1. Estimate one load case
Use the calculator’s stated assumptions to get a first-pass gravity moment.
It is not inverse dynamics and does not include measured joint forces.
Robot actuator sizing tool and RFQ guide
105 Nm Torque Robot Actuator Sizing Tool
A 105 Nm robot actuator load-screening guide with a simplified gravity-moment tool, QDD evidence limits, joint integration risks, and RFQ inputs.
Sizing and evidence105 Nm target-class screening with interactive load match and RFQ caveats.
Page reviewed October 9, 2026. Supplier-reported values remain unverified until matched to a signed configuration-specific datasheet.
105 Nm robot actuator joint load screen
Estimate one gravity moment from explicit assumptions. This is not inverse dynamics or a product safety check.
Robot layout
Loaded support count
Assumes equal load sharing across the selected supports. Choose the stance count from your own gait or load analysis.
35 kg
15 kg150 kg
0.30 m
0.15 m0.80 m
Assumed load multiplier
These are user-selected scenario multipliers, not measured gait factors or a validated impact model.
Scenario gravity-moment estimate
103.0 NmAt or below supplier-reported torque target
Page torque target105 NmSupplier-reported target class; rating and configuration are not independently verified.
Continuous thermal suitabilityNot assessedRequires RMS duty cycle, speed, and measured thermal data.
Method and limits
Torque = mass × 9.81 m/s² × lever arm × selected load multiplier ÷ loaded support count. The model assumes equal load sharing and omits robot geometry, joint dynamics, speed, impact, and transmission losses.
This scenario estimate is at or below the page’s supplier-reported torque target under the selected assumptions. It is a coarse gravity-moment comparison, not a prediction of joint peak torque or proof of actuator suitability; validate against trajectory torque-speed analysis and supplier test data.
Request configuration data review
Bring the load cycle, joint geometry, speed range, and thermal limits to the RFQ.
What the 105 Nm target does and does not tell you
The source page identifies a 105 Nm target class. Other performance and configuration details need signed, configuration-specific evidence before selection.
Published target
105 NmSupplier-reported target class; rating definition and operating conditions require confirmation.
Continuous rating
Not specifiedRequest the rated curve, duty profile, and thermal test conditions.
Reduction ratio
Not confirmedConfirm the quoted reduction ratio and assembly drawing.
Independent verification
Not suppliedRequest signed datasheets and test records before design freeze.
Performance Boundaries & Application Limits
A 105 Nm target alone does not establish fit for a robot joint. Review the complete load profile and verified data for the exact actuator configuration.
1. Application Fit
No universal joint application can be approved from a peak torque label. Compare the robot’s inverse-dynamics torque-speed profile, duty cycle, impact cases, and verified actuator limits before deciding whether the target is sufficient.
2. Thermal Saturation
The 105 Nm target does not establish a continuous rating. Pulse duration, duty profile, ambient, mounting, and cooling conditions are not documented here. Request measured torque-speed and thermal data for the quoted configuration.
3. Transparency vs. Backlash
Ratio can affect reflected motor inertia, but it does not by itself establish backdrivability, backlash, or impact capacity. Request measured lost motion, friction, stiffness, and shock limits for the exact assembly, then compare those values with the control and positioning requirements.
4. System Integration Reality
A configuration-specific mass and included hardware list are not published here. Confirm mass and interface boundaries from the drawing and BOM; separately validate housing and bearing loads for the joint.
A screening estimate needs load assumptions and measured limits
2. Ask for the torque-speed curve
Voltage alone does not establish usable torque at a target speed.
3. Validate risks before selection
- Load: trajectory torque and impact cases
- Thermal: RMS duty cycle, ambient, and heat path
- Transmission: ratio, backlash, efficiency, and shock limits
- Controls: bus, feedback, current limits, and fault behavior
ISO 6336 can inform gear rating calculations for applicable gear geometries; it does not certify an assembled actuator.
Separate supplier targets from verified selection data
The available page baseline is incomplete. Use this table to structure an RFQ and avoid treating missing configuration data as a confirmed product specification.
| Item | Current evidence | Request before selection |
|---|---|---|
| Published target class | 105 Nm supplier-reported target; rating and conditions not independently verified | Signed torque-speed curve, peak duration, voltage, and current limit |
| Continuous torque | Not specified for a signed configuration | Measured duty-cycle curve, ambient, mounting, cooling, and winding temperature |
| Backlash & Precision | Configuration-specific value and test method not supplied | Measured backlash or lost motion under stated torque, direction, temperature, and endurance conditions |
| Backdrivability and impact capacity | Not established by the ratio options alone | Measured backdrive torque, friction, permissible shock load, and the associated test method |
| Mass and ratio | Not confirmed for a signed configuration | Configuration-specific drawing and definition of included cables, driver, and hardware |
| Speed and efficiency | Not established by the available evidence | Measured torque-speed and efficiency maps at the selected bus voltage |
| Transmission and lifetime | Gear material, backlash, shock limit, and life data not supplied here | Gear drawings, material certificates, rating method, and endurance test profile |
| Electronics and feedback | Bus voltage, fieldbus, encoder, and fault behavior are configuration-specific | BOM, interface control document, firmware limits, and fault-response evidence |
Choose from the joint’s control and load requirements
QDD / low-ratio actuator
Consider where dynamic interaction and backdrivability matter. Confirm friction, impact capacity, thermal duty, and torque-speed data for the quoted build.
