Hi Wikkedy86,

I'm quite sure that the Trix Big Boys were designed for RP25. But since you did not provide the part number it might be different.

From trixtrians.com

HO 2-Rail DC for North American Model Railroaders

Built specifically for North American 2-Rail DC model railroaders, the TRIX Big Boy #22594 has many special features and a level of craftsmanship only found previously in brass at a much higher price.

RP 25 wheel flanges
Kadee® coupler #18
DCC connector for locomotive decoder installation
Diecast metal locomotive frame, boiler, tender body and tender frame, weight over 2lbs. 10 ozs.
The largest HO steam locomotive ever built by TRIX; scale length 18-5/16"
High-efficiency can motor with bell-shaped armature and flywheel in the boiler
All driving axles powered
LED headlight, number board lights, tender backup light
Tender ready for installation of sound effects system to be offered later
Factory-ready for installation of two Seuthe #11 (Märklin #0901) smoke generators
Initial delivery to authorized dealers expected at the end of 2001
Manufacturer's suggested retail price $598.00


Description of the Model

Prototype: Union Pacific Railroad (U.P.) class 4000 "Big Boy", 4-8-8-4 design. No. 4013 as it looked around 1959.
Model: Era III, high-efficiency can motor with bell-shaped armature and flywheel in the boiler, diecast metal locomotive frame, boiler, tender body and tender frame, 8 axles powered, articulated frame to enable locomotive to negotiate sharp curves, Boxpok wheels, center driving axles are spring loaded. Headlight, backup light on tender and number boards come with maintenance-free LEDs. Close coupling between locomotive and tender; steam lines can swing out with the cylinders. Separately applied metal grab irons. Many separately applied details. Two Seuthe #11 (Märklin #0901) smoke generators can be retrofitted on the locomotive. Figures of a locomotive engineer and fireman for the cab included. Length over couplers: 18-5/16".

Important information about the operation of this locomotive: This locomotive can be used on curved track with a minimum radius of 360 mm / 14-3/16", but we recommend larger radius curves. Due to the overhang of this locomotive's long boiler, signals, catenary masts, bridge railings, tunnel portals, etc. must be set out further from the curved track for clearance. The track must be well mounted for the high weight of the locomotive.

Regards,

Michel

i have 2 trix older big boys 22594 display cases etc
and both have RP25 printed on the outer box
alan plymouth

Hi Wikkedy86,

Very tough question to answer because no where does it state what type of wheels are on this 22063 Big Boy!?

But I believe this would be a NEM (Normal European Modeling) Model.

My conclusion is derived from the lack of reference to the RP25 wheels and the Kadee® coupler #18.



That information I found was based on this:

USA

22063 Steam Locomotive with a Tender.

Prototype: Union Paci c Railroad (UP) class 4000 “Big Boy” heavy freight locomotive. Version with the road number 4020. The locomotive looks as it did around 1950. Model: The locomotive has an mfx digital decoder and extensive sound functions. It also has controlled high-ef ciency propulsion. 8 axles powered. Traction tires. The locomotive has an articulated frame enabling it to negotiate sharp curves. It also has Boxpok driving wheels. The middle driving axles are spring-loaded. The headlight, backup light on the tender, and the number board lights are maintenance-free, warm white LEDs. 2 smoke genera- tors (7226) can be installed in the locomotive; the contacts for them are on constantly. The headlight, backup light on the tender, and the number board lights will work in conventional operation and can be controlled digitally. The cab lighting can be controlled in digital operation. There s a powerful speaker in the tender and the volume can be adjusted. Coupler hooks can be inserted in the pilot on the front of the locomotive. There is a close coupling between the locomotive and tender. Steam lines are mounted to swing out and back with the cylinders. The locomotive has separately applied metal grab irons. There are many separately applied details. Figures of a locomotive engineer and reman for the engineer‘s cab are included.

Length over the couplers 46.5 cm / 18-5/16“.
The locomotive comes in a wooden case.
Coolers of the second production run in front of the smoke box.
Changes to the headlight.
mfx digital decoder included.
One-time series.
The image of this model is a retouched digital image.
Notes for operating this locomotive: The locomotive can be used on curved track with a radius of 360 mm / 14-3/16“ or more, however we recommend larger radii. Due to the overhang of the long boiler, signals, catena-ry masts, bridge railings, tunnel portals, etc. must be installed for suf cient clearance on curves. The track must be well mounted due to the heavy weight of the locomotive. The locomotive can only be run through a turntable or transfer table. Car sets to go with this locomotive can be found in the Märklin H0 assortment under item numbers 45659 and 45660.
This model can be found in an AC version in the Märklin H0 assortment under item number 37996.


I hope this helps,

Regards,

Michel

Answer from Marklin recieved.

There are NEM wheels on All Big Boy models except item number 22599.

Great to know :-)