Installing DCC in the MNP Inc Track Cleaning Car for S-Scale
By Michael Greene
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WHAT?!?!? Is the title right? Aren't DCC decoders for locomotives? YES and YES. But DCC decoders can be used many places. Earlier we used one to control an American Flyer operating accessory. Here's another use of them...
MNP Dual Motorized Track Cleaning Car
Recently I purchased from S Helper Service one of the new dual motorized track cleaning cars manufactured by MNP Inc. These cars are available either built inside a S Helper Service 40' double sheathed wooden boxcar, or on top of a S Helper Service flatcar. I selected the 40' boxcar version in order that the mechanism is not visible. The car contains two geared motors driving two pads (in opposite directions). Pictures of the track cleaning cars are available on the MNP Inc web site by following the links above.
As delivered the unit is track powered, and contains a rectifier. This allows it to run on DC or AC powered layouts. It also ran on my DCC layout just fine, although there was no control over the speed of the pad rotation. MNP has replaced one of the trucks with a S Helper Service caboose truck for power pickup. Like all S Helper Service cars, scale wheel sets are included in the box.
Since I intend to use MNP tracking cleaning car on a DCC controlled layout, and as part of my maintenance-of-way track cleaning train, I decided to installed a DCC decoder in the car in order to allow me to be able to turn off the cleaning action. A side benefit of the installation is that I can also control the speed, although I don't see a practical need for that at the moment.
The installation is very easy. MNP has not re-glued the top of the boxcar after they finished their installation, which made the access even easier. One note is that the top holds the doors in place, so when you remove it the doors will come out as well. Just remember to re-install them when you put the top back on the car. Here's a picture of the inside of the car as delivered:
The cleaning pads are spring loaded to the rails, which means that it's less likely the pads will actually stall. Using a MRC Tech 9500 I measured the current draw, and it was a total of less than 0.2A with both pads spinning and at 16VDC. This small current draw means that any DCC decoder should work just fine. I chose a Lenz LE077XF decoder - a small 0.5A N scale sized decoder -- that I had on hand. (I use these decoders for a variety of rolling stock controls, due to the fact that they are inexpensive, they are small in size, and Lenz has a "goof-proof" warranty.) While the LE077XF will allow control of functions (e.g., lights) in addition to the motor, I only used the motor control in the application.
I cut the black and gray wires from the caboose trucks to the rectifier in approximately the middle of the run. I then connected the red & black track pickup wires on the decoder to the wires going to the trucks. I connected the decoder's orange and gray motor control wires, to the two wires going to the rectifier. NOTE: You do not need to make any changes to the wiring from the rectifier to the motors. I used this set of connections:
I cut the four wires on the decoder to approximately one-half their factory provided length in order to have less wire in the boxcar, but this is not necessary. A little heat shrink tubing on the connections, and it's all done. On the blue, yellow & white wires, I cut the exposed wire off and left the leads for the light control wires off to the side for future use if needed. Here's a picture of the finished installation:
Good luck with your installation!
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