.

Step 7: Test Brightness of the Light

Where we live, there are regulations on how bright a light needs to be over a distance. In our case, the rear red light needs to be visible from 200 metres.

To test this, we mounted the light diffuser on our bike and viewed it in the dark 200 metres away. It passed the test! Our light is also more visible from the side than regular lights.

Note: If your light is not visible from far enough away, you can cut a hole in the base of the bottle. This will allow more light to project behind you, but the diffuser will be less bright when viewed from the side.

Step 8: Ride Out!

Enjoy your new bike light diffuser! We hope you have as much fun using it as we have.

Recharging your light is easy. Unscrew the bottle cap (with the light in it) for easy access to your bike light.

<p>With any given light-source, the more you spread it out - the lower the intensity. The human eye is a peak-reading element with persistance (that is how a rapid sequence of still-images appear to move in a movie). You really want high intensity rather than a lower one over a bigger area. My own back light uses an edge-emitting 1W luxeon star and a couple of LiPoly phone batteries in parallel. It is agressively bright yet only tiny at source. This means it is easily visible at a great distance - close up it is unbearable to look at. Cars overtake giving a wide berth. I survive - so far. Grrrr.</p>
<p>Maybe a light orange for Halloween </p>
<p>Great! I always wondered what I could make out of these small plastic bottles some probiotic drinks (like Yakult) come in. Perhaps they are good diffusors to make a nice tent-light out of a normal flashlight ... I have to notice that on my shopping list and try it out later ...</p>
<p>I think the tent light is a great one.</p><p> It seems it would cost a lot less.</p>
<p>This definitely works with smaller bottles as well, a friend made his out of a shampoo bottle. I love your idea of using it to make a tent light!</p>
<p>I bought some small Actimel-bottles yesterday and tried it out - the result is perfect for my needs. Just had to cut off the bottleneck.</p>
<p>Excellent! Thanks so much for sharing :)</p>
<p>smashing idea! can't have too many lights on ya bike :) ...well...? XD</p>
<p>Thank you! I agree - a cheerfully lit up bike is a wonderful thing :)</p>
<p>There is a slight snag with this rear lights should be red on road vehicle natural assumption of a driver on seeing a white light at night is it is coming towards them and not being that bright that it is some distance away. Not that they are catching it up fast on the same side of the road.</p>
<p>Agreed - where I live the law mandates red rear lights so this is what I've used. It may be that you're perceiving the light as white in my first photo because the brightness of the light has overexposed that part of my photo. You can see by the reflection on the bike rack that the light is red. Certainly when on the road the red colour of the light is clearly visible.</p>
<p>ah yes hadn't noticed the glow on the carrier, was impressed by the idea just a little worried that it apeared to be a white rear light which now you pointit out it clearly isn't.</p>
<p>I agree with you it's really important that a rear light is red for safety and legal reasons. I'm sorry I don't have better equipment to represent the light more like it looks in person, because that photo does seem to have mislead a few people. I'm glad you think the idea is sound :)</p>
I see where the builder is going but your right about the red light being seen - that being said if the bottle was filled with water and the material clear plastic there are lots of folks around who have used a similar idea, single light into a liquid filled holder but in their case the power is from the mains, should work just as well with the battery unit though, the light is magnified more than diffused so if applied here, the visibility range might increase and the red lamp should be clearly visible now.<br>Someone just needs to apply the re mod and post the results.<br>Nice build from a person who's heart is very much in the right place.
<p>Fascinating and simple at the same time! As other viewers have commented if it is a rear light, it should be red. You can paint the bottle red with a pen or wrap it in semi-transparent red hue film.</p>
<p>I'm glad you like this build! In this instance I have used a red light, <br>but it looks like the overexposure of the image is making it appear <br>white to readers. I've tried to adjust the image to make it clearer, to no avail. The wording of the instructions does list a red light in the materials needed and state that a red light ought to be used for rear of vehicle installs.</p>
<p>This is such a simple and awesome idea!</p>
<p>Agreed! I'm glad you like it :)</p>

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