D&RGW C-25 2-8-0  (A Bachman Bash)

The F Gauge Steam Locomotives

D&RGW M-68 4-8-4
(2006-2009)

Delivered by the Baldwin Locomotives Works to the Denver & Rio Grande Western over the winter of 1937-1938, the M-68 4-8-4 was the Rio Grande's last standard gauge steam passenger power. With Baldwin's own proprietary 73" disc drivers, Elesco feedwater heater, multiple bearing crossheads, Commonwealth trailing and tender trucks, and all-weather vestibule cabs, these five locomotives (#1800-1804) were the epitome of modern steam power on the Grande. All were sent to the scrappers by August of 1954, but one of the class' tenders remains, in use upside down as a storage shed in Pueblo, Colorado! Fifteen copies of this same locomotive, with minor variations, were built for the Missouri Pacific in 1943, most notably lacking the all-weather cab.

Doug's locomotive is not only the first F scale 4-8-4 to be built, but it is also the first F scale two-rail electric, standard gauge steam locomotive to be built of any sort in 1:20.3 (my baby 4-6-2 is in third place, with George Konrad's D&SL 2-6-6-0 mallet in second). But Doug is not just building one 4-8-4: He has four of the same class under construction! And yes, three of them are for sale.

Elevation and section drawings for this project came from Kalmbach Publishing's Model Railroader Cyclopedia--Volume I: Steam Locomotives, whereas drawings of the distinctive Baldwin disc drivers were found in a late 1930s era Locomotive Cyclopedia. Additional help has come from an brass HO scale model of an M-68 imported by Overland Models. Additional prototype drawings of the M-68 may exist, most likely at the Denver Public Library, but as of 2008, none had been located.

With A Little Help From My Friends

Having friends to help on a project as complex a 1:20.3 scale standard gauge 4-8-4 makes all the difference in getting off the ground. In the first place, Doug has had the singular good fortune of a patron, Mr. Gary Bartlow, who commissioned the building of all four M-68 models. The late Doug Cockerham, another Texan who was well-known in the world of 2-rail O scale for repowering imported brass locomotives, machined and assembled the drivers as well as milled the main frames and various other bits of running gear for the latter three locomotives. And speaking of drivers, Mr. Bill Brisko of Pacific Locomotive Works provided the rapid prototype wax patterns for the M-68's Baldwin disc drivers based upon his own SolidWorks 3D CAD drawings (for about $2700 if you're interested in that side of the equation). Bill is also responsible for producing 3D CAD drawings of the valve gear, side and main rods. Rino Mechanical Components provided the custom built worm gearboxes (for about $337 a pop). A Pittman 14000 series DC motor powers each locomotive. 73" steel driver tires came from me. Tender, lead and trailing truck wheelsets were from my original stock, now sold by my good friend Don Niday. David Fletcher, a large scale modeler--in Melbourne, Australia--did the initial 2D CAD work for the main frames. Additional help has come from a consortium of modelers residing in the Houston area: (1) James Engle custom made the D&RGW decals,(2) Ward Hammond laser cut the production cab and tender sides from styrene (along with styrene casting patterns for the rods, valve gear, & Commonwealth tender truck side frames), (3) Barry Bogs is doing the battery, Airwire and sound installation, and (4) Jim Srenaski (famous for at one time cornering the market on all available Bachman GE 45 tonners) built the model's carrying cases as well as painted their cabs, pilots and air compressors.

The Tender
Doug made his tender body from styrene with many, many Peco track nails inserted into the sides to simulate rivets. The Commonwealth style tender trucks were originally solid urethane castings, reinforced with a bit of piano wire, but have now gone through several versions, the most recent using laser cut styrene pieces, laminated together; with separate, sprung journal boxes in order to improve suspension and tracking. The tender underframes are styrene sheet supported by brass channels. The tenders will house a substantial speaker for a Phoenix Sound System when complete.

 

Here are pics of the three latter tenders in various stages of construction (as of October 2008):

The Drivers

Pictured just below are the rapid prototype (RP) wax patterns which Bill Brisko produced on a stereo-lithography machine from his own SolidWorks 3D CAD drawings. Bill's SolidWorks drawing of the Baldwin disc driver centers specific to the M-68 was itself based upon a 2D drawing published years ago in a 1940s era Locomotive Cyclopedia (reproduced above). His two wax originals (heavy and light counterweights) were then burnt out in the investment casting process to produce the requisite metal casting patterns. These were then vulcanized in a rubber mold, and subsequent wax patterns, or "burn-outs" as they were known, were produced by injecting the rubber molds with wax. The copies generated from these burn-outs became the production driver centers, which are a cast in a variety of bronze alloy, suitable for machining.

The machining and fitting of the driver centers to plain steel 73" driver tyres was done by the late Mr. Doug Cockerham in his shop outside of Houston. Doug faced both sides of the driver centers, turned them to the proper OD, and drilled the axle holes using his lathe's tailstock. He also made a cup-like jig for pressing the centers into their respective tyres. Each axle is turned from 1/4" mild steel and is shouldered. Since these locomotives are to be compatible with 2-rail electric operation, each tyre is electrically isolated from its driver center using a thin section of .005" mylar, pressed between the tyre and the driver center.

