KEVOS® MAKEOS · Strength
Hand Lever Design Check (Effort, Fulcrum Reaction, Arm Bending, Fulcrum Pin)
For a hand or foot lever carrying one or more loads, what effort does it take, and are the lever arm and the fulcrum pin strong enough?
Check of a lever of any class: the effort at the effort arm or the arm needed for a given effort, the mechanical advantage and the fulcrum reaction (as the lever force tool), the largest bending moment along the lever and the bending stress in a rectangular arm, and the double shear stress and bearing pressure of the fulcrum pin from the reaction, against your allowable stresses.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Solve for | choice | Find the effort for a given arm, or the arm for a given effort. |
| Lever type | choice | Where the fulcrum sits relative to the effort and loads. |
| Effort arm (fulcrum to effort) | mm | Distance from the fulcrum to where the effort is applied. |
| Available effort (arm mode) | N | Effort available (arm mode). |
| Loads (distance from the fulcrum; 0 = unused) | ||
| Load 1 | N | Load 1. |
| Distance 1 | mm | Distance of load 1 from the fulcrum. |
| Load 2 | N | Load 2 (0 if unused). |
| Distance 2 | mm | Distance of load 2 from the fulcrum. |
| Load 3 | N | Load 3 (0 if unused). |
| Distance 3 | mm | Distance of load 3 from the fulcrum. |
| Arm and pin | ||
| Arm thickness | mm | Thickness of the rectangular lever arm. |
| Arm depth (in the plane of the loads) | mm | Depth of the arm in the plane of bending (at the most stressed section). |
| Allowable bending stress | MPa | Allowable bending stress for the arm material. |
| Fulcrum pin diameter | mm | Diameter of the fulcrum pin. |
| Allowable pin shear stress | MPa | Allowable shear stress of the pin (double shear). |
| Allowable bearing pressure | MPa | Allowable bearing pressure between pin and lever (lower for a bushed or greased pivot that moves). |
Method and formulas
- Effort = Σ W a ÷ x (or arm = Σ W a ÷ F); reaction = F + W for the first class, |W − F| otherwise (as the lever force tool).
- Bending moment found at the fulcrum, each load and the effort; arm stress = 6M ÷ (b h²).
- Pin shear = 2R ÷ (π d²) in double shear; bearing = R ÷ (d b).
- Example: 133.33 N effort; 80 N·m bending gives 53.333 MPa in the arm; the pin carries 933.33 N.
Limitations
- Uniform rectangular arm at the most stressed section; tapered arms need the depth at that section.
- Static load; add a factor for jerks and people standing on pedals.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Size a hand lever or foot pedal
- Check a clamping lever on a fixture
- Check the fulcrum pin of a toggle or brake lever
Who it is for
- Design engineers
- Toolmakers
- Fixture designers
What you get
- Effort, arm, advantage and fulcrum reaction
- Largest bending moment and arm stress
- Fulcrum pin shear and bearing
Interpreting the result
- The largest moment is at the fulcrum for a first-class lever and under a load for second- and third-class levers.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 167–168, 257–270. Topic reference; no source tables or recommended settings are reproduced.
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Open the Hand Lever Design Check (Effort, Fulcrum Reaction, Arm Bending, Fulcrum Pin) calculator
