Loading...
Enter your chassis conditions first to get ratio, torque, and shaft-fit direction. Then use the report layer to validate boundaries, compare options, and avoid interface mistakes between 12 mm and 1/2 in ecosystems.
These summary blocks are decision-first. They convert tool outputs and evidence boundaries into practical procurement direction for 1/10-scale planetary drivetrain builds.
Run calculator to generate a ratio recommendation and sample window.
Use this as a candidate window, not a final procurement lock.
1/2 in is exactly 12.7 mm, which is not equal to 12.0 mm hub ecosystems.
Direct-fit assumption is unsafe when ecosystem standards are mixed.
Shaft-stress risk is unresolved until required torque and shaft diameter are entered.
High startup torque or undersized shaft pushes fit from pass to watch/fail quickly.
Public data is enough for screening, not enough for fatigue sign-off.
Complete sign-off still needs supplier curves and instrumented endurance runs.
| Condition | Applicable | Not applicable | Action |
|---|---|---|---|
| Ratio screening | Candidate window inside 6.3:1 to 150:1 | Required ratio above 150:1 | Raise motor torque or lower speed/grade demand. |
| Shaft interface | Native 12 mm stack or native 1/2 in stack | Mixed parts without tolerance-verified adapter | Use validated adapter and runout check. |
| Startup transient | Measured startup within controller/battery limits | Unknown or repeated overcurrent protection trips | Tune ramp and gather current traces before RFQ. |
| Evidence quality | Supplier curve + endurance data available | Catalog-only numbers with no duty test evidence | Require bench report and thermal run before sign-off. |
Scenario zones summarize where teams usually move from speed-first designs to torque-reserve designs. Treat this as routing logic, then confirm with your own duty-cycle telemetry.
New evidence gain (stage1b): published 1/10 fitment pages show that hub standards vary by platform. Do not infer 12 mm or 1/2 in compatibility from scale label alone.
| Platform | Hub size | Official fitment evidence | Decision impact |
|---|---|---|---|
| ARRMA VORTEKS 223S BLX 4X4 (1/10) | 12 mm | ARAC9410 wheel-hex fitment list | Scale label alone does not imply compatibility with 12.7 mm (1/2 in) shaft stacks. |
| ARRMA BIG ROCK 223S BLX 4X4 (1/10) | 14 mm | ARAC9442 wheel-hex fitment list | Even inside 1/10 class, interface standards vary and must be verified before RFQ. |
If your ratio window is clear but shaft interface or startup risk is still uncertain, send the current inputs now. We can map a short supplier-ready candidate list before you commit bench budget.
This layer explains how the tool result is constructed, what is known vs unknown, and what trade-offs matter when choosing a planetary ratio and shaft standard for 1/10-scale robots.
| Step | Equation | Why it matters |
|---|---|---|
| Traction force | F = m(a + g sinθ + Crr g cosθ) | Captures acceleration, slope load, and rolling resistance in one force target. |
| Wheel torque | T = F x r | Converts force demand into drivetrain torque demand at the wheel. |
| Ratio by torque | Ratio = (Twheel x SF / eta) / Tmotor | Protects against under-torque sizing when load spikes or duty drifts. |
| Ratio by speed | Ratio = motor rpm / wheel rpm | Prevents selecting ratios that cannot reach target vehicle speed. |
| Shaft stress screen | tau = 16T / (pi d^3) | Flags early shaft-overload risk before detailed fatigue analysis. |
More stages can provide higher ratios but can reduce net efficiency and push thermal demand upward. New dataset check: maxon GPX 42 UP stage data (2025) extends ratio reach to 1526:1, but with lower efficiency and larger package size.
New factual increment (checked 2026-05-12): same-family stage data shows where higher ratio availability trades against efficiency, backlash, and package mass.
