Do you have any suggested CV values for acceleration and braking momentum? Obviously, with a model railroad you can’t match a prototype, so do you just try what seems to work best with the size of your layout?
Also, what about speed tables/curves? It seems so varied. Any guidelines for this? Maybe it depends on how much slow speed control you want?
It’s your layout. Two things to consider. 1. Try and use the same brand of decoder because of the non-standardization of momentum. 2. Speed curves are for speed matching and limiting top end speed. David B
It’s hard to make guidelines since most of it is personal preference. I usually put some momentum in sound locos because for most of them it enables more realistic sound control. I don;t put as much in most non-sound locos, unless they need to match up with others, because I can always simulate slow acceleration by simply advancing the throttle knob slower. It also takes getting used to, when you turn the throttle to stop and the train keeps going - unless you’re used to it and remember that your train will no longer stop on a dime, you might run into things
Rough guidelines on speed curves, either 3 step or using the 28 step speed tables, are usually to make locos that spend most of their time at slow speeds (switchers) have more control at the bottom end by pulling the middle of the curve down (on a 3 step curve, setting CV6 Mid to less than half speed), and for locos that spend more of their time at road speed, do just the opposite, raise CV6 to above half to the loco accelerates quicker and then has more control in the upper half of the speed range. Exact values to use will vary by loco and, again, personal preference.
I also like all my locos to start moving at step 1, which is actually pretty easy witht he TCS decoders I use, the automatic adjusting back emf mostly handles it without having to fool around with CV2. With non-BEMF decoders and some locos, notably Athearn Blue Box models, you cna sometimes have to put CV2 at a fairly high number, 50 or more, to get them to move at step 1. It all depends on the decoder and the loco. ANd even with the exact same decoder in two of the exact same locos, one might need 65, and the other might only need 40. These sort of things are easiest set up using programmin on the main, or ops mode programming, so you can see the change instantly and tweak it, rather than constantly going back and forth to the program track and main.
–Randy
this is a really interesting question that may get a better response in the prototype forum. Momentum makes the engine movement look so much more realistic and is very easy to set on the NCE PowerCab.
John Armstrong’s book, The Railroad: What is Is, What it Does has a diagram illustrating that the stopping distance is 200’ for a single car going 30 mph and 250’ for 4 cars, and is 800’ for a single car going 60 mph and 1000’ for 4 cars. He also indicates that stopping distance varies with the square of speed. I don’t understand why the distance varies a little with the number of cars.
I believe the thing to bear in minds is that each car including the engine has brakes, so that the stopping distance should not change with the number of cars, but the acceleration depends solely on the locomotive and therefore the time to full speed does vary with the number of cars. On the NCE PowerCab, both these values are easily settable, as they should be because of the dependency on train length for acceleration.
my nce PowerCab manual describes lists momentum values from 1-9 having times to full speed from 7-61 (essential the value * 7 sec). I don’t understand why it works this way, and isn’t a rate of change value (i.e. it should take twice as long to get to 60 mph than 30) maybe i don’t understand this correctly.
[quote user=“rrinker”]
It’s hard to make guidelines since most of it is personal preference. I usually put some momentum in sound locos because for most of them it enables more realistic sound control. I don;t put as much in most non-sound locos, unless they need to match up with others, because I can always simulate slow acceleration by simply advancing the throttle knob slower. It also takes getting used to, when you turn the throttle to stop and the train keeps going - unless you’re used to it and remember that your train will no longer stop on a dime, you might run into things
Rough guidelines on speed curves, either 3 step or using the 28 step speed tables, are usually to make locos that spend most of their time at slow speeds (switchers) have more control at the bottom end by pulling the middle of the curve down (on a 3 step curve, setting CV6 Mid to less than half speed), and for locos that spend more of their time at road speed, do just the opposite, raise CV6 to above half to the loco accelerates quicker and then has more control in the upper half of the speed range. Exact values to use will vary by loco and, again, personal preference.
I also like all my locos to start moving at step 1, which is actually pretty easy witht he TCS decoders I use, the automatic adjusting back emf mostly handles it without having to fool around with CV2. With non-BEMF decoders and some locos, notably Athearn Blue Box models, you cna sometimes have to put CV2 at a fairly high number, 50 or more, to get them to move at step 1. It all depends on the decoder and the loco. ANd even with the exact same decoder in two of the exact same locos, one might need 65, and the other might only need 40. These sort of things are easiest set up using programmin on the main, or ops mode programming, so you can see the change instantly and tweak it, rather than constantly going back and forth to the program track and main.