A reduction ratio changes the ideal speed–torque relationship. Actual output capacity still needs efficiency and the identified gear arrangement.
Separate kinematics from capacity
KHK's gearbox information lists ratio, torque and transmission-efficiency data as distinct quantities. Their separate presentation reflects different questions in a drive comparison. Primary reference: KHK gearbox technical information.
A reduction ratio defines the relevant speed relationship under its convention. In a simplified steady power balance, ideal torque multiplication follows that reduction, while efficiency accounts for modeled loss. The resulting arithmetic is not a replacement for the gearbox's permitted torque and duty ratings.
A hypothetical ratio-and-loss model
Assume a fictional 4:1 speed reduction, 2 N·m input torque and an explicitly assumed 90% transmission efficiency for the stated condition. The simplified output estimate is 2 × 4 × 0.90 = 7.2 N·m, compared with an ideal loss-free 8 N·m. The ratio did not establish the actual permitted output rating.
Make columns for ratio convention, input condition, assumed efficiency, modeled output and actual capacity reference. These invented inputs specify no HM reducer and no expected loss for a particular product. A transient or other duty may need a different assessment.
Request the complete operating case
Ask how efficiency and permitted torque relate to speed, loading and the selected configuration. Preserve those conditions instead of treating a headline efficiency as universal. Keep the shaft connections and other transmission elements within the complete drive review.
If an alternative ratio is proposed, examine its effect on required speed and torque together. Do not rank offers by multiplication factor alone. The final worksheet should distinguish a transparent model estimate from catalog capacity and from observed performance. Each can be useful, but none should be renamed as another.
Customer Questions
Does ratio alone establish gearbox torque capacity?
No. Capacity and duty require the identified gearbox rating basis.
Are the model's 90% and 7.2 N·m actual product values?
No. They are explicitly assumed teaching values.
Why retain the ratio convention?
Input/output conventions must be clear to interpret reduction, speed and torque correctly.
Primary References
These references support the technical principles discussed in this guide. The worked examples and review questions are educational.
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