Smallphry - diary of a model railway

Tuesday, March 28, 2006

Graham Farish Diesel DCC Fitting

Most Graham Farish diesels sold from the early 2000s use two variations on the same Bachmann chassis. This article shows how to fit a DCC decoder to the chassis fitted to the Co-Co locomotives (in particular a class 50), but the procedure for the Bo-Bo chassis is very similar. I’ll detail any differences as I go.

I’ve done Co-Co conversion on classes 37, 47, 50 and 52 (Western). I expect the same chassis is used for classes 40, 44, 45, 46 (Peaks), 55 (Deltic), 56 and 57. The Bo-Bo chassis I’ve converted are classes 31 and 33 (note that the 31 uses the Bo-Bo chassis, rather than the Co-Co). I would expect that the class 25 also uses the same chassis. The 158 and probably other DMU classes also use the same or similar chassis.

Classes 08, 20 and 66 (and any later models except the ‘peak’ classes 44, 45 and 46) use a very different chassis and are not covered by this article.

See the end of the article for extra notes on particular classes.

The Principles

Graham Farish use what is known as a ‘split chassis’. This means that the chassis is split into two halves, each being kept electrically separate from the other. Power from the pick ups is routed through each chassis half to the motor contacts which directly touch each chassis half. As with any DCC conversion we need to break this power route, in this case by milling away some of each chassis half where the motor contacts it. The motor wires from the decoder can then be soldered to the motor contacts. The track power wires get electrical contact with the chassis by being held under the screws which secure the chassis halves together.

The Conversion

Start by removing the body of the locomotive. This is held on by two clips each side of the bodyshell. The easiest method I have found is to hold the loco upright over something soft and slide a fingernail between the body and chassis on each side at one end. Give a little shake and the clips should come apart. You can then either repeat for the other end or gently pull on the undercarriage (be careful not to pull on the bogies). You also need to remove the undercarraige using the small screw underneath (on the Bo-Bo it just pulls off).

Take a look at the chassis from above. Note the black plastic bogie spacers at each end. These are used at the factory to vary the bogie spacing between models. Take a note of which notch on the chassis they are positioned in. Also note which end has the small dimple, since this also varies the bogie spacing.

Now remove the two screws holding the chassis halves together. The chassis should now just pull apart. Remove the plastic spacers (note the one which is positioned underneath the motor for holding the undercarraige in place) and extract the motor.

Each chassis half can now be milled to remove the part that contacts the motor, as shown in the before and after comparison shown above.

(If you’re unsure about milling, or don’t have the tools, a possible work around I’ve used successfully is to superglue a small piece of plastic on the chassis where it contacts the motor, but note that this may lead to increased pressure being applied to the brushed which could wear out faster).

You now need to solder the orange and grey wires to the terminals on the motor. It doesn’t matter which way round the wires go, but make sure they both head upwards from the motor (note that the motor will fit either way up - which direction is upwards is entirely arbitrary). I like to attach the wires to the motor with the motor out of the chassis and later route the wires between the two chassis sections. Others wire the motor in situ and run the wires outside the chassis. It’s entirely up to you, but I feel that with the outside method the wires have to squeeze uncomfortably between the chassis and the body.

You’re now ready to re-assemble. At this stage some people like to apply some insulating tape inside the milled part of the chassis to prevent any accidental electrical contact with the motor.

Pop the chassis spacers back in place. If using the Co-Co chassis I like to swap the spacers over on one end, so that one screw goes in from each side (this makes attaching the track power wires easier), but on the Bo-Bo chassis the screws will only fit one way around. Lay one half of the chassis on it’s side. You can now position the bogie spacers and lay the bogies in place, taking care to put the drive shaft in the motor and the locating pin from the bogie spacer in the hole in the top of the bogie tower. Don’t forget, also, to put the undercarraige mount back in place on the Co-Co chassis.

Attaching the other chassis half can be somewhat fiddly. Lay in on top in the correct position and you’ll probably find it helpful to slightly push the bogies downwards to help the chassis slip over them, but take care that the bogies don’t slip out from the bogie spacers and motor. If you get problems look from the end to check that the bogie spacers and bogie towers are correctly positioned on the chassis halves. With the Bo-Bo chassis the bogie power pick ups contact the underside of the chassis. Take care that they do not get trapped between the two chassis halves.

