I've covered the Athearn-RTR (a.k.a. Blue Box) 65ft Mill Gondolas before in two posts SP 65ft Mill Gondolas (Part 1) Overview from 2016 and Car Standards (Part 1) - Weight, Rolling, & CG Allowances from 2022, where I mention these cars as an unique example of some of the CG Allowances.
I've been meaning to get around to doing a deeper dive into individual cars and this conversion since about 2018. My family 'excitement' in 2019 and then the ensuing world experience since 2020, has kept me on other things. However, in late 2022, with the recent work on Modeling SP 94248 (Part 1) - Upgrading a 1990s Kitbash, this work on the SP 160550 is a quick one-evening project to complete after looking up the data in Anthony Thompson's SP Freight Cars Vol.1, which I had open anyway for SP 94248's work.
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| SP 160550 with original MDC trucks |
I picked this car up around 2004-2005 with a number of sister cars when Athearn brought them out. As I recall these were some of the newer cars that Athearn released just after they were taken over by Horizon Hobbies, which lead to some shuffling of the product line.
The work back then to put one of these cars into service was pretty much limited to replacing wheelsets with IMRC 110-tread wheelsets and Kadee couplers. Given that my personal cutoff date at the time was Spring 1953, these SP G-70-9 cars were basically brand new deliveries from Greenville Steel Car, the builder. The tight timing of the construction of the cars and my era limited the weathering to the trucks and a very light coat of dusty/grime on the exterior of the drop end doors. I can always add more later...
Prototype History
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| SP 160550, in service at LMRC - July 2016 photo |
The prototype history of SP 160550-160649, the 100 cars of G-70-9 class were built in early 1953 by Greenville Steel Car. Previous classes G-70-4 and G-70-6 were built to the same basic body design with slightly different trucks in 10-1942 and 6-1950 respectively. I'll cover converting the Athearn-RTR car to those classes in other future posts.
Truck Conversion
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| SP 160550 closeup photo of original MDC truck, lettering, and underframe of the car showing |
I'm specifically looking at replacing the original MDC generic 50-ton AAR-style U-section trucks with Tangent AC&F 70-ton A-3 trucks. It would probably be more accurate on this series of cars to use S-2 trucks from Red Caboose/IMRC, but the bolster holes would require more modifications. The A-3s look very similar for the normal viewing angles that the car will be seen in after the conversion.
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| B-End Underframe once the original MDC trucks was removed. |
I hadn't remembered, but the MDC trucks with IMRC wheels actually needed a Kadee 0.015" thick (red) washer to adjust the ride height of the car.
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| Tangent AC&F A-3 "Ride Control" truck with Tangent 33" wheelsets. |
Nothing much to say about the new Tangent trucks or the process of swapping out trucks. They are excellent models of the 70-ton truck, with the signature 2-3-2 spring package arrangement, longer wheel base, and plain bearings.
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| Tangent AC&F A-3 truck with wheels painted. |
The swapping of the trucks was super simple, as all I was needing to do was pull the screws holding the MDC trucks on and put the Tangent trucks on.
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| Right side of SP 160550 with Tangent trucks. |
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| Left side of SP 160550 with Tangent trucks. |
Weathering the New Trucks
Lastly, I'm painting the trucks SP FCR, and then doing some light weathering to the trucks to bring out the details before I put it back into service.
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| SP 160550's right side after trucking and weathering. |
I may decide to put on some very subtle dust/dirt weathering along the lower carbody and maybe a few minimal marks inside the car, but I do want to keep the cars pretty clean.
In Closing
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| SP 160550 with generic original Athearn-MDC trucks. |
Doing this side-by-side view of before-and-after. The new Tangent trucks are slightly longer wheel-base and heavier truck bolster. The Tangent trucks have a slightly flatter top profile than the MDC's which are noticeably arched.
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| SP 160550's left side after retrucking and weathering. |
I'll probably discuss loads for this car in a later post. The SP tended to use these for moving long and over-length structural steel, steel shapes, and long lumber loads. So reworking some of my loads from 15+ years ago could be fun to show here.
Jason Hill
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