In developing the True Action Throttle (TAT IV) Linn Westcott noted that by using pulse power at running speeds; " Noise is created, and wheels polish themselves on the rails, eventually losing as much as 25 percent of their adhesion. The square law creates momentary currents that overheat motors far above normal ratings for maximum loads." (Model Railroader, March 1969, pg. 12) Westcott designed TAT IV to use pulse power only for starting. When running, the pulse dropped out and the motor ran on filtered DC.
Do DCC decoders provide filtered DC to motors at running speeds? If not, is there subtle damage occurring such as wheel polishing, or side rod wear on steam locomotives? If such damage is occuring, can it be mitigated with the addition of a filter capacitor?
Effectively it is still a pulsed DC current that the motor gets, but it is sent at such a frequency that it appears like a fluid DC voltage that doesn't result in the zero-stretching buzzing, grinding, groaning, and yodeling that a DC motor will make if subjected to direct DCC power at the rails. The only heating is attributable to amperage draw, resistance, and the concomitant work the owner demands the motor to do.
I don't see much evidence of tire surface wear on my locos, but on my first, a BLI Hudson, the original chrome-like finish is now showing copper under it. I have no way of attributing that wear to what you describe, a scrubbing induced by pulsing the motor. Sorry, I can't answer your question about a filtering capacitor.
Crandell
The early pulse throttles wither use 60Hz by tapping off one of the rectifier lugs, or in the case of generated pulses they were often 60hz or LOWER.
DCC is much HIGHER - usually 10KHz or more.They can even drive coreless motors safely - an ordinary pulse DC pack will fry one quickly. There isno appreciable motor heating or wheel polishing occuring from DCC decoder outputs. I somewhat question the wheel polishing unless they were using long duration pulses or overloading the locos such that the wheels slipped. I can see if the pulses were of such aplitude it cause the wheels to slip slightly on every pulse, that would eventually be bad.
Some new wheels are turned, others are just plated - with enough run time, the plated ones will wear off the plating. Run enough and it will wear the rest of the wheel too and the loco will grind to a halt. It's not the type of power, it's the mileage traveled.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Rick Mugele In developing the True Action Throttle (TAT IV) Linn Westcott noted that by using pulse power at running speeds; " Noise is created, and wheels polish themselves on the rails, eventually losing as much as 25 percent of their adhesion. The square law creates momentary currents that overheat motors far above normal ratings for maximum loads." (Model Railroader, March 1969, pg. 12) Westcott designed TAT IV to use pulse power only for starting. When running, the pulse dropped out and the motor ran on filtered DC. Do DCC decoders provide filtered DC to motors at running speeds? If not, is there subtle damage occurring such as wheel polishing, or side rod wear on steam locomotives? If such damage is occuring, can it be mitigated with the addition of a filter capacitor?
Rick, motor designs have improved, and the frequencies used in square wave DC motor control have been improved/refined to prevent such problems.
But since the motor voltage does not travel through the wheels with DCC, how could it damage the wheels? DC is "created" in the decoder, then square wave pulsed to control the motor.
Also, I don't use DCC, I use square wave pulse width modulated DC, supplied by Aristo Craft Train Engineer wirelsss radio throttles. They have not damaged any of my motors or wheels. I know a number of other Aristo users who report none of the "supposed" problems of full time square wave pulse width modulated motor control.
Any kind of filter capacitor kills all the advantages of pulse power in the first place. In fact the Aristo throttle has a switch right on it to select pulse width modulation or "analog" - that switch simply puts a large capacitor in the circuit - and slow speed performance and starting is not as good.
With 1969 open frame motors, it might have been an issue with some equipment - with the products of the last 25-30 years, today it is not a concern.
Sheldon
ATLANTIC CENTRAL With 1969 open frame motors, it might have been an issue with some equipment - with the products of the last 25-30 years, today it is not a concern. Sheldon
I agree..I started using pulse power on my "Golden Throttle pack in the early 60s with no issues.
I still like the "Golden Throttle Pack" MRC released in the early 60s..I used one along side a Tech II well into the late 80s.
Larry
Conductor.
Summerset Ry.
"Stay Alert, Don't get hurt Safety First!"
BRAKIE ATLANTIC CENTRAL With 1969 open frame motors, it might have been an issue with some equipment - with the products of the last 25-30 years, today it is not a concern. Sheldon I agree..I started using pulse power on my "Golden Throttle pack in the early 60s with no issues. I still like the "Golden Throttle Pack" MRC released in the early 60s..I used one along side a Tech II well into the late 80s.
Those were great power packs, I sold hundreds of them when I worked the hobby shop!