Micro-Trains - 066 00 020 - Tank Car, Triple Dome, 40 Foot - Anderson-Prichard Oil - 7018

Prototype History: Triple Dome tank cars, while not as common as single-domes, are a railroad staple. They have been around since the first half of the 20th century.

The dome above tank cars serves as an expansion chamber as temperature affects the volume of any liquids contained within. With no dome, if the liquid did not 100% fill the tank, then it is possible for the liquid to slosh around inside the tank, causing instability and increasing the possibility of a derailment. The dome allows the tank to be slightly overfilled so that should the volume in the main section decrease due to colder temperatures or even a small leak, that there will still be sufficient liquid within to prevent sloshing. Similarly if temperature increases, the liquid can rise up inside the dome preventing excess pressure within the tank. While not as serious as an underfilled tank, an over-pressurized tank might present problems during unloading.

If you see three domes on a tank car it is because there are three separate compartments inside the tank car each containing a different liquid. This was desirable for many reasons.

Often times a delivery would consist of much less than a carload (LCL) of liquid. Remember the sloshing problem? So if you only had to fill a third of a tank with your commodity, then you can avoid the issue by using one of the three chambers within the tank car. Also, you might have several grades of a commodity to deliver such as unleaded, leaded and diesel fuel and you need them to be kept separate. Or you might be producing wine and you want your white wine kept separate from your red wine. Or maybe all three chambers had the same contents but were being delivered to three different customers. It can be very difficult to determine when one third of a single dome tank car has been discharged...

For all these reasons, three-dome tank cars were a common sight in the first half of the 20th century. However, with the rise of the interstate highway system and the modern trucking industry, LCL deliveries have primarily been accomplished with tanker trucks instead of tank cars and the three-dome tank car has gradually disappeared from the North American rail network.

Brand/Importer Information: Micro-Trains is the brand name used by both Kadee Quality Products and Micro-Trains Line. For a history of the relationship between the brand and the two companies, please consult our Micro-Trains Collector's Guide.

Manufacturer Information: Micro-Trains Line split off from Kadee Quality Products in 1990. Kadee Quality Products originally got involved in N-Scale by producing a scaled-down version of their successful HO Magne-Matic knuckle coupler system. This coupler was superior to the ubiquitous 'Rapido' style coupler due to two primary factors: superior realistic appearance and the ability to automatically uncouple when stopped over a magnet embedded in a section of track. The success of these couplers in N-Scale quickly translated to the production of trucks, wheels and in 1972 a release of ready-to-run box cars.

Micro-Trains Line Co. split off from Kadee in 1990 to form a completely independent company. For this reason, products from this company can appear with labels from both enterprises. Due to the nature of production idiosyncrasies and various random factors, the rolling stock from Micro-Trains can have all sorts of interesting variations in both their packaging as well as the products themselves. When acquiring an MTL product it is very important to understand these important production variations that can greatly enhance (or decrease) the value of your purchase.

Please consult our Micro-Trains Collector's Guide