EP-BGB9 Four-Ratio Lawn Mower Gearbox & EP-9.259 Speed Increaser – 30HP Specialist Pair

EP-9.259 · 1.46:1 speed increase · 14kg · 30.08° mount angle

EP-BGB9: Four Modules, One Housing — Precision Requirement

Producing four gear sets (M6.35, M5.0, M5.0, M3.5) to fit the same 101.5mm square housing while sharing the same bearing seat positions requires that each gear set's pitch diameter be engineered to use the available housing bore clearance without interference. Korea Ever-Power produces all four gear sets on the same CNC gear hobbing equipment, ensuring consistent tooth profile accuracy across the module range. The M6.35 gear set — the coarsest in the EP BGB range — requires the largest tooth form and has the least clearance within the housing bore; its hobbing accuracy is verified by contact pattern inspection during the 30HP load test.

EP-9.259: 30° Mounting Angle — Machined-In Precision

The EP-9.259's 30.08° mounting angle is machined into the housing casting — not a field-adjustable feature or an attachment angle set by a bracket. The 30.08° angle is precise to two decimal places, corresponding to the calculated shaft angle that places the output shaft at the correct geometry for the standard Korean and Japanese compact rotary mower blade shaft position relative to the tractor PTO axis. This machined-in angle means the implement frame designer uses the gearbox's own geometry to set the drive angle, without measuring and setting an adjustable bracket.

Speed Increaser Bearing Spec — EP-9.259

At 788RPM output — 46% above PTO input — the EP-9.259's output shaft bearing operates at a higher rotational speed than the input bearing. The output bearing is specified for its dynamic load rating (C) at 788RPM rather than for the lower-speed static load characteristic of typical speed-reducing gearbox output bearings. Angular contact ball bearings at the output position handle the combined radial and axial loads from the 1.46:1 speed-increase bevel mesh at 30HP and 788RPM, maintaining bearing temperature within the rated range during sustained operation.

100% Load Test — Both Models

Every EP-BGB9 is bench-tested at 30HP at the ordered ratio configuration. Every EP-9.259 is tested at 30HP with the output shaft loaded at 788RPM. For the EP-9.259 specifically, the load test verifies that the output bearing temperature stays within the rated range at the 788RPM operating speed — the critical parameter for a speed increaser where bearing heat generation at the higher output speed is the primary service life driver. Both models use carburised HRC 58–62 gears, consistent with the full EP series standard.

M6.35 direct drive and 1.46:1 speed increaser — same CNC production line

EP-BGB9: why does the 1:1 direct-drive ratio use M6.35 — a coarser module than the other three ratios?

At 1:1 there is no torque multiplication — the output gear carries exactly the input torque with no mechanical advantage from gear ratio. The 16-tooth output gear bears this full input torque load at every mesh contact. At 30HP and 540RPM, the input torque is approximately 397 Nm. Divided across approximately 2–3 simultaneously meshing teeth at M6.35, this produces a tooth root bending stress that M6.35 handles within the HRC 58–62 fatigue limit. The next ratio (1:1.35, M5.0) has a 17-tooth driven gear carrying 30% lower torque (input torque ÷ 1.35) — a smaller load that the more compact M5.0 cross-section handles adequately. The module choice follows the torque, not the ratio number.

EP-9.259: how do I confirm my mower needs a speed increaser rather than a speed reducer?

Three methods: (1) Check the original gearbox housing for a ratio marking — a ratio above 1:1 with the first number larger than 1 (e.g. "1.46:1") is a speed increaser; with the second number larger (e.g. "1:1.46") it is a speed reducer. (2) Tachometer measurement at any PTO speed — if the output shaft turns faster than the input, it is a speed increaser. (3) Inspect the gear tooth count — in a speed increaser the pinion (driving gear) has more teeth than the crown gear (driven gear); in a speed reducer the pinion has fewer teeth. For the EP-9.259, the 19-tooth pinion drives the 13-tooth crown: 19 > 13, confirming speed increase. Contact Korea Ever-Power with the original gearbox dimensions or markings if any of these methods is inconclusive.

What oil specification and maintenance interval apply?

Both models: SAE 90 GL-4 gear oil. Approximate fill volumes: EP-BGB9 ≈ 300–350ml; EP-9.259 ≈ 150–180ml (compact 84mm housing). Both ship without oil — fill before first operation. First oil change at 50 hours; subsequent changes every 200 hours or at the start of each mowing season. For the EP-9.259, check housing surface temperature at 100 hours of operation in summer conditions — if above 70°C, reduce the oil change interval to 150 hours. The 788RPM output speed generates more heat per unit time than a speed-reducing gearbox at the same power level, making the EP-9.259's thermal management slightly more demanding than standard EP lawn mower gearboxes.

What warranty and shipping apply?

12-month warranty from dispatch against manufacturing defects — both models. Not covered: operation above 30HP, oil neglect, dry running before initial fill. EP-9.259 specific: using the speed increaser as a speed reducer replacement (output torque insufficient for speed-reducer loads). Shipping: DHL or FedEx, 3–5 days Korea and Japan, 5–7 days SEA for 1–10 units; sea freight for larger orders (10–18 days). Full export documentation including Certificate of Origin for RCEP and ASEAN tariff applications on every shipment.