GearCalc Pro vs PDF Key

GearCalc Pro is the most professional gear ratio calculator and 3D simulator for hobbyists, makers, and engineers working with motorized projects. WHAT IT DOES - Calculate exact gear ratios for any motor + target speed/torque - Auto-suggest optimal gear teeth combinations across 1-6 stages - Real-time 3D visualization of compound gear trains with proper meshing - Simulate gear rotation at adjustable input RPM with live output display - Battery life estimation across 11 battery types - Reverse motor finder - given target RPM/torque, find the best motor MOTOR LIBRARY (18 models) - Ultra Micro: N10 - Micro: N20, N30, GA12-N20 gearmotor - Small: TT, DC 130/FA-130, DC 180, DC 260, DC 280 - Medium: DC 380, RS-540, RS-545, RS-550 - Large: RS-775, RS-895 - BLDC: 2208 drone motor - Stepper: NEMA 14, NEMA 17, NEMA 23 - Servo: SG90, MG996R - Custom motor input - add your own specs ENGINEERING FEATURES - Standard gear theory: D = teeth x module - Per-stage efficiency (Spur, Helical, Worm, Bevel, Planetary) - Gear pair recommendations from 21 standard tooth counts (8T to 120T) - Worm gear support with 1/2/4-start configurations - Standard ISO modules (0.3 to 4.0) - Motor dimension diagrams with shaft, bore, and mounting specs - Save/load configurations 3D VISUALIZATION - Real PBR-rendered gears with metallic shading - Color-coded stage badges - Auto-fit camera, free 3D rotation - Reset view to recenter - Start/stop animation with physics-correct rotation 8 LANGUAGES Traditional Chinese, English, Simplified Chinese, Japanese, Korean, Spanish, French, German. EXPORT - Generate spec sheet image - Copy text spec to clipboard - Share via standard iOS share sheet Whether you're designing a robot, toy, RC car, 3D printer, or CNC machine, GearCalc Pro gives you the math, the visualization, and the engineering data in one beautifully designed app.

PDF Key is a simple app for adding an open password to PDF files. Choose a PDF, enter a new password, and save it as a password-protected PDF. If the selected PDF is already password-protected, you can unlock it with the current password first. Leave the new password blank to export a PDF without a password. PDF Key does not include editing, merging, splitting, OCR, scanning, cloud sync, or password recovery features. It is focused on one job: protecting PDFs with a password. Features: ・Add an open password to PDFs ・Open password-protected PDFs ・Export without a password by leaving the new password blank ・Save as a new file without overwriting the original ・On-device processing ・No account