The Dash 8-40BW in Santa Fe Warbonnet is one of my all time favourite locomotives. They are boxy (and a bit ugly), but along with the GP60Ms and B units, they are icons of the short-lived four axle high horsepower era.
A pair of these were also my very first N scale loco purchase back in late 2005, so they have sentimental value too.
So I was quite excited when Atlas shipped new Dash 8-40BWs in late 2023 under their Silver and Gold series with ESU sound-ready chassis, and finally with operating ditch lights.
Unfortunately none of the Warbonnet road numbers in the new release survived into my 1999 era without being renumber/patched or with their flags intact, and so the first job was to try grafting the new underframe with ditch lights onto an old cab and long hood. I can confirm that this is possible with care and patience:
The next task was to evaluate the new ESU sound chassis. The copper pickup strips have changed to the new wired pickups — which I find to be more reliable over the last few years. I swapped out the ugly Atlas wheels with Kato 932090 fine scale wheels (with the stub axles pressed inwards to give a 0.540" axle).
The stock sound in these is truly terrible to my ears. So I removed the stock speaker, and milled as large a rear shelf as possible. I designed and 3D printed a BLW speaker enclosure with the 9x16mm speaker lined up with the negative space below the radiator panels. (I initially tried a 9x25mm speaker enclosure as well — but this sounded inferior in A/B testing).
I dislike the ESU 58721 decoders for Atlas locomotives as I have found the sprung copper contacts for the motor and speaker to be unreliable. Instead, I ended up milling out space for an ESU 58741 Kato decoder — as these have good array of AUX LED pads and pads for U+ and GND for the keep alive. I drilled and tapped two screws into the frame halves to provide reliable power via some copper strips…
I hardwired the motor, and installed a TCS KA-N1 Keep Alive in the vacated fuel tank:
My speaker enclosure includes a slot for the rear headlight LED, and this is connected to the AUX2 pads that support dimming.
The front LEDs were a bit more complicated as I wanted the chassis to be easily disconnected from the shell for maintenance. In the end I have developed a small two-part PCB with a Molex SlimStack connectors that allow one half to remain with the chassis and decoder, and the other half to remain connected to the LEDs and shell.
This board includes the necessary dropping resistors for the ESU 58741 AUX3,4,5 connectors, and a pad for the +5V common. I tried to keep this board as flexible in layout as possible, to allow for wiring independent flashing or common function ditch lights, wired nose headlights, as well as a built in LED for cab headlights or number board lights as suits.
For this Dash 8-40BW install, the nose light is wired to AUX1 to get dimming, the ditch lights are wired in common to AUX3, and the number boards are independently lit by AUX4.
So the end result is a four axle unit with a generous 9x16mm speaker enclosure, Keep Alive, and independent ditch lighting and number board lighting, all with a shell and decoder that can be removed for maintenance without de-soldering anything
I've also edited the stock ESU sound file to include a realistic Whoop compressor, and also to re-configured the notch samples to omit the unrealistic recordings for notches 7 and 8 (which sound awful)…
Unfortunately I was still not done!
Atlas has really dropped the ball with the re-engineering of their Dash 8-40B and Dash 8-40C models. The new ESU chassis results in the shell riding more than a millimetre too high. This is clearly a design flaw relative to the previous releases. It is particularly obvious when looking at the rear truck in profile, or at the space between the plow and the track, and at the fuel tank. The shell doesn't even sit level front-to-back.
In the end, I have milled off all the shell supports from the frame, which allows the shell to sit a lot lower:
With the copper pickup strips eliminated, I also took the opportunity to mill out the unrealistically shallow depth of the fuel tank…
I then designed new 3D printed underframe girders to fill the gaps. These include prototypical traction motor cables, bolster supports, lights, fuel fillers, and waste tank connections to the end of the fuel tank.
vs stock:
vs stock:
So there we have it: an original upper shell grafted onto a new lower shell with ditch lights, riding on a milled chassis, with new wheels, a new decoder, a custom sound file, a custom speaker, a custom light board, with a hardwired motor and Keep Alive, dressed up with a custom underframe. Easy!
I'm very happy with how these have turned out, and I'm going to produce a larger batch for painting silver once I've engineered a similar fix for the Dash 8-40CW.
