JBJacob Benjamin
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HUNTER INDUSTRIES / MECHANICAL ENGINEERING INTERN / 2025

LDN Sprinkler

Reducing assembly-induced deformation through combined-loading analysis, design iteration, and physical test-fixture development.

MY CONTRIBUTION

Bracket redesign, simulation comparisons, prototypes, and test-fixture development.

ENGINEERING FOCUS

Creo · Mechanics of materials · FEA · SLA · CNC fixtures

KEY OUTCOME

32.4% lower maximum stress in the documented FEA comparison.

LDN sprinkler with Dynamic Drive
SPRINKLER BRACKET REDESIGN

First-principles analysis, geometry iteration, and a custom fracture-test fixture.

32.4%lower maximum stress in FEA
01 / PROBLEM & OWNERSHIP

Assembly-induced deformation

Twisting the upper and lower sprinkler assemblies into position could deform the connecting legs. The redesign needed to improve structural behavior while remaining compatible with the product assembly and manufacturing approach.

My work: Creo design iterations, DOE / FEA comparisons, prototype development, and a CNC-machined 304 stainless-steel fixture for physical testing.

Exploded sprinkler assembly.
Original bracket showing deformation under assembly torque.
02 / FIRST-PRINCIPLES ANALYSIS

From assembly torque to leg bending

I simplified the assembly torque into a tangential load shared by three legs. That gives a quick estimate of bending stress and shows how increasing thickness and smoothing the root can reduce the local peak.

Original and revised geometry, with each leg represented by a simplified bending model.

Hand calculations

Inputs: T = 600 N·mm; n = 3 legs; R = 20 mm; L = 30 mm; b = 6 mm. Thickness increases from 2.00 to 2.25 mm. Yield reference: 45 MPa.

01 / LOAD PER LEGF = T / (nR) = 10 N

Using the end-restraint assumption in the hand model: M = FL / 2 = 150 N·mm.

02 / ORIGINAL SECTIONI₁ = bt₁³ / 12 = 4.00 mm⁴

σnom,1 = M(t₁/2) / I₁ = 37.5 MPa.
With illustrative Kt,1 = 1.60: σlocal,1 = 60.0 MPa.

03 / REVISED SECTIONI₂ = bt₂³ / 12 ≈ 5.70 mm⁴

σnom,2 ≈ 29.63 MPa.
With illustrative Kt,2 = 1.37: σlocal,2 ≈ 40.6 MPa.

The model estimates a 32.3% reduction in local stress, with the revised section below the 45 MPa yield reference. The stress-concentration factors are illustrative; this is a design estimate, separate from the FEA and physical testing.

03 / SIMULATION & PHYSICAL TESTING

Design iterations & fracture testing

The design study explored changes to leg depth, ribs, leg count, cross-section, and fillet geometry. The résumé documents more than 15 evaluated designs and five SLA prototype models.

Bracket iterations: leg depth, ribs, leg count, cross-section, and fillets.
Simulation setup and design comparison table.

A dedicated fixture translated the bracket evaluation into a physical test. The work included fixture CAD, a drawing for the machinist, a CNC-machined 304 stainless-steel fixture, and samples tested to fracture.

Fixture CAD, machining drawing, and manufactured stainless-steel fixture.
Bracket samples after fracture testing.
04 / RESULT

Analytical & FEA results

32.3%lower local stress in the simplified hand model
32.4%lower maximum stress in the documented FEA comparison
FEA comparison: 32.4% lower maximum stress in the selected design.

The simplified hand model and the documented FEA comparison both indicate lower stress. Their close percentages do not establish simulation-to-test correlation; the hand model uses illustrative stress-concentration factors.

ENGINEERING CONTRIBUTION

Connected geometry exploration and structural analysis with the hardware needed to test real parts.

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