Higher-ratio reducer
Compare when output speed, static load, stiffness, or packaging favors greater reduction. Measure reversibility, backlash, and shock limits for the exact assembly.
Series elastic actuator
Consider when intentional compliance and force sensing justify extra spring dynamics. Validate deflection, bandwidth, and fatigue against the task.
Risks and mitigation
Peak torque overuse
Do not use a peak target as a continuous rating; request pulse duration and measured curve.
Thermal mismatch
Provide the RMS torque-time profile, speed, ambient, and mounting conditions for a thermal test.
Configuration mismatch
Match the signed datasheet and drawing to bus voltage, ratio, feedback, and quoted batch.
How support-count assumptions change the estimate
These are formula examples only. They are not customer deployments, gait predictions, or actuator test results.
Biped, one support leg
Illustrative inputs: 35 kg total mass, 0.30 m effective perpendicular lever arm, 1.0× load multiplier, and one loaded support.
35 × 9.81 × 0.30 × 1.0 ÷ 1
The simplified estimate is 103.0 Nm. This is a formula example, not a gait prediction or actuator suitability result.
Quadruped, two support legs
Illustrative inputs: 50 kg total mass, 0.40 m effective perpendicular lever arm, 2.0× load multiplier, and two loaded supports.
50 × 9.81 × 0.40 × 2.0 ÷ 2
The simplified estimate is 196.2 Nm. The selected support count and load multiplier must match the buyer’s trajectory analysis.
Same quadruped, four support legs
Illustrative inputs: same 50 kg mass, 0.40 m lever arm, and 2.0× multiplier, but four equally loaded supports.
50 × 9.81 × 0.40 × 2.0 ÷ 4
The estimate is 98.1 Nm. The difference illustrates the load-sharing assumption; it does not establish that four legs share load equally in a real gait.
Sizing, limits, and evidence to request
Does 105Nm torque mean continuous or peak?
The linked supplier page identifies a 105 Nm target class but does not establish whether it is peak, stall, or continuous for a signed configuration. Confirm the torque-speed curve, peak duration, duty cycle, voltage, and thermal test conditions before using the value.
How does QDD compare to harmonic drive at 105Nm?
There is no universal winner from torque rating alone. Compare the quoted assemblies on ratio, output speed, measured backlash or lost motion, friction, torsional stiffness, shock limits, mass, and thermal duty. Request configuration-specific test data; architecture labels do not establish impact resistance or precision.
Is a 105Nm QDD actuator sufficient for a full-size humanoid knee?
A 105 Nm label alone cannot answer that. Check the knee’s inverse-dynamics torque-speed profile, duty cycle, thermal limits, impact cases, and the supplier’s verified configuration data. This page’s simplified gravity-moment screen is not a humanoid-joint sizing result.
What is the expected backlash for a 105Nm QDD actuator?
A configuration-specific backlash or lost-motion value is not available here. Ask for the measurement method, applied torque, direction, temperature, and any endurance change; then compare it with the positioning and force-control needs of your application.
Engineering boundaryThis first-pass gravity estimate does not replace inverse-dynamics analysis, a signed torque-speed curve, thermal testing, or prototype validation under the intended load cycle.
Data Sources & Evidence Ledger
Public engineering references support the architecture discussion. The QDD-105 figures are supplier-reported page baselines and are not independently verified. Source references were checked October 9, 2026.
Ref [01]Supplier product-page target class
Product page checked October 9, 2026; signed datasheet not published · Supplier-reported target class, not independent test evidence
Scope: The page identifies a 105 Nm target class but does not establish whether it is peak, stall, or continuous, or the speed and duration for a specific assembly. Request a revision-controlled curve and test conditions.
Ref [02]Proprioceptive Actuator Design in the MIT Cheetah: Impact Mitigation and High-Bandwidth Physical Interaction for Dynamic Legged Robots
Published 2017; reference checked October 9, 2026 · Peer-reviewed actuator design study for the MIT Cheetah
Scope: Shows application-specific motor and gear-ratio trade-offs for a dynamic quadruped. It does not establish torque, backlash, or continuous-duty benchmarks for this supplier module.
Ref [03]ISO 6336-1:2019, Calculation of load capacity of spur and helical gears
Current edition confirmed October 9, 2026 · Gear-rating method and scope
Scope: Provides calculation methods for cylindrical spur and helical gears; ISO states that these methods do not assure performance of an assembled drive system.
Next step
Request evidence for your exact joint
Include the operating point and the configuration evidence you need so the supplier can respond with a testable proposal.
Robot mass, joint geometry, trajectory, peak torque, and speed range
RMS torque-time profile, ambient temperature, mounting, and cooling
Bus voltage, current limit, feedback, fieldbus, and fault requirements
Signed datasheet, torque-speed curve, drawing, and relevant test reports
Contact engineering and request a quotation
Inquiry Email
Include robot type, joint location, torque/speed/voltage targets, quantity, and destination.
Instant Chat
+86 18857971991
Send QDD actuator specs, STEP files, or actuator references for engineering review.