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Can't decide on Conventional, DCC or Battery operation?
Rewire your Bachmann Big Hauler for all three!
If you are like me, you run your trains on several different layouts.
The only problem is, some of these layouts run with conventional control
using anything from pure d.c. to complex pulse power, other layouts are
wired for Digital Command Control, and still other layouts have no wiring
at all. Battery/radio control would be a partial solution but is
expensive and double heading with conventional or DCC locomotives becomes
a problem. An alternate solution is modify the locomotive by adding
a three position switch that can connect the motor and the headlight either
to the wheels (for conventional power) or to the output of a DCC decoder
(for DCC) or to the output of a battery control circuit (for battery power.)
figure 1 - schematic wiring diagram
|
Figure 1 at left shows how such a switch can be wired. The switch
is a four pole triple throw (4P3T) switch with two of the poles used to
switch the motor and the other two poles used to switch the headlight.
The switch is shown in the DCC position. As shown, it connects the
motor to the motor leads of the decoder and connects the headlight to the
headlight leads of the decoder.
Note that it connects the red wire of the motor to the grey wire of
the decoder and the black wire of the motor to the orange wire of the decoder.
This
is NOT an error! Bachmann and other manufacturers follow the
large scale standards set years ago by LGB (when you are first, you get
to set the standards.) LGB chose left rail positive for forward
motion. DCC decoders standards were based on NMRA standards for small
scale which for many years have required right rail positive for
forward motion. Unfortunately, NMRA recently muddied the waters by
trying to impose their small scale standards on larger scale equipment,
adding one more confusion to Goofy Gauge and creating headaches for buyers
of Bachmann's 4-4-0. The 4-4-0 was the first, and hopefully
the last large scale engine to be wired to NMRA standards. If you
have the misfortune of owning one of these backward engines, you will have
to reverse the motor wires in order to use this circuit. |
In the centre position, the 4P3T switch connects the motor to a very
basic motor control circuit and connects the headlight directly to the
battery. Although the diagram does not show it, the headlight bulb
is connected in series with the slide switch located under the smoke box
door. This allows the headlight to be turned on and off independently
from the motor, at least in battery operation. The basic motor control
circuit is nothing more than a cross-wired double pole double throw centre
off (DPDT-CO) toggle switch mounted on the side of the locomotive.
When pushed forward, the locomotive moves forward. When pushed backward,
the locomotive moves backward. When set in the middle, the locomotive
stops. Not very sophisticated, but it could easily (although not
cheaply) be replaced with a radio control circuit.
In the third position, the motor and the headlight connect to the rails
via the wheels, just like in the unmodified locomotive. In this position,
all conventional controllers that worked with an unmodified 4-6-0 will
work with a modified 4-6-0, even those with odd waveforms which do not
automatically switch DCC decoders to d.c. operation.
| INSTALLATION - The following installation instructions are presented
in step by step format. The easiest way to use these is to print
them out, then tick off the steps as they are performed. Hint:
to save ink in Netscape, go to Edit|Preferences then select Appearance|Colors
and check the "Always use my colours, overriding document". Be sure
to go back and uncheck this box after printing! |
The first step is to gather together the necessary parts and
tools according to the list below.
