Itu Penggaruk batu EP-EW-4000 is the highest-utilisation machine in the Korean highland stone management system — more Korean highland farms use the EP-EW-4000 for more hours per year than any other stone management machine in the Watanabe product range. Its 75 HP tractor requirement places it within reach of standard Korean domestic farm tractors; its 3.6 m working width delivers efficient coverage on agricultural field scales; and its surface collection capability addresses the most common Korean highland stone management task — annual frost-heave surface stone removal from established fields — more efficiently than any alternative approach.
Understanding how to use the EP-EW-4000 correctly requires understanding what it is designed to do and, equally important, what it is not designed to do. The EP-EW-4000 is a surface stone collection machine. It does not crush, does not penetrate the soil profile, and cannot address embedded stones below approximately 8–10 cm. Its effectiveness is absolute within those parameters — and its deployment on tasks outside those parameters produces inadequate results that lead operators to incorrectly conclude the machine is insufficient when in reality the task required the THOR 2.4 stone crusher instead.
EP-EW-4000 Confirmed Specifications
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The Core Decision — EP-EW-4000 Rake or THOR 2.4 Crusher?
The most important stone management decision in Korean highland farming is made every spring after soil thaw: which machine does this field need this year? Getting this decision right saves significant operating cost in the majority of seasons where the rake is adequate, while ensuring the THOR is deployed in the minority of seasons where it is genuinely needed. The decision framework:
| Field condition after spring thaw | EP-EW-4000 | THOR 2.4 | Decision basis |
|---|---|---|---|
| Surface stones all below 40 Kg, none above 15 cm | ✅ Correct | Over-deployment | Standard light frost-heave year — rake handles the full stone population |
| Occasional stones 40–80 Kg (below 25 cm) | ⚠ Partial only | ✅ Correct | Rake windrowed small stones; THOR crushes the above-40Kg stones the rake cannot move |
| Multiple stones above 40 Kg in each field section | ❌ Insufficient | ✅ Correct | Heavy frost-heave or new land: THOR crushing required before rake collection is possible |
| Post-THOR pass — crushed aggregate to collect | Not typically | Already passed | CT-2100 picker handles post-THOR collection; EP-EW-4000 for supplementary windrow sweeping if needed |
| Orchard, pasture, ginseng alley — surface only | ✅ Ideal | Unnecessary power | Low stone density, shallow collection: rake is perfectly matched to these light-maintenance applications |
How the EP-EW-4000 Works — Tine Drum, Windrow, and Collection
The EP-EW-4000 uses a rotating tine drum — a series of spring-steel tines mounted on a horizontal drum driven by the tractor’s 540 RPM PTO. As the tractor moves forward, the rotating tines sweep the soil surface in the opposite direction to forward travel, dislodging surface stones and rolling them backward into a concentrated windrow behind the machine. The tines penetrate the soil surface to a depth of approximately 5–10 cm (operator-adjustable through the rear skid height setting), collecting stones from this upper collection zone while leaving the soil largely undisturbed below the tine penetration depth.
↳ Tine penetration depth
Set by the rear skid height — lower skid = deeper tine penetration = more soil disturbance but better small stone collection. Raise skids on road surfaces and established turf to prevent unnecessary surface disruption. Target: tines should just penetrate the soil crust without forming visible furrows in firm soil.
↳ Windrow position
The EP-EW-4000 deposits its collected stone windrow behind the machine on the centreline of the working pass. Subsequent passes are planned so that the CT-2100 collection vehicle can follow in the windrow line — aligning pass direction with the CT-2100’s optimum collection trajectory for maximum pick-up efficiency.
↳ Maximum stone size
The EP-EW-4000 tines effectively collect stones up to approximately 40 Kg per stone. Stones above this size cannot be displaced by the tine rotational force — they stop the tine drum momentarily or are rolled sideways. Encountering multiple above-40 Kg stones in a field section during the rake assessment is the trigger for THOR deployment on that section.
Operating Setup — Speed, Skid Height, and Pass Planning
Three variables control EP-EW-4000 performance: forward speed, skid height (tine penetration depth), and pass-line planning. Correct setup for each application type:
Agricultural field — standard setup
Speed: 4–6 km/h. Lower end (4 km/h) maximises small-stone collection completeness on fine-stone passes. Upper end (6 km/h) for efficient wide-area coverage when stone density is low and completeness of very small stones is less critical.
Skid height: Set so tines just touch the soil surface crust without forming visible grooves on firm, slightly moist spring soil. Adjust at the first 20 m test pass — look back at the windrow profile and the surface behind the tines.
Orchard alley — narrow width setup
Speed: 4–5 km/h — orchard tractors typically operate more slowly than field tractors; confirm tractor forward speed matches the 540 RPM PTO engagement without excessive drum speed.
