Tools
Online Laboratory
The RailForge Online Laboratory is a free suite of browser-based engineering calculators built for HO scale model railroading. Every tool runs entirely in your browser — nothing to install, no sign-up, nothing uploaded — and turns the real math behind a reliable layout into quick, practical answers. Work out whether a grade will pull your train, size DCC power districts and bus wiring, check curve overhang and siding capacity, program decoder CVs, or convert scale measurements, then take the numbers to the workbench.
Each calculator gives first-pass engineering insight to guide your build — confirm critical values against the manufacturer’s specs or the relevant NMRA standard before you commit.
New to the terms? Read the glossary → See it fail: case studies → See the data: experiments → The glossary derives every term the tools use; the case studies trace real failures from symptom to fix; the experiments put measured numbers behind the physics.
The math & the sources
The engineering behind the tools
These calculators are not black boxes. Each one runs a published standard, an accepted engineering formula, or a clearly labeled rule of thumb — the same references a prototype engineer or an experienced modeler would reach for. The figures below are the actual constants the tools compute with.
Flange climb is governed by Nadal’s formula: the limiting ratio of lateral to vertical wheel force equals the tangent of the flange contact angle. A steeper flange face tolerates more lateral force before the wheel climbs the rail.
Nadal’s single-wheel L/V limit (1908), applied in the Wheel–Rail Interface tool
| Quantity | Value / formula in the tool | Source |
|---|---|---|
| Recommended car weight (HO) | 1 oz base + 0.5 oz per inch of body length | NMRA RP-20.1 (Recommended Practice) |
| Wheel contour (HO mainstream) | RP-25 code 110: 0.110″ tread, 0.020″ flange depth, 63° face | NMRA RP-25 (Recommended Practice) |
| HO track gauge | 0.649″ between railheads | NMRA Standard S-3 (track, standard scale) |
| Decoder configuration (CV29) | Bitfield: speed steps, DC, long address (CV17/18), speed table | NMRA Standard S-9.2.2 (DCC CVs) |
| Turnout frog angle | angle = 2 · arctan(1 / 2N) for a #N turnout | Standard turnout geometry |
| Bus voltage drop | drop = 2 × length × (ohms/ft) × current; 14 AWG = 2.525 Ω/1000 ft | Standard AWG copper resistance table |
| Curve resistance (HO) | equivalent grade % ≈ 32 / radius (inches) | Accepted HO rule of thumb (not a formal standard) |
| Vertical easement | break angle = |arctan(g₂/100) − arctan(g₁/100)| | Vertical-curve geometry |
- NMRA Standards & Recommended Practices — the official S & RP documents (RP-20.1 weight, RP-25 and S-4 wheel contour, S-3 track gauge).
- NMRA RP-20.1 car-weight guidance — the weight recommendation the Scale Converter computes.
- DCC-EX documentation — open-source command-station reference for CV programming and the standard DCC CVs behind the DCC CV Assistant.
- RailForge teaching glossary — every term the tools use (tractive effort, adhesion, overhang, Nadal’s L/V limit, CVs, bus voltage drop), each derived from the physics behind it.
- Real Railroad Parallels — how these same standards and practices work on the full-size railroad (FRA track safety, AREMA, NMRA), mapped to the HO analog.