WKA Series Worm Gear Reducer

Key Face Pressure

At the same output torque: WKA key face pressure ≈ 53% of WK key face pressure. Fretting fatigue initiates when surface pressure exceeds the material’s fretting threshold — the WKA sustains shock torques that push well beyond the WK’s fretting limit.

Micro-Slip Amplitude

The elastic deformation of the bore and shaft under load generates micro-slip between bore and shaft surfaces. A longer bore distributes this deformation over more contact area, reducing micro-slip amplitude per unit length — the primary mechanism that delays fretting corrosion onset.

Static Load Retention

The self-locking holding torque at 30:1 and above acts through the bore-shaft key connection. The WKA’s longer key engagement distributes this static load over more face area — reducing the bore fretting that occurs in shallow-bore units under sustained static gravity loads in vertical shaft applications.

WS-Class Bore Depth — Shock Tolerance

WKA HL at each size matches the WPS/WPKS/FCWDS class — the deepest bore engagement available in the worm gear reducer category. At size 135, HL = 215 mm. Stone strikes on auger shafts, conveyor jam events, and emergency stops impose 3–5× rated torque — the WKA’s bore depth distributes this over sufficient key face area to prevent fretting initiation.

Motor on Either Side — Full W-Series Flexibility

The through-shaft input allows the motor coupling to be placed on either side of the housing. The WPKS (WP-family equivalent) requires a single-ended solid input stub — the WKA’s through-shaft input is structurally more flexible in legacy equipment where the motor position is constrained by existing structural elements.

Size 200 — The Largest Available

The WKA extends to size 200 with a Ø85 mm bore at HL = 290 mm and 218 kg. The WPKS (WP-family equivalent) reaches size 175 as its maximum. For large Australian mining conveyor head shafts of 85 mm diameter under shock conditions, the WKA200 is the only hollow-bore specification that provides both the bore diameter and the depth.

Self-Locking with Deep Bore Static Retention

At 30:1 and above, the worm mesh holds stationary on power-off. The WKA bore depth distributes static holding torque over 88% more key face area than the WK — reducing the bore fretting that occurs in shallow-bore units under sustained static gravity loads in vertical shaft applications or loaded hoists.

W-Series Footprint — No Baseplate Modification

External dimensions match the W series convention. Retrofitting from a W series solid-shaft unit to a WKA hollow-bore unit requires only output coupling removal and bore sliding onto the driven shaft — the baseplate, motor, and motor coupling are unchanged. For legacy W series machines that need shock-rated shaft-mount output, this is the correct zero-modification specification.

Phosphor-Bronze Wheel — Proven W-Family Gear Set

The WKA worm gear set follows the W series specification: case-hardened alloy steel worm, centrifugally cast phosphor-bronze wheel. The same gear material couple that drives the W series, WS, and FCWDS — deliberately mismatched so the bronze wheel sacrifices ahead of the hardened worm shaft in abrasive wear conditions.

Motor + Jaw Coupling (Standard)

Jaw coupling to either WKA input stub. On shock-load applications, select a curved-jaw coupling with polyurethane spider over a standard straight-jaw — the curved profile provides progressive shock absorption that limits the peak torque transmitted into the WKA worm gear set during start events.

PTO Shaft + Friction Slip Clutch

PTO shaft with yoke coupling to input stub + a calibrated friction slip clutch at 1.5× rated input torque. Critical for agricultural applications — stone strikes can generate instantaneous torques of 5–10× rated, which even the WKA’s deep bore cannot sustain indefinitely without a clutch as the first line of protection.

Shrink Disc — Mandatory for Shock Loads

For all WKA shock-load applications, the output bore locking element must be a shrink disc — not a set screw. Uniform radial clamping over the full WKA bore depth (150–290 mm depending on size) prevents the progressive set screw loosening that repeated shock torques cause in any bore-mount reducer regardless of bore depth.

Heavy-Duty Torque Arm (Sizes 135+)

WKA size 135 and above have 80–218 kg housing weight. In shaft-mount configuration, the torque arm must carry this gravitational moment plus the reaction torque — a dual rubber-bushed heavy-duty arm is required at these frame sizes. Specify arm and bush for combined dynamic and gravitational loading, not reaction torque alone.

Blanking Cap — Critical Seal

The unused WKA input stub is sealed with a blanking cap and lip seal. In Australian agricultural environments (chaff, dust, moisture), fit a secondary labyrinth dust cap. Inspect and replace the lip seal at every 2,500-hour oil change — failed blanking cap seals are the primary contamination path that causes worm wheel bronze degradation in W-family units.

PAO Synthetic Oil (High Ratio, Hot Ambient)

At ratios 40:1+ in continuous duty in 40°C+ Australian summer ambient, PAO synthetic ISO VG 220 extends the thermal rating by 10–15% and service interval to 5,000 hours. For WKA units on agricultural conveyors that cannot be easily stopped for oil changes during harvest campaigns, the extended interval is a meaningful operational benefit.