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Analog on DCC

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  • Member since
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  • From: Canada
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Analog on DCC
Posted by Nagrom1 on Friday, February 1, 2008 12:08 PM
 Does anybody else do it? If so, I am wondering if you locos get warm. I had mine on for a while, then picked it up. The loco was warm, so I decided to pull the plug and take it off the tracks. I know my Zephyr manual says to not leave them sitting on the track for long periods of time, because they will overheat. Mine were running for about 4 minutes. Anybody have any experience?
  • Member since
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Posted by DigitalGriffin on Friday, February 1, 2008 1:05 PM

Typical behavior.

DCC is an alternating current.  Thereby you have pulses of full voltage switching back and forth rapidly through your DC motor.  This is hard on most motors.  Even when moving at full speed (least amount of current direction switching) DCC power still isn't great for your DC motor.

DCC controls the speed of one analog motor by adjusting the amount the time of the pulses.  For example, the left rail will have a typically longer average pulse rate time compared to the right rail.  When the left and right rail have equal pulse rate times, then the engine doesn't move.

Don - Specializing in layout DC->DCC conversions

Modeling C&O transition era and steel industries There's Nothing Like Big Steam!

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Posted by fwright on Friday, February 1, 2008 1:11 PM

The motors will run warmer in the DC mode (zero stretching) of DCC than on regular DC power.  Here's why:  The zero stretching mode makes the DCC signal (which includes motor power) have more time at one polarity than the other.  The overall average is more one direction than the other, so the locomotive moves.  However, while the polarity is reversed from the selected direction of travel, motor, drive train, and locomotive momentum prevent the locomotive from reversing direction.  So all the current flowing during the reverse polarity cycle goes into heat as it attempts to unsuccessfully reverse the motor direction.

Because there are limits on how much "unbalancing" of the DCC signal can be allowed, the top speed of an analog locomotive on zero stretching will usually be significantly less than on regular DC. 

When an analog locomotive is sitting still on a DCC-powered track, the zero stretching is turned off, and both polarities have equal time.  The motor tries to start spinning one way, then the other as the signal reverses polarity.  The result is usually buzzing and lots of heat.

Coreless motors, which do not have the heat dissipation, momentum, and hysterisis (resistance to change of magnetic field) of an iron armature, suffer the worst.  In fact, the smaller and more efficient and higher quality motors will overheat faster than an older, larger open frame motor.

For these reasons, there are many who refuse to use zero stretching to run DC locos on DCC.  NCE and MRC do not make any provision for zero stretching in their DCC systems.  These folks, if they are going to run DC locos at all, do so by switching the entire layout over to DC from DC power packs.  The DCC system is not used during DC operations.

There are others who use the zero stretching, and have no problems.  Personally, at the very least, I would heed Digitrax's advice about time limits on using zero stretching.

my thoughts, your choices

Fred W 

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  • From: Kansas
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Posted by jamnest on Friday, February 1, 2008 1:30 PM

I have some non-DCC locomotives which I like to run from time-to-time just because I like them.  I have some units which do not fit my modeling era.  I have a Digitrax Chief and the buzzing is anoying and they do get warm, but not hot.  The cost of simple non-sound decoders has really declined so I have purchased some additional limited function decoders to put in these units so I can run all DCC.


Jim, Modeling the Kansas City Southern Lines in HO scale.

  • Member since
    August 2007
  • From: Canada
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Posted by Nagrom1 on Friday, February 1, 2008 2:26 PM
I do plan on setting all of my locos up on DCC, but, need to allocate the funds. I don't see anything to be too scared of, so I will still run in analog, I'll keep it to small doses. I just can't stand having motive power sitting beside the track, not moving on it. Thanks for the help.
  • Member since
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  • From: Colorful Colorado
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Posted by Texas Zepher on Friday, February 1, 2008 4:15 PM

 Nagrom1 wrote:
 Does anybody else do it?
I used to but now only in a rare instance (emergencies) for a very short time.

my Zephyr manual says to not leave them sitting on the track for long periods of time, because they will overheat.
Not just overheat but also wearing out the magnets.  A long period of time, in my opinion, is anything over 1 minute.

Mine were running for about 4 minutes.
Running is different than sitting.  When I say sitting, I mean stopped on the DCC track with no channel zero throttle applied.  When we first started using DCC, my children ran their DC locos on DCC channel zero for time periods of exactly 1 hour blocks (their time allotment at train shows).   The locos were moving 99% of that time.  No apparent problems were observed. 

Anybody have any experience?
You might want to check out this thread:

I highly do not recommend this practice.  DCC decoders are so cheap now, why take the chance?

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