My son has the Bachmann Peter Witt Street car. We tried it on my overhead layout using the back and fourth reversing unit. For some reason it does not stop, it keeps going. My Kalamazoo 4-4-0 also does the same thing. All my other engines work fine from my HLW street car, LGB Porter and Bachmann Industrial Mogul. Any ideas why?
I have a MDC switcher engine that never worked on any reverse units, I have never been able to figure out why.
Vincent D’Agostino said:
I have a MDC switcher engine that never worked on any reverse units, I have never been able to figure out why.
Easy, the wiring is reversed.
I have a friend with an old Kalamazoo that does the same and when I switch the polarity on my engine that I can (to run in the opposite direction), it no longer stops after the diodes.
Run this MDC engine in a forward direction. Then put a “regular” engine on the tracks (that does stop) without changing the track polarity and I bet it runs the opposite way.
The diodes in the track are polarity sensitive. If you reverse direction of the diodes, this MDC engine should work properly…, but most everything else won’t.
I think you are correct Todd, the MDC is wired opposite of all my other locomotives
The purpose of the diode is to stop power at the end of the track for 1 direction.
Reverse units for single track runs do not care about engine polarities.
However there is a new issue in the new decoders. These have large capacitors and when power is removed they keep going (as they should for intermittent track power).
So, super caps are not your friend with reversing units for back and forth tracks with diodes.
That makes scenes then.
The Bachmann witt street car has the switch to change the polarity, Ill switch that and I should be fine. For the Kalamazoo, Ill just reverse the wires in the engine rather then the diodes on the track and then all my engines will be set up the same. Those dam sparkies.
Dan Pierce said:
The purpose of the diode is to stop power at the end of the track for 1 direction.
Reverse units for single track runs do not care about engine polarities.
However there is a new issue in the new decoders. These have large capacitors and when power is removed they keep going (as they should for intermittent track power).
So, super caps are not your friend with reversing units for back and forth tracks with diodes.
Dan think about it. If the polarity is one way, the rail past the diode is dead, causing the locomotive to quit moving when it is on that rail. When the polarity is reversed, the rail is live allowing the locomotive to move when its on the rail. If the locomotive moves opposite the way it should for a given polarity, then it will be going the wrong way. So when the dead rail is live to bring the locomotive back from the stop track, the locomotive will in fact continue off the end of the stop track.
So I switched the polarity seitch on the street car to the large scale setting and now it just goes the other way and does not stop still. If a reverse the diodes then my engines that fo work wont? Anything else I could do.
If the rail at the end is unpowered it has to stop. How long is the track at the end, the part insulated with the diode?
About 3-4 ft
The easiest solution Shawn is to just buy more sparkies, then the few that don’t work on the reversing track won’t matter!
I have never been able to figure out the one that I have that doesn’t work, it pretty much defies logic as it somehow remains powered on a dead section of track.
Go back to pull strings?
I don’t know how B’mann implements their LS/NMRA switch, especially coupled with their DCC ability, but the ability to stop after the diodes comes down to more than just changing the direction of the wires to the motor.
Though it may be difficult to explain in “lay” terms I’ll give it a try.
In my mind, it is easier to think of the direction that current travels (+ to -) rather than the flow of electrons. So, if the diode is put on the “right” rail aligned so that the arrow/line faces the end of the track, + can flow though the diode and make its way to this section when + is applied to the right rail.
If we put - on the right rail, it cannot get though the diode and we have a dead section after the diode. When the polarity is reversed, and + is again applied to the right rail, with the diode, it does get through the diode and the train can move.
If the motor is “synced” to the wheels such that when the engine receives - on the right wheel the train proceeds forward it will stop after the diode because the – cannot get though the diode. When the polarity is reversed and + is applied to the right rail, it gets through the diode and because the wheels and motor are “in sync,” the train reverses.
However, if the motor leads are simply reversed, when + is applied to the right rail, the current again gets through to the motor but the train proceeds in the other direction, right off the end of the tracks.
Vincent D’Agostino said:
The easiest solution Shawn is to just buy more sparkies, then the few that don’t work on the reversing track won’t matter! I have never been able to figure out the one that I have that doesn’t work, it pretty much defies logic as it somehow remains powered on a dead section of track.
Its very odd. It makes sense what Todd is saying but why the two I have do what they do. Ill just stick to live steam and battery, less complicated. Ill have to try reversing the wires on my Kalamazoo and see if it works. I should try my Bachmann Forney and see if that acts the same.
All of my Bachmann Spectrum series locomotives work fine on the reversing track, the forney should be fine.