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I'm currently building a medium size layout which will be DCC, and am as far as having the baseboards done. However........
For a while now I've been collecting locos and rolling stock and as part of this have picked up a couple of train sets at good prices...both new. As my main build is going slowly I've got a couple of boards and have set up a double oval with the track from the train sets, in order to run in locos and have a general play in the meantime.
The two tracks are not connected. One runs on a Bachmann controller, supplied with a train set, and this works fine. The other has a Hornby R8250 controller. When I use this, with the same loco that has run fine on the Bachmann track, the loco produces a loud hum as I wind up the power, will only then move off, and does not run as quietly or smoothly.
I'd be happy to get a new controller, as I'm worried about potential damage to my new locos, but wondered why this should be. Any thoughts please. This is my first post.

Hi
I feel the hum you're hearing is the Pulse Width Modulation (PWM) the controller outputs to the rails and onward to the motor. PWM is normally not harmful to loco motors, though some specialist motors do not like PWM. Assuming all your locos are Hornby or Bachmann etc and the motors have not been replaced then no harm should be done to them.
The R8250 controller is a very basic device and if your remaining with DC operation for any length of time (before the DCC changeover) then consider obtaining a better DC controller.

PWM can make motors run hot, due to them developing a lower back EMF. So called "coreless" motors are particularly at risk as there's no great lump of iron to conduct away the heat. They can also be damaged by the pulsing effect, if the pulses are too strong and short duration. This one reason why they shouldn't be used on address 0 of DCC systems, as once the speed drops to zero they will be receiving equal positive and negative going pulses at the frequency of the DCC supply. Effectively turning the motor windings into a buzzer and shaking them to pieces.

Thanks for your replies. Really helpful.
I'll ditch the Hornby controller, probably make do with the other track, but if not get a Bachmann 36-565 which matches the Bachmann I have, or a Gaugemaster Model Combi.

Bufferstop wrote:PWM can make motors run hot, due to them developing a lower back EMF. So called "coreless" motors are particularly at risk as there's no great lump of iron to conduct away the heat. They can also be damaged by the pulsing effect, if the pulses are too strong and short duration. This one reason why they shouldn't be used on address 0 of DCC systems, as once the speed drops to zero they will be receiving equal positive and negative going pulses at the frequency of the DCC supply. Effectively turning the motor windings into a buzzer and shaking them to pieces.

Every DCC loco uses PWM, as that is what a decoder outputs to the motor.. 99.9% of all RTR loco motors will have no ill effects. It is only the occasional coreless motor that has been changed or on a kit built/home made chassis where issues may arise, and even then its very rare today with high frequency PWM that many decoders output.

The Hornby DC controller may not use very high frequency PWM due to its relatively low cost?

Flashbang wrote:Every DCC loco uses PWM, as that is what a decoder outputs to the motor.. 99.9% of all RTR loco motors will have no ill effects. It is only the occasional coreless motor that has been changed or on a kit built/home made chassis where issues may arise, and even then its very rare today with high frequency PWM that many decoders output.

The Hornby DC controller may not use very high frequency PWM due to its relatively low cost?

That's the problem, a pretty old, cheap design, compared to what you find in present day DCC chips, and DC controllers from Gaugemaster. As long as they worked with the X03/4 motors and whichever cans Hornby were using they didn't spend money on anything more sophisticated.

JRMaybach wrote:Thanks for your replies. Really helpful.
I'll ditch the Hornby controller, probably make do with the other track, but if not get a Bachmann 36-565 which matches the Bachmann I have, or a Gaugemaster Model Combi.

If your eventual layout is going to be DCC why not get a DCC controller now?

If you want to stay with DC,then aim for something like a H&M 2000 or a Gaugemaster model D or a Morley. Something along those lines.
If your aim is to go DCC, then it is better to use what you have for now and make a start into DCC with one of your lines. Make sure it is co pletely isolated from the other DC line if you do that. Then you can slowly fit decoders to the locomotives as you go along.

Mountain wrote:If you want to stay with DC,then aim for something like a H&M 2000 or a Gaugemaster model D or a Morley. Something along those lines.
If your aim is to go DCC, then it is better to use what you have for now and make a start into DCC with one of your lines. Make sure it is co pletely isolated from the other DC line if you do that. Then you can slowly fit decoders to the locomotives as you go along.

Thanks Mountain (and Ironduke), good suggestion. Putting DCC on the"Hornby track" and DCC on the other will enable me to run in the locos on DC then fit and programme the decoders on the other (as the build goes on with the main project). Cheers