Scratch Building a Locomotive

USMRR crew show the result of battle damage on engine Leach

I am finally able to sit at my computer and get some work done. So, inspired by Eric Gates presentation at the ACWRRHS Zoom conference last week, I decided to proceed with a long desired modeling task - scratch building a locomotive.  My objectives are two fold- one, I relish the challenge of building the model, and two, I hope to build a locomotive that runs well and quietly.  Some of my current locomotives have noisy gearboxes. The noise is not as evident during op sessions, but is readily apparent when I record videos. To achieve those two objectives means that I am going to try some type of equalized suspension so that the loco can handle my rough track work.  I also plan to use a high quality gearbox from Slaters that I hope will run  quietly. If you never heard of Slaters, they are one of the major players in the British model railroad hobby industry. They offer a wide variety of parts for people looking to build a locomotive from scratch. When it comes to scratch building or just assembling kits of locomotives or cars, the British are orders of magnitude ahead of U.S. hobbyists. I hope to benefit from their experience.

The first step is deciding what to model. My eventual goal is to build a model of the 0-8-0 Washington flexible beam engine built by Baldwin. I have discussed this model on my blog previously such as here. However, I feel that might be too complex a model to try as my first engine scratch building experiment. So, instead I am looking at building the 4-4-0 Leach as shown in the photo above. The reasons for selecting Leach include it ran on the Aquia Line in the period I model, it's a chunky 4-4-0 with room for a 18mm diameter can motor in the boiler-firebox, and we have at least 3 photos of the engine. Also, John Ott, noted early rail locomotive expert,  sent me some photos of other New Jersey Locomotive and Machine Works engines that have similar details.

The actual Leach weighed 56,000 pounds, had 56 inch drivers, 16.5 inch cylinders, 24 inch stroke, 865 square feet heating surface,  a 1900 gallon tender, and a fairly large boiler judging by the photos. It is definitely one of the bigger 4-4-0s in USMRR service.  

In trying to decide what driver wheels I should order I discovered an odd fact. My existing SMR locomotive models are built to 1:45 scale, not 1:48, at least based on measurements of their actual drivers as modeled.  That scale ratio coincides with the scale of the track, that is, if you divide 4'8.5 inches by the 1.25 inch gauge of O Scale track you get a ratio of 1/45.2 The following table shows the data and calculations from my measurements.   I always suspected that the locomotives were a bit bigger than O scale, but I never systematically measured them. The difference is only 6 percent, but it is there.  I once asked Dave Schneider about this years ago and he said, they were built to 1/48. But the numbers support a different conclusion.  I suspect the builders made the models to be properly proportioned on O gauge track. This is a happy accident as I can now claim that my model railroad is built to the proper gauge. Also, it means that  British 7mm and 40mm scale war gaming model figures are closer to scale.

I selected the Slaters 7855A7 4'7" 15-spoke driver for my model. The 4'7" is computed at British 7mm scale or 1/43.5. So that makes the wheel have an actual diameter of 1.26 inches, about 0.02 inch larger diameter than a 56" driver at 1/45 scale.  Leach had a 16 spoke driver, but no manufacturer offers that driver in 1.25 inch diameter. I do have a set of Slaters 16 spoke driver with a diameter of 1.33 inches. Too big to use on Leach. The Slaters drivers have an ingenious squared axle design that makes quartering the wheel sets trivial. The drivers are secured to the axle ends with an allen screw, so disassembly for repairs is easy.  The drivers have insulated spokes making electrical issues simpler too. These British guys have this stuff figured out! 

 Next, I used the scale drawings of the Slaters gearboxes and motors superimposed on the photo of Leach to see if they would fit in the loco. Unlike many other small manufacturers, Slaters provides excellent scale drawings of their gearboxes and motor drives. It looks like there is plenty of room. 

So I ordered the parts needed. Next step will be to make the drawings based on the actual dimensions of the wheels and gearbox when they arrive. I may try to etch the major pieces for the model as I don't have a milling machine to make my own. I do have a lathe and two drill presses.  

I should mention that I already have a complete brass tender for this locomotive. It is an extra model that I got from SMR trains a few years ago for this task. It scales nearly perfectly to Leach's tender. 

A Slaters 1.33 inch 16-spoke driver in front of the extra brass tender. In the
background is the SMR Osceola

You might have noticed a change to my blog. The template I was using was several years old. I had customized it. Unfortunately, it was getting incompatible with the new Blogger. So I had to update to this new format. Hopefully it's more readable.