I have a Vespa scooter which is my typical transportation, weather permitting, and I wanted to replace all of the incandescent lamps with LED lamps. I was able to find viable replacements on the internet for all but the tiny license plate lamp and the head lamp. For the license plate, I fabricated a small cluster of three Nichia 3 mm LED's in series much like the module in my tri-clusters and this works fine.
The head lamp was a different story and I purchased a replacement head lamp housing assembly in anticipation of attempting a modification. I kept this housing on the shelf for many months until I felt up to the task. The real challenge was working within the confines and geometry that is already there and I needed to be able to go back to stock with no problems. Most of the housing and even the handle bar shrouds are all plastic and they provide no thermal relief mass or surface area. The only metal I was able to thermally tie into was the existing reflector itself and with a high polished surface over the cast aluminum piece, its thermal contribution is questionable.
I had a large anodized piece that I had designed for the Makita Flashlight and I used this as the heat sink and base upon which to cluster some LED's.
The stock head light has a dual element bulb and a side mounted bulb that was probably intended as a parking or indicating light but the scooter is wires such that the standard head light element is always on when the scooter is "live" and there is a high beam switch that turns that element off while turning another element on. For my LED system, I elected to use three each Cree XR-E driven in series at ~ 900 mA for my standard or normal head light and three each of the Seoul P7 LED's driven in series at 2800 mA for my high beam option. I rarely use high beam and when I do, there are no other motorists around and I seek maximum illumination!!
The electronic drivers were mounted in the back side of the heat sink:
The Cree LED's are driven by a Wayne Yamaguchi SOB converter set at 917 mA and the Seoul LED's are driven by a linear driver from LED-Tech.DE. As it turns out, the Cree LED's don't see the full power until the voltage to the driver is about 13.6 V which is in line with the scooter when the motor is running. When the scooter is brought live and prior to starting the engine, the voltage is only about 12V and the LED's are driven at about 200 mA. I appreciate this reduced load on the battery!
The Seoul LED's were mounted first and to insure proper placement, I used their reflectors to position them on the heat sink. I held the reflector assembly together with an O-ring that seated in a groove I turned into the reflectors. This groove is also where the key retaining washer seats and holds the whole package together.
The seoul reflectors drop into some cylindrical stand offs which were bonded to the heat sink using a thermal epoxy. The reflectors are clamped into place by the central retain screw and they become part of the thermal package.
Although I had many different ideas about how to manage the light output and shape the beam pattern, the reality restricted my options considerably. The one thing I did do was some "spill" enhancement to provide additional light in the foreground of the scooter. Unlike in a car, on a scooter, you can look almost straight down in front and at low speeds or while parking, it is nice to have good illumination in close. I removed portions of some of the reflectors to give foreground illumination both with the normal and high beam.
I also considered an over the top "blinder" of MCPET reflective film to chop the top of the beams and redirect the light down. However after viewing the beam pattern as it was and considering my typical driving conditions when I am often dropping into gullies or approaching a hill, I decided I preferred the additional light above the horizon and it seems that this light is not intense enough to be an issue for oncoming traffic. No one has flicked their high beams at me yet....
The stock head lamp and modified one:
I need to point out that the lamp used in the stock head light is an after market "true blue" type lamp and in addition to blue, it gives off some other tints and interesting colors!?!
Installed in the scooter:
I put a large hole in the stock reflector and the heat sink comes forward through it considerably. The heat sink has a flange on it that stops on the rear side of the hole in the stock reflector. I bonded the heat sink to the stock reflector at this junction and added a fillet of thermal epoxy both in front and behind the stock reflector. In mounting the heat sink this way, I was able to use the integrated head light adjustment screws of the scooter and dial in the beam direction.
Below are the stock headlight on low and then high beam:
Below are the LED's on low and then high beam:
The four beam shots were all done with the camera on manual settings with the same shutter speed and F stop. The camera had a wide angle lens and you can see the scooter in the right of the frames. The headlight was about 15-20 feet from the garage door.
My Vespa now sports solid state lighting and these lights require a fraction of the power that the incandescent lamps they replaced did. There is no way to justify this change over in terms of cost but that wasn't the point of the exercise.
Back to page 4