39 - O Scale Trains Magazine Online

Spring Loaded Power Pickup
Ray Grosser
General
While installing a dedicated DCC system in a MTH 2-Rail
2-8-0, I discovered that the locomotive did not have electrical
power pickup on the drivers. I wanted as much electrical
contact with the rails possible instead of having only two
axles on the tender picking up from each rail. Some kind of
power pickup was needed. After experimenting with phosphor
bronze wire and sheet stock, I opted to build an isolated
spring-loaded pin that would contact the inside of the
non-insulated driver, similar to the Atlas RS-1. I first thought
of fabricating the wiper pin from a 2-56 bolt with a spring
on it, but that was unsatisfactory because the threads on the
bolt interfered with the movement of the spring. So I started
experiments with plastic tubing, brass tubing, and brass rod.
First, I had to find a suitable spring. I found the one I
needed in a Kadee® G gauge coupler package. It is made
of bronze and is used as the draft gear spring for the coupler
shank. It is perfect for this wiper installation. Here is how I
did it.
Fabrication
I found some 0.072” brass rod in my accumulation of
brass off-cuts. The 0.072” X 1/2” long rod will be used for
the shaft of the assembly.
Cut a piece of 1/8” (0.125”) dia. brass tubing approximately
1/8” long. Apply soldering flux to the rod and the inside of
the tube and tin the rod with solder. Slip the rod into the tube
so the end of the rod sticks out a little on the other end and
solder the two pieces together, filling the void completely.
Finish the shaft assembly by chucking it in a hand-held motor
tool (unless you are fortunate enough to own a modeling
lathe). Clean it up with a file, then shape a slight radius on
the end of the shaft (Photo 1).
Next, cut a piece of 3/16” (0.187”) diameter plastic tubing
1
Sometimes liquid plastic cement will warp the pieces and this
could result in the spring and shaft not moving freely inside the
tube. After the glue is completely set, you will need to run a
5/64” drill bit through the tube to give the shaft some clearance
to operate smoothly.
Once the shaft and holder are completed (Photo 2), it is
2
time to make the clip to hold the assembly to the frame. I
used some 0.015” X 0.250” brass stock to make this clip. I
first bent a radius with coupler pin adjusting pliers. I used the
center section, and bent the stock 180 degrees to form the
holder. Once that was completed, I used flat-jawed pliers to
bend one leg 90 degrees, which will form the ear that will be
secured to the MTH brake shoe screw adjacent to the driver.
I drilled a hole in the ear to clear the screw so that the assembly
will clear the driver and all side to side play in the driver
(Photo 3).
The pickup wire cannot be soldered onto the pin after the
3
assembly is completed because the heat would warp and ruin
the plastic sleeve; so a wire had to be attached before the
shaft was installed into the sleeve. It cannot be soldered to
the pin on the outside because the installation of the spring
would be affected, so I drilled a 1/32” hole in the end of the
shaft to receive the wire. I then soldered a piece of #30 gauge
wire into the end of the shaft using flux and a very small
amount of solder (Photo 4).
4
3/8” (0.387”) long for the sleeve or holder. Take a piece of 1/8”
tubing and telescope it into one end of the larger tube approximately
1/16” and glue it in place. This smaller tube will be the
tail seat for the spring. I took some advice from my wife about
the type of glue to use and joined the two sections with CA.
July/Aug ’08 - O Scale Trains • 13