Project Overview
A USA client working on boat rental required a heavy duty stainless steel bracket to davit, here is his message: “I need 2 stainless steel U brackets, I need the space between the U to be 70mm, 70mm tall. 10mm hole at least 50mm up the side. Square proportions with 4 bolt holes in base, Thick steel capable of supporting 200kg, with matching backing plates “
Customer Requirements
Material: stainless steel
Inside width (U space): 70 mm
Leg height: 70 mm
Hole specification: Ø10 mm
Hole position: ≥50 mm from base
Load requirement: 200 kg static load
Environment: Marine
Customer only provide his demand without any drawing, and we made the drawing according to the requirement.
Engineering Challenge
Although 200 kg may appear moderate, the hole position at 50 mm from the base created a significant bending moment at the root of the bracket.
Key Risk Areas:
- Bending stress at the inner bend radius
- Stress concentration around the 10 mm hole
- Long-term fatigue in corrosive conditions
- Deflection control to prevent equipment misalignment
Designing too thin would risk deformation.
Designing too thick would increase material and bending costs significantly.
Engineering Analysis
Load Conversion
200 kg ≈ 1960 N
With safety factor 3:
Design load ≈ 6000 N
Bending Moment
M = Force × Distance
M = 6000 N × 0.05 m
M = 300 Nm
This bending moment became the controlling design parameter.
Thickness Evaluation
We evaluated multiple thickness options:
| Thickness | Result |
|---|---|
| 3 mm | Exceeded allowable stress |
| 4 mm | Marginal safety margin |
| 5 mm | Acceptable for static load only |
| 6 mm | Optimal strength + durability |
| 8 mm | Structurally safe but unnecessary cost increase |
Final Design Solution
Selected Thickness: 8 mm
Why 8 mm?
- Only 2pcs brackets
- Used for davit in marine environments.
Conclusion
By combining structural analysis with manufacturing expertise, we delivered a 8 mm thick 316 stainless steel U-bracket capable of safely supporting 200 kg under industrial conditions.
