Mechanical Engineer for Premium Dog Leash Emergency Release System

About the project

We are developing a premium adjustable dog leash designed to integrate with an existing premium dog collar. We need an experienced mechanical/product design engineer to evaluate the concept, simplify it where necessary, and create a safe, reliable, prototype-ready and manufacturing-oriented mechanical design. This is a functional engineering project, not only a 3D modelling or rendering project. CORE REQUIREMENTS 1. Adjustable premium leash - Three positively locked lengths: 1.2 m, 1.5 m and 1.8 m. - Length adjustment only when the leash is not under load. - Positive mechanical locking, not friction-only locking. - Initial prototype: approximately 25 mm wide, flat, multi-layer premium high-tenacity polyester webbing with a dense, smooth, soft-touch matte finish. - The leash webbing must independently carry the full pulling load. 2. Emergency-release handle - Ergonomic finger-operated release lever inspired by a trigger, but not visually resembling a weapon. - Protected lever with guard. - Separate mechanical thumb safety slider. - Two deliberate actions: unlock safety slider, then press release lever. - Clear mechanical travel and resistance. - Automatic return to the safe/locked condition. - One-handed operation for right- and left-handed users, including wet hands or gloves. - Must not release due to impact, accidental grip, friction, partial lever movement or safety-slider failure. - Padded handle loop with a small rigid external mechanism housing. - The rigid housing must not carry the dog’s pulling load. 3. Mechanical control cable - Stainless-steel control cable inside a protected low-friction sheath. - Excess cable/sheath created by the three leash lengths must be safely stored inside a protected handle cartridge. - No loose external cable loops. - Adequate bending radius. - Consistent lever force and travel in all three length positions. - Cable and sheath should be serviceable. - Cable failure, breakage or detachment must leave the leash locked. - The leash must remain structurally safe even if the cable is removed. 4. Leash-to-collar connector - Cylindrical leash-side connector. - Gentle funnel-shaped entrance for one-handed insertion. - Central concealed magnet for alignment only. - Spring-loaded stainless-steel locking pin passing fully through the cylindrical connector. - Clear mechanical click when fully locked. - Direct mechanical red/green lock indicator. - Hidden keyed/flat guiding feature to align the locking hole with the pin. - The magnet must not carry pulling load. - No 360-degree swivel in the first prototype because it may twist or complicate the mechanical release cable. 5. Normal and emergency release - Normal daily disconnection through a small protected button on the collar connector. - Handle release reserved for emergencies. - Emergency release path: thumb safety slider -> protected release lever -> control cable -> internal lever -> pin retraction. - Internal lever should reduce the force required to withdraw the pin. - Fail-locked behavior required: - Broken or loose cable must not release the leash. - Failure of the length-adjustment mechanism must not release the leash. - Release input removed -> pin returns to locked position. - The engineer must evaluate release under load. 6. Materials Preferred architecture: - Lightweight premium aluminum external housing. - Stainless-steel internal load-bearing parts. - Stainless-steel locking pin and cylindrical connector. - Replaceable low-friction engineering-polymer bushing. - Premium high-tenacity polyester webbing. - Aluminum exterior must not independently carry the full load. - Prevent galvanic corrosion between aluminum and stainless steel. - Final grades and dimensions must be selected through engineering analysis and prototype testing. 7. Serviceability Where practical, the following should be replaceable: - Internal bushing. - Pin/spring cartridge. - Cylindrical connector head. - Control cable and sheath. 8. Initial prototype - One medium/heavy-duty prototype first. - Small, medium and large versions only after the architecture is proven. 9. Existing collar - Existing collar design is available in editable CAD, STEP and STL. - The leash connector will mount opposite the main collar buckle, on the top/dorsal side of the dog’s neck. - Confidential collar files will be shared only after shortlisting, NDA acceptance and project award. - The connector must anchor to the collar’s internal load-bearing structure, not only silicone, padding or decorative surfaces. 10. Required testing approach Prepare a practical bench-test plan covering: - Static load and stress testing. - Sudden pull/shock-load testing. - Emergency release under load. - Testing in all three length positions. - Accidental-release prevention. - Repeated connection and release cycles. - Wear of pin, bushing, cable, spring, trigger and length-adjustment mechanism. - Basic exposure to water, sand, hair and light mud. - Cable-failure testing. - Verification that the red/green indicator cannot show locked unless the pin is fully engaged. Initial tests must be performed on a bench fixture, not on a live dog. MILESTONES Milestone 1 - Feasibility and mechanical architecture - Written feasibility assessment. - Proposed complete mechanical architecture. - Load-path explanation. - Cable routing concept. - Three-position length-adjustment concept. - Excess cable/sheath management concept. - Fail-locked behavior explanation. - Main failure, wear and manufacturing risks. - Standard versus custom component list. - Concept sketches or simplified CAD. Detailed final CAD must not begin before approval. Milestone 2 - Preliminary CAD - Preliminary complete assembly. - Internal section views. - Handle, safety slider and release lever. - Length-adjustment mechanism. - Cable-storage cartridge. - Cylindrical connector and collar interface. - Initial material/component selection. Milestone 3 - Prototype-ready CAD - Complete editable native CAD assembly and part files. - STEP files. - Required STL files. - Exploded views. - Assembly method. - Critical tolerances and clearances. - Replaceable wear-part design. Milestone 4 - Engineering documentation - Manufacturing drawings in PDF. - Complete BOM. - Pin, spring, magnet, cable, sheath, bushing, fastener and seal specifications. - Assembly instructions. - Cable-tension adjustment procedure. - Bench-test plan. Milestone 5 - Post-prototype revision - Review prototype/test results. - Correct issues found during assembly/testing. - Deliver updated final editable CAD, STEP files, drawings and documentation. PAYMENT AND ACCEPTANCE - Fixed-price project divided into separately approved milestones. - Milestone funds will be released only after the written deliverables are submitted, opened, reviewed and confirmed to meet the agreed acceptance criteria. - Screenshots, videos and renders alone are not accepted as final engineering deliverables. - Each milestone includes up to two reasonable requirement-related revision rounds. - If a milestone still fails the written acceptance criteria after those revisions, the client may terminate the remaining project and request cancellation or return of unreleased milestone funds through Freelancer.com’s applicable process. - Previously completed and formally approved milestones remain payable. - Uncompleted or unapproved future milestones will not be released. - Final payment only after all agreed editable CAD, STEP files, drawings, BOM, assembly instructions, test documentation and post-prototype revisions are delivered and verified. CONFIDENTIALITY AND OWNERSHIP - NDA required before confidential collar files are shared. - All paid and approved project-specific CAD, drawings, designs and engineering documents belong to the client. - Confidential project details may not be reused, sold, published or shared without written permission. APPLICATION REQUIREMENTS Please answer: 1. Describe one relevant project involving a small locking, spring, cable, pin or lever mechanism. 2. Explain your approach to a fail-locked emergency-release system. 3. Explain how you would manage excess mechanical cable across three leash lengths. 4. Which CAD software will you use? 5. Which editable files and documentation will you deliver? 6. Can you provide native editable CAD, not only STL? 7. Provide fixed price and estimated duration for each milestone. 8. Confirm NDA, ownership terms and two revision rounds per milestone. 9. Show your most relevant portfolio project. 10. Begin your proposal with “ALFA MECHANICAL”.

Skills required