|
Part
|
Author uses
|
Alternative
|
| P1 - 2 pin plug |
Molex 03-09-2022
(.093 terminals)
|
* Molex 03-06-2023
(.062 terminals)
|
| S1 - 2 pin socket |
Molex 03-09-1022
(.093 terminals)
|
* Molex 03-06-1023
(.062 terminals)
|
| P2 - 4 pin plug |
Molex 03-09-2042
(.093 terminals)
|
* Molex 03-06-2044
(.062 terminals)
|
| S2 - 4 pin socket |
Molex 03-09-1042
(.093 terminals)
|
* Molex 03-06-1044
(.062 terminals)
|
SW1 - 4P3T
rotary switch |
MODE Electronics #45-514-0 |
small 4 pole triple throw
rotary switch |
SW2 - DPDT-CO
toggle switch |
Radio Shack 275-664A
|
double pole double throw
centre off toggle switch to
fit 1/4" hole. |
Battery - 10 cells
rechargeable
nickel/cadmium |
** Radio Shack 23-190
subC 1400 mA hours
with solder tabs
|
available size C ** with
or without solder tabs,
minimum 1000 mAh |
| fuse holder |
Radio Shack 270-739
|
|
| fuse, 2 amp |
Radio Shack 270-1275
|
|
| red banana jack |
Johnson #108-0902-001
|
Radio Shack 274-1568 or
similar coaxial jack |
| black banana jack |
Johnson #108-0903-001
|
Radio Shack 274-1576 or
similar plug to match jack |
| DCC decoder |
MRC AD320
|
other 2.5 amp decoder |
| 1/16" PVC sheet |
4" x 7" or larger
|
1/16" Styrene sheet |
| 3/4" foam rubber |
1" x 6" piece
|
soft plastic foam |
|
tools
|
drill bits including 1/16", 1/8", 1/4", 9/32", 5/16" &
3/8"
3/8" hand drill, or preferably a drill press
small soldering iron, about 30 watts
rosin core solder, liquid rosin flux would also be an asset
ruler, preferably steel
glue gun and glue sticks
Dremel or other motor tool with cut off disks (optional)
hobby saw and hacksaw (if no motor tool)
needle nose pliers, gas pliers and small side cutters
#1 phillips screw driver
assorted heat shrink tubing
22 ga. stranded, insulated wire
1/4" squared paper for patterns (optional)
a pocket full of patience and a little bit of luck |
* The smaller Molex plugs & sockets with .062 pins are preferred
** C or subC cells with solder tabs are much preferred but cells without
tabs can be used if your soldering skills and equipment permit. See
warning.
|
Lets get started by taking the engine apart. First remove
the boiler and cab by removing 9 screws - 2 under the cab, 2 in the sides
of the boiler, 4 behind the air cylinders and 1 centred in the bottom cover
between the cylinders. Pry the pilot beam truss rods (1/16"
brass rods from the pilot beam to the sides of the smoke box) out of the
fire box to release the boiler.
Next remove the cast iron weight (2 screws) and then remove
the bottom cover (3 screws.)
figure 2 - locations of switches
|
Snip the wires to the pony truck somewhere near
the motor, and remove the pony truck. (The pony truck is the 4 in
4-6-0.) If you are ever going to replace the metal retaining washer
on the pony truck with an insulating Styrene one, this would be a great
time to do it.
Figure 2 shows the hole locations if using the MODE 4P3T
selector switch and the Radio Shack DPDT-CO switch specified in the table
above. Other switches may require repositioning the holes slightly. |
For the MODE switch, drill a small hole, about 1/16" diameter,
1/2 inch forward of the centre of the front post. See the top diagram
in the unscaled illustration above. Replace the bottom cover and
continue the hole through the next layer. A drill press helps here,
otherwise just be very careful to keep the drill exactly vertical.
Enlarge both holes to about 1/8" and then enlarge the top hole to 3/8"
for the switch bushing and enlarge the hole in the bottom cover to 9/32"
to clear the switch shaft. Starting with a small hole and enlarging
it with larger and larger bits helps keep the hole in its proper location.
If using a hand drill, use more intermediate sizes of bits to keep the
hole smooth and round.
Install the rotary switch in the top hole with the shaft downward.
If your switch has a torque tab to keep it from turning, mark the location
for drilling a tab hole by turning the switch back and forth until the
tab scratches a line in the plastic. Drill the tab hole on the scratch
line using a 1/16" drill then enlarge it to the width of the tab, usually
1/8".
figure 3 - rotary switch top view
A - rotary switch
B - weight mounting post, cut off |
figure 4 - rotary switch bottom view
A - torque tab
B - shaft, trimmed & slotted |
Reinstall the rotary switch, tighten the nut, and temporarily
reinstall the bottom cover. Using a knife or a fine point felt pen,
mark the shaft where it emerges from the bottom cover. Remove the
bottom cover and rotary switch.
