Fitting a Bachmann Chassis with DCC conversion and LED Lighting updates, to the Hornby DB Schenker Class 59/2
This web page provides a summary of the process adopted to generate a class 59 model, based on the DB Schenker variant of the Hornby Class 59 diesel locomotive, but utilizing the superior chassis and drive system of the Bachmann class 66 (OO gauge). DCC decoder and correctly operating external LED lighting are incorporated.
Note that the smaller pictures can be enlarged by clicking on the image.
Hornby Class 59 locomotive straight out of the box
|The Hornby DB Schenker red
liveried Class 59/2 Model:
The model has electrical pick-ups on all 12 wheels (although two contact strips needed remedial bending to work correctly). Only one bogie is powered. The 4 outside wheels of the power bogie are powered via a simple gear train from the bogie mounted 5 pole motor. Traction tyres are fitted to one wheel of each driven wheel set pair. A metal weight is fitted low down within the central region of the plastic chassis. The light housings form part of the upper body shell assembly, but these are non-operational with painted-on lens fronts.
|Reasons for the hybrid
The Hornby model has only 4 driven wheels. Two of these use traction tyres to partially overcome the limited tractive effort. The Class 66 has all-wheel-drive from a powerful motor and no traction tyres are necessary. The 66 chassis is significantly heavier than that of the Hornby Class 59. This results in near "best in class" low speed performance and a very impressive tractive effort. The plan is therefore to transfer the upper body shell of the Class 59 to a cosmetically modified Class 66 chassis, after removing the Class 59 light housings. The modifications to the Class 66 chassis will use parts from the Hornby chassis. In particular, the central fuel tanks, battery housings, air cylinders and pipework will be transferred and some further scratch built tanks will be fitted. The bogie side plates will also be exchanged and the boxes will be removed from the rear sides of the buffer beams. There are differences to the detailed structure of the main side chassis beams, but it is felt that these will not be sufficiently obvious to warrant further attention, with the overall level of accuracy and detail at a similar level to the original Hornby model, but.... hopefully, with superb operating performance .
|Class 59 Lighting:
Class 59/2 locomotives use a pair of UK standard light housings at each end of the locomotive. These incorporate a headlight, rear light and marker light. The day running headlights are in the right hand housings and the night running headlights are in the left hand housings. At the forward end of the locomotive, only one marker light is displayed, on the opposite side to that of the operating headlight. So in day running, the right hand headlight plus the left hand marker light are active. During night running, the left hand headlight and right hand marker light are active. At the rear of the locomotive, the rear lights in both right hand and left hand housings act together, but only if the locomotive is operating "light engine" or if it forms the final vehicle of a train. When pulling a train, the rear lights are switched off. (The rear warning light is instead provided on the back of the last vehicle of the train.)
(Curiously the Class 66/0 locos always operate with both lower marker lights on simultaneously, day or night.... the difference requires a new lighting circuit for the Class 59 model!)
Day Running Forward Lights
Night Running Forward Lights
The planned decoder and lighting solution:
The Bachmann Class 66 incorporates a 21 pin decoder socket. It is planned to use the new TCS 21pin decoder type EU621. This device has 6 function outputs, which will be used to control the lighting.
The missing left hand headlight 0603 sized LED and its cathode wire, will be added to the lighting PCBs at each end of the locomotive chassis. The inner headlight shrouds will be painted white to make the headlights brighter. Cab lighting will take the form of a warm white lighthouse LED fitted high in the rear wall of each cab. Finally, a job I don't look forward to! The painted marker lights on the Class 66 chassis will be carved out to enable operating chip LEDs to be fitted. Wiring tunnels will be incorporated at the rear of the marker light apertures. Pre-wired "nano lights" will be used here. A circuit diagram is provided later in the web page.
|Dismantling the Class 66
The Bachmann chassis must be partially dismantled to enable the central fuel tank and switch assembly to be removed and also to access the bogie frames.
First a careful note was made of the wire connections to the main PCB. The PCB was then unscrewed and raised so that the wire routing could be identified. This was also carefully noted. The non soldered wires were then disconnected from the PCB. The bogies were then removed by undoing the large cross head screws above the bogie centres. Each complete bogie assembly was withdrawn from the universal joints in the motor flywheel and the track contact wires were extracted from their holes in the main body casting. The four screws holding the underframe assembly to the casting were then removed and the fuel tank / battery box was unscrewed from the main body underframe. (Including a metal weight, for possible re-use).
