We designed and built a worm-and-spur gear train to lift a 20 lb load by hand. The prototype moved the load; testing then revealed where the printed gears and axial retention needed a stronger design.
My contributions: CAD, engineering calculations, machining, and prototype testing.
Built prototype · photo from our ME 329 final report
20 lbtarget lifting load
Worm + spurtwo-stage power transmission
2026four-person ME 329 team
Design challenge
Turn a hand crank into a controlled lift.
The gear train needed enough torque to raise a 20 lb load while keeping manual input within the project limit. The team chose a worm stage for high reduction and load holding, then a spur pair to transmit motion to the output shaft.
DesignModel the shafts, bearing supports, crank, and gear layout in CAD.
AnalyzeUse MATLAB shaft and gear models plus bearing and bolt calculations to guide component choices.
Build and testMachine shafts, assemble printed and purchased parts, and observe how the complete drivetrain behaves under load.
Engineering process
From calculations to hardware
01 · Layout
Fit the drivetrain
Positioned the worm, spur gears, shafts, and bearing mounts within a compact housing.
02 · Check
Analyze the parts
Used Goodman shaft calculations, an AGMA gear model, and bearing and bolt checks as design tools.
03 · Fabricate
Make it assemble
Machined shafts and fitted printed components. Undersized printed bores prompted a 0.008 in allowance and reprint.
04 · Test
Load the system
Hand-cranked the assembled prototype, observed load motion, and documented the failure points.
CAD and fabrication
The details had to fit in the real assembly.
CAD helped define support geometry and component placement before fabrication. A bearing housing had to locate the shaft while leaving room for fasteners and the adjacent drivetrain.
During assembly, the printed bores came out undersized. The team revised the fit allowance and reprinted parts—an early reminder that nominal CAD dimensions do not guarantee an assembled fit.
Manufacturing lesson: check critical fits on physical parts before relying on them in a loaded mechanism.
Bearing-housing CAD · image from our ME 329 final report
Prototype test
Motion transferred. Two weak points surfaced.
The assembled train lifted the test load and transmitted motion through the drivetrain. At the highest applied torque, the printed 48-tooth spur gear's keyway failed. When load direction reversed, the worm wheel shifted because its axial restraint worked in only one direction.
Printed gear keyway
The report links the early failure to material removed while sanding the undersized bore. The test showed that a nominal gear-tooth strength calculation did not capture this printed hub and keyway weakness.
Worm-wheel retention
The wheel stayed positioned during lifting, then moved axially when the force direction changed. Retention needed to account for both directions of operation.
Printed gear and keyed shaft detail · photo from our ME 329 final report
What I would change
Use the test to drive the next iteration.
Strengthen the torque path
Replace the printed load-bearing gears with machined metal components and revisit the keyway geometry.
Constrain both directions
Use shaft collars or retaining features so the worm wheel remains located when the axial force reverses.
Match analysis to the build
Recheck the design using the material, printed geometry, and actual loading of the next prototype before claiming a safety factor.
Team project with Aidan Dilworth, Ian Kaabi, and Kenny Heilsberg. Images are from the team's ME 329 final report.
