Warning Lights

Gyrating lights are effective warning devices. They instantly show the exact spot where danger lies. The beam color and wide sweeping action command immediate attention. A visual signal can be perceived long before an audible one. A moving beam of light can cover a much larger area than a stationary beam. These lights are especially useful in rural areas at grade crossings. They also are useful in areas of high noise levels where background noise might negate the sounds of the oncoming locomotive.

One can get an idea of what these gyrating light units looked like and how they worked by investigating some of the patent diagrams or photos in this site. The moving light beams proved very effective at grade crossings. The light reflected off buildings, trees, the road, etc. These rotating beams produced what is known as the "spectacular sky effect". To anyone unfamiliar with this, just think of the spotlights that were used at state fairs to attract people to the site. They were aimed vertically upward and moved back and forth. Perhaps people in the northeast US will have to think of this example because for some reason, gyrating warning lights never seemed to catch on for use in locomotives there.

Basically, the first locomotive moving light units had the "figure 8" pattern. This pattern gradually was replaced with circular or ellipse pattern of the contemporary gyrating lights. The "figure 8" lights were more complicated. This light used 2 eccentric parts to make the "figure 8" pattern as opposed to 1 in the more contemporary ones. The illustration of US Pat. 2,409,046 shows one of these types. The mechanical maintenance probably caused railroads to opt for the more contemporary elliptical pattern lights.

Strictly speaking, a Mars Light is an oscillating light unit manufactured by the Mars Signal Light Company, being developed by its sole owner Jeremiah D. Kennelly. A Gyralite is an oscillating light unit developed and manufactured by The Pyle-National Company, now manufactured by Trans-Lite, Inc. [The Gyralite has been referred to as "Gyro-Lite", "Gyro", and "Roto-Beam" (Rota-Beam was a Pyle-National portable vehicular beacon). A label on a control for an oscillating light reads "GYRO LT. OFF" (the label was apparently at the 12 o'clock location and labels the control as well as the "OFF" selection. The correct trademark name for the Pyle-National or Trans-Lite line of oscillating light, however, is "Gyralite".]

In conventional language, a Mars Light is interpreted as being a light unit having a sweeping "figure 8" pattern and a Gyralite as one having a circular or elliptical pattern. Also, some consider a Mars Light as being a "red" light and a Gyralite as being "clear" (or white). It should be noted that none of the patents of The Pyle-National Company, hence the Gyralite, show a mechanism which produces a "figure 8" pattern. There are, however, patents that show circular or elliptical beam patterns for oscillating light units by Jeremiah D. Kennelly, hence the Mars Signal Light Company. It should also be noted that colored light filters or lenses were used on both Mars Lights and Gyralites.

The Mars GWR-5000 Light used a rotating reflector with a stationary light source. The resulting design and resulting circular light pattern was similar to the concept used in the reflector Gyralites of Pyle-National. This unit together with the "figure 8" Mars WR-816, produce red light by use of a butterfly shutter which was activated by a separate motor. These units were available without the shutter if desired. It may have been the overall design of this unit with the concept of the method of producing the red light that prevented a conflict of patents in effect for Pyle-National's reflector Gyralites. The usage of the stationary light source and a moving reflector was not seen in the patents issued to Kennelly (Mars).

It is interesting to note that it appears railroads did not want to show a headlight company preference during the era of the "E" and "F" locomotives. In a combination of oscillating headlight with a fixed headlight, one would be a Pyle-National while the other would be a Mars. The oscillating headlight would be the topmost headlight in these streamlined locomotives.

The descriptive term "lens" is used in this presentation because it's use is widespread in the references on these light units. It has been stated that the term "roundel" may be the correct choice for a descriptive term since there are no "lens properties" present (convergence or divergence of light beam) in a transparent glass piece. However, there are actual lenses present (15100 Gyralite) in which the light passing through it takes on a new pattern.

Circular or elliptical beam sweep patterns were the favored course in the development of these oscillating lights. One can see from the illustrations of the following patents, however, that they were not the only ones developed:

US Pat. 2,342,202 The light unit is comprised of stationary mounted lamps together with lateral oscillating ones. The oscillating lamps serve, not only as a warning device, but also reinforce the locomotive's headlight.

