I was running my engines today on a small test layout that I have equipped with a Digitrax system and noticed my locomotives that arent equipped with decoders tend to hum in varying high pitched frequencies, depending on the throttle setting. Though they still run fine, I was wondering if they will continue to hum after I install decoders, or if a decoder will silence the problem.
The noisiest of the engines is a brand new Athearn GP38-2. I plan on installing a decoder in it as soon as I get a second unit so I can MU them together.
Has anyone else ever had this problem?
Thanks,
Cahrn
That is the hum of the motor trying to figure out which way it should turn. The DCC signal it sees is pretty balanced at that point, so the motor has no more torque in one direction or the other. That is why they can sit and hum while a DCC locomotive is moving around the track. The hum is caused by the fact that you are not using a pure DC waveform on the track.
If you were to select address zero, all your DC locomotives would begin to move as you open the throttle. The waveform allows the motor to begin turning in one direction.
If you install a decoder, the noise should (for the most part) go away. Some decoder/motor combinations may be noisy due to the high frequency drive used at low speeds.
Still, it is not a good idea to leave DC locomotives on the track, or run them for long periods of time with a DCC system. The motors can get hot when exposed to DCC waveform.
Ditto what Betamax said. The hum will go away with a decoder. Old Tyco style pancake motors REALLY don't like the DCC signal. They get hot fast. Doesn't seem to effect can motors as bad.
I did this back inJanuary 2009. I did not try this while running on a layout and pulling rolling stock.
Since there have been some questions about running DC only locos with a DCC controller capable of running DC only locos, Yes, it is kind of technical. I had no way to measure the mechanical vibrations which will eventually affect a motor.I did some temperature measurements as an experiment. The applied DCC signal is 30 volt pulses at a frequency of about 6khz.Remember, the motor signal is the same as the track signal and at zero throttle, the pulses are still affecting the motor.I recently used a MRC 2000 DCC controller that can run DC only locos to look at motor temperatures. The first was using a small can motor used in my HO scale 4-4-0 locos. The motor temp was 68F at the start. With zero throttle, the temp went up to 92 F after ten minutes.At one third throttle, the temp went to 105F after five minutes. Back to zero throttle, the temp dropped to about 96 F after five minutes.I then did the experiment with a open frame motor from a older MDC box cab.At zero throttle, the temp went to 85F after five minutes.At one third throttle after five minutes, the temp went to 104F.After five minutes at zero throttle, the temp was 95F.In both cases, the motor is in open air with only a flywheel for a load.With the motor enclosed and sometimes run near max throttle and pulling a load, a more heat can develop.I had no desire to do life testing or take measurements at higher speeds. The few results speak for themselves. May not be important to some people.I used a Raytek Mini Temp infra red thermometer with laser pointer for temp measurements.
Some people have been running a DC loco on DCC for some time will no issues, except for noise.
Again, your mileage may vary.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
I have to chime in with one more thing here. I have several older soundtraxx decoders in some locos. When some one in the club was running a DC loco on 00 with the clubs lenz system. The Soundtraxx decoders started having fits. Start stop and random sounds and one started blowing the whistle while not even selected. As soon as 00 was not running any more the locos started acting normal again. There were 2 LCB280 and one LC 110. All are DCC only and will not operate on DC.
Pete
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I started with nothing and still have most of it left!
richg1998 recently used a MRC 2000 DCC controller that can run DC only locos to look at motor temperatures. The first was using a small can motor used in my HO scale 4-4-0 locos. The motor temp was 68F at the start. With zero throttle, the temp went up to 92 F after ten minutes.At one third throttle, the temp went to 105F after five minutes. Back to zero throttle, the temp dropped to about 96 F after five minutes.I then did the experiment with a open frame motor from a older MDC box cab.At zero throttle, the temp went to 85F after five minutes.At one third throttle after five minutes, the temp went to 104F.After five minutes at zero throttle, the temp was 95F.
I love it! What a great experiment. Real data, for the first time. Thanks.
But, how scared should we be? Is there any way you could repeat this with a DCC motor, and/or with a DC motor on plain DC? Is this effect just from running the DC motor on DCC, or is it the same kind of motor heat-up we should expect regardless of the power source?
It takes an iron man to play with a toy iron horse.
No way should you get the same level of heating using a decoder. Yes, the decoder still drives the motor with variable width pulses, but those pulses are all in the same polarity (phase), not back and forth like the DCC signal the motor sees when operating without a decoder. Older decoders without a high frequency 'supersonic' or 'silent' drive will heat the motors more - which is why they are death to coreless motors which have no armature mass to dissipate the heat. Such motors are also quickly destroyed if put on DCC track without a decoder. High frequency drives reduce this heating and allow coreless motors to be safely used with DCC.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
The whine is common to all non-DCC locos. The motor should be fine as long as long as it's not run for long periods at low speed (1-3 hours) or left sitting on a powered track. If it's left to sit on a powered track the motor can be badly damaged. I did an experiment with a couple of DC locos a year or two ago to see how long the motors could take being left idle on a powered track. They were both Athearn motors. One lasted less than an hour (burned out a brush) and the other lasted almost 6 hours before the windings were damaged. On a good system the time would probably be less. I used a Bachmann EZ Command DCC system for the test.
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When I did my test. I used a infra red temp unit that has a laser pointer. The highest temp point was seen on the case of the can motor and was very close to the position of the brushes.
Guess I have to get some more decoders then...