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Version 3

Materials:

  • MR-16 (~50mm) 20W 12V Halogen globe (sealed front): from Jaycar ~$5
  • Halogen globe holder: from Jaycar ~$3 each
  • Switch: from Jaycar ~$1 each
  • 50mm PVC pipe: from hardware shop ~$a couple
  • 50mm PVC pip endcap: from hardware shop ~$3
  • Hose clamps: From servo/auto shop/hardware ~$3
  • Assorted odds and sods: from home $0

"Why make a new version if V2 worked well", I hear you ask? Because it's there!... Hmm no wait... 42! .... Nope, still not right.. Ahhh! Because it's FUN!

This version is similar to the main beam from my Version 2 lights, but uses 50mm PVC conduit for the housing. This is the stuff that is lying around every building site, used for plumbing. You only need about 10cm for the actual light, so you can probably find some lying around. If not it'll only cost you a few dollars at the local hardware shop. To seal the back I used a standard press fit cap, which was about $3.

There are two ways to go about construction - build the housing, then do the wiring (which I did), or wire it up, then build the housing (which is probably easier). The first way has the advantage that you know what you're doing, and it's easier to paint the housing if you want to make it look flashier. The second way means you're not trying to solder joints in the bottom of a 50mm diameter cup.

To attach the various bits of PVC to each other, I used a plumber's adhesive specially designed for conduit. This is relatively cheap, but if you're really feeling like doing this cheap, araldite or other common "glue anything" adhesives might work. Don't ask me, I'm a computer geek, not an industrial chemist! Oh oh, now I sound like a Trekkie...

Since the endcap provides a flat surface I moved the switch to the back of the light. This looked pretty plain, so to provide a low-tech on-off indicator I drilled a hole and put an old red miniature light cover in it. Light coming through the reflector of the bulb shines out through this, and it works disturbingly well

The internal wiring is almost identical to the Version 2 . The wires come in, get tied in a knot to provide stress relief, then one goes to the switch while the other goes to the bulb. Another wire betwen the other switch contact and the other bulb contact completes the circuit. You could use a variety of methods to attach the wires but I'm happy with the cheap solution of solder. A standard RCA plug provides a quick release method of attaching the light to a battery, and comes undone easily in a crash.

Construction Schematic

I throw my battery into a backpack, which helps keep it reasonably warm, improving performance. It's reasonably comfortable. You might prefer to bodge together some kind of bike mount - I've tried a bag in the main triangle of my old hardtail, but since it got replaced with a duallie there's now a spring in the way...

To lock the bulb in I used a similar method to the lock ring in Version 2 , but an advantage of PVC piping is that a 5mm section of conduit makes a great lockring. Just cut about 1cm out of it and it should fit into the main housing. Use a bit of adhesive to lock it in place, and put a few screws around the outside to lock the bulb in place. Assuming you've put it all together OK, you should be ready to attach the lights to your bike.

Probably the easiest way to mount your lights to your bike is to use a couple of hose clamps. Put a large one around the light, and wrap a smaller one through this. The smaller one then clamps on to your handlebar. So long as you're reasonably competent with a screwdriver (and why are you reading this if you're not?) it only takes a few minutes to mount or remove the light.

A problem with PVC is that it's a pretty boring white, with weird bits of text on it. Granted these lights are always going to look a bit industrial compared to commercial systems, but they don't have to look that ugly. If you've got some paint lying around home give the housing a quick going over with sandpaper, then wack on a few coats. Light colours such as yellow take a few coats to mask any marks on the housing. In cold temperatures (under about 15 Celcius) most water based paints will be very slow to dry. Either use an oil based paint, paint in a heated room or similar, or use the heat from the light itself; Hook up the battery, put it on trickle charge, then turn the light on. Just be careful not to start a fire - I'm guessing some paints could potentially ignite.

It's also really easy to adapt this design for smaller MR-11 globes, like the 10w one described in my Version 2 lights . The only trouble is finding appropriate sized PVC pipe - try a few different places, and remember it's easy to make a lock ring to make the internal diameter a few mm smaller. Currently something like this is my main bar light, since it lets me run a smaller battery for a given run time.

I'll get some piccies up soon!


Previous: Version 2
Next: Version 4

If you want to abuse me: lights@hired-goons.net