Introduction: How to Transform a Flashlight Into a Bicycle Headlight

Do you like biking at night, but don't want to drop $40 on an official bike headlight? Especially when you have all these perfectly good cheap flashlights lying around? Well, I got an Instructables for you!


  • Some kind of 3D printer, whether hired or owned.
  • An old flashlight of some kind. Try to find a shorter one, because a longer one can be unwieldy on your handlebar.
  • A 3D cad program, I used inventor, but you can use any cad programs and it should have similar steps.
  • Caliper or ruler.
  • Zip ties, or a small bolt and nut.
  • velcro cable ties.

Step 1: Measurements

You need to get three different measurements.

  • The width of your flashlight handle
  • The Length of your flashlight handle
  • The width of your bicycle handlebars

(Pardon me for not using Metric, my inventor is stuck in standard units)

Step 2: Clasp

Let's start by designing the clasp. Using the width of your handlebars, design two concentric circles and add a rectangle sticking out. Using another rectangle, cut a slit in the side of the circle. This makes an opening to slip over your handlebars. extrude about half an inch

(I printed this before I realized that as an improvement, I'd suggest designing a hinge to open the clasp better)

Step 3: Cradle

Next, we'll design the cradle to hold the flashlight. Start a sketch on the origin plane perpendicular to the clasp. using the width of your flashlight, make two concentric circles with the inner one being the same diameter as your flashlight. the outer one being around .1 - .2 inches bigger. About 3/4s of the way down, using the line tool, connect a horizontal line between the two circles on both sides. Make sure that the circles overlap your previous clasp so that when you print, it will print together. when you finish, extrude the length of the flashlight with it centered on the plane. (if it is a short flashlight). If your flashlight isn't very short, extrude it about half the length of your flashlight handle.

Step 4: Secure Flashlight

Now we get to where we need to find a way to secure the flashlight to the mount. The way I figured out is to design a slit that extends up from the top of the curve. Start a sketch from the plane on top of the curve. At every corner, design a square the width of .1 and the length of the edge it is on. Extend a half-inch and design another one. Extrude these up .1 inch. then start another sketch on top and make a rectangle from one square to its partner. extrude up .1 inch.

Sorry if you're confused, it's hard to explain. Please look at the pictures, they help.

Step 5: Export and Print

Export and bring it into your printers slicer.

My settings

  • You can use a raft or no adhesion depending on your printer
  • I printed with support structure
  • I printed it on its side because my printer doesn't print arches very well.
  • It took about 2 hours to print on normal settings.

Step 6: Attach to Your Bike

This is where the zip tie/bolt and nut comes in. you must have noticed the hole, this is for the bolt or the zip tie to attach securely to the handlebars. Then, take the velcro cable ties and slide them through the slits to secure your flashlight to the mount. When you go to mount it, I'd suggest either sliding it from the side or using a heat gun to slip it over.

Step 7: Have Fun

Enjoy biking at night safely!!

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