Copyright — George Pierson, MMR #367
My HOn3 modeling is almost exclusively in steam on my Tuscarora Valley RR/PRR layout. But I do make concessions to infernal combustion. Some years ago I scratch-built/kit-bashed a working HOn3 model of the gas-mechanical motor car that today runs at Strasburg on standard gauge trucks but was originally built for the Lancaster Oxford & Southern, a 3-ft. pike in eastern Pennsylvania.
So when a friend asked if I could get his HOn3 Northwest Short Line GE 50-ton SP #1 diesel running better and do a decoder installation, I had an idea of how I would proceed. I could use the same mechanism that had worked for my LO&S motorcar.
So why make these changes? The NWSL 50-ton model had an open-frame motor with a flywheel that also engaged a ball on the rear gear tower. The truck at the bottom of this gear tower was connected to the front truck with a ball-and-cup shaft.
And it ran badly. I have heard that this is a common experience with this NWSL model.
On my friend’s engine the flywheel was slightly out of true, which caused the engine to shake. Also the gearing was such that the engine would not operate above a very slow speed and with lots of gear noise. I’m sure I’m not the only person who wondered about a re-gearing and re-powering of this otherwise nice little engine, a model of the n.g. prototype used by the SP’s Owen Valley n.g. line in the 1950’s.
Because of my experience powering my gas-mechanical LO&S engine, I knew that the mechanism for the GE 44-ton engine from the Keystone Locomotive Works had almost perfect characteristics to get this SP narrow gauge diesel working well. This Keystone model has excellent NWSL gear tower/trucks front and back and comes with a good can motor. And the 44-ton trucks are virtually the same as the 50-tonner. And, most important of all, the standard gauge wheels/axles can be easily narrow gauged. One down-side is that Keystone model has not been available new for a number of years but they do show up on Ebay often enough that I was able to get one for about $40. The following photo story illustrates how I changed this poor runner into a good one.
With the cab/hood removed from the 50-ton engine, you find an open-frame motor screwed down to the frame over the un-painted spot. Unscrewing the motor is simple and here is what you see. The flywheel at the front of the motor (upper right) engages a ball-and-shaft at the top of the gear tower.
Here is the Keystone 44-ton standard gauge engine with cab/hood and truck side frames removed. Like the 50-ton model, the side frames (removed in this photo) are press-fit onto the two hollow Delrin shafts between the wheels.
Just inboard of each gear tower is a vertical shaft on the top of each truck which extends through a hole in the engine frame. The E-rings (lower left and right) fit around each shaft and keep the trucks from falling out of the frame. These E-rings will not be needed when these gear towers are installed on the 50-tonner.
This photo shows the 44-tonner gear towers and trucks removed from the 44-tonner frame. The vertical shafts onto which the E-rings are pressed are more visible in this image. Notice that the gear tower/truck housings are considerably narrower than the standard gauged wheel sets. This is what allows narrowing the gauge. Each truck has phosphor bronze wheel wipers on both sides, providing all-wheel pick-up, another improvement over the pick-ups in the original 50-ton model.
The un-modified gear tower/trucks from the 44-tonner from above. The wheel/axles are kept in place by semi-cylindrical Delrin “ears”. These will need to be trimmed back when the wheel sets are narrow gauged. The phosphor bronze wipers are press-fit onto the tubular shafts between each wheel set. These tubular shafts will also be shortened for narrow-gauging.
The wheel/axles are press fit into the semi-cylindrical “ears” on the side of each gear tower-truck. While the 44-ton model has Delrin C-rings (not shown) that snap onto these semi-cylindrical extensions, most are usually broken on these models. No problem – they will no longer be needed when the semi-cylindrical extensions are cut back to accommodate the re-gauged wheel/axle sets. I have run my original motor car for 15 years without these retaining C-rings and never had a wheel set drop out of these trucks so the absence of the C-rings is no problem.
Note as well that the wheel wipers have had their holes slightly enlarged so that the wipers can be pressed flush with the sides of the truck frame. I have also cut back the shafts holding the wiper so that the truck frames can be installed prototypically close to the wheels. I also CAREFULLY drilled out these shafts so that the male nubbins on the truck sideframes can be press-fit onto these shafts.
This photo shows the modified gear tower/truck with the lower set of semi-cylindrical extensions trimmed back for 3-foot gauge. The upper set of extensions has been left un-modified for comparison. BE CAREFULL when you do this – these extensions not only hold the axle in place but also keep the axles properly centered in the truck. This is important because the gears are fairly narrow and might not engage properly if the extensions are not properly trimmed to keep the wheel/axle centered in the truck. ALSO NOTE – the insulation for the left wheel in the photo sticks out from the inside of the wheel. This is why the lower left extension is cut back closer to the truck than the lower right extension.
