Design Philosophy & Concept
Electric stairlifts are expensive and rely on consistent grid power, making them inaccessible for low-income and low-resource environments. MechLift is a manually operated, self-locking staircase chair lift designed to assist mobility-impaired individuals. Recipient of the 1st Prize at the VIT Prodinno Club exhibition, the system utilizes mechanical advantage to optimize operation, allowing elderly users to lift themselves with minimal torque.
Mechanical Transmission & Gearing
The drive kinematics bypass electrical components entirely and rely on a high-ratio mechanical gear train:
- Worm Gear Box (30:1): A central 30:1 worm gear set multiplies input torque and acts as a passive safety brake. Due to the friction angles, worm gears cannot be back-driven, meaning the chair is locked in place even under full load.
- Spur Gear & EN24 Rack: The worm wheel is keyed to a spur gear (EN24 steel, Module 2, 20 teeth), which meshes with a fixed linear rack bolted along the staircase guide rail.
- Aluminum T-Slot Guide Rail: A 40x40 mm Al 6063-T6 T-slotted extrusion rail is fixed parallel to the staircase, directing the guide shafts and sliding blocks without lateral play.
Figure 1: Worm gear (30:1) and spur gear drivetrain assembly bolted on the carrier carriage
Drive Shaft & Structural Specs
The system utilizes a hardened EN8 ground drive shaft (Ø20 mm) supported on both ends by deep groove ball bearings (6204 ZZ) to maintain precise gear mesh alignment. The user operates the system via a manual steering handle mounted to the armrest.
Figure 2: Complete carriage assembly with the mild steel chair frame mounted to the guide shaft
Guide Rail & Framing Elements
To ensure modular assembly, the main rail comprises dual T-slot extrusions with sliding blocks to absorb passenger weights:
Figure 3: Aluminum T-slot extrusion profile
Figure 4: Welded mild steel chair frame
Bill of Materials (BoM) & Economics
| Component Detail | Material Class & Sizing | Estimated Cost |
|---|---|---|
| T-slot Frame | Aluminium 6063-T6, 40×40 mm, 2 m | ₹1,500 |
| Worm Gear Set | Bronze Wheel + Steel Worm, 30:1 ratio | ₹1,000 |
| Spur Gear & Rack | EN24 Steel, M2 pitch, 20 teeth, 1.5 m | ₹1,000 |
| Shaft & Bearings | EN8 Steel Ø20 mm, Bearings 6204 ZZ (4 units) | ₹800 |
| Chair Frame | Mild Steel square tubes, rigid, welded | ₹1,200 |
| Hardware & steering | M8/M10 fastners, steering wheel handle | ₹500 |
| Total Project Cost | Fully functional mechanical system | ₹7,000 – ₹8,000 |
Awards & Exhibition Success
MechLift was entered into the VIT Design Sprint 2025 organized by the Prodinno Club. The prototype won the 1st Prize, praised by evaluators for its simplicity, cost efficiency, and ease of installation in narrow, non-electrified residential buildings.
Figure 5: Design Sprint 2025 1st Prize Award Certificate from Prodinno Club VIT
Key Innovation Summary
MechLift achieves complete electrical independence. The self-locking worm gearbox eliminates rollback hazards, creating a retrofittable, affordable, and safe stair-climbing solution.