For selected handle torque T, axial pitch p and lumped efficiency η, conditional axial force is F = 2πTη/p. For effective handle radius L, the corresponding selected tangential hand force is T/L.
Where actuator force enters the Screw-clamp (handle and Lever Holder) Mechanism design
When screw-clamp (handle and lever holder) mechanism is driven by a linear actuator, the actuator force changes through the travel as the geometry changes. A comfortable static force number at one position can still leave the actuator overloaded near the start or end of stroke.
With leverage, force is traded against travel. A bracket change that improves force can also increase required stroke, slow the output motion, or move the actuator into a poor mounting angle.
A senior review would normally separate the required output force from the actuator force. Output force belongs to the mechanism; actuator force belongs to the installed geometry. Confusing those two numbers is one of the most common causes of undersized linear actuators.
- Calculate actuator force at the worst bracket angle, not just at mid-stroke.
- Check stroke, retracted length, and extended length against the mechanism envelope.
- Confirm the structure can accept the higher loads created by a stronger actuator.
For a FIRGELLI actuator application, run the FIRGELLI actuator force calculator, then compare available stroke, force, and mounting envelope in the FIRGELLI linear actuator range. If the goal is to replace an existing unit, use the linear actuator replacement finder before assuming the new actuator is a direct fit.
Selected-Torque Screw-Clamp Work Model
Explore selected-torque screw-clamp work balance, hand force, pitch travel and selected loss.
Equation Used
- Torque is selected at the handle axis.
- Pitch is ideal axial travel per revolution.
- Efficiency is a selected lumped work ratio.
- Handle length is the effective radius for the selected tangential force.
- Thread, collar, pad and frame stress, deflection, wear and ratings are excluded.
Do not treat the conditional axial force as a clamp rating.
Connected screw-clamp reference
The animation shows a handle connected to a translating screw, a fixed threaded boss, a swivel pad, held work and a rigid frame. One presentation revolution advances the screw by one selected pitch.
The force result is a selected-efficiency work balance; no thread-contact or component-stress model is present.
What the calculator determines
Select handle torque, axial pitch, lumped efficiency and effective handle radius. Outputs are conditional axial force, tangential hand force corresponding to T/L, travel per turn and selected loss percentage.
It does not calculate thread friction from geometry, clamp stiffness, frame load, thread stress, pad pressure, proof load or safe working load.
Selected-efficiency work balance
Input work per turn is 2πT. Conditional axial work is Fp, so F = 2πTη/p. Tangential hand force is Fhand = T/L, ideal travel per turn is p, and selected loss is 100−η.
Selected-input example
For T = 30 N·m, p = 1.75 mm/rev, η = 40% and L = 100 mm, conditional axial force is about 43.1 kN, corresponding tangential hand force is 300 N, ideal travel is 1.75 mm/rev and selected loss is 60%.
Scope and design boundary
Lumped efficiency is selected, not predicted. A friction-based screw model would require thread form, mean diameter, lead angle, friction coefficients and collar or pad losses. Real capacity is limited by every component.
The former page's different friction-angle equation, generic efficiency ranges, damage thresholds, measurement advice and unsupported maintenance claims are removed.
Questions
Is η calculated from the thread?
No. It is selected.
Does handle length change axial force at fixed torque?
No; it changes the tangential hand force needed to create that torque.
Is the conditional axial force a safe clamp rating?
No.
Can this diagnose a clamp?
No.
References & Further Reading
- Wikipedia contributors. Clamp (tool). Wikipedia
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