VLB-44
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The VRB-25 is a
lighthouse A lighthouse is a tower, building, or other type of physical structure designed to emit light from a system of lamps and lens (optics), lenses and to serve as a beacon for navigational aid for maritime pilots at sea or on inland waterways. Ligh ...
optical system designed and built by Vega Industries Ltd. in
Porirua Porirua, () a list of cities in New Zealand, city in the Wellington Region of the North Island of New Zealand, is one of the four cities that constitute the Wellington#Wellington metropolitan area, Wellington metropolitan area. The name 'Poriru ...
,
New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...
. It was originally designed in 1993–95 with the assistance of the
United States Coast Guard The United States Coast Guard (USCG) is the maritime security, search and rescue, and Admiralty law, law enforcement military branch, service branch of the armed forces of the United States. It is one of the country's eight Uniformed services ...
to meet USCG requirements for a robust mechanism requiring minimum maintenance. It has become the Coast Guard's standard 12 volt rotating beacon. The company's literature says there are more than 400 installations worldwide. More than a quarter of the active lighthouses in Maine have one installed.


Components

A microprocessor controlled 12 volt DC motor drives an array of six or eight acrylic
Fresnel lens A Fresnel lens ( ; ; or ) is a type of composite compact lens (optics), lens which reduces the amount of material required compared to a conventional lens by dividing the lens into a set of concentric annular sections. The simpler Dioptrics, d ...
es around a bulb at one of 248 speeds ranging from 0.5 to 15.9 revolutions per minute (RPM). In the simplest case, all six lenses are used, so that for Boon Island Light, which shows one flash every five seconds, the mechanism rotates at two RPM. Eight lenses are used only when required to achieve more complex characteristics. Maximum range is achieved by using the slowest possible speed, but for grouped flashes, it is necessary to blank off lenses and rotate the mechanism faster. So, for example, for The Cuckolds Light, whose characteristic is group flashing two every six seconds, all but two of the six panels are blanked off and the mechanism rotates at ten RPM. The mechanism is driven by a DC thirty-pole three phase brushless direct drive motor which consumes approximately 1.5 watts. The microprocessor controller keeps the motor speed within 2% of that chosen, using optical sensing of a circular pattern of alternating black and silver lines located around the bottom of the turntable. This provides a feedback signal for speed control. The unit is designed to accept voltages ranging from 11 to 30 volts. Since the life of an
incandescent Thermal radiation is electromagnetic radiation emitted by the thermal motion of particles in matter. All matter with a temperature greater than absolute zero emits thermal radiation. The emission of energy arises from a combination of electro ...
lamp decreases dramatically as the applied voltage increases, the lamp voltage is carefully maintained at 12.00V using
pulse-width modulation Pulse-width modulation (PWM), also known as pulse-duration modulation (PDM) or pulse-length modulation (PLM), is any method of representing a signal as a rectangular wave with a varying duty cycle (and for some methods also a varying peri ...
. The lamps, standard marine signal lamps which may be from 10 to 100 watts as required to produce the necessary range, typically have a life of 2,000 hours. The unit contains a bulb changing mechanism which holds six bulbs, so that a unit could go approximately three years between maintenance visits to change bulbs. The acrylic lenses and cylinder surrounding the whole mechanism are designed to be UV resistant, but still require replacement approximately every five years. In practice, since working lights are critical to navigation, the Coast Guard actually services lights more frequently. Except for that maintenance, the unit is expected to last twenty years.


Predecessors and successors

In the 2010s,
LED A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (corresp ...
lamps began replacing incandescent lamps in lighthouse applications, Article is also availabl
as PDF
from U.S. Lighthouse Society
so it seems likely the twenty year replacement will use an LED light source. In fact, several VLB-44 LED beacons, also made by Vega Industries, have been installed by the USCG at several locations, including White Island Light and
Wood Island Light Wood Island Light is an active lighthouse on the eastern edge of Wood Island in Saco Bay (Maine), Saco Bay, on the southern coast of Maine. The light is just outside the entrance to Biddeford Pool and the end of the Saco River. The lighthouse is ...
. In at least one case, a VLB-44 was removed and returned to a VRB-25 in 2022 at
Whaleback Light Whaleback Light is a historic lighthouse marking the mouth of the Piscataqua River in Kittery, Maine. It is located on a rocky outcrop offshore southwest of Fort Foster and south of Wood Island in Kittery. The present tower was built in 1872. I ...
to maintain the rotating light signature. From the first use of lighthouses with flashing lights, the light source has been continuous, because turning a flame on and off is impractical and flashing an incandescent electric lamp reduces its life substantially. The flashing light signature seen by the observer has been achieved by rotating a lens system. Since LEDs can be flashed on and off without degrading their lives, it is likely the VRB-25 is the last use of rotating beacons in lighthouses.


Issues

Although the units have been successful in their adoption, there has been occasional controversy (at Egg Rock Light in Maine, for example) when the Coast Guard has removed the lantern from the tower after installing a VRB-25. This seemed logical since the lantern required maintenance and the VRB-25 is designed to sit outside, but it changed the traditional look of the towers. After public protest, a replacement lantern house was installed at Egg Rock Light in 1986. All the VRB-25s listed below, except Piedras Blancas, still have lanterns. While the beam is visible at its listed range, it is a more focused beam than that produced by a glass Fresnel lens. Some navigators don't like this, finding it harder to see under some conditions. It is easy to see the difference from many points around Boston Harbor, where the VRB-25 at The Graves Light and the 2nd order glass Fresnel lens at
Boston Light Boston Light is a lighthouse located on Little Brewster Island in outer Boston Harbor, Massachusetts. The first lighthouse to be built on the site dates back to 1716, and was the first lighthouse to be built in what is now the United States. The ...
are both visible. Of course, the original first order Fresnel lens at The Graves stood twelve feet high and weighed several tons. Its many pieces of glass required periodic careful cleaning and alignment.


Examples of lights using the VRB-25


References


External links


Terry Pepper, Seeing the Light "Vega VRB-25 Rotating beacon"
{{Lighthouses Lighthouse fixtures