Mr. Cockerham also made use of an unusual method for quartering his drivers: He set up his tool post on his lathe as a 90 degree stop, used a block of squared material placed upon the carriage cross-slide as a second stop, and then placed the driver centers, lightly held by their respective axles, between two spring-loaded plungers. Like a dead centers used in lathe work, each plunger is held either by a fixture mounted in a collet in the lathe headstock, or by a Jacobs' church in the tailstock. The crankpins, having been pressed into each driver center, were then aligned against their respective rests at 90 degrees from one another, and the whole assembly then gently pressed together using the tailstock ram. This is all very different from my own method, which was to build a substantial quartering jig (more on that in another part of this website in the future).

The Frame & Chassis

The frame for Doug's first M-68 4-8-4, #1801, was manually milled by him the hard way--on a desktop Mini-Mill! Frames for locomotives #2, #3 and #4 were milled by a commercial machine shop in San Diego, CA and then trued up by Doug Cockerham. Initially, since the completed drivers were not yet available, Doug turned simple aluminum discs in order to continue work on the rest of the chassis as well as the boiler and cab. Frames were milled from 1/4" thick brass flats, with slots for separate "hat" style axle boxes, each of which houses a ball-bearing. Suspension is by coil springs placed above each axle box. Like many large scale brass models, there is no working equalization, only springing (a dummy spring rigging is attached to each frame at a later point in construction). Sufficient clearance is allowed for each leading and trailing truck to swing in an uninhibited arc about their respective attachment points. The goal has been to engineer the locomotive to negotiate a 18' minimum radius curve (see last pic below right).

The Drive Train

Each frame is matched up with a Pittman 14000 series 24 volt DC motor and a custom-made Rino Mechanical worm gearbox. A set of brass & delrin universals, from W. M. Berg, complete the drive train. Since a multi-thread worm is used, the mechanism is able to freewheel, enough to allow for a shop goat to hostle the M-68 dead. Power is delivered to the motor leads through the Airwire control system from rechargeable ni-cad batteries.

Cylinders, Lead & Trailing Truck

Doug used plain steel 36" wheelsets for his lead, trailing & tender trucks as offered by my friend Don Niday. The lead truck is fabricated from brass and is attached via an arm from a point just ahead of the #1 driver. The trailing truck is a music wire reinforced urethane casting as are the cylinders. The pilot and air pump shields were built up from various bits and pieces of brass.

Valve Gear, Hangars & Misc. Suspension

Several of the valve gear and rod patterns were made not by Doug, but by two of his Houston area friends. Ward Hammond laser cut the main, side rod, and the valve gear patterns from styrene. Doug Cockerham made the valve guide and hangar as well as the brake shoe and hanger patterns. Doug Hemmeter created patterns for the M-68's crosshead, crosshead guide and all of the power reverse parts. The various styrene patterns were then burned out and cast in white bronze by Mr. Dennis Mashburn (KD Castings) in Abilene, Texas. Dennis is a master at what he does--and an O scale model railroader as well, so he understands what a multiple bearing crosshead is without batting an eye! Here's a smattering of pics showing all the bits and pieces coming together to make a chassis.

The Completed Chassis

Boiler & Cab

The oiler and cab on Doug's locomotives are made from a combination of ABS tube, overlaid with a thin sheet of brass embossed with rivet detail where appropriate, various styrene shapes to made up the cab and firebox sides, and then urethane castings for the domes. The stack is a brass investment casting made by Bill Brisko and cast by Trackside Details. What appears to be a cardboard mock-up of the boiler is actually an overlay for a brass wrapper which surrounds the inner acrylic tube. Each rivet is a Tichy Train Group plastic rivet, about 500 of which are in each boiler, with an additional 300 in the firebox. The bottom row of pictures in this section shows Doug's progress as of February 2008.

The (Nearly) Completed Locomotive

As of January 2009, the first M-68, #1801, is almost done, save for electronics, sound system, lighting, and a small smattering of detail parts. Want one? Check out the first video clip below of the 1801 on the test stand. And then drop Doug a note at whemmeter@sbcglobal.net

Standard vs. Narrow Gauge

So why build a large standard gauge locomotive when only a handful of people have an outdoor track large enough to run it on (and even fewer an indoor one)? Part of the explanation is the stark contrast in size between standard gauge and narrow gauge. Pictured below is Doug's first M-68 at various stages of construction pictured next to a D&RGW narrow gauge K-27 2-8-2. The difference speaks for itself. Anyone ready to build the F scale version of John Allen's Gorre and Daphetid Railroad with walk-through scenery?

These excellent photos are the work of Mr. Bob Werre. My thanks go to Doug and to Mr. Werre for allowing me to share Doug's fabulous work with fellow model builders and F scale enthusiasts.

Last update: 29 September 2009