Skid height: Raise slightly above field setting — orchard alley turf or ground cover should not be disturbed unnecessarily. Rake should collect surface stones without leaving bare soil strips in the orchard alley.
Post-THOR supplementary sweep
Speed: 5–6 km/h — post-THOR stones are already fragmented and at the surface. The rake pass concentrates them into windrows for CT-2100 collection more efficiently than CT-2100 direct collection from scattered surface distribution.
Skid height: Standard field setting. THOR-crushed soil is already loosened — tines penetrate easily to the collection depth without special adjustment.
Orchard, Ginseng Alley, and Legume Year Applications
The EP-EW-4000’s 75 HP requirement and relatively gentle surface action (no crushing, no soil inversion) make it the standard choice for a wide range of Korean agricultural applications where the THOR 2.4’s 180 HP power and stone crushing action is either unavailable or unnecessary:
Korean apple, pear, and persimmon orchards
Highland orchard alleys accumulate frost-heave surface stones annually in the same granitic soils as field crops. The EP-EW-4000’s 3.6 m working width is typically wider than a standard orchard alley (2.5–3.5 m) — requiring offset passes. Tine height set to preserve ground cover turf. The CT-2100 collection follows in the windrow line. Annual orchard alley clearance in March prevents tyre punctures from harvest equipment during the August–November orchard harvest period.
Ginseng field alleys (during 6-year cultivation)
As described in the ginseng stone clearing guide, the EP-EW-4000’s annual role during the ginseng growing cycle is alley maintenance — not bed stone clearance. The 60–80 cm alley width requires narrow-width operation: one tractor wheel in each alley, EP-EW-4000 overhanging slightly into adjacent alleys on either side. Some Gangwon-do ginseng farmers use narrower specialty rakes for ginseng alley work — confirm with Korea Watanabe whether EP-EW-4000 width is compatible with your specific ginseng bed geometry before deployment.
Legume year in the 4-crop rotation
The legume year (Year 4 in the potato–radish–cabbage–legume rotation) has minimal stone management requirements. Annual frost-heave is the only stone emergence mechanism on established fields. The EP-EW-4000 handles this light annual maintenance in the legume year — the THOR 2.4 is not needed and should not be deployed on fully established, light-stone legume fields. This correct machine selection during the legume year reduces the THOR 2.4’s annual operating hours and tooth consumption by approximately 20–25% on a 4-block rotation farm, extending the THOR’s maintenance intervals and reducing annual operating cost.
EP-EW-4000 Annual Maintenance — Simple but Essential
The EP-EW-4000’s maintenance requirements are significantly less demanding than the THOR 2.4’s — its mechanical simplicity (tine drum, PTO driveline, skid adjustment) means fewer wear items and shorter service intervals. However, deferred maintenance on the tine drum bearing and tine replacement produces a noticeable performance decline that operators often attribute to “field conditions” rather than machine wear:
| Selang | Tugas | Symptom if neglected |
|---|---|---|
| Before each season (Feb) | Inspect all tines — replace bent, shortened (below 70% of new length), or cracked tines; grease tine drum bearings; check PTO shaft joints; confirm skid height adjustment mechanism free | Bent tines miss stones and reduce windrow quality; worn tines reduce collection completeness on smaller stones |
| Setiap 8 jam operasional | Grease tine drum end bearings; check for any tine fracture after heavy stone contact; confirm PTO shaft shielding intact | Dry tine drum bearings squeal under sustained rotation load — failure requires drum removal and bearing replacement |
| Mid-season inspection | If collection completeness has visibly declined: re-measure all tines and replace worn items; re-check skid height setting drift (skid bolts can loosen under vibration) | Skid height drift causes inconsistent tine penetration — varies from too shallow (missing small stones) to too deep (soil disturbance) |
| Akhir musim | Replace all tines below replacement threshold; clean soil from tine drum and PTO shaft; grease all points before storage; protect PTO shaft joints from winter corrosion | Machine stored with borderline tines begins next spring at reduced performance — the low-cost, high-impact maintenance action |
EP-EW-4000 in the Complete Korean Stone Management System
The EP-EW-4000 is not a standalone machine — it operates as part of the three-machine Korean highland stone management system alongside the THOR 2.4 stone crusher and the CT-2100 rock picker. Understanding how the three machines interact clarifies when each one is deployed and how their combined coverage achieves zero-residual stone standard across all field types and stone conditions:
The three-machine system’s total operating cost is dominated by the THOR 2.4 (highest HP, highest tooth wear cost). Correctly identifying the years and field sections where the EP-EW-4000 is sufficient — rather than defaulting to the THOR in all situations — is the management decision that keeps the system economical across the full Korean highland farming calendar. On a well-managed 10 ha highland farm running the 4-crop rotation, the EP-EW-4000 typically operates 30–40 hours/year while the THOR 2.4 operates 15–25 hours/year — the lighter machine covering more total hours at lower hourly cost, while the heavier machine is preserved for the tasks that genuinely require its capability.