Once the two halves are together insert the screw or screws which are accessible from that side before turning the chassis over for the other side. When turning the chassis over try to keep it ‘top-down’. If you hold the chassis ‘bottom-down’ the undercarraige mount will probably fall out and you’ll have to start reassembly again (after finding it).

You’re now ready to attach the track power wires of the decoder. This is done by running them under them under heads of the chassis joining screws such that they are held in place when the screws are tightened (For the Bo-Bo one side needs to be secured on one of the plastic securing piece on the other side of the chassis since you can’t reverse the screws. You’ll find it best to tin the ends of the wires before attaching them (tinning means applying a small amount of solder to the bare wires to keep the bare strands together). To make attaching the wires easier, run them around the screws in the appropriate direction so they’ll be ‘pulled in’ as you tighten the screw.

It’s now time to put the complete chassis on the programming track to check all is okay and program in any required settings (including, of course, the decoder address) and give a quick test run on the layout.

The decoder can now be secured in place on it’s self adhesive mound, the function wires can be removed or wrapped in insulating tape ready for later modification (trim them to different lengths first, so they don’t short) and the wires can be held in place on the top of the chassis.

To provide room for the wires on top of the chassis it’s also necessary to file away a small notch on the inside roof of the body, as shown in the photo.

Reattach the undercarraige and put the body back on (note that it will only fit one way around) and everything’s complete.

Notes

Class 158 (and probably the class 170). Before dismantling this model make a note of which way around the bogies are fitted, since they are different at each end. The chassis on this model is very slightly different than described above with two screws holding the undercarraige and two extra plastic lugs inserted between the chassis halves to attach it. It’’s nice to note that these lugs have been redesigned and are less likely to fall out during reassembly. The roof moulding can be removed by inserting a couple of finger nails into the gap between the roof and body and pulling. This will reveal that the body moulding has a solid roof with limited space above the chassis. To create space for the decoder it is necessary to cut a hole in this solid roof. I also recommend cutting the wires as short as is practical since any obstructions in the roofspace will prevent the body from sitting snigly down on the chassis.

See also: Soldering

The Easy Way to Solder

When I was younger I studied electronics and hence spent some time soldering up electric circuits. Soldering such circuits is fairly simple - slide the wires of a component through the board, lay the board upside down on the bench, touch the wires and board with a soldering iron and apply some multi-core solder. Job done.

Railway modelling also requires soldering but rarely has a nice board to solder onto. Consider soldering a wire to a din plug. You hold the plug in one hand, the wire in the other, grab the soldering iron in a third and apply some solder with… oh dear, you’ve run out of hands.

But that’s the method multi-core solder. There’s two parts to multi-core solder. The solder itself which is just a metal alloy with a lowish melting point, and flux which helps the solder flow over the surface of the components being soldered.

You can also buy separate flux and non-cored solder. This makes soldering tasks such as that described above much easier:

• With a small paintbrush brush on some liquid flux to the places you want to join.
• Take your soldering iron and touch it against the solder so that you have a small blob of solder on the tip.
• Hold together the pieces to be soldered (use one of those ‘helping hands’ stands if necessary).
• Touch the tip of the soldering iron briefly against the ‘fluxed’ joint. You will hear a fizz from the flux and the solder will flow wherever the flux has been applied.

Occasionally you’ll find that you didn’t have enough solder on the tip of the iron and you’ll need to go back with some extra, or you may need to re-apply the flux, but things will improve with practice.

The above process may sound slightly complex but once you get into a routine you can get soldering at a reasonable pace, and with only two hands.

Tuesday, March 21, 2006

Farish Class 66 DCC Fitting

(For fitting instructions for other Bachmann/Graham Farish diesels see here).

At the time of writing the Bachmann/Graham Farish class 66 is unique among N gauge British outline models in being the only one which has a chassis that was designed with DCC in mind. It therefore seems like the ideal candidate to use as the subject of a first DCC conversion. Full instructions for conversion are included with the model, but this article should prove of use to anyone who has yet to purchase or who has lost their instructions.

