Live Steam Locomotives

USRA 4-6-2 Heavy Pacific Live Steam Chassis-on-air

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Our 7 1⁄2 - inch gauge live steam USRA 4-6-2 Heavy Pacific is offered as a completed ready-to-run locomotive chassis-on-air.

We fully machine, paint or plate and assemble all of the castings and parts required to build a completed, working 4-6-2 locomotive "chassis-on-air."

Benefits of our chassis-on-air offering:

  • Ready-to-run chassis-on-air: Saves you time and mistakes, guarantees results
  • Precision CNC machined: Greater accuracy, better finishes, smoother running
  • Hardened and ground parts: Less wear, longer life expectancy
  • Powder coated: Long-term protection and durability
  • Fully assembled: Our experience saves you time and guesswork
  • Tested and adjusted: We make it run right before we deliver it
  • Ready for custom finishing by the hobbyist: Add your own finishing detail

The completed chassis includes the following assemblies:

4-6-2 Assemblies:

A USRA 4-6-2 Pacific under construction
USRA 4-6-2 Heavy Pacific chassis-on-air w/ boiler
A USRA 4-6-2 Heavy Pacific chassis-on-air with pressure-tested boiler. Click to enlarge.

 1. Frame
 2. Drivers & Axles
 3. Pilot Truck
 4. Trailing Truck
 5. Spring Rigging
 6. Brake Rigging
 7. Cylinders
 8. Valve Gear
 9. Side Rods
10. Main Rods

"Those chassis are beautiful...You have the right idea...I love the doing the finish work, but hate the tedious machining involved in building the chassis." - T.S., Lufkin, Texas

USRA 4-6-2 Heavy Pacific Chassis-on-air Specifications

Drivers: 17 Spoke x 10" Diameter
Cylinder Bore: 2.750" Diameter
Cylinder Stroke: 3.500"
Piston Valves: 1.500" Diameter
Overall Length of Frame & Pilot Beam: 71"


USRA 4-6-2 Heavy Pacific Optional Smoke Box and Boiler Specifications

Smoke Box: 10" Diameter
Boiler: Conical 10" Nominal Diameter (10 3/4" actual OD) x 45 Tubes


USRA 4-6-2 Heavy Pacific Chassis-on-air Quality Features

Castings: Top Quality Castings from Top Quality Commercial Foundries
Accuracy: Precision CNC Machine Work
Axles: Hardened and Ground
Axle Bearings: Needle Roller Bearings
Crank Pins: Hardened and Ground
Side Rod Bearings: Needle Roller Bearings
Main Rod Bearings: Needle Roller Bearings
Cylinder Block: One Piece Casting, Fully Cored Including All Intake & Exhaust Passages, Very Free Breathing
Baker Valve Gear Frame: Silicon Bronze Casting
Baker Valve Gear Internals: Stainless Steel Lost Wax Investment Castings
Spring Rigging: Fully Equalized Including Pilot Truck and Trailing Truck
Brake Rigging: Fully Equalized
Paint: Powder Coated


What is a "chassis-on-air"?

  • This stage of locomotive completion is what we call a chassis-on-air. The fully machined, painted, plated and assembled chassis-on-air can actually be "run" for testing or demonstration purposes by supplying compressed air to the cylinders.

    Testing the completed chassis by running it on compressed air confirms that all of the machine work and assembly of the locomotive chassis has been performed correctly before you move on to the next phase of construction.

    And more...

  • In addition to providing you with a chassis on air, we can also provide you with a completed and pressure tested boiler.

  • We can then put you in contact with a number of other qualified suppliers who specialize in a variety of additional items needed to complete your locomotive.

    Their offerings include everything from injectors, check valves, safety valves, water gauges, pressure gauges, pumps, hand rail components, etc., to completed tender tanks and even ready-to-run tenders.

Our chassis-on-air approach gets your
4-6-2 building project going fast and helps get you on the track sooner:
  • We realize that many first time builders get bogged down with the tedious precision machine work required to build their locomotive chassis. Consequently, we offer a solution that gives builders a "running" head start on their locomotive building project.

  • Our 4-6-2 Heavy Pacific is designed to put a high quality, CNC-machined chassis within the reach of hobbyists without requiring them to have either extensive machining experience or as elaborately equipped machine shops.

  • This approach allows you to custom finish and detail the rest of the locomotive and tender according to the railroad that you want to model after and your own desires.

"I received the cylinder casting set yesterday.  WOW! The castings are just excellent!  Fantastic castings; I couldn't be more pleased! They are definitely worth every penny!  Thank you so much!  I'm taking them to our central Illinois live steam meet today to show everyone." - J.R., Springfield, IL

4-6-2 Pacific modeled after an American prototype
USRA 4-6-2 Heavy Pacific
USRA 4-6-2 Heavy Pacific built from our chassis-on-air. Click to enlarge.

4-6-2 Pacific modeled after a Canadian prototype
4-6-2 Pacific
This Canadian model shows the versatility of our Heavy Pacific chassis. Click to enlarge.

Bob Dean's ERIE K5a 4-6-2 Pacific, 1942 revision
Built using some of our Pacific castings. Click to enlarge.

Proud engineer admires his newly completed Pacific
4-6-2 Pacific
Blowing down after successful first run. Click to enlarge.

Roger Goldmann * 413 Morrison Lane. * Santa Paula, CA * 93060 * USA