HI
I'm speed matching a QSI equipped loco with an NCE D13SRJ loco. What does the momentum button on the power cab do? Does it change CVs or change something in the power cab? I'm confused.
Thanks
Lee
yankee flyerWhat does the momentum button on the power cab do? Does it change CVs or change something in the power cab?
Lee,
The momentum button on the Power Cab allows you to quickly add or subtract momentum without the need to go into programming mode to do it. It gives you a choice of values between 0 and 9. (0 being no momentum; 9, maximum momentum.) The number you set is multiplied by the momentum CV default.
If you are speed matching locomotives, it's probably best to leave momentum off.
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
tstageThe momentum button on the Power Cab allows you to quickly add or subtract momentum without the need to go into programming mode to do it. It gives you a choice of values between 0 and 9. (0 being no momentum; 9, maximum momentum.) The number you set is multiplied by the momentum CV default.
Tom:
Would it be correct to say that the end result is a change to one of the CV values? And out of curiosity, does that momentum button change acceleration and deceleration momentum, or only acceleration?
tstageIf you are speed matching locomotives, it's probably best to leave momentum off.Tom
Hi Tom
Just wondering how having the momentum button on would affect two loco's I am trying to speed match. I have two Trainmasters from Atlas and they both run at different speeds depending on the direction they are going. One runs faster than the other in one direction and then the other runs faster when the consist is reversed. Could this be a momentum button issue? Thanks.
Brent
"All of the world's problems are the result of the difference between how we think and how the world works."
Maxman,
I think it would be fair to say that the momentum button is a generic, one-step, convenient way to quickly add momentum to your locomotives. After entering a 0 up to 9 value, it changes both acceleration and deceleration - all at the same time.
IIRC, deceleration is half of what acceleration is. In other words, if it takes 20 seconds for your locomotive to accelerate up to a certain speed, it will take only 10 seconds for it to decelerate to a stop. The advantage of adding or changing momentum in CV3 & CV4 is that you can fine tune it to any locomotive - or, consisted locomotives once you've speed matched them.
I don't bother adding momentum to any of my yard switchers, as I find the fine speed buttons on the Power Cab quite adequate in mimicking it. Besides, I prefer the fine control at low speed anyhow.
According to the PowerCab manual:
When you press the momentum button you are prompted to enter a momentum level.There are 9 levels of momentum (1-9) plus ‘direct drive’(0). Pressing a digit buttonfrom 0-9 will automatically set the acceleration and deceleration rates of thelocomotive(s) being controlled.Pressing 0 sets the momentum of the train to 0 effectively turning it off. 1 is thesmallest amount of momentum, 9 is the most.If you are operating an Advanced or Old Style consist setup in the command stationall locomotives will have their momentum set. If an Old Style consist includes one ormore Advanced consists all locomotives in the Advanced consist (up to 6 peradvanced consist) will also have their momentum set properly.Technical stuff - what happens when you set momentumThe digit entered is multiplied by 8 (factory default) and sent to CV3. The valuesent to CV4 is ½ the value sent to CV3. You can change these multipliers.You can setup the following momentum parameters in the SET CMD STA menu:The acceleration multiplier can be set to a value in the range of 0-25.The deceleration can be set to FULL or HALF the value sent to CV3.You can disable the sending of momentum commands to consists.If a decoder follows NMRA Recommended Practice 9.2.2 the rates will be as shownbelow with the factory default settings (multiplier = 8 and deceleration = half).Rate 1 = 7 seconds to full speed, 3 seconds to stopRate 2 = 14 seconds to full speed, 7 seconds to stopRate 3 = 21 seconds to full speed, 10 seconds to stopRate 4 = 28 seconds to full speed, 14 seconds to stopRate 5 = 35 seconds to full speed, 17 seconds to stopRate 6 = 42 seconds to full speed, 21 seconds to stopRate 7 = 49 seconds to full speed, 24 seconds to stopRate 8 = 54 seconds to full speed, 27 seconds to stopRate 9 = 61 seconds to full speed, 30 seconds to stop
BATMANJust wondering how having the momentum button on would affect two loco's I am trying to speed match.
Brent,
A lot. If you are trying to speed match two or more locomotives, it's best to remove all momentum until after you've successfully speed matched them together. Otherwise, you'll get back-and-forth action between your locomotives. Even once speed matched, you should probably check the two locomotives to see how well the work together at the same momentum setting and adjust accordingly.
I have two Trainmasters from Atlas and they both run at different speeds depending on the direction they are going. One runs faster than the other in one direction and then the other runs faster when the consist is reversed. Could this be a momentum button issue? Thanks.
Brent, I'm no expert on this but I have heard a few other modeler's mention this same problem. My guess is that it's not a momentum issue but a locomotive issue. And I'm not entirely sure how you would go about rectifying the problem. Maybe someone with more expertise on the topic will chime in.
BATMANJust wondering how having the momentum button on would affect two loco's I am trying to speed match. I have two Trainmasters from Atlas and they both run at different speeds depending on the direction they are going. One runs faster than the other in one direction and then the other runs faster when the consist is reversed. Could this be a momentum button issue? Thanks.
You can fine tune forward and reverse with CV #95 and I did find out that the momentum button does change CVs #3 and #4. I believe my problem is exacerbated by my having two different decoder manufacturers. It took me a week to speed match an A & B unit that Litchfield had used different decoders in. Old well such are the joys of modeling.
Enjoy
AGree with Tom, don;t use momentum, either the setting via the PowerCab or by actually programming the momentum CVs in the decoder, when trying to speed match.Start with Start/Mid/Top settings, CV2, CV6, and CV5 (in that order - yes, the Mid CV is 6 and comes after CV5 for top - because it is a bit of an afterthought and not every decoder supports it). For locos that are similar, this should be sufficient to get them to run together without bucking. For vastly different models, you may have to resort to a 28 step speed table to get them evenly matched.
As for different speeds in forward and reverse - this is more common in steam locos, where they have a tendency to run better in reverse than forward. It COULD be decoder settings, there are the forward and reverse trim settings which apply to speed tables to bump the speed table one way or the other depending on direction. To elminate any posisble decoder settings, yoiu cna alway sreset the decoder to defaults and see if it behaves the same way. Eliminating all possible decoder settings, it then becomes a mechanical problem, which is most likely the culprit. As the motor turns one way or the other, the drivetrain wants to shift, but sometimes there is too much free play in the motor and universals and you cna get bindign in one direction or ther other. This is also the cause of severe bucking when going downgrade, as the mechnism shifts enough to literally jam, then frees itself, over and over, resulting in very jerky operation. The cure for this usually involves adding additional thrust washers on either side of the worms to keep the free play in check.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Another thing that can be tried when there is a different speed in reverse is to match the loco's in the direction that they will be used.
When doing advanced consisting I believe that the rear facing engine has it's direction bit changed so that it's actually going forward in the decoder's eyes.
Springfield PA
Sorry Guys
I have another question. Assuming we have, for example, F7 and GP or SD 7s all from Bachmann. would they speed match better if all had the same manufactures' decoder installed. They would all have the same motor and same friction losses except possible the SD 7 ?
Thanks in advance.