User:Will King2013/ENES 100/Model Railroad/here

Problem Statement
To understand how Kadee Couplers are designed, as well as how they work when applied for HO scale trains.

Requirements for each element or component derived from system level goals and requirements
For the couplers to uncouple when driven over a magnet. Allowing train cars to detach from each other. Then, if needed, recouple when moved away from magnet.

Alternatives in design
These Couplers are designed and manufactured by Kadee. The model number is 321. Their website: http://www.kadee.com

Modeling, simulation and test
The couplers are located on each ends of the train car (see images, circled in red). The couplers are designed to be interlocking, so a coupler on the end of a train car can attach to a coupler on the end of another car. That now locks two train car together allowing them to be pulled or pushed along the track as "one". When you need to detach two cars from each other, the two connected couplers must be positioned over a magnet, which allows the couplers to disconnect. Kadee Couplers are designed with a piece of metal hanging from each coupler (see third image, circled in blue), when placed over the Kadee magnet in between the tracks, the magnets polarity pulls those two metal pieces and their couplers in opposite directions. this disconnects the couplers allowing the cars to come apart. Once a car is moved off the magnet the coupler returns to the normal position because it is spring loaded. See video for demonstration of this here: Kadee Couplers in action(remember to select HD quality).









Aesthetics
Kadee couplers are designed to look realistic compared to a coupler on a real train car. A real train car has a brake line hose hanging near the coupler, like the brake hose circled in blue, in the 3rd photo of the HO scale train car. The "brake line" on the Kadee coupler plays the key role of being attracted by the polarity of the magnet, detaching the train cars.

Operations

 * To uncouple two coupled cars: The cars couplers must be stopped directly overtop the Kadee magnet placed in between the rails. Next you must release the tension between the two car's couplers by gently pushing the two cars together. This then allows the magnet to pull the arms of the couplers away from each other. The two cars are now detached, or "uncoupled", and can be pulled apart now.
 * To reconnect two cars simply push two cars together, and the couplers will connect.
 * Note: As long as there is tension kept on two cars coupled, their couplers will not disconnect. Also, two couplers will not reconnect if the couplers are still overtop magnet, because the magnet is still pulling the couplers away from each other.

Maintainability, and reliability
Kadee couplers are very reliable, as long as directions are followed. Coupler "brake lines" can drag on magnet if magnets are placed to high. Resulting in a failure to uncouple properly. See Kadee #321 instructions on proper placement for magnets here: http://www.kadee.com/html/321-322ins.pdf