I know you folks here are use to my dumb questions, right now your are more than likely shacking your head and thinking to your self "Cuda Ken is a frigging idiot, add a decoder dumb #%$!" Before you folks start chipping in to send me to Funny Farm there is a reason I ask.
I have been running some of my old DC engines on the DCC layout, most make a god awful humming sound. But, a few are just about as quite running as the DCC engines. There all so seems not to be a rhyme or reason when it comes to the manufacturer.
The quite ones are.
PK 1000 Erie Bulit, no hum at all.
PK BL2's, the old brown box verson, just a little hum at low speed.
3 year old Blue Box super weight F7 and its powerd B unit that I kit bashed and used the same motor that came in the F7A.
I am thinking it has something to do with the number of windings in the motor it self.
Cuda Ken
I hate Rust
It's not the windings, it's how the motor is put together. The old Blue Box motors aren't fasteend together by anythong more that the top and bottom clip. The magnets are not glues to the motor case, they sit in there loose. All these loose pieces vibrating back and forth is what makes all the noise. The old P2k was a direct clone with slight motor improvements of the BB. The new P2K/P1K motors are more tightly put together. Want DCC hum, fire up an old Bowser. Besides the motor, the metal shells tend to amplify the noise.
Theoretically you could glue the magnets in place in the BB motor and it should quiet down quite a bit.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
"How do you stop a loco from humming?"
"Play a tune it does not like"
Hey Ken,
You know, I don't think there is a whole lot you can do other than install a decoder.
The boys and I had a good time at K10 last weekend. It was very busy with lots of derailments!!
Simon Modelling CB&Q and Wabash See my slowly evolving layout on my picturetrail site http://www.picturetrail.com/simontrains and our videos at http://www.youtube.com/user/MrCrispybake?feature=mhum
rrinkerThe magnets are not glues to the motor case
If I read this right if I glue the magnets, there would be no HUM? Boy that sounds way to easy. Are DCC motors made different?
Simmon, I am for now off Sundays. Maybe I can stop by and have your son's teach me a thing or two.
Store the loco on a siding and switch off at least one rail. DCC controllers for operating DC locos with no decoder put out low frequency pulses that are in the audio range, around 100 to 200 HZ (cycles per second).
Locos with decoders get essentially the same pulses but the pulses go away with zero throttle.
Gear slop can cause noise or anything mechanically loose on the motor and drive train.
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.
richg1998 Store the loco on a siding and switch off at least one rail. DCC controllers for operating DC locos with no decoder put out low frequency pulses that are in the audio range, around 100 to 200 HZ (cycles per second).
Rich, the hum is while they are running. All my lines have spots where I can kill the power. That from mty DC days.
OK, I misunderstood. It has to be mechanical issues. Plastic shells on locos are great amplifiers. I remember a lot of noise from a MDC Climax but it was much quieter with no plastic shell on the loco. I had the same issue when using a MRC 2000 some years ago. I converted a couple with decoders and using a NCE Power Cab, no more noise since the operating frequency is higher. But I cannot run DC only locos anymore.
My completely rebuilt MDC Climax is much quieter now the the motor and drive chain have been rebuilt but it cost over a hundred dollars to do it. Just my way.
OK Dave, there is no such thing as a DCC motor. But why do some of my DC engines make little or no hum at all when ran on DCC?
What I said is still valid. The BB motors are 'loose' all over, not just the magnets. A coreless motor probably woun't hum at all. Of course it would also be ruined in seconds. The number anf gauge of the windowing, the if the armature is skewed or not, and yes, the loose magnets are all factors in how much a particular motor will buzz when AC is passed through it.
The few I tried, the BB motors, while noisy, actually seem to run at a decent speed on address 00. Some of the quieter ones like P2K move at a fraction of the DC top speed, but they don;t make a lot of noise. Go figure.
The only real solution, like Dave said, is to install a decoder. It's the only way the motor will run quietly and safely long term on DCC.
cudakenBut why do some of my DC engines make little or no hum at all when ran on DCC?
Yup the new forum search engine is working fine. Here it is:http://cs.trains.com/trccs/forums/p/105396/1222435.aspx#1222435
cudaken"Cuda Ken is a frigging idiot, add a decoder dumb #%$!"
You just gave yourself the best advice. Running a DC engine on DCC, (Especially while sitting still) is very hard on the motor. It will cause it to overheat quickly, shortening it's life!
