Train Speed

[ernies railroad]

[?]Is it common for engines to run at a slower speed, in a DCC mode than they would in DC. Is it because the decorder regulates a closer speed control in accordance to scale speeds?

[Anonymous]

Yes, simply put, DCC gives you finer control over speed with being able to set speeds in steps and starting voltage.

[conrail92]

with my DCC my engines run faster at full speed then dc at full speed, but dcc it takes longer for it to reach high speed but thats because its more realistic and depending on your speed step setting it will change how fast it gets up to full speed i have my on 28, in the middel of the two other options

[ernies railroad]

You know whats so great about this hobby, someone is always willing to help a fellow model railroader. Have been in the hobby for 35 years and it's the people that make the hobby. Converting over to DCC, your answers make sense, THANKS

[Anonymous]

QUOTE: Originally posted by ernies railroad

You know whats so great about this hobby, someone is always willing to help a fellow model railroader. Have been in the hobby for 35 years and it's the people that make the hobby. Converting over to DCC, your answers make sense, THANKS

We're all in this together Ernie and watching out for each other.
If you are concerned with slow speed operation, be sure the decoder you choose at least has back EMF. I have a personal preference for Lenz products. I would recommend their Gold or Silver series decoders.

Have you decided which system is right for your layout?

[ernies railroad]

What is EMF/

[Anonymous]

QUOTE: Originally posted by ernies railroad

What is EMF/

Sorry Ernie, I'm on lunch now. Too much to write. Click here for Back EMF

Also see Lenz's Law

[twcenterprises]

QUOTE:
What is EMF/

Electro Motive Feedback (or something like that). Basically, it allows the decoder to measure how much current the motor is using, and how fast the motor is turning, and when the train hits a grade and the motor slows down, the decoder will give a little extra throttle to maintian speed. I would assume that it would also have effects on sound equipped locos as well.

Brad

[Anonymous]

Well, lunch is over, back to work. (burp, ahh!) Since you have been in the hobby for thirty (belch) five years Ernie, I'm sure you already know a locomotive needs a flywheel (toot!) to run smooth. Just thought I'd mention it for the benifit of newbies (toot, toot, ahh!)

[ernies railroad]

Thanks for the info on EMF, looked it up and under stand, all my engines are equipped with flywheels, thous which were not have been rectified

[Medina1128]

Actually, EMF stands for Electro Motive Force... and back EMF is just that. It's a voltage signal that is a lower voltage and flowing in reverse, or 90 degrees out of phase of the main signal. What this does is allow minute changes in voltage, allowing the motor to turn very slowly. The downside of back EMF, is that it generates more heat.

[Anonymous]

I think I need to disagree with some of this:

QUOTE: Originally posted by Medina1128

Actually, EMF stands for Electro Motive Force... and back EMF is just that. It's a voltage signal that is a lower voltage and flowing in reverse, or 90 degrees out of phase of the main signal. What this does is allow minute changes in voltage, allowing the motor to turn very slowly. The downside of back EMF, is that it generates more heat.

Yes, it is Electro Motive Force, big words for voltage. But the back EMF is the voltage generated by the motor when the decoder is not providing power, between pulses. That voltage is going to be proportional to the speed of the motor, so by sensing it, the decoder can have a means to see the speed of the motor, and adjust for changes due to grade, etc. So the biggest part I disagree with is the more heat, the back EMF is there whether the decoder is looking or not, some decoders do, some don't

[JimValle]

Comparing DC with DCC speeds I think DC runs faster, particularly the older engines.
DCC equipped engines usually have some type of can motor which generally run slower than open frame types or the older Athern motors. DCC, sound modules and headlights take up a lot of amps so many of the newer engines don't even start to move until nine or ten volts are showing on the meter so there's not much speed potential to be realized before your throttle is wide open. Our modular club had to dedicate one mainline to the DCC locos because they couldn't get out of the way of the older, simpler power, espically the 'seventies vintage Japanese brass steamers.

[nobullchitbids]

Just a reminder to everyone that there is no such thing as a 12-volt motor -- provided the heat can be dissipated, a motor can be run at any voltage that is not so great it flies apart. So, if one wants to compensate by putting 16v. on the motor, don't panic; but, do make certain the motor does not get too hot (a function of power). P = IE.

[fsm1000]

Gee I suppose I should upgrade my locos with the rubber bands [as opposed to the newer universal joints [:P] ] eh? [:-^] Anyone remember those things? lol That was a while ago.
EMF is also in drills, saws and other things as well. In case you wanted to know this lol.
Stephen

[Medina1128]

Baldwin, I stand corrected, and a doff of my engineer's cap to you. I remember now, not only does an electric motor USE electricity, it also generates some of its own, but the same principle that makes an electric motor work (conductors moving through a magnetic field).

[MisterBeasley]

Gee I suppose I should upgrade my locos with the rubber bands [as opposed to the newer universal joints ] eh? Anyone remember those things? lol That was a while ago.
EMF is also in drills, saws and other things as well. In case you wanted to know this lol.
Stephen

I've still got several old rubber-band drive engines.  These were made by Athearn in the 1960's.  When I unboxed them after 40 years, I found I had some that still ran, so I put decoders in them.  Well, they ran, but not very well.  I pulled out the decoders to use elsewhere, and converted 2 of the engines to dummies (or "honorary locomotives") which I run around in consists.  I just got the gear conversion kit for the third engine, an Athearn Hustler.  I went to my LHS to order the conversion kit (now, remember, this kit is only for this obscure 40-year-old engine) and he had the kit in stock.

But back to the slow-speed performance on DCC, remember that slow speed puts a premium on good trackwork, and particularly good electrical contacts.  When you run your trains fast, they will coast over electrical "gaps" and you may not even notice.  At slow speed, and particularly at the almost-stopped "yard speed" we like for switchers, your engine may stall at turnout frogs if there are any loose rail joiners, etc.

[wjstix]

When you first install a good decoder, it should be 'invisible' that is, it shouldn't change how the engine runs from what it did using DC power...or at least a very little change. Now, once installed, you can adjust the CV's (control values) of the decoder to allow for slower speed operation, better control range, momentum effects etc. that should enhance the engines performance.

[ShadowNix]

Good article on what Stix just commented on in September MR... very basic, but just what I needed and it explains this effect PERFECTLY! 

 

Brian