After version 1 of my Hippy lights exploded, I decided to use what I'd learnt to rebuild a new set. The new design was based on The Fat Hippy's Mk3 lights, using a towball cover for the main housing. After turning up a 12V 10W halogen globe in K-mart, I decided to make a dual beam system. The 10W draws around 1 Amp, so in theory I should get around 3hours out of a 4Ah battery, even after derating for load and cold. The 2001 Mont 24Hr proved that this is about right, when the night laps got a little muddy.
With my earlier efforts at a Hippy Light, I'd simply attached the wires to the back of the light. This was fine in the workshop, but on the trail where you're falling off, catching wires, and otherwise being nasty to your lights, the wires had a tendency to fall off. Great fun at 60 km/h down rough bits of The Oaks... Since there's a reasonable amount of room inside the towball cover, the easiest way to solve this is to put all the delicate connections inside, and put a simple knot in the wiring just inside the cover.
The internal wiring is very simple. 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.
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...
One problem with the original Hippy Light is the way the halogen globe is mounted in the towball cover - The Fat Hippy addressed this by gluing a ring of PVC pipe to the globe, which is then clamped in place by a hose clamp around the whole assembly. This means that to replace the globe means gluing a new bit of pipe to it - while this might not happen all that often, I wanted something easier...
To solve the bulb-falling-out-of-the-housing problem, I cut about 5mm of the end of a tube of silicone - the style of tube that fits a Caulking Gun. After cutting this so that I could expand it, I glued it in place in the towball cover. The globe fits snugly against this, and 4 screws hold the bulb so it doesn't fall out the front. To replace the globe I simply remove the 4 screws, pull the globe out of the socket, put the new one in, then replace the screws
The MR-11 5W bulb presented problems because it was only about 30mm in diameter - I might have been able to get it into a towball cover, but it would have been silly. A trip to the local hardy turned up a PVC conduit joiner with an inside diameter of 30mm - BONUS!
To lock the bulb in, I used a similar locking system to the one in the towball cover - except that I had to chop a bit out of the ring to allow for the smaller circumference. The end cap of this part of the light is the end cap off the tube of silicone and an old film canister cap. A little glue, another hose clamp, some zip ties to hold the two lights together, and it was time to work out a mounting system...
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 few minutes was annoying to me, so while I was building lights V1 I'd gone to an LBS and got a mounting clamp for $deity knows what. It was a big ugly thing, with the sole good points that it worked quickly and was free. A couple of bolts later, I'd attached it to the towball cover, and it was ready to test!
Testing turned up a few problems - the main one being that over time the towball cover would rotate around on the bolt holding it to the mounting clamp. Unfortunately there's no room to put a second bolt, so the first thing I tried was some glue - this worked fine until I'd hit a big bump, when it'd break.
After a little thought, and a leaf through the backyard engineer's bible (whatever was lying around the bottom of the toolbox), I decided a few zip ties were the answer - one large one to reinforce the join between the PVC joiner and the towball cover, then two smaller ones to clamp this to the mounting bracket. voila - one Hippy Light PLUS TM
This system worked for a while, but I was never all that happy with the zip tie, and it also meant that the quick release clamp was offset, since it would only be solid if it was directly under the towball cover. A large hose clamp replaced the zip tie, and I realised that I had fluked the spacing of the components so threading the quick release clamp through the large hose clamp meant that it was solidly held in place. Excellent!
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