| Stage | Ratio band | Max efficiency | Avg backlash | Max cont. torque | Max radial load | Length | Mass | Decision note |
|---|---|---|---|---|---|---|---|---|
| 1-stage (UP) | 3.9:1 to 5.3:1 | 96% | 0.3° | 45 Nm | 350 N | 48.0 mm | 400 g | Lowest loss and smallest package, but limited ratio reach. |
| 2-stage (UP) | 16:1 to 35:1 | 93% | 0.4° | 80 Nm | 525 N | 67.0 mm | 540 g | Balanced for many builds; moderate size and loss increase. |
| 3-stage (UP) | 62:1 to 231:1 | 90% | 0.5° | 120 Nm | 750 N | 86.0 mm | 660 g | High ratio access with clear backlash and packaging penalties. |
| 4-stage (UP) | 243:1 to 1526:1 | 87% | 0.6° | 120 Nm | 750 N | 104.5 mm | 790 g | Counterexample to the 150:1 planning window; feasible but usually heat- and size-sensitive. |
| Scenario | Mass | Target speed | Grade | Likely ratio zone | Outcome note |
|---|---|---|---|---|---|
| Track sprint, light payload | 5 kg | 4.2 m/s | 5% | 12:1 to 22:1 | Speed-prioritized; verify startup spikes before race tuning. |
| General 1/10 exploration rover | 7-8 kg | 2.8-3.4 m/s | 10-15% | 24:1 to 45:1 | Balanced zone for torque headroom and controllable heat. |
| Crawler-style high climb | 8-10 kg | 1.2-2.0 m/s | 25-35% | 55:1 to 110:1 | Use lower speed and higher ratio; watch gearbox efficiency drop. |
| Payload + coarse terrain + tight accel | 10-12 kg | 2.0-2.8 m/s | 20%+ | 90:1 to 150:1 | Upper ratio boundary zone; verify thermal rise and shaft stress. |
| Option | Ratio band | Shaft interface | Known strength | Main risk | Best fit |
|---|---|---|---|---|---|
| 6 mm motor shaft + 12 mm hex adapter | 6.3:1 to 70:1 common | 6 mm D shaft to 12 mm hex wheel | Large ecosystem and easy wheel sourcing | Adapter/set-screw loosening under repeated reversals | Prototype and fast iteration builds |
| 12 mm direct output planetary | 10:1 to 150:1 common | Direct 12 mm output, fewer stacked adapters | Lower interface count and better concentricity potential | 1/2 in ecosystem mismatch (0.7 mm dia gap) | Higher repeatability with 12 mm wheel ecosystem |
| 1/2 in (12.7 mm) output planetary | Application dependent | Native 1/2 in keyed/clamped hubs | Direct fit with 1/2 in drivetrain hardware | Weight and packaging penalty for small 1/10 chassis | Heavier or high-shock builds using 1/2 in driveline parts |
| Outrunner + external reduction | Custom (belt/spur/planetary mix) | Custom hub stack | Very high peak power density | Integration complexity and protection burden | Teams with strong controls/mechanical integration capability |
New decision-critical guardrail: this table uses published Pololu 37D 12V 50:1 data to show why startup telemetry matters before final ratio lock.
| Condition | Published value | Risk if ignored | Action |
|---|---|---|---|
| Continuous torque planning (Pololu 12V 50:1 example) | Recommended upper continuous load: 10 kg·cm (~0.98 Nm) | Sustained operation near stall heats motor/gearbox quickly and shortens life. | Keep continuous demand near validated thermal zone; verify with timed temperature trace. |
| Short burst / transient event (same model example) | Instantaneous upper load: 25 kg·cm (~2.45 Nm) | Repeated burst use can drive rapid wear or abrupt failure under shock loads. | Allow only brief bursts and set controller current/torque clipping for repeated cycles. |
| Startup current screen | Model stall current: 5.5 A at 12 V; practical screening target: <=25% stall current for routine operation | Battery sag, current foldback, and unstable acceleration make ratio results look better than reality. | Log current and battery voltage during launch; rerun tool with measured startup multiplier. |
Evidence-discipline update: where public evidence is insufficient, we explicitly mark pending status instead of overstating certainty.
| Boundary | Current rule | Evidence status | Next step |
|---|---|---|---|
| Fit-band shaft stress thresholds (watch/fail MPa) | Watch >70 MPa, fail >100 MPa (screening gate only) | Pending (待确认) | Replace with material-specific allowable stress from your shaft cert and fatigue case. |
| Default ratio window padding | Recommended ratio x 0.85 to x 1.20 for candidate sweep | Pending (暂无可靠公开数据 for universal multiplier) | Use at least one speed-priority and one torque-priority neighbor then bench-compare heat/current. |
| Risk type | Trigger | Impact | Mitigation |
|---|---|---|---|
| Misfit ratio | Torque ratio and speed ratio diverge too much | Either overcurrent or top-speed miss | Sample three adjacent ratios and run load trace. |
| Interface slip | Mixed 12 mm and 1/2 in parts without proper adapter | Backlash growth and steering drift | Use verified adapter stack and runout screening. |
| Shaft overload | High startup multiplier + small diameter shaft | Plastic deformation or early fatigue | Increase shaft section or reduce startup shock. |
A practical hybrid-page workflow: use tool output for immediate direction, then add evidence until the decision is robust enough for procurement lock-in.
