Tech Question

[mikel]

On a Bachmann Highroller (N Gauge), with regards to the headlight!  how does the incandescent bulb obtain a voltage difference of potential allowing it to light.   The bulb appears to be sandwiched between the half's of the locomotive body.  The bodies are insulated from each other, but yet the bulb lies between both halves.
Be easy on the new guy

Thanks in advance Mikel

[Conrail Quality]

Well, on a simple DC circuit here's what happens. Current flows out of the negative terminal of the power pack to one of the rails. One of the locomotive wheels riding on said rail then picks up the current. The current is conducted by copper strips to one of the electrically isolated frame halves. Since the frame halves are isolated, the electricity is forced to go through the lightbulb and motor since they are the only bridges between the frame halves. The process is then the same as before, but in reverse. The electricity flows through the second halve to the second rail, and then to the positive terminal of the power pack. This completes the electrical circuit. 

Does this answer your question?

Timothy

[jward]

say you have 12 volts applied to the track. using a voltmeter you can measure and prove for yourself that the voltage difference between the two rails is 12 volts. the wheel pickups transmit this voltage to the two halves of the frame, with minimal losses. you can thus place the locmotive on the track, and using the same voltmeter, read approximately 12 volts between the two halves of the frame. this is more than enough to light the headlight. the headlight is in parallel with the motor, and we know the voltage difference between the two rails is what causes the motor to spin and move the locomotive.

[mikel]

Folks I most certainly appreciate your returns, however, the issue is that the lamp is lying on the frame sandwhiched between to two halves, and the frame is showing continuity between both halves. This is the first time i have taken the unit apart and could not understand that dilemma. i.e. my question as to how we obtain a difference of potential to complete the circuit for the lamp.
Do i have to insulate both halves ( which appears so ) if yes can you recommend how? had Bachmann neglected to insulate?

much appreciated...Mike

[Jim Banner]

The two halves of the frame are electrically isolated.  One half connects to the left wheels, the other half to the right wheels.  The motor connects from one frame half to the other frame half.  Same for the headlight bulb.  The continuity you measure between the halves of the frame is via the motor and headlight and should be around 10 ohms, not a dead short.  If it is a dead short, then you have problems somewhere, such as a missing insulator washer.

[jward]

on split frame locomotives, the frame halves must be insulated from each other. on bachmann units this is accomplished by a metal screw thascrews into a plastic housing which is seated in the frame. there is also a plastic washer which fits between the frame halves. if you are shorting, then one of the plastic pieces is probably missing. if it is the washer, you may be able to use fibre washers from kadee as an easily available substitute. if the plastic housing is missing, you'd have to go to bachmann for parts.

if neither of these is missing, then i'd try taking the locomotive apart, and checking the frame halves assembled without any other parts, then each truck. in each case, you shouls read infinite ohms between the sides. not that on a truck you willl read a between the wheels on the same side, as they are normalls in contact with the same rail.
if none of these reads a short, you probably have a bad motor.

[mikel]

Jim and Jeff

Thank you for your reply and patience.  Both were of great assist.

Mike