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Nigel's Workbench - On Members Workbenches. - More Practical Help - Your Model Railway Club
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 Posted: Mon Mar 31st, 2014 04:30 am
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BCDR
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Bachmann Fairbanks Morse H16-44 Baby Train Master DC to DCC conversion.

I have two undecorated pre-DCC Bachmann Fairbanks Morse H16-44 (8-cylinder, opposed piston, 1600 hp) diesel electrics waiting for conversion to DCC (and Canadian National green and yellow 1950’s color scheme). These are “new” old stock, undecorated, with split frame chassis’. The following procedure may be useful to those with an older, split-frame chassis locomotive (steam or diesel) and wanting to convert to DCC. These older models are often good value for money, as the same motor and gear arrangement is often used in the latest DCC ready version. In this case, $20.00 versus $85.00. In this conversion, I also used a Bachmann Europe 8-wire DCC harness/female plug, which eliminates the need to hard-wire decoders (and allows decoder swaps with the minimum of fuss).

Two issues have to be addressed in converting split-frames to DCC operation: Firstly, making good connections to the MAZAC frames. Aluminum solder is available, but the type of flux used requires very good ventilation systems as it generates hydrofluoric acid and elemental boron. In this conversion, I drilled and tapped holes in the frames and used machine screws to ensure good electrical connection; Secondly, the motor terminals have to be wired to the decoder and isolated from the frames. This is not as difficult as it sounds, as some sort of spring is used between the motor terminal and the frame. Remove these or insulate them, wire the terminals, and insulate against contact with the frames.

Disassembly. The body is fixed to the chassis by four screws. These were removed, and the body lifted off. The two frames are held together with three locating screws and plastic anchors with O-rings in between the two chassis halves, and two plastic spacers at the bottom into which the fuel tank cover screws locate. The screws were removed, and the two chassis halves separated. [Note: This combination of screws, insulating rings and plastic frame spacers is commonly used in UK models such as the early Bachmann 0-6-0’s, as well as some more recent models such as the Manor and all but latest Jubilees.]

The bogie/gear/tower assemblies were removed, and the motor/freewheel assembly taken out. DC contact is made using two spring arms, one on each terminal. There is a very basic electrical pick-up attached to the underside of the body shell that powers the directional lights. This was removed, as the spring arms contacting the upper surface of the frames are where I want the decoder and speakers to go. I will rewire the lights using LEDs, and control them from the decoder.




Bachmann Fairbanks Morse H16-44 Baby Train Master as supplied. Like most North American undecorated locomotives, details such as grills, lights, handrails, etc., are the responsibility of the buyer (they are supplied).





Split frame chassis with leg-challenged crew.





Split frames showing screws at top and bottom ends.




Motor-flywheel assembly. Note brass strip top and bottom which contacts the motor terminals to the frames. These have to be isolated when rewired. White plastic pieces are frame spacers.





Bogie and gear pillar showing butterfly wing electrical pick-ups that ride on the bottom of the frames. Primitive but reliable and no wiring to go wrong.





Inside of frame showing the pocket in which one of the terminal springs rest (upper RHS of motor seating).




Conductive paint removed and the surface ready for sealing with epoxy.

Frame modifications. A tapped hole for #2-56 flat-head machine screws was made in each frame on the top surface using the appropriate Kadee drill/tap (part no. 246). The metal alloy used for these chassis’ (MAZAC) drills easily. I used the bench drill press and a small amount of machinist’s oil to make the holes 3/8” deep), which were then tapped by hand using plenty of oil and frequent cleaning out. The areas on the inside of the frames where the motor contacts touch the chassis halves were cleaned of conductive paint. The white metal surface was then scored with a scalpel blade. A thin coating of 5-minute 2-part epoxy was applied, and left to harden. This provides an insulating barrier.




Kadee tap and drill set.





The pointy bits. Tap on right, drill bit in middle, pilot drill if required on left (to countersink screw heads if required).




Holes drilled. I did this on the bench press drill, it doesn't need to be that accurate regarding spacing.




Tapped hole in top of frame. Not yet cleaned out.





Machine screws in top of frame ready for wiring. The head of these is flat so that a washer wire terminal can be seated flat.



Electrical connections and modification. The motor terminals were polished with #600 emery paper, cleaned with IPA, and the grey and orange leads from the wiring harness soldered to them using 145° solder and no-clean flux. Heat shrink tubing was used to cover the terminals. The black and red leads from the wiring harness were connected to the screws on each frame. I was intending to solder the wires to some brass washers, none to hand, so I will come back and do that later.




Electrical modification "kit". Wiring harness, heat shrink wide enough to go over motor terminals, epoxy just to make sure.





Heat shrink 1. This has to be slid over the grey wire before soldering.





Heat shrink 2. This has to be slid over the soldered terminal after soldering the orange wire.





Soldered up, reassembled, wired up and running-in. Note grey heat shrink isolating the terminal spring from the frame. Idem for the opposite side (orange wire). DCC wiring convention has been followed - electrical pickup to the decoder harness red and black, DCC output to the motor orange and grey, red and orange one side, black and grey the other. There is now plenty of room on top of the frames for a full-size decoder and 2 speakers (when a sound decoder becomes available).

Reassembly. Reassembly followed the disassembly in reverse. The only tricky bit is making sure the connecting wings on the wheel pick-ups are properly located under the chassis. I cleaned the old lubricating grease off the worm and gears, and replaced it with some Labelle #106 lubricating grease (plastic compatible).

The converted chassis is currently on the rolling road being run-in. No sound decoders for this model, so plain vanilla decoders until they become available.

Nigel



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 Posted: Tue Apr 1st, 2014 02:15 am
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Petermac
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A nice, easy to follow tutorial Nigel. :thumbs

You didn't mention what as pig it can be to get the chassis halves back together with those spacers ...............:roll::roll::roll::roll:



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 Posted: Tue Apr 1st, 2014 05:25 am
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BCDR
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Hi Petermac,

Thanks. The trick to getting those small white spacers in the bottom locating slots is to assemble the frames, but only partially screw together. Place it upside down and at an angle of 45° facing you, and using tweezers then insert the spacers. Close the frames together from the bottom (clamp together using a small spring clamp or a large bulldog clip) and then the top. Sometimes a bit of persuasion is required to get the screw locators into their holes in the frame. Large tweezers usually work.

What often happens with these oldies is that the plastic locators into which the screws go split (because of age). Bachmann will supply new ones. The electrical pick-up wings often get located inside the frames instead of underneath. Turn the bogies fully right or left, use a toothpick to slide the loops down so they are now underneath.

I forgot to mention the time it took. One hour including a tea-break (while the epoxy set).

Nigel



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 Posted: Tue Apr 1st, 2014 11:09 am
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Petermac
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I already know about the spacers (and "nuts" for the screws) shearing Nigel ...........don't ask how :oops::oops::oops::oops::oops::oops:

It took me about a week to separate the halves on an old split chassis V2 - and no tea break - you ask John Dew !!!! :mutley:mutley



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 Posted: Tue Apr 1st, 2014 05:05 pm
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BCDR
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Hi Petermac,

That's when you reach for the lump hammer and cold chisel. Those fasteners can be pretty tight after a few years, often better to cut through them or drill them out and replace rather than fiddle around. I suspect they were not intended to be reused when the engine was sent in for a service (as if).

Just checked the Bachmann Trains website, the split chassis is still in the current H16-44 model, which is fo course still not DCC ready.

Nigel



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