Accucraft GP40 Electronics and Wiring

Although Accucraft can supply the GP40 loco with their own control system, I opted to install the Mini Train Systems PS7 control system so it would match the Planet 2 loco.

I already had a set of 4 batteries, 12 V 75 Ah sealed lead acid type, which had previously been used in a ride-on mower.  Although the batteries were somewhat degraded to about 50% of their original capacity, the remaining capacity should be ample for locomotive use, as the maximum power required is around half that of the ride-on mower, and only for shorter intervals. 

Each pair of batteries is wired in parallel to give 12 V, and the main circuit breaker connects both pairs in series to provide 24 V for the power controllers.  When connected to the battery charger, all four batteries are connected in parallel and charged at 12 V.  The four batteries occupy most of the long hood portion of the loco.

I intended to mount the main circuit breaker inside the cab of the loco where it could be operated through the open side window, but the window opening was too small to get a hand inside.  Instead I mounted the main circuit breaker in the low short hood, which has an removeable top for easy access.

Main circuit breaker mounted in the low short hood.

Due to the GP40's power requirements (1400 W @ 24 V), it needed separate power controllers for each bogie, which are effectively connected the same as two locomotives in multiple unit (MU) operation.

The loco included an aluminium tray for the various electronic bits in the top of the long hood, at the rear.  The major items of equipment are the two motor controllers, circuit breakers for both 24 V and 12 V circuits, and a number of relays for auxiliary items including lights and horn.

Two relays also function as a safety interlock and are controlled via a cable plugged into the first wagon of the train to shut off motor power if the couplings become separated for any reason this preventing a runaway locomotive.

The main "electronics tray"

The motors used on the Accucraft bogies (two motors per bogie) also include an electromagnetic brake.  This brake defaults to the ON position and requires continuous 12 V power to release the brake.  Although useful as a parking brake, the magnetic brakes engage very suddenly and can only be used when the loco is at a standstill.

I wired the brake circuit independently of the safety interlock and 12 V/24V circuit breakers with a separate fuse, so that the brakes would not engage suddenly if the loco became separated from the train.  In that event, it would be preferable for the loco to coast gently to a stop rather than having the brakes suddenly lock up.

I completed the basic wiring and battery installation relatively quickly so that the loco was able to run under its own power 48 hours after delivery.  Although I expected to have to do more of the wiring myself, Accucraft had provided and labelled long enough cables for the motors, brakes, front and rear lights, horns and speakers for on-board sound effects, if desired.

Wiring in progress.  Two of the batteries are visible near the centre of the loco.

The tethered control panel from Mini Train Systems connects via a 15-pin connector, the same type as used for VGA computer monitors.  A later stage of the wiring is to fit these connectors to the headstocks at each end, so that the control panel can be plugged in to operate in either direction.  This work is still in progress.  For the initial testing, the cable for the control panel was routed via the open cab window, as this was the only opening available when the roof panels were in position.

Accucraft GP40 Loco Arrival

A very exciting day for the railway with arrival of an Accucraft GP40 locomotive which had been on order since January 2025.

Towards the end of 2024, I had been thinking about building or buying a larger locomotive, which would be able to handle the grades of up to 3% on the railway.  After exploring some ideas of building a loco using commercially available drive bogies, I decided that the Accucraft GP40 locomotive would be a good option, as I preferred a nicely-detailed loco based on an actual prototype rather than a freelanced design.

The initial inspiration came from a YouTube video of a US miniature railway with a loco in the Florida East Coast Railway livery, as the red-orange, yellow and black reminded me of the 1970's experimental International Orange livery applied to a couple of then WAGR (Western Australian Government Railways) standard gauge locos, including L Class L257.  

Although there are significant differences between the US GP40 loco and the L class, the overall shape is similar including the low "nose" on the short hood.  In the mid 1970's, when this livery was current, I was inspired to hand paint a Bachmann GP40 loco to act as a "good-enough" L class for my HO scale model railway.

L257 "International Orange" Livery - WAGR 1974 Publicity Photo from Rail Heritage WA

When I first enquired with Accucraft, they advised that the loco was made in Japan, but shipped to China for custom painting, and that I would have to arrange shipping from China to Australia.  Fortunately, an online search revealed a company - Shipping Solutions - which was able to handle all aspects of the importation, by sea container, including customs and GST payment.  Once I had confirmed that the import process was manageable, I paid an initial deposit to Accucraft to secure the order.  

A friend was able to source an original WAGR drawing showing the details of the paint scheme, and I prepared a drawing showing the livery overlaid onto an outline drawing of the GP40 locomotive.  I bought 1 litre tins of painted tinted to the appropriate Australian Standard colours for International Orange and Golden Yellow, which I used to prepare colour samples which I posted to the factory address in China.

Accucraft initially estimated that the finished loco would be ready to ship from China in May, but that proved optimistic, partly due to the US tariff situation which meant that other locos being prepared for US customers took precedence to beat the tariff deadline.

One issue that I became aware of some time after placing the order was the difference in wheel standards for 7¼" gauge in the US compared to Australia.  The common US profile is defined by the International Brotherhood of Live Steamers (IBLS).  The corresponding organisation in Australia is the Australian Association of Live Steamers (AALS).  The area of concern was the wheel check gauge, which affects how the wheels interact with the frog and check rails when negotiating points (turnouts).  Despite the common 7¼" track gauge, the IBLS wheel check gauge was 3.5 mm wider.  

Accucraft offered a choice of the IBLS wheel profile or an alternative RMI-25 profile which has a slightly deeper flange which more taper on the front of the flange.  I elected for the RMI-25 flange profile, hoping that the more tapered flange would help when running through points.  Although I was confident the US wheel profile would run ok on normal (plain) track, I was expecting that negotiating the curved, diverging leg though points could be a problem, which turned out to be the case.  

Around the end of June 2025, Accucraft advised that the loco was ready to be shipped from China and the previously arranged shipping plan swung into action, after I had paid a 50% deposit for the shipping component.  The crated loco was loaded into a shipping container with other small LCL (Less than Container Load) freight, and on a ship bound for Fremantle.  

A few days after arrival, the container was transferred to a freight depot in Welshpool, WA, where it was to be unloaded ready for pickup and final delivery.  This proved to be a complication as the freight depot had a slot booking system for freight to be picked up, and the company based near Albany which I had engaged for the final delivery, didn't understand that they needed to make the booking prior to pickup.  Their next schedule run to Perth wasn't for another 2 weeks, so I sought a quote from Freight Lines Group (FLG) for the transport to Denmark.  Although this hiccup resulted in a delay of 3 days, FLG did a good job and made the final delivery right to our door using a small truck with tail lift.  As this was the last delivery for the shift, the delivery driver even offered to wait while we unpacked the crate and helped lift the loco onto the track.  What service!  

The loco strapped to the base of the shipping crate.

After removing the ratchet straps and most of the packaging.

After some heavy lifting to place it on the rails.

First test run, although without the electronics installed, it was being pushed by the Planet 2 loco.