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Torque Required in Lifting Load with Acme Threaded Power Screw Calculator

Torque Formula:

\[ M_{tli} = 0.5 \times d_m \times W \times \left(\frac{\mu \times \sec(0.253) + \tan(\alpha)}{1 - \mu \times \sec(0.253) \times \tan(\alpha)}\right) \]

m
N
rad
N·m

1. What is Torque Required in Lifting Load?

Definition: This calculator determines the torque needed to lift a load using an Acme threaded power screw, accounting for friction and screw geometry.

Purpose: It helps mechanical engineers and designers properly size power screws and select appropriate drive mechanisms.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ M_{tli} = 0.5 \times d_m \times W \times \left(\frac{\mu \times \sec(0.253) + \tan(\alpha)}{1 - \mu \times \sec(0.253) \times \tan(\alpha)}\right) \]

Where:

  • \( M_{tli} \) — Torque for lifting load (N·m)
  • \( d_m \) — Mean diameter of power screw (m)
  • \( W \) — Load on screw (N)
  • \( \mu \) — Coefficient of friction at screw thread (±5%)
  • \( \alpha \) — Helix angle of screw (rad)
  • 0.253 — Half of Acme thread angle in radians (14.5°)

Explanation: The formula accounts for the screw geometry (mean diameter and helix angle) and friction characteristics to determine the required lifting torque.

3. Importance of Torque Calculation

Details: Proper torque estimation ensures screw mechanisms can safely lift loads without failure and helps select appropriate drive motors.

4. Using the Calculator

Tips: Enter the mean screw diameter, load, friction coefficient (default 0.15 ±5%), and helix angle (default 0.0785 rad ≈ 4.5°). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Why is there a ±5% on friction coefficient?
A: Friction coefficients can vary due to material pairing, lubrication, and surface finish, so we indicate this uncertainty.

Q2: What's a typical helix angle for power screws?
A: Common helix angles range from 2° to 5° (0.035 to 0.087 rad) for most power screw applications.

Q3: How do I find the mean diameter?
A: For Acme threads: \( d_m = d - 0.5 \times p \) where d is major diameter and p is pitch.

Q4: What affects the coefficient of friction?
A: Material pairing (steel-bronze common), lubrication, surface finish, and operating conditions all affect friction.

Q5: Does this account for efficiency losses?
A: Yes, the friction coefficient and screw geometry account for mechanical efficiency in the calculation.

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