kb0rrg
Enlightened
The Petzal Mega, even with the halogen bulb, was just not sufficient for high speed mountain biking in the woods, in the dark. I can not afford/justify one of the fancy off-the-shelf biking light ($150- 300). So I set out to build a better light.
The heart of any light is the bulb. I have found a bulb/reflector assembly that is commonly available at Walmart or Target stores. It is 50 watts and 12 volts...about 4 amps. About $5. The reflector is made of glass and is coated with something to make it reflective. It has an integrated glass lens. The glass may be Pyrex, I don't know. This bulb is commonly used in track lighting that is becoming very popular in architectural lighting (fancy cafeterias, coffee shops, and art galleries). I have been playing with this lamp assembly for a while now. I would describe the beam pattern as a moderate spot. The beam is flawless; I don't own any SF lights but I don't think that they could be any better. No rings or wedges at all. Very white. The diameter of the reflector is about 2"
The hardest part about the project was developing a holder for the bulb/reflector. It is an odd shape, and gets quite hot. It just so happens that it fits perfectly into the head of a Maglite if the mag reflector is removed. The only problem is that when the outer ring is installed, it does not hold the bulb tightly from moving in and out. There is about .150" of movement. I attempted to grind the ring and head in such a way to allow it to tighten a bit more. I was able to get the movement down to .020", but this still allowed the bulb to rattle...unacceptable. I wanted to put a spacer ring in there to take up the space, but I had no means to machine such a part. Instead, I made a 2" ring out of aluminum antenna grounding wire. This was put into the outer ring of the Maglite. When reassembled, the bulb was very securely mounted...I was happy. Wires were soldered directly to the bulb. Some light from the bulb passes through the reflector to the backside of the light. This light appears blue and can be seen from behind since the back of the Maglite head is open. I actually like this because cars can see me better from behind. I did not want to use any materials that could not withstand high temperatures. The Lexan lens from the Maglite was not used as it was not necessary and would have surly melted. In hind sight, the wire ring is all that is needed, the grinding was not necessary. Five .250" holes were drilled into the head of the light. This was to help with cooling, reduce the weight slightly and to allow cars to see me from the side.
The battery was the next part. I bought a sealed lead acid battery for multi-purpose use. I recently installed a bilge pump in my sailboat (500gph, 1 amp) so I will be using the battery for this too. It has a capacity of 7.4 Ah. I am guessing that that will give me a run time for the light of about 1 hour. (I do not want to run the battery too low) One hour would be sufficient for my needs. I estimate the weight to be 7 lbs. It is kinda heavy, but I guess that I will just have to deal with it. Lighter batteries exist, but for $20 this will work for now.
A flat spot was ground in the Mag head and two holes were drilled and tapped to allow for mounting to my helmet. I wanted a helmet mounted configuration so that there is always light in the area where I am looking and the vibration from the road is not transferred directly to the bulb. I built a quick release bracket to attach it to the helmet and installed a switch. I left a 12" wire hanging from the light where a quick disconnect electrical connector was installed. This is for convenience and safety. It should pull apart if the wire were to snag something instead of applying a dangerous torque to my neck...ouch!
Initially I wanted to mount the battery on my bike rack. But I had worries about the extreme pounding that is would be subjected to. The trails are very rough. In addition, it was cumbersome to run a wire from the bike to my head. It was always in the way, and I had to unplug every time I got off. The solution was to put the battery in a waist pack that I wear for x-county skiing and long bike trips. This has an advanced strap system with shoulder straps. I am quite accustom to carrying 5-10 lbs in this pack and found it to be very comfortable with the 7lb battery. Since the entire system is on me, there is no need to constantly plug/unplug and I can walk away from the bike with the light still operating. Before I took my test ride, I mounted a mini-mag holder to the bike frame. The mini-mag would serve my low speed, smooth terrain needs (like hill climbing) when 50 watts was unnecessary.
The big light turned night into day. AWSOME The beam pattern and shape was perfect. I Could see as far as I wanted, but still had more than enough sidelight to see EVERYTHING. I did not have to hold back at all. Full speed. It almost takes the fun out of night riding. No problems with heat. I was only running it in 2-5 minute bursts while on difficult or fast sections. Plus, the 10-20 MPH of forced air convection from the wind aided cooling. These bulbs are designed to run at a 100% duty cycle without a wind blowing across it. The mini mag was running the whole time, but it was too dim even at low speeds. I need to upgrade to something in the 4-8 watt range for my mid power option. There was some difficulty when the light was turned on while riding. It is so bright, that there is a slight disorientation and momentary blindness, but it only lasts a second or two. Since it is only on half the time, I expect I could ride about 2 hours.
I don't know what the lumen rating of the light is. According to Brock's site a 12PM/M6 is about 30 watts and 500 lumens. My light is 50 watts. Most car headlights are 55w each. If my light has a similar efficiency, then my light is nearly 700 lum. This is a very rough figure though. My best light is a 3D mag, and that is not even a comparison. I would like to test it against a 500 lumen light some day. I will admit, it is not as light or compact as a 12PM/M6, but I have little invested and I suites my needs (bright, rechargeable, 1+ hour run time, head mounted.)
