Urban legend??
Don't tell my 0-6-0 that,,,,It ate the 1st decoder when I first insulated the brushes from the motor.
I slid some tape under it and anchored it with a nylon screw, and the 2nd decoder lived! Motor wobbles a little with the nylon screw,,,,but until I can get one of Dan's cans in it,,,it'll do. The moral of the story?
Not all open frame motors can be trusted,,especially 40 year old ones!! Check the motor frame to ground before you waste a decoder (like I did!!)
toggle quoted message
Show quoted text
--- In yardbirdtrains@..., john Brazaitis <vytis1952@...> wrote:
Actually, this business of isolating the frame of the motor is a DCC "urban legend" along with the idea of "DCC friendly" turnouts. ?I think it got started because certain popular brands of locomotive, like the old Athearn Blue Box diesels, used a design that grounded the motor brush directly against the frame. ?On those engines it is necessary to prevent contact between the motor and the frame, but actually what you are really doing to make it work is isolating the motor brushes. ???On most conventional open frame style motors, isolating the brushes is a simple operation. ?Generally, one brush, the one picking up from the tender or left hand rail is already isolated.The other brush, picking up from the drivers or r.h. rail, may also already be isolated as it is on most of the bowser steamers with the later motor and some of the MDC larger steam engines. ?Usually a jumper or some other wiring device is used to ground the brush to the motor, and
thru the motor to the frame, etc. ?A little study will show how to interrupt this circuit and you're ready to wire for DCC.??On motors such as the ones used on the Mantua engines, the RH brush is grounded thru the spring that tensions the brush. ?To isolate it, all you have to do is slip a piece of wire insulation over the brush spring where it prevents the brush spring from contacting the brush, and you are good to go.As far as this "DCC friendly" switch business goes, if you study either Mallory or Westcott on how to correctly wire and gap all rail frog turnouts, you won't have any problems. ?It's really fairly easy, the basic rules (which apply the DC wiring as well) are gap behind the frog and provide power from the point end, not the frog end, you'll be ok. ?Some turnouts such as the older Shinohara use a contact system that causes shorts in DCC, but it's because of the design of the contacts to the point rails, not the frog wiring.JBB
