Agricultural Primary Gearbox

Designing for the field, not the test bench

Agricultural drives take punishment that factory machinery never sees — shock loads when an implement hits buried stone, dust and slurry ingress, long periods standing idle, and servicing done in a yard with hand tools. A gearbox that survives a laboratory duty cycle can still fail in a season if those realities are not designed in.

Where the engineering effort went

The drive turns through a right angle on an intersecting bevel pair — a splined input shaft carrying the pinion, meshing with a crown wheel on the intermediate shaft. The spline lets the input take a PTO coupling directly rather than relying on a key to carry shock. Gear face width and shaft diameters were sized against peak shock torque rather than steady running load, because it is the shock case that breaks agricultural drives. Bearings sit in rigid pockets formed into the casing to take the radial and thrust reaction the bevel mesh generates.

Serviceability

Perimeter hex bolts clamp the casing across its parting line, holding both the oil seal and the shaft alignment under load. Threaded ports in the bottom and side faces handle draining, filling and level checking, and the drain sits where it can actually be reached with the implement on the ground. These are small decisions in CAD that make a large difference to whether a machine gets maintained properly over its life.

What was delivered

A parametric 3D assembly, manufacturing drawings for the housing and shafts, a gear specification sheet for the gear cutter, and an assembly bill of materials.