The need for a proper bike light is more than just a safety issue. While most are happy with a small blinking LED-based light, others need a more powerful solution. A LED flasher does nothing to improve forward visibility. Better LED flashers allow you to be seen (if riding on the streets) by incoming motorist, but it doesn't help the actual rider see any better.
This is compounded by the need to have different lighting on different situations. For a well-lit street with designated bike lanes, a low-powered light might be sufficient. For trail riding at night (or riding in inclement weather), a more reliable high-output light is a necessity.
A quick look at what's available for supplementary lighting yields a myriad of models and devices. Some are simple LED multi-mode, blinker-type lights powered by AA or AAA batteries. The midrange versions are 1-2 watt LED units that are still insufficient to see with. The high-end and high power models are very good for both street and trail use but they also command a hefty price tag usually US$200-500. Being a casual biker, I simply cannot justify spending that much for a bike light.
Articles on the internet regarding homebrew DIY solutions abound. Some are simple solutions requiring just a handful of parts. Quite a few of these have questionable build quality and longevity. The better ones are usually well planned and yield both satisfactory and safe results. The most complex designs may require specialized parts and equipment and may even add up to a few hundred dollars to construct. I understand why some people would prefer the latter, but in my case, cost was still the predominant factor.
My ultimate goal was to have the satisfaction of making and customizing my own bike light using materials that I already have. I want to make it safe to operate, reliable, and use tools for construction that most people already own. The objective of this project is the construction of a street and trail capable forward facing light. (For general street riding at night, see my additional notes at the end of this write up.)
My Parts List:
- a 20watt Halogen MR16 bulb 12Volts
- a stainless steel spice jar approx 5.7 x 7.8 cm
- several 8" velcro cable ties
- 5Ah Sealed Lead Acid rechargeable battery
- Battery charger (Motomaster Model 11-1543-6, 12V 1A charger)
- Computer power cord
- 2 pcs 1/2 inch right angle corner support
- rocker switch
- JB weld or any suitable heat resistant epoxy
- 4 pcs female spade connectors with insulation
- rivets
- heat shrink tubing
- inline fuse holder
- silicone adhesive/sealant
- paint (optional)
- 4 inch length of aluminum (1/2" x 1/8")
- 2 bolts and nuts
- cyanoacrylate glue (super glue or anything similar)
The MR16 bulb is a halogen bulb commonly used in under-cabinet and track lighting. It usually comes in various brightness (luminosities) and power consumption. The most common are 10, 20 and 50 watt versions that need 12 volts AC or DC. It also comes in different beam patterns ranging from a 8 degree narrow spot (highly focused beam)to a 36 degree wide floodlight. (These bulbs are similar to automotive bulbs with the added advantage of having a built-in optimized reflector. Local hardware stores may sell these for about $5-10, I got mine from a dollar store. I decided to go with a 20W globe with what appears to be a narrow flood beam pattern and a manufacturer claimed 700 lumens as the best compromise for a single light setup. If I was making a dual beam setup, I would probably go with a combination of a narrow and a wide beam MR16 for best coverage.
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Sidebar:
Some brand name globes in the 20W range may be brighter than others. One brand claims up to 850 lumen output. If you want to increase the light output of quartz-halogen bulbs, you can over-volt them by 10-20%. The efficiency of a halogen bulb increases with a corresponding increase in voltage. The downside is a proportionate decrease in bulb life. A 20W/850 lumen globe overvolted by 10% or 13.2 volts gives an output of 23.6W/1181.5 lumens. Running it at 14.4 volts (+20%) yield 24.8W/1555.5 lumens. A typical MR16 globe has a runtime of 3000 hours. When overdriven, it is difficult to predict when it is going to fail, but it is usually less than a third of the expected lifetime.
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The most critical part of the light assembly for me was the housing. It has to be able to hold the light properly as well as not look like an afterthought. I wanted it cheap but I did not want to compromise in terms of looks. I've read online that some people have had good results with PVC pipe, trailer ball covers, plastic end caps, etc., but with a 20 Watt bulb, I was more concerned about the heat that was going to be generated by the setup. I definitely need a metal housing. I experimented with various possibilities, then I came across a stainless steel spice jar that was almost the perfect size. The jar had a removable lid with glass-covered hole. That hole was about a millimeter smaller than the MR16's effective reflector size.