US Pat. 2,353,082 The light unit is also comprised of stationary mounted lamps together with lateral oscillating ones. One of the main objectives of this patent was to devise a way to scare wildlife off the tracks of an oncoming locomotive as well as functioning as a warning light to humans. Reference is made to the problems railroad companies had in regard to domestic animals and their owners. Apparently an animal that was not worth a great deal to an owner suddenly became invaluable on being killed or injured by a train. There was also the problem of injury to the train, its cargo, or crew that could result.

From illustrations for both these patents, it can be seen that they are very much alike. Both of these patents were granted in 1944. US Pat. 2,342,202 was granted to Kennelly (Mars) and US Pat. 2,353,082 was assigned to the General Motors Corp. The patents both depict a locomotive headlight using 7 clustered bulbs, 2 of these which could be put into lateral oscillation. (It is stated that other bulb combinations could also be used). These were the only patents I ran across illustrating a 7 bulb clustered headlight. There could have been a crossover here between Kennelly's company (Mars) and General Motors.

The book entitled: A Railroad's Decision to Dieselize - D-Day on the Western Pacific- by Virgil Staff, discusses a 7 bulb clustered headlight on page 94. The unit was purported to be 14 inches in diameter and as having the capability of manually adjusting the focus of the bulbs. It is stated that all of the 5400 hp locomotive units (set of 4 FT A and B units: 1350 x 4 = 5400) were delivered to Western Pacific with these 7 bulb clustered headlights. It could be concluded that these lights were manufactured under the patent assigned to General Motors Corp. based on the manual focus described above and in the patent. General Motors, manufacturer of the locomotives, would also tend to use its own product. Also, this shows that General Motors was involved in oscillating headlight design.

US Pat. 2,442,569 Both lamps of this unit oscillate laterally. One oscillates parallel to the tracks while the other is directed upward. It was recognized that serious accidents had resulted when trains passed through valleys or irregular country which diminished visibility of approach. The upward directed beam's visibility is enhanced by it's changing effect on clouds, the sky, and other elevated objects together with the changing position of the locomotive bearing this light unit.

US Pat. 2,455,497 The unit is comprised of 2 bulbs attached to a pendulum arm. Each swings laterally, in opposite directions. Its advantages are low power consumption by the motor and its small size for an impressive warning light, equal in effect to larger units.

US Pat. 2,456,287 From the implications in this patent, the light unit described was designed for use on emergency vehicles. It is of interest to note that an illusion of speeding approach is created by the mechanism in this device. The frequency of the vertical movement of the light beam is greater than that of the horizontal. (7x in the patent). The observer's mind interprets the difference in the 2 frequencies to be due to the speed of the oncoming vehicle equipped with this device. An illusion of a speed greater than exists is therefore perceived.

US Pat. 2,571,895 The light source in this unit is alternately rotated clockwise and counterclockwise while the support for the light source is moved back and forth laterally. The reversal of rotation of the light produces a sharp contrast to the lateral back and forth motion, which effectively captures attention.

The original circular pattern light from The Pyle-National Company had a 360 watt, 12 volt lamp with a glass reflector and produced a 1,120,000 candlepower beam. This proved to be a great advance over the stationary headlights as a warning light.

Next it was decided to make the light pattern ellipsoid, not only to eliminate the hollow spot at the circular beam sweep's center, but to allow more coverage of the beam in the horizontal direction where it was felt that it was needed. Later a compressed ellipse pattern was developed. Through the reflector design and the special prismatic lens the beam was able to cover a larger horizontal sweep. The angular distance between the upper and lower beam sweeps in one series of reflector Gyralites was kept to 3° to 4° and nearly parallel in order to produce the maximum flash effect. What this meant was that an observer of an oncoming train actually saw 2 flashes of the beam per revolution of the train's light. There was some sacrifice in the sky effect using such a pattern but it was felt that the safety factor was greatly increased by this double flash effect. Mars promoted the "figure 8" horizontal beam pattern as having this advantageous double flash also.

It appears that the oscillating lights from both companies were designed so that there would be a position along the beam's path that would point straight-ahead. The engineer could, by way of a control, manually stop the movement of the light at this point and have the unit function as a headlight (or reinforce the existing stationary headlight). The engineer could also selectively aim the beam to any point along the normally transcribed path, thereby using the oscillating light as a searchlight.

All the Gyralites currently made by Trans-Lite, Inc. (successor to Pyle-National's railroad lighting products line) have either circular or elliptical beam patterns.