The dismantled chassis of the Bachmann Class 66
The bogie frames from both Class 59 and Class 66 bogies can be sprung free. The side plates of each are sliced off using a sharp Stanley knife. The central part of the Class 66 frame is then refitted to the bogie and the Class 59 side frames are super-glued to the ends of the horizontal frame beams, aligning the frame side wheel bearings with the wheel centres. The upper edge of the side frame must not protrude above the edge of the wheel flanges, to avoid contact with the locomotive body.
Class 66 bogie with original side plates removed and Class 59 sideplates ready to fit
The Modified Bogies
The sand pipes in the bogie corners need some adjustment to keep them above rail level. These may need to be lifted a little more.....we'll see when I run it over the first set of points!
The sand boxes immediately behind the Class 66 buffer beam are removed. The Class 59 has a simple truncated triangle shaped reinforcement web supporting the bottom of the buffer beam. This is modelled in plastikard. The 4 sand boxes mounted on the central under-frame beams are also removed.
The smaller fuel tank, air cylinders? and pipework are cut from the Hornby chassis and glued to the Class 66 under-frame between the bogies. There is room for two of the Hornby steel strip weights inside the moulding, covered by a thin plastikard sheet to insulate from the motor contacts. Photographs of Class 59/2 locomotives also show a pair of horizontal red cylinders (fire protection system?) mounted one above the other, attached to the under-frame above the fuel tank. These are absent from the Hornby model, and have been modelled from tubular plastic (a conveniently sized moulding sprue). All white plastikard parts are painted semi-gloss black. The peripheral cylinders, moulded in red plastic on the original Hornby model are also painted semi-gloss black, in line with photographic evidence.
Further detailing and light weathering is still to follow
|Fitting the marker light
Rectangular marker light apertures are cut into the light housings, using the painted rectangle as a guide (although the apertures need to be wider). Small tunnels are drilled through the rear of the apertures, emerging at the top rear of the yellow front panel. Pre-wired chip LEDs are available from the Australian company DCC Concepts via Bromsgrove Models. Using these avoids the chore of mounting thin wires to chip LEDs with a soldering iron...... a job I happily leave to DCCC! The Wires are routed through the tunnels and the chip LEDs are super-glued within the apertures. The wires are thin enough to route under the removable cab moulding and up to the top of the body internal metal block. Insulating tape is first applied around the end corner of the metal block to reduce the danger of abrading the thin layer of enamel insulation around the chip LED wires.
The Proposed Circuit Diagram
The main PCB is retained to carry the decoder and to act as a terminal for the motor, wheel contact and function wires. The routing diodes, LED series resistors and the rear light switching transistor circuit are mounted on double sided tape fitted to the top of the body metalwork, adjacent to the main PCB. Most connections to the circuit board can be made by soldering wires to the relevant SMD pads as shown below. The two exceptions are the brown and pink function wire outputs from the decoder. These are soldered directly to the 21 pin socket pads on the main PCB, below the decoder, using very thin wire.
Two redundant pads (labelled 3 and 2 on the PCB) are isolated by cutting the top tracks. These are used as convenient anchor points for the brown and pink function wires. The pair of parallel 470 ohm resistors are shorted with a link, to provide a direct connection between the the common positive decoder connection (blue) and the centre pad at each end of the PCB.
The motor and track wheel contact wires are soldered to their pads as a more reliable fixing than the clips used on the original Bachmann chassis.
PCB top view above a "through the board" view of the PCB underside (to help trace the tracks).
|The Decoder CV
TCS EU621 Programming
electrics check and resistor value optimisation:
Before mounting the electrical components on to the double sided tape, the lighting circuit was constructed as a temporary "rats nest", the decoder was programmed and a basic electrical check was carried out. This revealed a few problems: The bad news was that the upper lead had become detached from the motor, the pink wire was connected to the wrong decoder socket tab and I had made an error programming the button activating the pink wire. The good news was that I found and corrected the problems fairly quickly and the rats nest electrical circuit worked fine!
Next, the painting around the marker light LEDs was finalised with the lights on. A dilute coating of yellow/brown water colour paint was then applied to the marker lights to establish the yellowish glow produced in the real world by these lights. Then the LED series resistor values were adjusted where necessary to achieve the desired light levels. (The values given in the circuit diagram above are those used as a result of this process).
The modified class 66 chassis complete with "rats nest" electrics.
