POWER TRANSMISSION
Calculate speed reduction, ideal torque multiplication and rotation direction for a pair of external spur gears.
Values are calculated locally in your browser.
Theoretical result · verify applicability below
Schematic illustration · not to scale
External gears rotate in opposite directions. Negative output speed denotes reversal. Torque is an ideal magnitude; friction losses are excluded.
A larger driven gear turns more slowly while multiplying ideal torque. The negative speed sign expresses the direction reversal across a single external mesh. Both gears must have compatible module or diametral pitch and pressure angle.
An input gear with 20 teeth driving a 60-tooth output gives i = 3. At +1,200 RPM and 10 N·m input, the output is −400 RPM with ideal torque magnitude 30 N·m.
The initial inputs reproduce this example. Material values are illustrative inputs, not a material database or certified design values.
One external spur-gear mesh with rigid teeth, no slip and 100% ideal efficiency. Tooth strength, undercut, interference, center distance, bearing loads and real drivetrain losses are not assessed. The diagram is schematic and does not specify tooth geometry.
No factor of safety or design-code allowance is applied unless explicitly stated. Read the engineering disclaimer before applying these results.
Confirm the load direction and units first. Check the schematic against your actual supports and geometry, then compare the worked example with your own independent calculation. A valid numerical result does not establish that the model is appropriate for a real component.
For background, consult the Air Force Stress Analysis Manual’s column analysis and MIT’s Mechanics of Materials learning modules. Use applicable design standards and certified material data for real designs.