| Source | Use | Scope | Checked | Confidence |
|---|---|---|---|---|
| NIST Handbook 44 (2026), Appendix C length conversions Published: 2026 edition | Anchors inch-mm conversion used for 1/2 in shaft checks. | Exact reference: 1 inch = 25.4 mm. | 2026-05-12 | Primary |
| Pololu 37D Metal Gearmotors category | Confirms common hobby/robotic gearbox ratio envelope and encoder availability. | Reference ratio band 6.3:1 to 150:1 for quick candidate windowing. | 2026-05-12 | Primary |
| Pololu 37D Metal Gearmotor datasheet (Rev 1.2) Published: Rev 1.2 PDF | Provides ratio-specific no-load speed and stall-torque examples for scenario sanity checks. | Benchmark only; final values must come from selected supplier curve and controller setup. | 2026-05-12 | Primary |
| Pololu 12 mm hex adapter for 6 mm shaft (item 2686) | Documents common 6 mm shaft to 12 mm hex interface seen in 1/10 RC wheel ecosystems. | Used to explain 12 mm ecosystem vs 12.7 mm (1/2 in) interface mismatch risk. | 2026-05-12 | Primary |
| maxon GPX 42 catalog page EN-405 (2025) Published: 2025 catalog page | Provides stage-by-stage ratio range, efficiency, backlash, radial load, length, and mass. | Used to quantify trade-offs when considering >150:1 ratios in one vendor family. Caveat: Do not treat this single-vendor trend as universal across every planetary gearbox platform. | 2026-05-12 | Primary |
| Pololu 37D 12V 50:1 gearmotor, item 4743 | Adds concrete continuous vs instantaneous load limits and startup-current guardrail language. | Used for first-pass startup and duty-cycle caution, not as a universal limit for all motors. Caveat: Numbers are for this model family and voltage setup; always replace with your selected motor curve. | 2026-05-12 | Primary |
| ARRMA 1/10 wheel hex 12 mm fitment page (ARAC9410) | Shows one official 1/10 platform using 12 mm wheel-hub interface. | Evidence that 1/10 naming does not guarantee 1/2 in shaft hardware. | 2026-05-12 | Primary |
| ARRMA 1/10 wheel hex 14 mm fitment page (ARAC9442) | Shows another official 1/10 platform using 14 mm interface. | Counterexample against assuming one fixed hub standard from scale label. | 2026-05-12 | Primary |
| RoyMech: Torsion equations for solid and hollow shafts | Provides the solid-shaft torsional shear equation used in boundary checks. | Secondary sanity check for tau = 16T / (pi d^3) modeling. Caveat: Equation is first-pass only and does not include keyway notch, fatigue spectrum, or shock factors. | 2026-05-12 | Secondary |
| NEMA motor terminology and performance characteristics | Supports startup/inrush planning language for current and torque transients. | Reference line: locked-rotor current can be multiple times full-load current. Caveat: This NEMA guide is broad and not specific to every 1/10 brushed gearmotor/controller pair. | 2026-05-12 | Secondary |
| DOE Small Electric Motors overview | Defines U.S. policy boundary around covered motor classes. | Compliance boundary reminder when comparing hobby and industrial motors. | 2026-05-12 | Primary |
| Evidence gap | Status | Reason | Action |
|---|---|---|---|
| Backlash growth after impact cycles in 1/10-scale off-road duty | Pending | Public datasets rarely expose backlash drift vs. crash/impact count under dust and vibration. | Run a controlled reverse-impact endurance test and log backlash every 2k cycles. |
| Real controller torque limit vs battery sag at high C discharge | Pending | Most open catalogs report nominal current but not foldback behavior under voltage droop. | Capture current/voltage traces with your target battery and ramp profile before freezing ratio. |
| Adapter concentricity and wheel wobble with mixed 12 mm and 1/2 in parts | Pending | Tolerance stack varies by wheel hub, adapter, and set-screw quality; no unified cross-brand table exists. | Measure runout at the wheel under assembled torque and qualify only proven adapter stacks. |
| Universal torsional-stress pass/fail limit for mixed shaft materials | Pending | No reliable public dataset maps one MPa threshold across all steel/aluminum shafts, keyway forms, and duty spectra. | Treat MPa gate as screening only; confirm with supplier material cert + fatigue test before release. |
FAQ is grouped by what engineering and sourcing teams actually need to decide next.
This hybrid page gives immediate directional output and the evidence context to avoid premature lock-in. If you want a supplier-ready stack, send your result and we can map candidate motors, ratios, and shaft interfaces to your actual duty profile.
Start inquiry opens your default email client with a prefilled RFQ template.