Pertanyaan yang Sering Diajukan
How do I know if a stone is above or below the 40 Kg threshold in the field?
A practical field method: a 40 Kg stone of Korean granite (density approximately 2,650 Kg/m³) is approximately 15–18 cm in diameter in spherical equivalent. You can estimate this: a stone that a single person can pick up and carry is almost certainly below 40 Kg. A stone that requires two people to lift but can still be moved manually is approximately 40–80 Kg — borderline for the EP-EW-4000, and indicates THOR deployment for that section if multiple stones of this size are present. A stone that two people cannot move without mechanical assistance is above 80 Kg and requires THOR 2.4 crushing. During the spring walk, systematically note how many stones require two people to move — if more than 3–5 per 100 m² of field area, deploy the THOR on that section. If all stones can be moved by one person, the EP-EW-4000 is the correct machine.
Can the EP-EW-4000 work on wet Korean highland spring soil without damaging soil structure?
The EP-EW-4000 is less damaging to soil structure on wet soil than the PSW-3200 rotavator because its tines do not invert or smear the soil — they simply sweep the surface and collect stones. However, operating the EP-EW-4000 on very wet, plastic soil (where the soil surface deforms visibly under tractor weight) does cause tractor wheel compaction in the wheel tracks. This wheel-track compaction is unavoidable in wet conditions regardless of which machine is used. The recommendation: wait until the soil surface can support tractor weight without visible deformation (roughly 3–5 days after heavy rainfall on typical Korean highland granite soils) before commencing EP-EW-4000 operations. The tine drum itself has minimal soil compaction effect at the surface — the compaction risk is from tractor wheel loading, not from the rake mechanism.
What is the annual tine replacement cost for the EP-EW-4000?
The EP-EW-4000 tine replacement frequency on Korean highland granite soil depends on annual operating hours and stone hardness. Typical tine life is 60–120 operating hours before tines reach the 70% replacement threshold. On a 10 ha farm running 30–40 hours/year, tine replacement is typically needed every 2–3 seasons — some tines replacing annually (those that contact harder stone concentrations) and others lasting 3–4 seasons. Korea Watanabe holds EP-EW-4000 tine replacement sets in Korean local stock. Contact Korea Watanabe for current tine set pricing and lead time confirmation — order tine replacements in January as part of the standard pre-season service preparation alongside THOR tooth sets and PSW-3200 blade sets to consolidate parts ordering into a single annual procurement.
Is the EP-EW-4000 eligible for Korean agricultural machinery subsidies?
Yes — the EP-EW-4000 qualifies under the Korean agricultural machinery purchase support program in the farmland improvement machinery category, the same category as the THOR 2.4 and CT-2100. Korea Watanabe holds the Korean agricultural machinery certification for the EP-EW-4000 and provides full subsidy documentation at no charge. For farms purchasing multiple stone management machines (EP-EW-4000 + CT-2100 + THOR 2.4), all three can be included in a single annual subsidy application — subject to the per-farmer annual subsidy cap. Korea Watanabe advises on structuring multi-machine applications to maximise subsidy access across the full system in a single or phased application.
How many passes does the EP-EW-4000 need to achieve a clean field on a 5 ha highland vegetable plot?
On an established highland field with light-to-moderate frost-heave, the EP-EW-4000 achieves commercially adequate surface clearance in one pass per row spacing aligned with the subsequent CT-2100 collection lines. A single rake pass at 4–5 km/h across 5 ha (at 3.6 m working width = approximately 14 passes across the field width + headland turns) takes approximately 2–3 hours of effective machine time — typically half a morning. The CT-2100 collection following the rake windrows takes a similar time, giving a complete 5 ha EP-EW-4000 + CT-2100 annual clearance operation in a single working day. Compare this to the same 5 ha with THOR 2.4 + CT-2100 (180 HP machine, deeper penetration, lower forward speed): approximately 1.5–2 full working days. The EP-EW-4000’s time and cost efficiency advantage on light-stone established fields is the core reason for having both machines in the Korean highland system.
EP-EW-4000 Configuration and Stock Confirmation
Farm type (highland vegetable / orchard / ginseng) + area (ha) + annual stone history → EP-EW-4000 alone or EP-EW-4000 + THOR 2.4 recommendation with subsidy documentation preparation. Korea Watanabe, Ansan-si, Gyeonggi-do.
Editor: Cxm
