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Locomotive doesn’t seem to cruise smoothly

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Locomotive doesn’t seem to cruise smoothly
Posted by nscsx on Tuesday, December 12, 2017 9:59 PM

I recently purchased a Kato locomotive and it seems like I can here the motor slowing and speeding as it cruises the track. Kinda like the cruise control in a car would to maintain the current speeD. But I know something isn’t right because before I converted to DCC I didn’t notice it. i have an sw1 too and it’s a lot better but I believe it still does the same thing. I just have a 4x6 island layou. 

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Posted by mbinsewi on Tuesday, December 12, 2017 10:28 PM

I have a few Katos, c44-9ws and SD45s.  There is kind of a moan to the engine as it pulls a train around curves, and up and down grades.  It's not loud, but you can here a difference, like any other locomotive brands.

I've never found it to a problem, they all start out and accelerate slowly, like they should.

If your locos are "NOS" (new old stock), you might want to check the lube in the truck gears, if it bothers you.

Mike.

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  • From: Ludington, MI
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Posted by Water Level Route on Wednesday, December 13, 2017 6:13 AM

nscsx
before I converted to DCC I didn’t notice it

Have you tried turning off the back EMF of the decoder to see if that helps?

Mike

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Posted by nscsx on Wednesday, December 13, 2017 6:17 AM

I don’t know what that is

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Posted by mbinsewi on Wednesday, December 13, 2017 7:32 AM

Well, I'm no wiz-kid at this stuff, but,  back EMF, or BEMF , has to do with the voltage generated by a motor while in operation.

It's defined here:

http://www.dccwiki.com/Back_EMF

Some decoders, and DCC systems allow you to adjust the CV values that control the BEMF.  I use Digitrax, and CV's 55, 56 and 57 are used to adjust BEMF.

with BEMF on, your loco will be on a type govenor, or like the speed control on your car or truck.  The loco, or your car, will maintain the same speed as it goes up and down hills.  You can here the difference in the motor as it does this.

If BEMF is turned off, you have control of the loco, or your car, and it's speed going up and down hills.

I've never had a problem with BEMF on any of my locos, but, the steepest grade onmy layout is 1%, so yes, I can hear the difference in the sound of the loco, as it pulls a train around curves and up and down my 1% grade, I've just never felt it necessary to mess with it.

Check the manuals on the DCC system you are using for info that pertains to your set up.

As I said, I use Digitrax, and their web site and manual gives the information on CV's and BEMF.

Mike.

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Posted by nscsx on Wednesday, December 13, 2017 8:09 AM

Hey mbinsew, thanks for telling me about that. I use ESU/LOK for my DCC decoders. All three of my locomotives have the same decoders. But I noticed it with the Kato the worst. It doesn’t really speed up/slow down to the point were you can see it but you can here it though. (you can see it when I pull cars because the couplers are some what jerky when the locomotive is in motion). It bothers me because it makes me feel I wired something wrong underneath and I struggled my way through running all the feeders and bus wires. Every joint is soldered though. 

By the way, awesome layout. Hope I can build one that looks that nice one day. 

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Posted by mbinsewi on Wednesday, December 13, 2017 8:20 AM

I'm sure your track wiring is just fine.  How does the loco run without any cars?  If you notice some hesitation, maybe some track cleaning is in order.

I have no experience with ESU decoders, but the guys on here that have them say they are the best, and future sound decoder installations on my locos will include ESU and LOK sound.

Oh, and, thanks for the compliments!

Mike.

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Posted by nscsx on Wednesday, December 13, 2017 9:12 AM

It Still sounds the same even running locomotive by itself. My layout is completely flat too

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Posted by Water Level Route on Wednesday, December 13, 2017 1:31 PM

nscsx
before I converted to DCC I didn’t notice it.

This tells me that your issue is most likely decoder related.  Typically (as I understand it) back EMF (BEMF) is normally turned on from the factory and most modelers don't have issues.  However, I've seen elsewhere in the forums where BEMF has caused similar issues with locomotives and others have had to adjust the settings.  I'm sorry I can't be more specific as I've not run into the issue personally.  Do look for what CV(s) control BEMF and try turning it off.  You will notice changes in speed in the locomotive when it goes up or down hill, but if speed changes on the level go away, then you know where your issue lies.  If the speed issues stay, then you've eliminated BEMF as a possible problem.

Mike

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Posted by wjstix on Thursday, December 14, 2017 4:33 PM

nscsx

It doesn’t really speed up/slow down to the point were you can see it but you can here it though. 

With Back EMF, the engine doesn't speed up or slow down, the intention is that the engine runs the same speed whether running uphill or downhill or on the flat. To do that, the decoder senses the motor slowing down when going uphill and adds more power so it keeps going the same speed; when going downhill it does the opposite and reduces power so the engine doesn't race downhill.

There are CVs you can use to turn BEMF on and off (as noted, decoders normally come with it turned on) and CVs to control how much of an effect it has. My guess is your decoder has a CV mis-set to too high a sensitivity and that's whats causing the jerkiness...basically, the drag of the cars is making the decoder think the engine is going uphill, and adding power, then when the engine speeds up, it thinks it's going downhill and lessens the power to the motor.

Unfortunately, LokSound decoders can be difficult to set because they have several 'layers', so you may have to punch in several numbers to change one CV.

Stix
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Posted by nscsx on Thursday, December 14, 2017 5:22 PM

 

 

 
nscsx

It doesn’t really speed up/slow down to the point were you can see it but you can here it though. 

 

 

With Back EMF, the engine doesn't speed up or slow down, the intention is that the engine runs the same speed whether running uphill or downhill or on the flat. To do that, the decoder senses the motor slowing down when going uphill and adds more power so it keeps going the same speed; when going downhill it does the opposite and reduces power so the engine doesn't race downhill.

There are CVs you can use to turn BEMF on and off (as noted, decoders normally come with it turned on) and CVs to control how much of an effect it has. My guess is your decoder has a CV mis-set to too high a sensitivity and that's whats causing the jerkiness...basically, the drag of the cars is making the decoder think the engine is going uphill, and adding power, then when the engine speeds up, it thinks it's going downhill and lessens the power to the motor.

Unfortunately, LokSound decoders can be difficult to set because they have several 'layers', so you may have to punch in several numbers to change one CV.

Thank for this reply, seems like you really know what your talking about. I haven’t ventured into too much programming yet, kinda scared because it seems complex... 

[/quote]

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Posted by rrinker on Thursday, December 14, 2017 5:23 PM

 Loksounds are one of the easiest to set the BEMF on - they do it automatically! 

Make sure you have plenty of clear track - no other locos or cars blockign the way. Set CV54 to 0, hit F1, and the loco will take off on its own for a couple of seconds. Once it stops - BEMF is tuned, all those parameters will have values that should be prety close to ideal. You cna repeat the process a few times if necessary. 

                              --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by wjstix on Friday, December 15, 2017 3:08 PM

NSCSX - don't be intimidated about setting CVs. You normally only have to change a couple to fine tune things, and if it gets messed up, you can always do a factory reset and start over.

Randy - I forgot about that! Would be worth a try, might solve the problems.

Stix

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