Slower in DCC then in DC
#1
Guys can anyone answer this? I have noticed that my locomotives run slower in DCC then in just regular DC. Has any one come across this before and how do you rectify it, if you even can. Be interested to see your input. BTW, I am using a Helix Humper motor in A Bowser E6 Atlantic with a NCE decoder.


thanks, Mark Wallbang
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#2
The top voltage can be adjusted in the decoder, but I don't think it is abnormal for them to run a little slower. What kind of top speeds are we talking?
I have no trouble getting any of mine to run at scale speeds of 100 mph, but I set the top voltage (and it varies by locomotive) so the passenger units top at 60 scale mph and freight around 50 scale mph.
Charlie
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#3
For me it's not so much speed it's power. The E6 can only pull 3 passenger cars without struggling around our club layout and that is at max. I've made speed table adjustments but it has been a while since I've look at what they are set at. I'll have to put on the program track and see what they are set at. I'm pretty sure they are at max. I have been wondering lately that I have the motor seated down to hard on the drive gear.


Mark
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#4
Does it run great in dc, and are you refering to before you added DCC? Adding DCC can help with a little better control and fine tuning, but it will do nothing to improve a mechanical problem. If the drive train is free and it runs good on dc it should run fine on DCC. You might check the back emf settings and the kick start settings as well.
This gal should be able to creep around a level layout with 5 cars IMHO, and the NCE decoders are among the best.

Charlie
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#5
This is odd indeed. My experience has been that particularly with back EMF on a good decoder etc, the motor has a lot of torque from a low speed onwards. This is because it get's 'kicked' with the full available track voltage. One test is to carefully hold the loco with your thumb and index finger while increasing the throttle from 0, you should feel more pull than you were used too on DC , a sign of a good working BEMF feature in a DCC decoder , the more 'resistance' you give, the harder the loco starts to pull (and you can probably hear the tone of the motor change, either in more pulses (higher pitch) or a bit louder/ pronounced) all within reason , be gentle of course but you'll get the idea.

I have a feeling you need to take some time tweaking the decoder, Back EMF can also be set too in-sensitive. Play with a few values, go for some 'extremes' first and see which response this give you, that way you should be able to work out which way you need to go. Only work one CV at a time, otherwise you'll get confused real quick, and do not know what caused what response.


Koos
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#6
I might add to Koos very good reply, use a pencil and paper to record what settings you are using. That way you don't forget and undo something that you have all ready done.
Charlie
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#7
twilight Wrote:For me it's not so much speed it's power. The E6 can only pull 3 passenger cars without struggling around our club layout and that is at max. I've made speed table adjustments but it has been a while since I've look at what they are set at. I'll have to put on the program track and see what they are set at. I'm pretty sure they are at max. I have been wondering lately that I have the motor seated down to hard on the drive gear.


Mark

Hey, its Chris.

It seemed to be running fine last monday, but then you didn't have a train hooked up to it.

When you say struggling, are the wheels slipping, or are they grinding, or is the model just not going as fast as you thought it would?

Try the draw-bar pull meter (its up by the work bench), first on the locomotive, and then set the passenger cars on the moutain and let them hang from the meter. That should let you know whether you're loosing power or if the locomotive is just slow.

Its posible that the decoder is the problem. If all else fails, reset it and see what happens.
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#8
Hey Chris and guys, I just feel the loco should have a little more emmph! I guess I wasn't too clear about how the locomotive operates. When I built it I made sure the drive mechanism moved clear and freely. I was told to use a piece of glass and set the drive mechanism on it without motor installed and lift on side of the glass and see how the mechanism moves. Keep doing this until you see the mechanism move freely across the glass. It took a little while filing the burrs out but I eventually got the drive mechanism to glide freely across the glass. So I do not believe this is a mechanical problem. At the time I was still tossed up on what motor to put in it. The orginal DC-71 or a Helix Humper. I opted eventually for the Humper, hopefully to get a quieter motor. But I tried both motors in the mechanism, without a decoder, and the engine flew down the test track. After I installed an NCE D13SR decoder I could see a noticable speed/power difference. In the NCE manual for this decoder I do not see anything about back EMF but I do see information about setting kick rates. I'll have to give them a try. I believe I've tried these before but I do not recall the results. See this locomotive hasn't been on a layout since last year at my club's open house.(I had the same feeling about the E6 last year) Won't be able to really get into it till after the show though, which is this weekend.


Thanks, Mark Thumbsup
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#9
Guys, I've been able to get into this a little further now, here is what I have been able to come up with as of tonight. I have been able to apply dcc power directly to the motor leads and I can see and feel the motor respond with more power and speed. Not as much still as in dc, but better. So, I am thinking I have some dirty contact points with where loco is picking up it's signal from the track. Obviously, I have cleaned the tender wheels and drivers, but that has not made a difference. I have a few ideas to try but I am open to suggestions.

Thanks, Mark Thumbsup
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