This wheel form tool is made from hardened tool steel using the highly accurate wire-EDM process. This tool is based on the RMI-25 profile, which is 100% compatible with the standard IBLS draft wheel profile, but corrected to provide better tracking and wear properties. It is highly recommended for all 2.5" scale and larger engines, and will work with any locomotive on 7.5" or 7.25" gauge rails, including the entire Allen Models lineup.
The advantages to the RMI-25 profile are as follows:
- The 15 degree taper on the outside edge of the flange and the larger inside radius keeps the flange from making a three point contact on the inside edge of the outer rail and reduces or eliminates the grinding off of the rail head.
- The 1/8" inside radius on the flange keeps the wheel further away from the head of the rail, making it harder for the wheel to pick and climb up over the rail.
- The slightly deeper flange (1/16 of an inch deeper, or .25" total) decreases the chances of derailment on twisted or uneven track, without interfering with the vast majority of cast switch frogs.
- The unnecessary 10 degree radius on the inside of the flange has been eliminated, thickening the flange and preventing climbing on frogs and close-set guards.
Dave Coster of Roll Models, Inc. has made the specifications for this profile available to the wider live steam community free of charge, in the hopes that it will be adopted as a new, backward-compatible standard. The full specifications for this standard are available in this PDF file.
This wheel form lathe tool is designed to provide cleanup of a rough-machined profile. Because there is a large contact area, it is recommended that this tool be run at very low speeds (60 - 70 RPM MAX) or hand-turned during the final phases of machining of the profile to remove chatter on less rigid machines.