A pair of 1/2 inch right angle corner supports were carefully bent to shape to follow the contour of the stainless jar. These supports are commonly used in cabinet making and woodwork. They were glued to each other using JB weld and then glued to the housing. To make sure that they stay in place, 2 holes were drilled on the housing for blind rivets. Now my supports are bonded both chemically and mechanically.
Drilling rounded polished stainless steel is difficult. Avoid using a dremel as its rotational speed is too fast and will result in a burned out drill bit. Mark the location of the hole with a center punch and drill at the slowest speed possible.
To attach the MR16 globe to the jar's lid, I initially tried Elmer's Glass and Ceramic glue. It did not seem to work too well and I ended up using a combination of JB weld, silicon sealant and a lenght of tubing. The tubing was actually a leftover piece of the power cord. The contour of the lid allows the globe to be glued into place. The tubing presses against the lip of the jar and high temp silicone adhesive holds it further in place. Two small holes were drilled onto the lid which corresponds to another two holes on the jar's lip. When mated, a pair of tiny self-tapping screws hold the two pieces together.
Another hole was drilled on the bottom of the jar so that a rubber grommet could be fitted. The grommet would prevent the power wire from being stripped and shorted by the steel housing, as well as make the housing look more professional.
Standard insulated female spade terminal connectors were used for connecting to the MR16 globe. A better way was to use proper MR16 ceramic holders. My local Homedepot wanted $5 for one, so I just ordered one from eBay for under a dollar. I will update the connector when it arrives.
A rocker switch was obtained from a broken computer power supply. You can use any type of switch as long as it is rated to handle at least 3 Amps of current. The switch was housed in a homemade enclosure constructed from plastic recycled from computer case bay covers. I just cut them to size, glued them together with cyanoacrylate based glue and sanded it smooth.
Version 1.0 had the switch closer to the light's housing. I initially intended the switch to be strapped onto the bike's toptube but the final result didn't look too good. I did not mount the switch on the stainless steel jar for two reasons: First, it would be exposed to the heat inside the housing and may melt; and Second, if I needed to turn the light off after prolonged use and accidentally touched the warm housing, it might surprise me enough to cause me to fall off the bike. Technically, the stainless housing doesn't get that warm, but as a safety precaution, it was probably best not to have the switch and the housing as a single unit. Another option was to mount the switch assembly on the handlebar, but this route would result in more wires and clutter on my already crowded handlebar.
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Sidebar: To test the feasibility of using the spice jar as the housing, I inserted the halogen globe all the way into the steel housing and ran the bulb indoors using a 12 volt car battery for about 2 hours. I wanted to simulate a worst case scenario of little or no air flow with the light on. A temperature reading of about 50 degrees Celcius was observed. While it was very warm to touch it should be noted that the bulb was actually facing into the stainless jar. All of the heat radiated from both the front and back of the globe was being contained within the steel jar. This was an acceptable result that allowed me to conclude that the chosen housing was sufficient.
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Version 1.1 relocated the switch right underneath the seat. For me, this was an ideal location that not only provided less clutter but was accessible and relatively shielded from direct rain since the switch itself isn't waterproof. Note the "obligatory" warning label to make it look more professional :-p
In order to have the power wire blend a bit better with the bike, I decided to recycle a computer power cord. This is a standard cord with 3 insulated wires inside. For my setup, I only needed to use two wires. The wire looks like the brake and shifter cable housing so it doesn't stand out too much. Velcro-style cable ties are used at strategic areas to hold the cable in place. Since I did not need the lighting setup permanently installed, velcro makes a sturdy yet easily removable system.
The nice thing about these velco straps is that they already have a sewn loop to hold the power cable. All I needed to do was run the power wire through each loop.
Upstream of the switch, the cable goes into the underseat mounted bike bag. This bag contains a 5Ah sealed lead acid rechargeable battery. Depending on the light wattage and desired run time, you may be able to use different battery types or a different SLA battery size. On my system, the 5Ah should give me a derated run time of at least 1.5 to 1.75 hours. Should I decide to go with a lower wattage bulb, that runtime would also be proportionately increased.
Hard plastic terminal covers protect the battery connections.
Despite being such a simple setup, it is always recommended to use a fuse. A 5Amp glass tube fuse is connected as close as possible to the battery.
When removed from the bike, this is what the assembly looks like.