One of the most important characteristics of a movable light beam is the flash effect given to the observer when the light beam enters the observer's visual field. This flash effect only occurs when there is a complete traversing of the beam across the visual field or when there is an intersection of the beam with the visual field. If the projected beam of light which is describing a circular or elliptical field is too wide then it will not traverse the visual field and a flash effect will not be produced. The observer could look at the oncoming movable light source and it would appear as a steady continuous light.

Red screens were used on some of these lights as signals of the train stopping or an emergency braking situation. Red was chosen because it not only emphasizes the signal but its transmission distance under unfavorable atmospheric conditions is greater than for white light.

There was a setting on a control mechanism which caused the red light to go on and the other headlights off (for maximum visual effect of the red) whenever the brake pressure fell below a certain preset value. The pressure therefore dropped when the train was stopping or if there was a problem with the brakes.

The electrical system controlling these lights was usually set up to automatically extinguish the locomotive's headlight(s) when the Red oscillating light was turned on for maximum effect. It also would turn the locomotive's headlight(s) back on in the event of a failure of the oscillating lamp.

There were innovations using mercury switches to sense momentum changes such as acceleration and deceleration of the train and which were incorporated into some units to turn on an oscillating warning light (white or red) under these conditions. Schemes were also used in railcars with axle generators where the oscillating red came on with a drop in speed of the train.

Some of the lights were one bulb units utilizing a rotating reflector where the optical axis was inclined to the longitudinal axis of the light (or locomotive). Others used 2 or 3 lights attached to a vertical plate which transcribed an elliptical (The Pyle-National Co.) or "figure 8" (Mars Signal Light Co.) movement.

When these light units were used on steam locomotives the shock proved disastrous to the mechanism of the unit. Later the unit's case was made shockproof even though the shock experienced on diesels was not as bad as the steam locomotives due to the more even transmission

The oscillating warning lights used in the early locomotives were large diameter (23 inches) drum-like units. Some had lengths of this same amount. The front piece of glass was usually 18 inches in diameter. For a flush mount, a hole of 18 inches was needed in the locomotive body to accommodate the front of the light with it's lens. It was recommended that the oscillating light be the highest light for maximum effectiveness. Sometimes this meant having to bore out the existing headlight hole to accommodate this light and/or moving the existing upper headlight to a lower position. In mounting such a light in the early streamlined diesels, the manufactures made it possible to maintain the gyrating light from inside the diesel since they did not have catwalks. External mountings of these oscillating lights of this nature had the appearance of an ash can or barrel.

The standard locomotive voltage of 74 volts proved excessive for the design of bulbs and motors of these light units. A dropping resistor(s) was therefore used to get the desired voltage. A 32 volt light unit was offered as well as a 12 volt version in 1955.

This site deals mainly with the warning lights that were applied to locomotives.

The first patented mechanical oscillating light for vehicular use was the Roto Rays Light. The trademark states that this product first was used in 1931. It is interesting to note that this light is popular today.

The oscillating lights for locomotive use caught on with the advent of the many light devices developed by Jeremiah D. Kennelly (subsequently Mars Signal Light Co.). The Pyle- National Co. had begun producing locomotive headlights and turned to producing it's version of the locomotive oscillating light. (Arthur C. Heehler main inventor at Pyle-National was formerly employed at Mars).

Mars later discontinued it's locomotive line. Pyle-National sold off it's railroad lighting line to Trans-Lite, Inc. Arthur C. Heehler became president of a company called Mercor and developed a solid state oscillating light for locomotive use called the "Oscitrol Light". This light never caught on and was replaced with beacons and strobe units on railroads who opted not to have the former mechanical oscillating lights. One popular solid state beacon marketed was the PM-8911 by Prime Manuf. Corp. The PM-8911 had a lower base profile than the PM-8901, which made for easier clearance in tunnels, or other overlying structures.

The next stage of warning lights were the Ditch or Crossing Lights. (Crossing Lights are being called Ditch Lights.) This is the main locomotive warning light package used today and is endorsed by the FRA. They are solid-state and cheaper than the mechanical units but the effectiveness, as evidenced by feedback from those who have used both, seems to favor the former mechanical units.

The listing of progression in this site, shows the Pyle-National Gyralites first, followed by Mars oscillating lights. This was done because the information on the Gyralites was more readily available and gives one a better understanding on facets common to both.

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