The Aristo 0-4-0 Switcher:

       This little workhorse has been around for quite a while.  It was originally introduced as an 0-4-0 with a coal bunker and no tender.  The tender could be purchased separately, and the coal bunker could then be removed.
       The 0-4-0 is uniquely a Pennsylvania Railroad creation, but comes in a variety of roadnames.  I wish Aristo had come up with an 0-6-0 so that we could model other roads and have a model that was more prototypical.
       The 0-4-0 performs well and with proper lubrication and care, will give the operator a great deal of pleasure.  The only two problems that I have observed with my locomotive are power pick-up and pulling ability.  These two areas are easy to remedy by any modeler.
       Power pick-up is a problem due to the short wheelbase of the locomotive and the wheel material that the drivers are made out of.  The drivers tend to "crud-up" quickly, on the older versions, and this makes operation erratic.  The newer versions of the 0-4-0 have a new wheel material that resists the accumulation of dirt.  These wheels are available as replacements from Aristo.  Even with the new wheels, the locomotives may stall, especially when going through turnouts.  To resolve this situation, jumpers to the tender are the remedy of choice.  This gives you eight more wheels for power pickup and extends the length of wheelbase so that the chances of your 0-4-0 stalling on a turnout are minimized.
       The 0-4-0 is fairly light in weight and you will find that the tender may derail when being pushed through sharp curves or turnouts.  The weight of the locomotive also limits the number of freight cars that it can push or pull.  The easiest fix for this situation is to glue two 8 ounce fishing weights in both the locomotive and the tender.  I have found that this aids in tracking and also helps with traction when pulling or pushing a string of cars.