Now that I have a headless Mag-lite, any ideas for it?
The heart of any light is the bulb. I have found a bulb/reflector assembly that is commonly available at Walmart or Target stores. It is 50 watts and 12 volts...about 4 amps. About $5. The reflector is made of glass and is coated with something to make it reflective. It has an integrated glass lens. The glass may be Pyrex, I don't know. This bulb is commonly used in track lighting that is becoming very popular in architectural lighting (fancy cafeterias, coffee shops, and art galleries). I have been playing with this lamp assembly for a while now. I would describe the beam pattern as a moderate spot. The beam is flawless; I don't own any SF lights but I don't think that they could be any better. No rings or wedges at all. Very white. The diameter of the reflector is about 2"
The hardest part about the project was developing a holder for the bulb/reflector. It is an odd shape, and gets quite hot. It just so happens that it fits perfectly into the head of a Maglite if the mag reflector is removed. The only problem is that when the outer ring is installed, it does not hold the bulb tightly from moving in and out. There is about .150" of movement. I attempted to grind the ring and head in such a way to allow it to tighten a bit more. I was able to get the movement down to .020", but this still allowed the bulb to rattle...unacceptable. I wanted to put a spacer ring in there to take up the space, but I had no means to machine such a part. Instead, I made a 2" ring out of aluminum antenna grounding wire. This was put into the outer ring of the Maglite. When reassembled, the bulb was very securely mounted...I was happy. Wires were soldered directly to the bulb. Some light from the bulb passes through the reflector to the backside of the light. This light appears blue and can be seen from behind since the back of the Maglite head is open. I actually like this because cars can see me better from behind. I did not want to use any materials that could not withstand high temperatures. The Lexan lens from the Maglite was not used as it was not necessary and would have surly melted. In hind sight, the wire ring is all that is needed, the grinding was not necessary. Five .250" holes were drilled into the head of the light. This was to help with cooling, reduce the weight slightly and to allow cars to see me from the side.
The battery was the next part. I bought a sealed lead acid battery for multi-purpose use. I recently installed a bilge pump in my sailboat (500gph, 1 amp) so I will be using the battery for this too. It has a capacity of 7.4 Ah. I am guessing that that will give me a run time for the light of about 1 hour. (I do not want to run the battery too low) One hour would be sufficient for my needs. I estimate the weight to be 7 lbs. It is kinda heavy, but I guess that I will just have to deal with it. Lighter batteries exist, but for $20 this will work for now.
A flat spot was ground in the Mag head and two holes were drilled and tapped to allow for mounting to my helmet. I wanted a helmet mounted configuration so that there is always light in the area where I am looking and the vibration from the road is not transferred directly to the bulb. I built a quick release bracket to attach it to the helmet and installed a switch. I left a 12" wire hanging from the light where a quick disconnect electrical connector was installed. This is for convenience and safety. It should pull apart if the wire were to snag something instead of applying a dangerous torque to my neck...ouch!
Initially I wanted to mount the battery on my bike rack. But I had worries about the extreme pounding that is would be subjected to. The trails are very rough. In addition, it was cumbersome to run a wire from the bike to my head. It was always in the way, and I had to unplug every time I got off. The solution was to put the battery in a waist pack that I wear for x-county skiing and long bike trips. This has an advanced strap system with shoulder straps. I am quite accustom to carrying 5-10 lbs in this pack and found it to be very comfortable with the 7lb battery. Since the entire system is on me, there is no need to constantly plug/unplug and I can walk away from the bike with the light still operating. Before I took my test ride, I mounted a mini-mag holder to the bike frame. The mini-mag would serve my low speed, smooth terrain needs (like hill climbing) when 50 watts was unnecessary.
The big light turned night into day. AWSOME The beam pattern and shape was perfect. I Could see as far as I wanted, but still had more than enough sidelight to see EVERYTHING. I did not have to hold back at all. Full speed. It almost takes the fun out of night riding. No problems with heat. I was only running it in 2-5 minute bursts while on difficult or fast sections. Plus, the 10-20 MPH of forced air convection from the wind aided cooling. These bulbs are designed to run at a 100% duty cycle without a wind blowing across it. The mini mag was running the whole time, but it was too dim even at low speeds. I need to upgrade to something in the 4-8 watt range for my mid power option. There was some difficulty when the light was turned on while riding. It is so bright, that there is a slight disorientation and momentary blindness, but it only lasts a second or two. Since it is only on half the time, I expect I could ride about 2 hours.
I don't know what the lumen rating of the light is. According to Brock's site a 12PM/M6 is about 30 watts and 500 lumens. My light is 50 watts. Most car headlights are 55w each. If my light has a similar efficiency, then my light is nearly 700 lum. This is a very rough figure though. My best light is a 3D mag, and that is not even a comparison. I would like to test it against a 500 lumen light some day. I will admit, it is not as light or compact as a 12PM/M6, but I have little invested and I suites my needs (bright, rechargeable, 1+ hour run time, head mounted.)
Now that I have a headless Mag-lite, any ideas for it?