Cut the rotary switch shaft to length with a Dremel tool, a
hobby saw or a hack saw. If you clamp it in a vise, be sure to clamp
down on the scrap end of the shaft, not on the switch body.
Set the switch to its centre position, gently using a pair of
pliers if necessary. Slip it into position in the engine frame and
mark a line on the end of the shaft. This line should be parallel
to the centre line of the engine. Remove the switch yet again.
Using a Dremel tool or hacksaw, cut a slot in the end of the
shaft where you made your mark. If you are using a hacksaw, clamp
the shaft in a vise with the switch body below the jaws and the mark parallel
to the jaws of the vice. This will allow you to cut downward between
the jaws. But be careful, the shape of some vises will crush the
switch body if you try this trick.
The DPDT-CO motor control switch is a #275-644A mini toggle
switch from Radio Shack. It has a body less than 1/2" square and
mounts in a 1/4" hole. Drill the 1/4" hole 3/8" up from the bottom
of the frame and 1-3/4" back from the front of the frame. This is
shown in the bottom diagram in the unscaled illustration above. Please
note that the diagram shows the frame with the bottom cover removed and
that the measurements are from the edges of the frame, not the bottom cover.
As before, start with a 1/16" drill and then gradually enlarge the hole.
figure 5 - power jacks
installed in smoke box
|
While you are in the mood for drilling, you might as well drill
some holes for charger jacks in the boiler front. First remove the
boiler front by pressing up on the tab at the bottom and hinging the front
forward. (Grip the boiler front by the edges - the hinged front cover
isn't strong enough for pulling on.) Then unsolder the wires from the switch.
The jacks shown in the photo are the Johnson banana jacks with
the insulators filed down to allow the smoke box door to close. Coaxial
power jacks would also be a good choice. But do not use miniature
phone jacks as these short when you install the plug and will blow the
fuse.
To mount the banana jacks, hold them in place and trace
around them to mark their position. Then drill 5/16" holes.
As usual, start with 1/16" holes and gradually enlarge them.. |
Before continuing with the wiring, there are three plastic posts
that need trimming. These are the weight rear post, the weight front
post (shown at B in figure 3) and the vestigial post half way between the
weight front post and the rotary switch (visible in figure 3). The
latter post is a left over from the days when Big Haulers came equipped
with radio control receivers. Trim them down slightly below the level
of the side ledges that the battery pack will sit on. Grooves can
be cut in the weight front post to make guides for neat wiring.
figure 6 - DCC mount of 1/16" styrene sheet
|
Next mount the DCC decoder. An MRC AD320 decoder has
proved satisfactory and fits on end in the rear of the boiler. To
mount it, make a bracket out of 1/16" styrene sheet. Notch
and chamfer the corners like the piece shown at left. If you like
working with patterns, you can make one from the figure either by printing
it so that the squares measure 1/4" or by transferring the 12 corner points
to 1/4" graph paper and drawing the lines with a ruler. Alternately,
you can start with a 2-1/8" x 2-3/8" rectangle of styrene and lay out the
points directly on your piece. Don't forget the two holes, which
should be about 1/8" diameter. |
figure 7 - DCC decoder on
bracket glued to frame.
|
Glue the decoder mounting bracket into the frame just behind
the short, fat posts that the cab screws pass through. The arrow
in figure 7 points to one of these posts. Hot melt glue applied to
the posts and along the horizontal edges works well. |
figure 8 - front side of DCC decoder mounting board.
Arrow indicates heavy wires under cable tie.
|
Mount the decoder by strapping it in place with a cable tie.