The body is attached by a clip at each corner. The best way I have found to remove it is to hold the chassis each side of the buffer beam with one hand, gently grip the cab sides with the other and wiggle the body free. Repeat this at the other end.



Remove the small screw at each end of the circuit board and lift it straight upwards. Be careful not to damage the motor power clips underneath the board (see the next photo).



The decoder wires are soldered to the connectors marked 1-8 on the board. Remove the two ‘DC clips’ from the circuit board, then solder the wires in the following sequence:

Connector	Colour
8	Red
1	Orange
2	Yellow
4	Black
5	Grey
6	White
7	Blue

(Note that the connector numbers are out of sequence on the circuit board and the above listing is from left to right).

Attach a small piece of insulating tape to the top of the chassis under where the connectors will go to prevent any shorts and screw the board back on.



The decoder can now be secured onto a self adhesive pad in the recess to the right of the connectors. Normally the decoder would fit underneath the lighting wires, but I managed to cut the wires a little too short and have fitted it above them, as shown.

Programming

Reattach the body and put the loco on the DCC programming track to set the decoder address and any other settings you want to change.

Pop the loco on the main track and off you go. Select function 0 to turn on the directional lighting…

...and at the press of a button…

Sunday, March 19, 2006

Class 33/1 Ups and Downs

The class 33/1 conversion is now complete. Well, more or less.

The conversion kit is very simple, if a little fiddly. It consists of two replacement ends for the Farish 33, an etch with pipe details and some replacement headcodes.

All you do is: remove the old ends and extract the glazing; drill holes in the new ends for the pipes; paint the ends and an extra glazing bar in the windows (which is missing from the Farish original); attach the pipework (the fiddly bit); paint the pipes; and (if you want) change the headcodes.

It was my first experience of painting a model and turned out much better than I’d expected. I even managed to paint the handrails silver without getting paint everywhere.

But now for the downs I mentioned in the title.

The model I’m converting is painted in NSE livery, and I want to convert it to banger blue. I had some paint stripper from Expotools and tests inside the shell showed it appeared to be safe on the plastic. Applying it to the outside of the shell stripped the paint fairly well, but when I used some Cif cleaner and started scrubbing the paint off with an old toothbrush the brush started digging into the surface of the plastic. Ouch.

I assume the stripper had softened the plastic enough for the toothbrush to gouge into it, but not done enough damage to show up in my test.

I’ll have to obtain another body and have a go with either acetone (nail varnish remover) or isoropyl acohol, both of which seem to be recommended for paint stripping on Farish models.

The problem left me feeling pretty down at first, but one of the best ways to learn is by making mistakes. I just hope for better things on the next try.

And the nice paint job on the new ends left me eager to make a start painting some wagon kits I made up last year. I’ll post some pictures later, but the results so far are looking rather good.

Tuesday, March 14, 2006

Stage 2

I decided the software writing was taking too much time away from the time I should be writing software to sell, so I’ve put that on hold for a few weeks.

But being bored with only having a simple oval, I’ve ordered the track for the next stage. This will be the second loop on the twin track main line. I’ve also ordered that track for the single track branch line, since this only needs two sets of points and a few lengths of flexi-track, and it wouldn’t be economic to place a separate order.

I grew up near the Waterloo to Weymouth line and have a soft spot for 4-REPs, 4-TCs and class 33/1s. I ordered a TPM class 33/1 conversion kit last year but was put off about having to paint it before assembly. In fact I’ve been put off painting anything by my complete lack of artistic ability. But I’ve decided it’s time to bite the bullet.

So I’ve started the kit by painting the ends of the conversion kit with Railmatch warning panel yellow. It’s taken three coats so far and the original resin still isn’t completely obscured, which is a little disappointing, but apart from that they’re looking good now. The next step is to add the etches for the jumper cables and to strip and repaint the body from my NSE liveried donor.

Tuesday, March 07, 2006

How to load a JCB onto a train

http://siri.uvm.edu/ppt/darwin/darwin.htm

I posted this link on the n gauge modern yahoo group and a couple of people reported it was standard practice in some parts of the US. Presumably involving a brave (or stupid) JCB driver.