Section I: How Big is the MDC Tank Anyway?As mentioned in the earlier tank car thread, I stripped an old MDC tank car that I was using to test paint. After stripping, I started looking at the model, and what it might represent.
The tank car is actually about 48’ long. It is noticeably shorter than the Atlas 20700 GS tank, but also wider. I wanted to know what the prototypical volume in gallons would be. To measure the volume of a cylinder your need to follow this simple formula: πr2h=v. In this case the tank is 3.428” long and .7” wide giving us a volume of 1.319 cubic inches.
To calculate what the volume would be for the prototype I need a known ratio of a model cylinder to its prototype. For this, I used the Atlas 20700 and 25500 gallon tank cars. The 20k tank measures 3.783” x .666” giving us a volume of 1.379 cubic inches. Using cross multiplication we get a volume of the MDC car, 19,799 gallons.
Using the 25500 tank, with a model volume of 1.798 cubic inches, we get a volume of 18,706 gallons for the MDC car. Since I was looking for an approximate volume, let’s split the difference and call it 19,500 gallons. There are other things I didn't take into account such as the tapered ends, prototype insulation, and the body getting slightly wider in the center for the funnel flow cars. Again, all I wanted was an approximation.
Looking at the MDC car, it bears a strong resemblance to Athearn’s HO acid tank. In fact, Athearn has painted the MDC cars in the same paint schemes as their acid car. The main problem is that the Athearn car is listed as a 20900 gallon GS car in some parts of the website and 13,000 (and 20,900) gallon acid in other sections. For the purposes of sanity, I believe the MDC car to be in the 19-20k gallon range.
Section II: Comparison to Prototypes.As stated above, the tank resembles the HO Athearn Acid tank car and their 20900 gallon general service car. I don't have one of these cars to take measurements, so the tank may be wider/longer than the MDC car. Looking at photos of the Athearn car, it looks a bit skinnier than the MDC car. Let's look at the prototype:
http://www.railcarphotos.com/PhotoDetails.php?PhotoID=13351Not much information here. We know this is close to the same car as Athearn’s acid car. We know Athearn painted an MDC car in this scheme. How does it's side compare to the MDC car? The MDC car measures 9’6” wide. Using the 5’10” wheel centers on the 100T truck in the above photo, we can calculate the tank prototype tank is 9’3” wide, a very close match.
Next, let's look at the car I originally wanted to model:
http://www.rrpicturearchives.net/showPicture.aspx?id=123473I measured the truck centers of a print out at 1.08 inches and the tank height at 1.713 inches. If the wheel centers are 70 inches on the prototype, the tank would be about 9’3” wide, about the same as the white tank.
Measuring car lengths can be a bit trickier using this method because the car may be photographed at an angle or using a zoom lens which can compound distortion over the length of the car. This is the reason why a full size freight car may appear longer and skinnier than a correctly proportioned model. The quick and dirty method I use is how many freight car trucks look like they would fit between the trucks of the prototype. In this case both prototypes could fit about three, the same as the MDC car.
So my conclusion is that the MDC tank could be used as the starting point for either prototype.
Modeling GATX 2684For the GATX car I used the Con-Cor Funnel Flow upgrade kit by Gold Medal Models. It's not an exact match, but the roof top handrails are a closer match than the upgrade kit for the MDC car.
This tank was used to test some weathering. Total failure.
This MDC tank has been upgraded with GMM parts and brass wire.In addition to the ladders, roof handrails and end platforms, I added the handrail along the bottom of the car. Two stanchions per side proved to be too weak so I used 4. The handrail with is .01” wire. I added brake lines under the tank using the same stanchions and .015” wire.
Close up of the tank platform and railings.The brake gear was salvaged from a plastic MTL underframe. I used .015 wire to approximate the brake lines at the end platform.
The original car lacks most platform details and brake gear.
The end platforms and brake gear have been upgraded. I still need to add the brake chain.I still need to add new wheels, brake chain, decals and weathering. I am waiting on parts. More to come.
