Hoist Load Inputs
Example Data Table
| Scenario | Load | Rigging | Points | Angle | Speed | Shock | Safety | Design Load |
|---|---|---|---|---|---|---|---|---|
| Large hanging basket | 18 kg | 2 kg | 2 | 60° | Normal | Minor | 4.0 | ~101.2 kg |
| Raised bed panel lift | 45 kg | 4 kg | 3 | 45° | Slow | None | 3.5 | ~241.6 kg |
| Greenhouse fan removal | 32 lb | 6 lb | 2 | 30° | Fast | Moderate | 5.0 | ~712.4 lb |
Formula Used
First compute gross load: GrossLoad = LoadWeight + RiggingWeight
Apply multipliers to estimate a conservative design load:
DesignLoad = GrossLoad × DynamicFactor × ShockFactor × ConditionFactor × SafetyFactor
Sling angle increases tension per leg. With β as angle from horizontal:
AngleFactor = 1 / sin(β)
Required working load limit per leg is approximated as:
WLLperLeg = DesignLoad / (LiftPoints × sin(β))
How to Use This Calculator
- Enter the lifted item weight and any rigging weight.
- Select lift points and the sling angle from horizontal.
- Choose lift speed, shock level, and rigging condition.
- Set a safety factor that matches your uncertainty.
- Optionally add hoist rated capacity for utilization.
- Press Calculate to see results above the form.
- Download CSV or PDF to keep a lifting record.
Garden lifting risks and planning
Hoists used in gardens and greenhouses often lift awkward loads such as hanging baskets, water barrels, trellising frames, fans, or bagged media. These items can swing, snag on foliage, or shift as roots and soil settle. A structured load estimate helps prevent sudden overloads, protects plants, and reduces strain on anchors, beams, and tripods. For overhead rails, check that fasteners are not pulling out and that wood members are not cracked. For masonry anchors, verify embedment and corrosion. For temporary frames, confirm leg spread and ground bearing before lifting each time.
Inputs that drive the design load
The calculator starts with gross load: the item weight plus rigging weight. It then applies multipliers for lift speed, shock events, and environmental condition. Wet, muddy, or worn rigging can reduce reliability and add uncertainty. A chosen safety factor expands the margin so the lift remains controlled when conditions are imperfect.
Sling angle and leg tension behavior
Sling angle strongly changes tension. As the angle from horizontal decreases, each leg must carry more force to support the same vertical load. The angle factor is 1/sin(β), and required WLL per leg is DesignLoad divided by lift points times sin(β). Keeping β higher, or using a spreader bar, can significantly reduce leg tension.
Capacity checks and selection guidance
Enter a rated hoist capacity to see utilization. When utilization approaches 80% you are near the practical limit, especially for repetitive lifts. If utilization exceeds 100%, select a higher-rated hoist or reduce the design load by improving angle, adding lift points, lowering speed, or minimizing shock. Always confirm hardware ratings and attachment strength.
Recordkeeping and safe operation steps
Exporting CSV and PDF results supports maintenance logs and repeatable setups for seasonal work. Before each lift, inspect hooks, slings, and fasteners; verify the center of gravity; clear the path; and apply smooth starts and stops. Keep people clear of the load line, avoid side loading, and store rigging dry to preserve performance.
FAQs
What is the difference between gross load and design load?
Gross load is item weight plus rigging. Design load adds multipliers for speed, shock, condition, and your safety factor to better represent real lifting stress.
Why does sling angle matter so much?
Lower angles from horizontal increase leg tension because each leg contributes less vertical support. The calculator uses 1/sin(β) to reflect this effect.
How should I choose a safety factor?
Use higher values when weights are uncertain, pick points are improvised, or shock is possible. For well-known, smooth lifts you may use lower values, but never ignore inspection.
Does this replace manufacturer load charts and site rules?
No. Use it for planning and comparisons. Always follow rated capacities, approved rigging methods, and local safety requirements, and consult a qualified professional for critical lifts.
Can I use three or four lift points?
Yes. Select the number of lift points, and the tool splits the design load across legs while still applying the sling-angle effect. Ensure load sharing is realistic in your setup.
Can I switch between kg and lb?
Yes, but keep inputs consistent. If you change units, convert every weight and rated capacity to match, or the utilization check will be misleading.