Mechanical Design Engineer Needed — Retractable Reel “Single-Lock @ 75%” (Tug-N-Back) Mechanism + CAD + Prototype STL
Budget: ₹12,500 – ₹37,500 INR
I need an experienced mechanical product designer to redesign a retractable reel (badge-holder style) to support a single lock position at ~75% extension, with tug-to-release and reliable full retraction.
We have existing designs (TNB1 / TNB5 / TNB6) and some concept sketches/proposals. The last concept was too complex (too many parts). Now we want a simpler, manufacturable mechanism based on the shortlisted ideas already on the table:
Cam detent / indexed cam
Axial pin lock
Over-center toggle
Brake band lock
(We want you to pick the best approach and design it.)
What the product must do (plain English)
Mode 1 (RA – retract always)
Pull cable out → release → it retracts normally.
Mode 2 (TNB – single lock)
Pull cable out → when user releases, it should lock only at ONE position around ~75% extension (not every revolution).
Then user does a 6–12 inch tug → it unlocks → when released, it must fully retract to home without re-locking during the “snap-back”.
Stretch goal (“moonshot” – optional)
No manual switch:
If user releases slowly near 75% → it locks
If user lets go fast → it bypasses lock and fully retracts
Key constraints
Target reel diameter: ~30 mm (must be scalable 27–40 mm)
Cable length: <48” (some models ~30”)
Cable dia: ~2.7 mm
Plastics: ABS / Delrin typical
Must be easy to assemble, low parts count, tolerant to reel wobble, no “spring tuning” during assembly.
Deliverables
Phase A (Concept Selection)
Review existing designs and propose 2–3 simplified mechanisms from the shortlist above
Recommend 1 best option with reason (manufacturability + reliability + parts count)
Simple diagrams explaining how 75% is created and how it can be adjusted
Phase B (CAD + Prototype Files)
Full 3D CAD assembly + part files
STL files for 3D printing
Exploded view + simple assembly steps
Phase C (DFM / Manufacturing Package)
2D drawings with tolerances
BOM
Notes for injection molding + assembly
(Optional) If you can also 3D print and test, quote separately.
Required experience
Mechanism design (ratchets, pawls, cams, detents, spring mechanisms)
DFM for injection molded plastic
CAD: SolidWorks preferred (or compatible)
To apply (please answer)
What mechanism from the shortlist would you choose and why (cam detent / axial pin / over-center / brake band)?
How would you ensure no re-lock during snap-back after tug release?
How would you create one lock position only and allow adjustment (70/75/80%)?
Share 1–2 relevant mechanism/consumer product examples you’ve designed.
Note: Please avoid generic/AI-only proposals. I’m looking for a real mechanism thinker.
We have existing designs (TNB1 / TNB5 / TNB6) and some concept sketches/proposals. The last concept was too complex (too many parts). Now we want a simpler, manufacturable mechanism based on the shortlisted ideas already on the table:
Cam detent / indexed cam
Axial pin lock
Over-center toggle
Brake band lock
(We want you to pick the best approach and design it.)
What the product must do (plain English)
Mode 1 (RA – retract always)
Pull cable out → release → it retracts normally.
Mode 2 (TNB – single lock)
Pull cable out → when user releases, it should lock only at ONE position around ~75% extension (not every revolution).
Then user does a 6–12 inch tug → it unlocks → when released, it must fully retract to home without re-locking during the “snap-back”.
Stretch goal (“moonshot” – optional)
No manual switch:
If user releases slowly near 75% → it locks
If user lets go fast → it bypasses lock and fully retracts
Key constraints
Target reel diameter: ~30 mm (must be scalable 27–40 mm)
Cable length: <48” (some models ~30”)
Cable dia: ~2.7 mm
Plastics: ABS / Delrin typical
Must be easy to assemble, low parts count, tolerant to reel wobble, no “spring tuning” during assembly.
Deliverables
Phase A (Concept Selection)
Review existing designs and propose 2–3 simplified mechanisms from the shortlist above
Recommend 1 best option with reason (manufacturability + reliability + parts count)
Simple diagrams explaining how 75% is created and how it can be adjusted
Phase B (CAD + Prototype Files)
Full 3D CAD assembly + part files
STL files for 3D printing
Exploded view + simple assembly steps
Phase C (DFM / Manufacturing Package)
2D drawings with tolerances
BOM
Notes for injection molding + assembly
(Optional) If you can also 3D print and test, quote separately.
Required experience
Mechanism design (ratchets, pawls, cams, detents, spring mechanisms)
DFM for injection molded plastic
CAD: SolidWorks preferred (or compatible)
To apply (please answer)
What mechanism from the shortlist would you choose and why (cam detent / axial pin / over-center / brake band)?
How would you ensure no re-lock during snap-back after tug release?
How would you create one lock position only and allow adjustment (70/75/80%)?
Share 1–2 relevant mechanism/consumer product examples you’ve designed.
Note: Please avoid generic/AI-only proposals. I’m looking for a real mechanism thinker.