To mount the light on the bike, I tried to experiment with different locations and configurations. I did not want the light on top of my handlebar. An easy location would be on the shock tower loop or front brake bolt hole. The problem with this location is that the light would cast a shadow on the wheel. A quick release handlebar mount would also be nice but again, I did not have the handlebar space. I also needed up-down-left-right adjustability. Eventually, I decided to mount the assembly slightly below the handlebar and between the headset and left brake lever. To do this, I just needed a plastic loop, a large bolt and a 4 inch piece of half inch aluminum bent into an L-shape.
The white loop is any piece of the pliable plastic (nylon, abs and pvc may also work). I got mine from an old sliding door. (The guide rail and decorative sash of most sliding doors, windows and even drawer guides use this type of plastic). After carefully heating over a stove and forming the plastic, it retains its shape really well and is quite strong and relatively rigid.
A piece of 1/2" x 1/8" aluminum bar was obtained, bent into an L-shape and cut into the desired length. Two holes (one for the light housing and another for the bolt that mates it to the plastic loop) are needed. The three other holes are just for aesthetics.
Mounted on the handlebar...
Light assembly and mounting bracket from POV of rider
Side view of the assembly
The plastic mounting bracket, the aluminum bar, and the mounting bolts were painted black to "blend" better with the handlebar accessories. I kept the housing unpainted (polished stainless steel) just to show it off and leave it recognizable as a spice jar :-D
The final result
Finally here are the beam shots (I do not have exposure or apperture settings for these photos since they were taken with my iPhone). The resulting light is whiter than expected.
(20 Watt MR16 Halogen)
Possible modifications:
The good thing with this setup is that I can easily change or swap bulb assemblies. I purchased two more jars and just took the lids. On one lid I will install a 10 Watt globe and use this as my backup and carry-on spare. On another lid I will install a 4W - 4 LED MR16 "bulb" purchased from a well-known online retailer. This LED setup may be more usefull as a street light and will also provide a longer run time. If the LED globe turns out to be capable of providing adequate light, then I may switch to a smaller SLA, a NiMH battery pack or even a Li-ion pack. I will update the beamshots when the new bulbs are installed.
Version 2.0 may be a dual beam setup (either dual halogen or a halogen-LED hybrid). Another idea is a triple beam design using 2 smaller MR11 globes (one wide beam and one spot) and an LED blinker, all in one-unit.
Project Cost (My actual cost):
Less than $20! The Bulb, velcro and spice jars were purchased from a dollar store. The battery was purchased new for about $15 and I already had the charger. All the other materials I recycled or already had on-hand. My motomaster charger is a 1A charger with a finish charge rate of 0.3A. (Although I measured the actual output of the charger and got about 782mA). I could still probably make my own lower rate trickle charger with a current limiting resistor.
(If anybody wants to replicate this project and needed to purchase almost everything, the cost should still around $40 to $50 with the battery and charger taking most of the cost - still much better than purchasing a commercial unit at around $200).
For the meantime, I've got the charger connected to a cheap household timer that's configured to cut power off between 4.5-5 hours inorder to avoid overcharging the 5Ah SLA. While this setup is not optimal, this length of time should be sufficient for a fully drained 5Ah. If I use a smaller SLA, I may eventually purchase an automatic smart charger. The smart chargers retail for about $40 but they will make the battery last longer as well as give me the ability to charge 6 Volt SLA's as well.
Overall, I'm quite pleased with the result. Good light output, safe to operate, does not look "ghetto" and relatively inexpensive. The ability to swap bulb assemblies is also a plus.
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Additional Note:
Forward lighting is not sufficient for street biking at night or during inclement conditions (rain and snow). The same analogy applies to motor vehicles. Any road user need both headlight and tail lights. Do not rely on a single LED blinker as a tail light. If you really need to ride on the streets at night as part of your daily commute, install or add supplementary lights. Front LED blinkers, pedal reflectors, front and rear reflectors as well as wheel spoke reflectors. Some people might think that a simple LED tail light is sufficient. This is simply not true. LED's have a very limited viewing angle. Beyond this angle, the light is barely visible. LED tail lights also have very limited luminance and could easily be overpowered by vehicle headlights. If you want a blinker for the rear, I would suggest a xenon strobe. Cheap ones are available online and on eBay for under $10.
