Prototyping a Tiny DIY Train Controller

Let's Get Rolling Due to some embarassingly impulsive late night purchases on Ebay, and my children's occasional clumsiness, I have a small but growing collection of model engines that don't run very well. To figure out what's wrong, I need to get them on a rolling road. DCC Concepts make a nice 8-axle Multi-Gauge Rolling Road , but how best to power it on a workbench? Requirements: DC speed…