A timing belt drive is a positive-engagement transmission — the belt's teeth mesh with the pulley's grooves, so torque transfers with no slip. Profile choice (HTD, GT, T, AT) decides how much torque the drive can carry and how quietly it runs. Get it wrong and the belt ratchets under load, wearing both belt and pulley in weeks.
SEC. 01
Compare the profiles
- HTD (Gates 3M/5M/8M/14M) — curvilinear, high torque, industrial standard.
- GT (Gates 2GT/3GT/5GT/8MGT/14MGT) — modified curvilinear, higher torque and quieter than HTD.
- T (T2.5/T5/T10) — trapezoidal, moderate torque, common in Europe and precision positioning.
- AT (AT5/AT10/AT20) — reinforced trapezoidal, high torque, low backlash for servo drives.
SEC. 02
How to size a synchronous drive
Start with motor power and driven-shaft speed. Multiply power by a service factor from the manufacturer's chart (1.4–2.2 for typical industrial duty). Read pitch, belt width and pulley diameter off the sizing chart at that adjusted power.
Always confirm the smaller pulley has at least 6 teeth in engagement with the belt — anything less and the drive is under-sized regardless of the calculated horsepower.
SEC. 03
Materials and mounting
- Aluminium pulleys — light, low inertia, standard for servo drives.
- Steel pulleys — heavy-duty industrial drives above 5 kW.
- Taper-lock bushings — quick installation and removal on production lines.
- Flanged both sides on driven pulley — keeps the belt tracking on inclined drives.
Key Takeaways
- HTD is the industrial default; GT beats it on torque and noise.
- AT profiles are the safe pick for servo and positioning duty.
- Minimum 6 teeth in engagement or the drive will jump under load.
- Flange the driven pulley on both sides to keep the belt tracking.