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Converting a Farish 47 to DCC

If you are going to attempt this conversion on a new locomotive, then I would strongly recommend that you run the loco in first to ensure proper running. Please also be aware that this conversion will almost certainly invalidate any warranty on the loco.
This process will take you through the various stages required to convert a Bachmann/Farish RES Liveried Class 47 diesel locomotive to DCC. The decoder we will be using is a Lenz Silver Mini with wires.
The decoder you use may be any decoder that will fit inside the body shell above the chassis. Please note that the images below can be clicked on to show the full sized images.
This is the loco we are working on. If your chassis looks nothing like this then you may have an earlier or later locomotive.

RES47 we are going to work on

RES47 with the body removed

Now that the body has been removed you can go about identifying a few of the relevant items. The two screws that hold the top part of the split chassis together; the fuel tanks that hold the bottom part of the split chassis together; the bogie slide plates, also note which slot the bogie slide plates are slotted into and which end of the slide plates is the small hole. On this loco the slide plates were in the second hole from the loco centre and the small hole was outermost on both bogies. The additional slide plate locating slots are for alternative locos that need shorter or longer wheelbases.

Screws that hold the split chassis together and the fuel tanks

The bogie slide plates

Having identified the parts, we need to strip the chassis down. Start by removing the fuel tanks from the bottom, this is held in place by one screw. Now remove the top two screws, carefully holding the two halves of the chassis together so that items do not drop out. Now lay the chassis down on its side and lift off the upper half of the split chassis. Notice that the motor brushes connect directly with the chassis and it is this section of the chassis we will need to remove later. Take a look at the left hand picture immediately below and this is what you should now see. Now lift out the two bogies and the motor unit to leave the chassis empty except for the fuel tank retaining plate. Remove this to safe area along with the fuel tank and screw.
You should now have two empty half chassis sections. At this point we now need to remove the part of the chassis that directly connected with the motor brushes. You can achieve this in any number of ways depending on the tools you have available and what you are comfortable with. You could mill, drill, grind etc etc. I used a small 6 mm cross cut file. Take a look at the right hand picture immediately below, I've marked the section to remove on each half of the chassis.

One half of the chassis removed

The areas of the chassis to be removed

Having selected your chosen method to remove the parts of the chassis required, go for it. You will need to remove ALL the section to all 4 edges. See the next 2 pictures showing the section removed from 1 half of the chassis. While you are about it, also remove the paint around the upper screw holes.

The section removed from the inside

The section removed from the outside

Having completed the first half, repeat the process for the second half. Remove the section to ALL 4 edges and remove the paint around the upper screw holes.

Both halves completed, inside view

Both halves completed, outside view

Having completed the chassis work we have one more task before we can start to rebuild the chassis. We have to connect the decoder to the motor brush connections. Using a soldering iron and good soldering technique connect the orange and grey wires from the decoder to the motor brush connections ensuring that both wires are laid in an upwards direction. These two wires will come up through the gap in the top of the split chassis when the chassis is rebuilt.
Now lay one half of the chassis paint side down on the bench with only ONE of the upper screw retainers fitted (We will fit the second one the other way round when we fit the other half of the chassis). Refit the motor to the centre section with the decoder wires uppermost and then refit the two bogies making sure you get the orientation correct. Ie the slide plates the right way round and in the correct slot. Lastly refit the fuel tank retaining plate.

Decoder motor wires connected

One half of the chassis rebuilt

Now for the second half. Fit the second chassis screw retainer and washer into the half of the chassis still to be fitted. Use the hole not used in the first half. See photo above right to see what I mean. Ensure that the two motor wires are up through the gap in the chassis and then carefully place the second half of the chassis in place. Make sure that the bogie slide plates seat correctly, make sure that the two screw retainers go through the chassis blocks and that there is no interference when closing the gap between the two halves of the split chassis. Make sure also that you do not trap the motor wires. Insert and do up the two chassis screws. Make them just tight enough to hold the chassis halves together. We will return to these soon. Now refit the fuel tank, one screw into the retaining plate. Now make sure that the bogies rotate freely and that the motor turns freely.
One last task on the chassis is to connect the black and red wires from the decoder to the chassis. Remember we removed the paint from around the retaining screw holes, now you know why. Trim back the red and black wires and solder them to make a single strand. Now fold that end into a small loop to go round the screw shaft. Loosen one of the screws and loop the red wire around the screw shaft and then retighten the screw carefully. DO NOT overtighten. You could break the wire or worse, strip the thread in the retainer. Repeat using the other retaining screw and the black wire.

Split chassis together again and wired up

Neat and tidy and nearly finished

The Lenz silver mini decoder (as many others) comes with a double sided sticky pad. Cut this to size and stick it over the bogie at one end. Carefully stick the decoder to the pad. Trim the 3 function wires Blue, Yellow and White to different lengths and lay carefully along the chassis block. Fold the motor and chassis wires along the chassis block to make a neat and tidy finish. You may wish to use a small smount of insulation tape around the function wires and to tape the other wires to the chassis (Personal choice). Final task is to file a small 2mm slot into each of the body bulkheads to make room for the cabling. Now place the body on the chassis until it clicks into place. That's it all done in about an hour.

2mm Slots filed into the bulkhead

Place on the track, program as required and away you go.

You may wish to test out the decoder and do any reprogramming BEFORE you fit the body (Personal choice). Enjoy your latest DCC locomotive.