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THE MOMENTUM BUTTON
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 button
from 0-9 will automatically set the acceleration and deceleration rates of the
locomotive(s) being controlled.
Pressing 0 sets the momentum of the train to 0 effectively turning it off. 1 is the
smallest amount of momentum, 9 is the most.
If you are operating an Advanced or Old Style consist setup in the command station
all locomotives will have their momentum set. If an Old Style consist includes one or
more Advanced consists all locomotives in the Advanced consist (up to 6 per
advanced consist) will also have their momentum set properly.
Technical stuff - what happens when you set momentum
The digit entered is multiplied by 8 (factory default) and sent to CV3. The value
sent 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 shown
below with the factory default settings (multiplier = 8 and deceleration = half).
Rate 1 = 7 seconds to full speed, 3 seconds to stop
Rate 2 = 14 seconds to full speed, 7 seconds to stop
Rate 3 = 21 seconds to full speed, 10 seconds to stop
Rate 4 = 28 seconds to full speed, 14 seconds to stop
Rate 5 = 35 seconds to full speed, 17 seconds to stop
Rate 6 = 42 seconds to full speed, 21 seconds to stop
Rate 7 = 49 seconds to full speed, 24 seconds to stop
Rate 8 = 54 seconds to full speed, 27 seconds to stop
Rate 9 = 61 seconds to full speed, 30 seconds to stop
If a consist is active when MOMENTUM is pressed the button will do nothing unless
“CONSIST MOMENTUM” is enabled (factory default) in the SET CMD STA menu.
Momentum commands will be sent to a limit of 6 locos per Advanced consist.
Notes regarding momentum commands and decoders:
There are special commands for setting consist momentum (CV23 and CV24) but
most decoders do not support these CV’s.
CV3 and CV4 are required and have standardized values in decoders per RP-9.2.2.
Support for consist CV23 and CV24 is not required in decoders, this is why we use
CV3 and CV4 for consist momentum..
Sound equipped locomotives that verbally speak the value of CVs must be turned off
by setting CV 62 to a value of 0 for momentum to work properly. Setting CV 62 to a
value of 1 turns the verbal response back on.
Some European makes of decoders require locomotive power to be interrupted
before the new CV vales will take effect.
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