This 9mm N Scale standard guage power unit will power our N Scale locomotive Shay kit and is sure to find its way into many other applications. It comes with an extended driven shaft to allow you to experiment with PTO drive extensions. This extended shaft can be cut to length using regular wire cutters. Please click on the instructions tab to see more information about this power unit.

Suggestions from Tom Knapp

A 12VDC train power pack puts out 12VDC (in some cases more) when turned fully flat out. The loco will fly off the track before that happens. At normal operating speeds for the Showcase power unit, the power pack will probably be putting out no more than 3VDC at the track. Operating the power unit flat out for an extended period is impractical at best and careless at worst. In short, just because a power pack says it is 12VDC, doesn’t mean you have to run the train at 12VDC. There are two exceptions to this.

1. Pulse-Width-Modulated throttles
These throttles put out short bursts or spikes of voltage – reducing the gap between bursts as you increase the throttle to increase speed. Depending on the manufacturer, these can be 12VDC spikes. In the past I have had some Märklin Mini-Club iron-core motors get very hot is run for long periods of time at train shows using PWM throttles. I have not experienced that heating in the coreless motors in these power trucks. Some manufacturers such as Rokuhan and Varipulse have PWM throttles which are “kinder” to low voltage motors – both coreless and can-type.

2. DCC
DCC motor decoders are basically PWM throttles. The decoder can be programmed to get a better range of speed vs. throttle setting for these small motors. Bryan Vianco has a very good tutorial on setting the motor voltage CVs on his web site at tutorialstipstricks. In addition to this, voltage can be reduced electronically using voltage reduction devices between the power unit and track.

Customer question: What form of voltage protection you recommend so I can use them on a standard 12v dc layout?

Answer from Tom Knapp: I am not an electronics expert, and the following is based on my experience and observations. The 12VDC nomenclature used for model train power supplies is misleading. A straight DC power pack can supply a voltage from a low end of maybe 1VDC (for better units) up to the maximum the power pack puts out on full throttle. Full throttle on cheap power packs that say they max out at 12VDC can actually be more, especially if power is stepped down to DC using an old-fashioned transformer. But, unless you are a child whose only concern is “how fast will it go”, you probably never run locomotives on full throttle. Of more concern are 12VDC output “pulse width modulated” power packs or throttles, which put out their maximum voltage for short bursts – the spacing of these bursts defining an “average” voltage. Running a locomotive with a motor whose “rating” is under the rated output of the PWM throttle for long periods of time may cause a heat build-up in the motor. Usually not a problem for typical home layout operation, but I have had locomotives with motors rated at 10VDC get quite warm after long periods of operation at train shows with a PWM throttle rated at 12VDC output. For DC operations, I have found the Rokuhan RC02 throttle works well with motors rated as low as 6VDC and up to typical N-scale locomotives with motors rated at 12VDC, and without any special provisions on the motor, even for Rokuhan “Shorty” locomotives rated at 6VDC and other Z-scale locos rated at 9VDC. For DCC, I use a 12VDC switching power supply for my DCC command station, thereby reducing the input and subsequently the peak output voltage on the rails of the DCC command station, typically measured at the rails at a maximum of 10V.