The buzz is caused by the reversing of the current across the motor. These is no fix for this without adding a high frequency decoder.
Randy is partially right. The loose construction with the reversing current is what causes the noise. And the older Athearn/Blue box motors ate a ton of current, which only increases the problem.
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
DCC motors are not made different, they are just not connected to the track as the motors are in a DC loco.
The "ac" put out by DCC systems does not go to the motor in a DCC loco. The wheels pick it up, pass it to the decoder and the "ac" signal stops there. If that loco is given a command to move, the decoder will convert the "ac" voltage from the tracks to a DC voltage that has a magnitude and polarity based on the commanded speed for that loco to move.
A DC loco sitting on an active DCC track will have a motor that is reacting to the "ac" voltage applied by the DCC system, so the motor will oscillate forward and reverse with the DCC signal. I would guess the hum variates between locos comes from different motor mounts (not isolating as well) or slop in the drive train.
I have to differ with you. The motor in a DCC decoder equipped loco gets pulse power when the loco is commanded to move. Only the lights get pure DC power.
Put a dual decoder loco on a DC controlled power pack and the motor gets pulse power when commanded to move. Lights get pure DC.
The pulses go away when the throttle is at zero with either system.
Non DCC locos on DCC systems always get pulses.
Typical diagram of a DCC decoder. The decoder sends PWM, Pulse Width Modulation to the motor.
Pulses for stretched zero application DCC controllers are hard on DC motors. Motors receiving pulse power from a DCC decoder are different. Someone with digital experience can explain it better than me.
Lastly, I have used an Oscilloscope to verify all of this.
Sure they get pulse from a decoder. The components would burn up if it was constant.
DC motor gets pulse while on a DC layout using a pulse throttle. The pulse is full voltage for a period of time, then no voltage. The polarity stays the same on analog. In this case, the motor is being turned on and off. As speed is increased, the on time gets longer. The same is true when a DC motor is powered by a DCC decoder motor output.
What it does NOT get is an AC form where the "polarity" turns the armature Clockwise half the time and Counterclockwise the other half. That's the cogging that makes a DC motor buzz when run on DCC.
With zero stretching, the motor will get both polarities but the length of time it sees one polarity will be longer than the other as the speed is increased. Faster the motor turns, the shorter the "wrong" polarity pulses but the number of pulses remains the same. Less cogging, less buzz. Hard on a DC motor because they just aren't built to be reversed hundreds/thousands of times per second
Martin Myers
I am well outside my level of expertise and comfort on this particular issue, but a DC motor on a DCC powered track system is getting full voltage from the rails...is it not..so max amplitude. The DC motor getting modulated and modified DC pulse current from the decoder is getting a graduated voltage, so less amplitude of the energy causing vibrations.
Or something along those lines may explain. I will be interested to learn what the cause actually is, although it should be in English and as many monosyllabic words as possible....please.
Thanks for all the kind answers. I will install some decoderss as I have the funds.
Far of the life of a DC engine on DCC, so far so good. By Athearn F-7's have 60 plus hours on DCC and the BL 2 around the same. I never let a DC engine sit for longer than a minute.
selector I am well outside my level of expertise and comfort on this particular issue, but a DC motor on a DCC powered track system is getting full voltage from the rails...is it not..so max amplitude. The DC motor getting modulated and modified DC pulse current from the decoder is getting a graduated voltage, so less amplitude of the energy causing vibrations. Or something along those lines may explain. I will be interested to learn what the cause actually is, although it should be in English and as many monosyllabic words as possible....please.
When powered through a decoder the motor gets nearly full amplitude. The duration, or width, of the pulse is adjusted to control speed, hence pulse width modulation - PWM. The difference between this and a loco without a decoder is with the decoder, the pulse are all the same polarity, there is no negative going pulse that makes the motor try to turn the other way. The reason for all this is to get the decoders small enough - if the power wa sapplied to the motor continuously like a rheostat DC power pack or a non-pulse transistor pack, when runnign at slow speeds all teh excess voltage would have to be dissipated by the drive transistor, mainly as heat. You'd need a much alrger transistor to handle the same current level. With the drive circuit in a decoder, the transistor is either fully on or fully off, no in between. Thus a transistor capable of handlign 1 amp or more can fit in a Z scale loco - actually there are 4 transistors in the output of a decoder.
Thanks, Randy.