The wheel/axle in bottom of the photo has been narrow gauged. I used a NWSL arbor press to do this but you could also use the NWSL Wheel puller tool. Be sure to use an NMRA HOn3 gauge to properly gauge the wheels. When all four axles are properly re-gauged I cut off the excess axle material on the outside of the wheels with a good pair of heavy wire-cutters and smoothed the rough ends with a mill file. After you re-install the wheel/axle sets, turn the gear tower drive shaft by hand to make sure each re-gauged wheel set are operating smoothly.
Now it’s time to modify the 50-tonner’s frame. Note the two ears on the right-hand end of the frame. They slip under two corresponding “clips” at the front of the 50-ton car body. The right-hand opening for a gear tower is almost ready to go but the hole to engage the new gear tower’s vertical shaft needs to be enlarged. But a more radical modification is needed to create a hole for the left-hand gear tower.
You can see (left) that I cut out a section of the 50-tonner frame with a jeweler’s saw. The original hole’s center for the original rear truck on the 50-ton model will need to be moved slightly inboard so that the new rear truck will not rub against the rear of the cab floor. Note the two small holes on the left end of the frame. These are for the screws that hold the cab end of the cab/hood onto the frame.
Believing that I would need to use the E-rings to hold the trucks in place, I epoxied these pieces of styrene onto the upper side of the 50-ton engine frame to raise the frame floor level to that of the E-ring slots. But it turned out that the NWSL ball-and-cup I used to connect the new motor’s shafts to the gear tower drive shafts actually hold the trucks in place. So if you use the NWSL ball-and-cup you do not need to add these styrene shims.
Now is the time to test fit the gear tower/trucks into the modified frame to make sure they move freely. Notice that there is very little material between the front of each hole and the gear tower opening. Be careful not to make this area too thin.
Note the white styrene “washers” I created to provide enough space between the bottom of the frame and top of the gear tower to allow for vertical flexibility when tracking. Otherwise, if the top of the gear towers were simply resting on the bottom of the engine frame, the resulting inflexibility might mean that any vertical irregularities in the track could cause the truck to climb over the rails.
Next, properly locate and mount the new can motor. It turned out that with almost no modification the double-shafted motor that came with the Keystone engine will fit between the gear tower drive shafts. I used the appropriate NWSL ball-and-cup to make the connection. This resulted in the motor riding a bit above the frame. At this point you could use Blue RTV Silicone gasket maker to attach the motor directly to the frame but I prefer to make the motor removable.
To do this, I cut a length of brass u-channel, tapped and threaded a 2-56 hole in it to correspond to the original motor screw hole, and then used the silicone gasket maker to attach this brass channel longitudinally to the bottom of motor.
With this much assembled, check that the 50-ton cab/hood fits over the new mechanism (it should) and test-run the engine to make sure the motor and gear towers all operate freely.
NOTE – the assemblies that hold the coupler pockets and include cowcatchers should be mounted ONLY AFTER making sure that what you see in the above picture is running well. Once the coupler pocket pieces are mounted you will not be able to remove the gear tower/trucks.
Since the 50-tonner’s original frame weight was removed, I glued as much lead weight as I could fit into the hood and cab roofs. I also added window “glass” to the cab windows.
To get the new mechanism to fit into the cab/hood it was necessary to grind away some material. See the rough curved area at the end of the frame closest to the pilot. Do this carefully – I used my Dremel with an abrasive cutting disk – and DON’T cut into the hood front! I had to do something similar to the rear floor of the cab.
In the above picture please note that I have added lead weight on the bottom of the frame in the space through which the original ball-and-cup drive shaft to the front truck ran. Small engines like this can use all the weight you can add!
I next installed a DZ 123 Digitrax decoder – no room for sound in this critter. This is an older model decoder – use whatever Z-scale decoder you prefer. It’s the small size that you’re after.
But now a problem cropped up. To install the frame onto the cab/hood the front of the frame has to slide under some “clips” on the front underside of the hood/frame. The problem was that the angle of the motor-truck frame necessary to do this caused the rear of the cab floor to interfere with the top of the rear gear tower/truck. You can see this in the photo at the right.
To fix this I CAREFULLY ground away more of the cab floor, almost breaking through the cab rear wall. I also shorted the “ears” on the front of the frame. These modifications plus, some authoritative wiggling, got everything to fit. This is when I installed the coupler pocket/cowcatcher parts. I also press-fit on the truck side frames that came with the Keystone 44-tonner. And that’s it!
You now have a smooth-running and much quieter Disease-el for your HOn3 empire. The engine is painted and lettered for my friend’s railroad. I’m still a dyed-in-the-wool steam guy but it’s nice to know there is a way to improve a decent brass model of an internal-combustion locomotive for HOn3.
