Two tooth counts are enough to determine an ideal ratio, but not enough to choose or manufacture a working gear pair. Real gears must share compatible tooth geometry and operate within material, lubrication, alignment, load, speed, and service constraints. GearTrain deliberately stops before those questions so a clean arithmetic result is not mistaken for engineering approval.
Compatibility needs more than tooth counts
Module or diametral pitch, pressure angle, helix angle, profile shift, center distance, face width, backlash, tooth form, and manufacturing tolerance all affect whether two gears can mesh. Even equal ratios can come from physically different and incompatible pairs. Use the drawing, catalog, standard, or manufacturer calculation that controls the actual parts instead of inferring geometry from a ratio.
Ratio does not predict usable torque
An ideal reduction is often described as multiplying torque, but usable output depends on efficiency, tooth and root stress, contact stress, material, heat treatment, shaft and bearing capacity, lubrication, alignment, shock, duty cycle, and a suitable safety factor. GearTrain omits torque entirely rather than multiplying an entered value by a ratio and presenting that number as available mechanical output.
Ideal RPM is not a safe operating speed
The RPM result follows only the kinematic ratio and assumes the input speed remains as entered. It does not check pitch-line velocity, balance, vibration, critical speed, lubrication regime, temperature, noise, enclosure, guarding, or motor behavior under load. Confirm maximum permitted speed and every installation constraint from the current technical data before operating a physical mechanism.