So yesterday I was playing with speed settings on my locos looking for the ideal cv2 for each. What I came up with works but one loco is way off from the other 2. All 3 are atlas Classic. Here's what I have so far: C424 TCS MC2 cv2 at 20, rs32 DH123 cv2 20, u23b DH123 cv2 40. Thats quite a difference to me and the U boat definitly could use a kick start (dither?) adjustment. Preliminary fiddling with CV5 shows the Alcos will end up close but the U boat will need to be reigned in quite a bit. Is this a problem with the U23B or is it just because of different gearing? I plan to get CV5 and 6 dialed in today so I have some real numbers there.
Modeling the Cleveland and Pittsburgh during the PennCentral era starting on the Cleveland lakefront and ending in Mingo junction
Runner, the range of CV 2 is not uncommon. It depends the quality of the motor and gears in the trucks. All so some decoders do a better job than others at lower speeds.
On my Athearns my CV 2 is in the 20 to 40 range yet my Protos starting moving at step 1 with CV 2 sat 2.
Cuda Ken
I hate Rust
Note that the "ideal" CV2 value for a given decoder/motor/drive combo can change within a few minutes of running! When things warm up the tolerances change and that can affect how much voltage the engine will need to do any type of movement at any speed....including reverse versus forward.
T'is the nature of the beast.
OK good. I've not seen any posts/mentions of what "normal" values are for CV2 and had no idea if I was in the ballpark or not. FWIW the U23B will run at step 1 with CV2 set to 25 but I have to crank it up to step 3 before it moves then dial back. Would I be better off maybe changing the DH123 with the MC2 which supposedly has BEMF?
And alas the batteries in my stopwatch were dead so no results for CV5 and 6...
FWIW I like to keep CV2 as low as possible and adjust dither to kick start the loco. If CV2 is too high the loco tends to jack rabbit start.
Having BEMF is great on a single loco but consisting a group of locos with BEMF can lead to undesirable results. Some locos will spin their wheels wildly when consisted and others will drag their wheels. TCS uses CV10 to shut off BEMF at a predetermined speed step so that will not happen. I usually set CV10 =20 so BEMF is off at speed step 5. Dither takes over from there so it will have to be set or the loco slows. Other makes of BEMF decoders are adjustable to limit motor power as the loco speeds up but you will have to spend some time programing on the main to get them right.
Speed matching can turn out to be a hobby in itself. Like others have said, At times locos can run fantastic and others finicky. All you really have to do is get them close and run from there. You are matching road diesels from the same maker. Its not like trying to get a switch engine to run with a road diesel. Like the prototype rail roads do not speed match but use the idea as any loco can help when needed. You will find that the slower loco will coast along and the faster loco will be slower when coupled to a slower. If you are running your consist as distributed power than good track work with broad curves and properly weighted cars are most important.
Pete
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As noted, different decoders work differently too. It can depend on what you have for momentum settings too. Most decoders will start applying power per the CV settings a little at a time, without regard for whether the engine is moving or not. I believe NCE decoders are set so that first it rapidly applies power until the engine "grabs" and starts moving, then begins to apply momentum to ensure a slow start from there.
p.s. CV2 is usually the last thing I adjust, after doing CV 5 and 6 to set the running speeds so they match, and CV3-4 momenum so the engines start and stop together. Then if they still aren't running exactly alike I may tweak CV2.
Well I got em speed matched at top speed, they vary maybe 1 foot over a 100 foot run. Due to short runs between towns on my layout I'm not concerned with momentum, I leave it off. Next to match em at mid speed. And fiddle with the U23B kick start. Then I'll move on to consists, although with only 25 piceces of rolling stock and 3 locos for 2 operators I won't be doing that often. Thanks guys.
Momentum really doesn't have anything to do with how long your run is between towns, it's just a way to make your starts and stops smoother and more realistic. It also makes it more like handling a real train, which can't "stop on a dime". You don't need to have a huge amount of momentum, just a little can really make the engine run nicer - plus you can use the momentum to help make two engines start and stop together. If one engine always stops before the other does, adding a little stopping momentum to the one that stops too soon can make it "drift" a little longer so it stops at the same time as the other one.
I'd take an engine and set CV 3 and 4 to maybe 15 and try running it to see how you like it.