Precision Scale/D&D (Korea) Brass 4-6-2 PRR K-4 Pacific

Introduced: 1994

These Iron Horse Models / Precision Scale K-4's were available in a number of different permutations - prewar with slat pilot and 130-P-75 tender, prewar with slat pilot and scullin drivers, wartime streamlined, and postwar with steel pilot and skyline casing. They seem to be pretty rare, and given the enduring popularity of the prototype, seem to have held their value very well. The ones that do occasionally show up on eBay generally sell for at least their original retail value (and sometimes even more). Unfortunately, they're not really worth the prices they're going for (but more on that in a moment).

The chassis is all metal and quite flimsy (with most of the model's weight provided by the shell). The motor is a cheap looking five-pole / straight-wound Mashima. Right-rail current is collected by the pilot truck, trailing truck and two of the right-side drivers (the center drivers are equipped with traction tires). Left-rail current is collected by the four left-side tender wheels and transferred to the engine by way of a stiff wire on the tender drawbar. The motor and worm box are mounted on a torque arm that is equipped with a leaf spring. The motor driveshaft and worm shaft are joined by a plastic sleeve (which I'm told has a tendancy to disintigrate over time). Only the center driver set is geared, with all gearing (apart from the worm) being plastic. Each axle has a set of bearing blocks where it mounts to the chassis. There is no lighting. The pilot is equipped with a non-operational knuckle coupler. The tender does not come with a coupler, although a Micro-Trains friendly mount is provided. Wheels are low-profile, so no problems on Code-55 rails.

The shells are nice looking and finely detailed, so they at least have that going for them. On the downside, the paint seems a bit thick and the colors are somewhat inaccurate (or so I've been told by Pennsy fans).

"As delivered" these models have so many mechanical issues it's hard to know where to start. But anyway, here we go -

- The traction tires are too thick, causing the other drivers to lose contact with the rails (and thus either stalling out the locomotive or flat out derailing it). As noted in the MR review below, sanding the tires is one way to alleviate this problem (and I suppose simply replacing them with thinner tires would be another way to go about it). I tried sanding the tires on mine, and although performance did improve, they still seem a bit unstable (with either the forward or rear driver set being slightly raised above the rails as it rolls along). The leaf spring may be the culprit here - providing too much downward pressure on the center drivers.

- The tender truck springs and drawbar wire are so stiff that it's hard to get the tender to sit down on the rails and track properly. Further, the drawbar wire can place undue upward force on the back of the engine - to the point where the engine will lift up and lose traction or electrical contact. One suggested solution would be to replace the stiff wire with an insulated mini-wire (this would also provide more reliable conductivity).

- The engine's trailing truck is virtually useless as far as pickup is concerned because there is no spring on its attaching screw. The solution here would be to take a thin bronze washer, bend it slightly, and install it on the screw (ala what the Minitrix K4 uses).

- At least some of these came with their pilot trucks installed backwards (thus leading to short circuits). The solution to that particular problem should be too obvious as to require elaboration. FWIW, the pilot truck on mine was installed correctly. However, the spring on the pilot truck screw is laughably ineffective, with the end result being endless derailing. I was able to solve that problem by installing a more robust spring.

- If the driveshaft and worm shaft are not properly aligned, binding will result (and thus impact slow speed performance). If such is the case, loosening the motor screws and adjusting the motor up or down to get the shafts aligned correctly will improve performance significantly.

- The running gear is just kind of a mess. Frankly, "loose, floppy and all over the place" doesn't even begin to cover it. I had to spend hours adjusting the various cranks and rods on mine before I could get it to the point that it wasn't seizing up every few feet. The crossheads and associated cranks are particularly problematic - literally tying themselves into knots when things (inevitably) get out of whack.

Unfortunately, even after applying a few of the simpler fixes (sanding the traction tires, replacing the pilot truck spring, and straightening out all the running gear), mine still didn't run particularly well. Slow speed performance is basically nonexistant - IE, it's either not moving, or it's moving very fast. And overall, it's just plain jittery and uneven (no doubt owing to that unreliable "stiff wire on the drawbar" electrical connection between the tender and engine and the somewhat unstable driver situation).

I'm told that expert locomotive tuners can turn one of these misbehaving little beasts into a respectable runner (with a lot of time and effort). But as for the rest of us, these models are good for looking pretty in a display case and not much more than that.

To remove the locomotive shell, unscrew the pilot truck and remove the two small screws on the back of the cab. The shell should lift right off at that point.

Grade: F (and maybe C after a lot of tweaking and tuning)

Reviewed: 10/94 Model Railroader ("These brass N scale models, imported by Precision Scale Co., represent locomotives that were the backbone of the PRR's passenger service from WW I until the 1950s... Precision Scale is importing three versions: A prewar locomotive with the early slatted steel pilot; a postwar version with a cast steel pilot and skyline casing; and a streamlined engine of the early 1940s. These models are all made in Korea and share a common mechanism... Our samples closely matched the dimensions of the prototype except for overall length. The pilots have been extended about a scale foot and the pilot truck wheel diameter is reduced (a scale 30" instead of 36"). This increased clearance between the lead truck and the cylindars allows the engine to negotiate tight model railroad curves.

"These models are neatly fabricated from brass sheet, wire, and lost wax castings. Most of the formed sheet brass parts feature fine etched rivet detail and joint lines. There's even a backhead and seats for the crew in the cab. The wire piping is neatly done and firmly attached. All the tenders include water scoops and the major brake componants. The scale 80" drivers have individual brass bearings rigidly mounted in the frame. A small can motor is concealed within the firebox and transmits power through a gearbox riding on the middle axle. The side rods carry the motion to the other drivers. All the locomotive and tender wheels are nickel plated and have the rounded RP-25 flange contour. I checked all three with an NMRA standards gauge and found some variation. One model was perfect, but the others had several tender wheelsets and trailing trucks that were too narrow. I was able to correct this by gently twisting the insulated wheels along the axles.

"Our sample locomotives did not run well at first due to excess thickness in the traction tires on the main drivers. The rubbery plastic was thick enough to raise the other drivers off the rail a bit and prevent good electrical pickup. By sanding a little off each engine's righthand traction tire, contact was restored and the engines ran fine. Each locomotive's starting speed was high... the overall speed ranges were also on the high side, but the 1.4-ounce drawbar pull is sufficient to pull about 16 free-rolling passenger cars on straight and level track. The tender floors have a flat pad that accept a MT 1016 coupler. There is no similar provision in the locomotive pilots... All three of our sample K4 Pacifics came beautifully factory painted in PRR's Brunswick Green highlighted with graphite smokeboxes and fireboxes. All lettering is neatly done in gold and the keystone number plates are red. These beautiful models give Pennsy fans a nice choice of passenger motive power. Prewar: $388, Skyline Casing: $385, Streamlined: $425")

Streamlined version -

Prewar version -

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