I have not been a huge fan of generator lighting. Part of the reason is that I am loathe to do anything that would reduce the efficiency of my pedaling efforts. And, I usually only have to ride at night during the winter months when the daylight is scarce. Since my commute is 30 to 40 minutes each way, battery powered lights work fine for me. Guilt can be assuaged by using rechargeable batteries, and further assuaged by using a solar powered charger.
The other reason may be that my few experiences with generator lighting involved very inefficient bottle generators on old clunky bikes that belonged to friends and that I would occasionally borrow to ride as a child (my own childhood bikes were generator-free). While I was busy contemplating how the generator worked, I would get more and more fatigued trying to ride up the hill to my house. These devices put way too much drag on the tire, so I banished them to my minds’ nether-regions for decades.
Adding fuel to my flame, generator lighting is also often part of the standard equipment on a production hybrid or city bike, with poorly designed too-bright optics, which are sold to the enthusiastic masses, who then point their lights straight ahead, proceeding to blind all oncoming traffic. I cannot tell you how many times I have been blinded in this way, one time from behind by a rider who was naively drafting too close at dawn, with her big bright light aimed horizontally, and when I looked behind to set up for a 3 lane left hand crossing, her light literally shocked and blinded me to such a degree that I nearly lost control of my bike. And I could not see past her light to the traffic I would soon try to cross. Needless to say, I missed that turn.
Recently, I needed to install lighting on a few bikes I was working on, all of which used sidewall driven generators. That got me thinking about installing lighting on my Meral, since I have begun using it as my primary commuter. I thought long and hard about that, and researched the pros and cons of bottle generators vs. hub dynamos. I even explored a new technology – the rim driven dynamo built by Velogical.
If you are not an electrical engineer, dealing with the set up of a bottle dynamo can seem challenging. First of all, it is very difficult to find wiring schematics and instructions for sidewall-driven generators. These, I learned, are not technically dynamos, which generate DC power, but magnetos, which generate AC power. The only vintage shop manual in my collection which had more than a passing mention of generator lighting was Glenn’s New Complete Bicycle Manual, which is actually one of my favorite manuals because it has extensive guidance on rebuilding internal hubs.
Reading through Glenn’s guidance (who, in my mind, I refer to affectionately as “Dr. Glenn”), it is not hard to accept the old saying that mechanics do mechanical things and electricians do electrical things, and never the twain shall meet.
In days gone by, pretty much all bicycles were steel, and could be grounded with a simple contact to the bare frame or some other steel component. This fork mounted dynamo on the Peugeot Mixte 650b that I recently restored is a good example of that:
The horizontal screw at the mount point provides the needed ground for this system. As I was setting it up, I didn’t worry about much of anything as I wired up the lighting to this dynamo. Thoughts of resistors, amps, volts, ground wires, and wattage never entered my brain. And, after I connected the wiring, everything worked perfectly. In fact, this little dynamo puts very little resistance on the sidewall, and I had fun riding around on this bike with my lights blazing.
But, that is a vintage system which requires only 1.8 watts at 6 volts. Enter the new times, where 3 watts and 12 volt systems are the standard. (Question: what are watts and what are volts – don’t ask me!)
Do you need resistors, double wires, and ground wires? How do you set up a new system? As I mentioned before, I seriously considered setting up generator lighting on my Meral, and toward this end I purchased a front wheel which featured a Shimano Deore LX hub (model DH-T670-3N), mounted to a Velocity Synergy 650b rim matching my existing rims.
I sourced a headlamp and tail lamp from Harris Cyclery and proceeded to test the system prior to mounting to my bike, to make sure I understood the wiring requirements. Once I figured out how to make the wires connect properly to the hub, I was able to mount the wheel into my truing stand, give it a whirl, and watch the lights illuminate my shop. I even generated enough power to engage the standing lights, which remain on when the bikes is not moving. But what really shocked me was the amount of resistance in the hub whenever I switched the lamps to the “on” position. I had already read about these hubs having their cones being too tightly adjusted, which turned out to be true, and had fixed that. Yes, these hubs were adjusted way too tight from the factory. After that, I expected to experience only modest resistance when engaging the lights. Not so. Not so at all. So I mounted the front light and installed the wheel into my Meral just to see if I was panicking for no reason. As it turned out, the resistance in these hubs with the lights engaged is totally unacceptable to me, and I immediately switched back to my original wheel and battery powered lights.
I am still interested in rim driven dynamos, and in generator hubs which have less resistance than the Shimano hub I tested. Those are spendy options. So for now, I will happily re-charge the batteries for my lights on all my bikes, and sleep well at night.