RRHMA has been working nonstop to boost forward progress for Union Pacific #3985 and Union Pacific #5511. While updates have been quiet since the start of this year, it does not mean RRHMA crew has stopped work- in fact quite the opposite!

This June 2026 Update is jam-packed with lots of new additions, changes, and accomplishments compared to most of our other updates. So much information, in fact, that we are splitting it into two parts. This update will cover important milestones with Union Pacific #3985, and the next update will cover important milestones with Union Pacific #5511.

Each tube and flue was individually cut to length based on measurements taken directly from each of the tube sheets in the boiler. Once a length was determined, it was cut on our bandsaw and then taken to a set of rollers to be cleaned and polished. We polish the ends of the tubes to remove additional millscale added during the manufacturing process. Millscale is a layer of iron oxides that forms on the surface of steel when it is hot rolled in the manufacturing process. 

After tubes have been successfully rolled on the smokebox side and the firebox side, the process of beading and seal welding can begin.

Beading the tubes and flues means using unique tools in pneumatic air tools (air hammers) to flare the edge of the tube that sticks out of the sheet back onto itself and onto the sheet, rounding the edges and assisting in sealing the tubes under steam. The primary purpose of beading tubes and flues is to protect the ends of the flues from excessive stress caused by temperature variation, which can cause cracking.

The firebox side of the tubes and flues are receiving a seal-weld, which is 1-2 passes of 7018 type welding rod around the diameter of the tube or flue. Once a seal weld is completed, the tubes and flues are then ground flush with the weld to prevent excessive stress on the tube, similar to a bead.

A steam locomotive injector is a no-moving-parts device that uses some of the boiler’s own steam to force fresh water back into that same boiler. Steam is squeezed through a narrow cone so it speeds up and its pressure drops, creating a low-pressure pull that drags water in with it — the basic steam-jet entrainment, or Venturi-style, effect. When that fast steam meets the cooler water, it condenses almost instantly, collapsing back into liquid and giving its energy to the mixed stream; in the final cone, that speed is turned back into pressure high enough to open the one-way check valve into the boiler, while the valve prevents boiler water from coming back out. 

Nathan Manufacturing Co. was founded in 1862 just 3 years after the earliest attempts to manufacture injectors. Focusing initially on items like lubricators and water gauges, they did not introduce their first injector until 1880. Their injectors quickly gained popularity, and towards the end of the steam era, the 4000C was required to keep up with the heavy demands of modern superpower locomotives- just like Union Pacific #3985.

With the decline of steam locomotive service in the 1950’s, examples of the Nathan 4000C Injector became few and far between. The Pennsylvania T1 Trust, a 501(c)(3) restoring the famous 4-4-4-4 T-1 #5550, sought after these very injectors for their locomotive. The decision was made to create brand new injectors for the engine, and as groups heard about this venture it in turn became a joint effort for multiple Nathan 4000’s to be cast. RRHMA was amongst the many groups included in this endeavor- having two created for UP #3985 and #5511.

Manufacturing was entrusted to Valv-Trol in Stow, Ohio, with key support from Huffman Machining and Eccentric Engineer. After months of intense engineering, casting, and precision machining, the first Nathan 4000c was installed on NKP 765—and on April 11, 2025, it fired up flawlessly under 245 psi of steam.

In addition to the Nathan 4000 Injector being constructed, the PRR T1 Trust also worked with RRHMA to create brand new blowdown valves for UP #3985. These valves were made from cast steel- based on original drawings and original castings removed from the locomotive. 

Substantial progress has been made towards the completion of UP #3985’s tender. As of June 2026, the current goal is to have the centipede tender back onto it’s wheels in preparation for final assembly of all brake rigging components.

One of the most notable modifications that have been made to the tender’s axle components is the conversion of the roller bearing boxes to adapt to a sealed freight car style roller bearing.

Originally, these boxes were designed to enclose two roller bearings pressed onto the axle. RRHMA decided to remove and modify these boxes to adapt to a more common freight car style sealed roller bearing, to minimize servicing and increase service life. This was done by creating a custom adapter that matches the radius of the inside of the box, and matches the radius of the new roller bearing. A lip was added to prevent additional lateral from being added, and the adapter plates were then welded into place in the original boxes. The weight of the tender will keep these adapters held in place.

With the adapter plates installed in the roller bearing boxes and the conversion complete, the boxes can now be placed onto axles and upon completion of suspension work can be placed back underneath the tender. RRHMA staff and volunteers have been working extremely hard to accomplish this goal, and have successfully completed a significant part of that goal; the centipede tender truck. This truck has been completely disassembled, inspected, and now reassembled, ready for reinstallation.

In addition to the completion of the tender truckset, RRHMA crews have also successfully installed the suspension components for the centipede tender. Installed with new pins, bushings, wear pads, and shimmed to the correct dimensions based on Union Pacific drawings; this tender will ride the best it ever has since it originally left the factory.

There has been so much more going on behind-the-scenes at RRHMA-Silvis to be covered in just one update. Tune in soon for our next upcoming update… highlighting Union Pacific #5511, the Caboose project, and a variety of appliances!