Circuitry tidied up and mounted using double sided tape
The modified chassis ready for testing
Below are low light images to give a better impression of the colours
End 1 Daylight running
End 1 night running (including cab light)
End 1 Rear Lights (enabled)
(End 2 is virtually identical)
Not shown is double strobe on all headlights via button 6 (which works successfully).
|Fitting the Upper Body
The Class 59 upper body shell incorporates non-operational cosmetic light housings. These are carefully removed and the remaining body shell ends are matched to the light housings of the Class 66 chassis, using appropriate needle files & the trusty Stanley Knife. On the Class 66 chassis, it is necessary to remove the clip on the front of each cab and to remove the front edge of the dash from the cab moulding. The body shell is then fitted to the chassis.
Some camouflage painting is required to hide the bogie electrical pick-up strips
The body is a reasonable fit, but some form of positive attachment between the upper body shell and the heavy chassis is essential (confirmed by nearly a nasty accident when I lifted the combination off the tracks).
The Hornby upper body shell has six "clip-on" tabs moulded on the lower inside edge (3 on each side). Simple slots for the tabs were created by super-gluing strips of 1mm thick plasti-card to the sides of the chassis metal slab.
These were initially cut "safe" and then trimmed in situ with the Stanley Knife, to get a good fit. This worked far better than I expected!
|Front and back
The Class 59 may be required to join the snow plough train. Tension lock couplers are therefore required at both ends. The "dams" fitted below the buffer beam at each end are both modified by cutting a slot for the coupler, before glueing into place and appropriate hoses are fitted just out of contact with the couplers. The Class 59 yellow ends require a yellow paint extension down to the centre line of the buffers and the (class 66) lifting lugs are removed.
The finished Class 59
|A bit of a
The Class 59 operates well enough for most purposes, but needs to more closely match the performance characteristics of the other Bachmann class 66 locos that may be paired with it in consist on the snow plough train. When testing with this in mind, I came across a problem trying to match speed and acceleration/deceleration of the EU621 controlled class 59 with the mechanically identical class 66 units, previously fitted with Bachmann 21 pin decoders for motor control. I got some helpful inputs from the guys at TCS -----Thanks Jordan!------ which threw some light on the probable mechanisms involved, but in the end, to achieve the best match, the obvious move was to change the motor control on the Class 59 to exactly the same system as used previously in the Class 66 locos (5 of them at last count).
So after a drive over to "Trains 4 U" in Peterborough this morning, to pick up their last Bachmann 21 pin decoder plus a TCS FL4 to control the night lights, here is the revised circuit:
The circuit concept is similar to that used before except for the division of the lighting between the two new decoders and the deletion of the headlight strobing arrangement. To avoid the need to separate out the positive LED wiring for the lighting between the two decoders, I have simply routed the (blue) common positive feeds from each decoder through a 1 Amp isolating diode to to a common positive bus. The spare pink function wire will be used to power a pair of equally imaginary Dorman style shunting strobe lights, to be attached to the lamp brackets on the front of each cab.
The default programming on the Bachmann controls the day running lights via button zero. The TCS FL-4 programming is as follows:
Select button zero for day running or button 1 for night running. The rear lights are enabled using button 9 and button 6 will eventually activate a pair of add-on strobe lights.
TCS FL4 mounted on double sided foam tape, beside the replacement Bachmann / ESU decoder. The components are not too neat after circuit modifications, but they are all
correctly connected, bonded to the tape and hidden from view when the upper body shell is replaced!
some new discoveries in programming dual decoder locos:
The loco behaved faultlessly with the Bachmann (ESU designed) decoder, exactly matching the performance of the Class 66 units. Silky smooth....very impressive! The common positive bus appears to work O.K. with the lighting all operating as expected. (Day lighting, care of Bachmann/ESU and night lighting plus rear light enabling, care of the TCS FL4 function decoder).
Instead of carefully separating the decoder track contact wires before subsequent fine tune programming, I got adventurous..... or lazy, you decide! and tried programming with both decoders connected. Surprisingly all went well:
a) Programming of non contentious CVs on main track appears to be completely successful, with both decoders wired to the track contacts. e.g. CV3 and CV4 adjustment to the Bachmann (ESU) decoder.
b) Changing the loco address on programming track occurred successfully with both decoders accepting the address change simultaneously.
The '59 with amber strobe lights finally fitted (for use in the yard)
They look very impressive driven by the TCS double strobe output
but the effect does not show well in a photo.
|Supplier website links: