| Colas livery Bachmann Class 70 from Olivia's (livery by R3Sprays). |
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Introduction: Bachmann's own proposed Colas Class 70 looks as far away as ever, so when Olivia's kindly offered me an alternative to their now withdrawn new logo DRS 37, The Colas 70 was an obvious choice. R3Sprays have worked their usual magic and done an excellent re-spray job! So now I have the opportunity to modify the lights on a Colas 70, in line with recent RMweb forum contributions from "Big Jim" who regularly drives these machines and has described the lighting operation in some detail. Bachmann's original day headlights are dimmer than the marker lights. This needs fixing, night headlights are added and automatic control of the marker light configuration is incorporated. (When operating in the yard, all three markers are active, with no headlights. When operating on the main line, day or night headlights are activated and the marker immediately adjacent to the active headlight, automatically switches off.) Previous Class 70 lighting update web pages outline the details of similar modifications to the Freightliner Class 70. Although I plan to use a LokPilot FX V4 function decoder this time, in support of the same Bif LokSound V4. That way, there is no need for the discrete PNP transistors and MOSFET buffers. I'll omit the detonator flash LED and double strobe warning lights this time as neither get a lot of exercise on the previous Freightliner unit. |
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Illustrating the Class 70 lighting options with photos obtained from the RMweb forum, with many thanks to "Big Jim" for permission to use them!
In the yard with all three forward markers illuminated, but no headlight.
Showing the dual function lower marker lights in rear light mode
Day running lights with right hand headlight on and the right hand marker light off.
Night running lights with left hand headlight on and the left hand marker light off. |
| The Proposed
Circuit diagram:
Keeping it simple with a LokPilot FX V4 function decoder. Activating each headlight, disables the adjacent marker light via the diode connecting the two. Reverse bias protection diodes are also required. All lighting at End 1 (driver's end) is via the LokPilot FX function decoder. Lighting at the other end is via the LokSound decoder.
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| Mods to the
lighting PCBs adapted from the previous project: The original lighting circuit is as follows:
A few changes are needed:
The additional series resistors are at the main Board end of the interconnecting cables. The links and track cuts shown above need to be implemented. I'll also replace the original stiff cables between the lighting boards and the main board with more flexible types. Lighting PCBs with the key tracks indicated in green:
NB: The lower picture is a photo shopped mirror image to make it easier to see how the vias link the top & bottom tracks! Black rectangles on the upper photo show where original resistors have been removed; red line = track cut; blue line = new link. Yellow triangle shows connection points for the now remotely mounted day headlight LED leads. Yellow arrow = extra wire link back to main board. |
| Proposed new FO mapping
arrangements:
Programming LokPilot CVs for new lighting arrangements:
Programming LokSound CVs for new lighting arrangements:
All working as planned!
The completed function list mirrors the freightliner Class 70 except for the lighting, which is now simpler to set up and has slightly different functionality. |
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The physical circuit implementation: The function decoder, end 1 series resistors and diodes will sit on a thin plasticard substrate in Bachmann's speaker bay at the driver's end of the chassis block. The end 2 resistors and diodes will sit on another small plasticard sheet glued to the top of main PCB (in place of the original SMD parts towards the end 2 end of the board). There will be unused cable(s) in the connectors to the upper body shell. These will be used (together with a shared common positive feed) to drive the night headlights in the upper body shell.
Wheel contacts, motor connections and speaker tabs will remain active on the main board, while common positive and function outputs will be linked on to the new plastic substrates. New connections and track cuts will be made as necessary to the two 4-way connectors on the main board for interfacing to the upper body shell. Stay-alive 25V capacitors will be fitted in any remaining space in Bachman's speaker bay. Only room for 2000uF, but every little helps! |
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Cosmetics: The conspicuous lamp brackets that should be fitted to the inside edge of the right lighting boxes are missing. So a bit of plasti-card construction will be necessary to remedy that omission. The set of 4 circular observation windows in the orange painted zone of the body side have been over-painted with orange. A drop of gloss black paint is required here. The triangular cab side panel extensions immediately behind the obstacle deflector should be matt black rather than the orange or yellow Colas colours. Another minor paint job required here! ........Done! |
The completed Colas Class 70
To see a brief video of the Colas 70 please click here
| Supplier website links:
Photos of the real class 70s were taken by "Big Jim" & copied with his permission (Thanks Jim!) from the RMweb forum site. The photos of the model were taken via EOS 760D in the loft. |
