I’d mentioned in one of my more recent posts, that I was attempting to model the PRR G-39 ore jennie in O Scale 2 rail, using a combination of traditional scratchbuilding techniques and digital fabrication. This is the car I am talking about -
The PRR built 1000 of the G-39 ore jennies in the earlier 1960s. They were to augment the thousand car fleet of G-38 ore jennies, that PRR built around 1960. The underframe, general construction, width and length of the G-39 was essentially the same as the G-38, however, the G39 was 18” higher. The extra height became necessary with the emergence of taconite ore. Taconite pellets were lighter and, because of their rounded shape, there was more air space within the load. The G-38 ore jennies were maxing out in volume, but not weight with taconite. Adding 18” to the car, increased the amount of taconite that could be carried, up to the weight capacity of the car. Some other improvements were made, notably, the oversized bumpers at each corner of the car. These bumpers were to minimize damage at the ore piers by the narrow gauge pusher cars.
Overall, the G38 and G39s were successful as purpose built cars. They were four or five tons lighter and significantly shorter than the hoppers the PRR had been using to haul ore. They had no bottom doors, meaning they could only be unloaded using a rotary dumper. They were used in service between PRR ore docks in Cleveland and Philadelphia, to the inland steel mills, including my favorite, Bethlehem Steel. Both the G38s and the G39s survived well into the Penn Central and Conrail Eras.
I am modeling the Penn Central in O Scale, roughly 1968-1976. How this all started was the purchase of two Alco 630 locomotives. The big Alcos were concentrated by the Penn Central in and around Mingo Junction, specifically for use pulling mineral trains to and from the steel mills. I thought a string of these cars would look great behind them. The only trouble with this plan, was that this car was never offered in O-Scale (it was in HO). Looking at scratchbuilding 40-50 of these cars, I realized the laser and CNC were going to be important tools, to produce exactly identical parts, allow for the use of tabbing and slots to align parts without measuring tools or squares, etch markings in the plastic for part locations, and my personal favorite, and you will know what I mean if you have ever built a resin kit, laser cutting/drilling 95% of the holes for the grab irons and other wire parts.
The car floor is .125 acrylic. The car sides, rim, steps/ladder verticals, coupler mounts, and underframe parts were made of .060 laser cut acrylic. The ribs were CNC cut from .100 styrene. There is also some .020 styrene laser cut parts, as well as .020 laser cut polybacker for much of the detail. Additionally, there is a mix of Evergreen strips and structural members used, along with wire, and Grandtline brake parts. I’ll get into the actual development and construction of this model in more detail in a later blog or YouTube video.
This is the first completed car - technically Version 5.0. There were some very minor corrections made and construction of the first ten cars of Version 6.0 are underway. Looking at more prototype photos while designing and constructing the model, I realized that Penn Central ore trains were a mix of G-39s and the older G-38s. The ratio was typically 2-1, with the 39s being the more prevalent car. Being that the G-38 is similar or identical in many aspects, a slight redesign of the CAD files enabled me to make the G-38 also. I still have to work out the ladder, end details, and the 32 steam lance portholes. Despite this cars simple appearance, it is very difficult to model, especially the ladders and end gear. I believe this is because you are dealing with sloping sides, ladders that joint on the corners, and partially rest on poling bumpers, that are themselves extremely angular. I hope, as I build more, these elements go faster.
