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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.
Iniciar consulta abre tu cliente de correo predeterminado con una plantilla RFQ precargada.