What's a Mars Light?

[AntonioFP45]

QUOTE: by David Foster…What did the white light display?

David. Unlike the Mars light which usually moved in a figure 8 pattern, the Gyra light moved in a simple circular pattern. I believe that http://www.richmondcontrols.com offer fully functional Mars and Gyra light kits for model locomotives from N scale and larger. Circuitron offers the “ML-1” Mars light kit. (part #800-1500 cost about $17.)

QUOTE: Can I ask for more information on the beacons please?

Several railroads did use the yellow beacons on the roof. You can see them on photos of BN F45s and the E units used in commuter service back in the 80s. Santa Fe used them on various units as well. Also available by the two above mentioned companies for model locomotives.

Hope this helps.

[nssr9169]

To my knowlage they were common lights to allert attention by occillating in a figure 8 pattern. We have I think 3-4 loco’s/cars with “mars” lights at the r.r. museam i work at.

[Bill_H]

[quote]
QUOTE: Originally posted by David Foster

As far as I know (correct me someone please) these lights are just for examination and to aid getting on and off the loco safely.

-----Examination? Examination of what? ONLY at the cab end???-----

As for not slipping when pulling away… you’d have to hang a long way out of the cab to see the wheels which is neither safe practice nor what you want to do in most of the weather that contributes to slipping.

-----I believe I said see the GROUND.-----

Also modern locos with these lights often have traction control. Again, drivers regulat slippage by feel (through their bum) and by sound. When these guys know their stuff they will react to a slip approaching before I would ever see it. That is part of the skill… the slip doesn’t really get to start.

-----OK, we can agree on this, sort of…-----

http://www.railspur.com/Process%20Locomotives/Adhesion.htm

Process locomotives put the throttle control and the control of the voltage and current to each traction motor into program that is installed on the master PLC microprocessor which in turn controls the locomotive. The PLC can make adjustments in 1/20th of a second that the operator would take at least 2 to 3 seconds to respond to. By making corrections 40 to 60 times faster than a human operator can the process locomotive can control wheel slip much more precisely. Process locomotives with AITMC or AITMC-PT automatic traction control systems can control each traction motor independently of the others on the locomotive. If an axle begins to slip the AITMC system will pick up the voltage and current changes in about 1/200th of a second.

[Anonymous]

Didn’t mean to annoy you Bill H.
But (nicely) what would the crew be looking at the ground for?
Yes traction control is incredibly fast… sometimes too much so. The old (real) drivers (excuse the bias) used to use a controlled amount of slip to clean/dry the rail so that they could get traction. This especially applied with multiple power. the lead would slip and the second push… they gotn through. I’ve known modern computer “assisted” systems blow the computer and end up dead becuase the system kicked in and out so fast… train went nowhere… until pulled out by an “old fashioned” loco that had no trouble at all. modern drivers aren’t trusted by “the management” to “Drive” their expensive trains… shame the computers blow them up instead.
Not that I’m biased
Oh yes “examination”… I don’t know… they spend a lot of time doing it though. I wouldn’t dare to suggest that it’s a heck of a good cover for other reasons for running late…
Anyone out there know the correct anwer on these lights?

[Bill_H]

Annoyed? Not in the least.

As for the “white lights under the carbody on the cab end which illuminate the ground” lights, and why the crew would have reason to “look at the ground”:

http://www.trainweb.org/sp5623/detail1.htm

QUOTE: This is what is commonly refered to as a “ground light”. There is one on each side of the frame, near the center of the front truck. Old timers have told me that they are used because it is nearly impossible to tell when a diesel locomotive is moving a very slow speed as there is no change in sound. A steam locomotive will give off an occasional “Chuff” when starting but a diesel will just sit there and grrowl. The lights give the engineer and fireman a visual reference to the ground.

… and when described in today’s governmrnt legalese:

http://www.volpe.dot.gov/opsad/lcnsrpt/lcnsch3.html

QUOTE: 3.3.4 Ground Lights

Low-intensity locomotive exterior side lights were historically known as the “American-style” ditch light. However, the term “ground lights” is used in this report to denote any 15- to 20-watt lights located underneath the locomotive sill. (See Figure 3-1.) As shown in Figure 3-3, the lights are aimed toward the ground and the beam focus is designed to illuminate the immediate area of the track and right-of-way, near the crew stairway, to enhance train crew safety in mounting and dismounting from the rear or head-end of the locomotive.

Due to their low intensity and beam direction, ground lights are not considered effective in enhancing locomotive conspicuity to motorists and are not included in the FRA Interim Rules. Accordingly, ground lights are not discussed further in this report.

Figure 3-3. Ground Light Beam Focus Angle

It should be noted t