Throttle physics

[CR4125]

Evening guys,

Now first off, I'm not an engineer, so I don't know how the physics are exactly, but when you put a locomotive to 13% (notch 1), the speed just keeps climbing. Now that's if you have an engine, and maybe 8 or 10 cars. It seems that notch 1 should keep the speed up, but not keep gaining? It gains maybe a mph every 20 seconds or so. So I don't know if this is realistic, or just something with the program.

Thanks guys, looking forward to open discussion

[buzz456]

Taking basic physics if the resistance is less than the inertia being provided it keeps going faster. Put more resistance (weight) and at some point this will equalize. I have watched almost all locomotives that aren't hauling a long train go back to idle after reaching speed for a time if they are on level ground. That's not unrealistic.

[MontanaRails]

I agree with Buzz456. I think, if there isn't an additional headwind, and on a flat stretch of track, its probably pretty accurate. From the manual I have (SD50 - might have been a C&NW modified EMD manual), it says:

3-12
HANDLING LIGHT LOCOMOTIVES
With the engine started and placed "on-the-line" and the preceding inspections and precautions completed, the locomotive is handled as follows:
1. Place the engine run switch and generator field switch in on (up) position.
2. Place headlight and other lights on as needed (per company policy).
3. Insert reverser handle and move it to the desired direction of travel, either forward or reverse.
4. Release locomotive air brakes.
5. Open throttle to position No. 1, 2, or 3 as needed to move locomotive at desired speed.

NOTE
Locomotive response to throttle movement is almost immediate. There is little delay in power buildup.

NOTE
Locomotives roll freely and care should be used in judging speed and acceleration!

6. Throttle should be in IDLE before coming to a dead stop.
7. Reverser handle should be moved to change direction of travel only when locomotive is completely stopped.

Then further down it says:

3-18
ACCELERATING A TRAIN
After the train has been started, the throttle can be advanced as rapidly as desired to accelerate the train. The speed with which the throttle is advanced depends upon demands of the schedule and the type of locomotive and train involved. In general, however, advancing the throttle one notch at a time is desired to prevent slipping and undue shock stresses.

NOTE
Light or multiple unit locomotive sets will quickly reach track speed at low power settings. Use caution to avoid exceeding track speed limits.

The load indicating meter provides the best guide for throttle handling when accelerating a train. By observing this meter it will be noted that the pointer moves toward the right (increased amperage) as the throttle is advanced. As soon as the increased power is absorbed, the meter pointer begins moving toward the left. At that time, the throttle may again be advanced. Thus for maximum acceleration without slipping, the throttle should be advanced one notch each time the meter pointer begins moving toward the left until full power is reached in throttle position No. 8. A short time operation nameplate is located directly beneath the load current indicating meter.

[Grovestreetgman]

Interesting tidbit from that manual...

I would also agree that what you are experiencing is perfectly normal.

[CR4125]

I agree with Buzz456. I think, if there isn't an additional headwind, and on a flat stretch of track, its probably pretty accurate. From the manual I have (SD50 - might have been a C&NW modified EMD manual), it says:

3-12
HANDLING LIGHT LOCOMOTIVES
With the engine started and placed "on-the-line" and the preceding inspections and precautions completed, the locomotive is handled as follows:
1. Place the engine run switch and generator field switch in on (up) position.
2. Place headlight and other lights on as needed (per company policy).
3. Insert reverser handle and move it to the desired direction of travel, either forward or reverse.
4. Release locomotive air brakes.
5. Open throttle to position No. 1, 2, or 3 as needed to move locomotive at desired speed.

NOTE
Locomotive response to throttle movement is almost immediate. There is little delay in power buildup.

NOTE
Locomotives roll freely and care should be used in judging speed and acceleration!

6. Throttle should be in IDLE before coming to a dead stop.
7. Reverser handle should be moved to change direction of travel only when locomotive is completely stopped.

Then further down it says:

3-18
ACCELERATING A TRAIN
After the train has been started, the throttle can be advanced as rapidly as desired to accelerate the train. The speed with which the throttle is advanced depends upon demands of the schedule and the type of locomotive and train involved. In general, however, advancing the throttle one notch at a time is desired to prevent slipping and undue shock stresses.

NOTE
Light or multiple unit locomotive sets will quickly reach track speed at low power settings. Use caution to avoid exceeding track speed limits.

The load indicating meter provides the best guide for throttle handling when accelerating a train. By observing this meter it will be noted that the pointer moves toward the right (increased amperage) as the throttle is advanced. As soon as the increased power is absorbed, the meter pointer begins moving toward the left. At that time, the throttle may again be advanced. Thus for maximum acceleration without slipping, the throttle should be advanced one notch each time the meter pointer begins moving toward the left until full power is reached in throttle position No. 8. A short time operation nameplate is located directly beneath the load current indicating meter.

Very cool! Thanks for that, makes more sense now. Thanks guys