Install the cable tie loosely then thread the small lighting wires up between
the front of the decoder and the cable tie (figure 7). Loop the large
motor and power wires over the top of the mounting bracket and down between
the bracket and the cable tie (figure 8). Finally, tighten the cable
tie using just your fingers i.e. not too tight. Immobilizing the
wires in this manner prevents them from breaking off the circuit board. |
figure 9 - chassis wiring
A - direction switch
B - direction switch toggle
C - wires hot glued into notches in weight front post |
The chassis wiring may be installed at this point. The
author assumes the reader can follow the schematic diagram and makes only
one suggestion at this point - print out the diagram and mark off the connections
one by one with a red pencil. If any reader has difficulties following
the schematic diagram, please contact
us for help.
For plugs and sockets, the author uses Molex with .093" terminals
because
he stocks that series. The smaller series with .062" terminals are
probably a better choice. |
Next up is making the battery pack. The base of the battery
pack is made in two pieces to accommodate the step in the side ledges of
the frame. Either 1/16" PVC or 1/16" Styrene sheet may be used.
For the rear section, cut a rectangular piece 2" x 4".
figure 10 - front section of battery pack base.
|
For the front section of the base cut a 1-7/8" x 5-3/4"
rectangle and trim it according to the pattern at left. |
Place the front section of the base, top side up, in the front
part of the engine frame. The notch should engage the square post
to the rear of the toggle switch.
Test fit the rear section of the base. The rear edge
should rest against the fronts of the short, fat posts that the cab screws
pass through. Trim if required. Note that the rear piece overlaps
the front piece by about 3/4". Lift out the rear piece, apply a generous
bead of hot melt glue within the overlap, and press the rear piece into
place.
Wire the battery cells in series in three sets of three.
If the cells have solder tabs, this is easy - just bend up the tab, solder
on a wire, bend down the tab. Use about an inch of wire between cells.
|
WARNING: treat all nickel/cadmium cells as if
they are charged.
Be sure that you do not accidentally short circuit them, either by miswiring
them or by having them contact metallic items on your work bench.
Using eye protection, or better yet, a full face mask is highly recommended. |
|
WARNING: nickel/cadmium cells can explode
if over heated.
If the cells have no tabs, they must be soldered with great care to avoid
damage. This means placing the cell on end, fluxing the centre 1/4"
or so with liquid rosin (not acid!) flux, loading a clean soldering
iron with solder, and pressing the hot iron into the centre of the flux
until the solder melts onto the cell, but not longer than five seconds.
If
your iron will not melt the solder onto the cell in less than five seconds,
try recleaning it or use a larger iron. Once you have a tinned spot
on the end of the cell, let the cell cool. Then tin the end of the
wire, add flux to the wire and the tinned spot, and sweat the joint together,
but again not longer than five seconds. |
figure 11 - battery pack from the rear
Glue the sets of three cells to the battery pack base.
The two rear cells in each set sit on the higher, rear portion of the base
and the front cell sits on the lower, front portion. The offset is
clearly visible in the above photo. Glue the two bottom sets of cells
down with generous beads of hot melt glue both under and beside the cells.
Be sure the cells do not extend beyond the rear edge of the battery base.
Then add hot melt glue between the cells at the offset - this will strengthen
the joint between sections of the base.
Run a wire lengthways in the groove between the sets of cells
and hold it in place with small dabs of hot melt glue.
Add the top set of cells in the groove between the lower sets
and fix in place with hot melt glue. Again add hot melt glue between
the cells over the offset.
Glue the tenth cell to the base in front of the other nine cells
and glue the fuse holder on top of it, as in figure 12 below, but
position the cell slightly farther ahead. In the engine used for
figure 12 the tenth cell was positioned a little too close to the other
nine cells, necessitating a piece of styrene as an insulator between them.
Wire the sets of cells plus the tenth cell plus the fuse holder
in series and attach the two pin socket. Exactly how you do this
is not important as long as you do not accidentally short any cells or
sets of cells.
 |
With the batteries in place, connect the plugs, pop in a fuse
and reassemble the engine. The batteries will probably require charging
before the engine will operate properly, but even if the batteries are
dead it should still operate on conventional power or DCC, depending on
the setting of the rotary switch. |
For our next trick, we will build a battery charger.
|
