EP-EW-4000 Rock Rake — Complete Professional Guide: When to Rake, When to Crush, and How to Choose

The EP-EW-4000 is not a smaller alternative to the stone crusher — it is a different machine solving a different problem. 75 HP, 3.6 m, 540 RPM: it windrows surface stones without breaking them, in conditions where crushing is unnecessary, impossible, or the wrong solution.

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The stone clearing equipment range from Korea Watanabe covers two distinct mechanical approaches to the same field problem: stone crushers fracture rock in-place, leaving crushed aggregate on the surface; the rock rake gathers whole surface stones into windrows for CT-2100 collection, without fracturing them. These two approaches are not interchangeable — they address different stone sizes, different field conditions, and different downstream requirements. Understanding when the EP-EW-4000 rock rake is the correct choice — and when the THOR 2.4 stone crusher is necessary instead — is the starting point for efficient Korean highland stone management.

EP-EW-4000 Rock Rake — Confirmed Specifications

EP-EW-4000 rock rake — 75 HP, 3.6 m working width, Cat.2, 540 RPM PTO, rear windrow discharge

75 HP

Min. tractor power

3.6 m

Working width

540 RPM

PTO requirement

Cat.2

Three-point hitch

4–6 km/h

Working speed range

All specifications from the Watanabe official product brochure.

How the EP-EW-4000 Works — The Raking Mechanism

EP-EW-4000 rock rake internal structure — rotating rake tines, stone gathering pan, and rear windrow discharge channel

The EP-EW-4000 operates on a fundamentally different principle from the stone crusher. Rather than fracturing rock with high-speed impact, the rake uses a rotating drum fitted with hardened steel tines that sweep through the upper 5–8 cm of the field surface as the tractor advances. The rotating motion of the tine drum carries surface stones rearward and deposits them into a windrow along one side of the machine’s working path.

Surface stone capture: The tine drum’s hardened steel tines engage surface stones — from approximately 3–5 cm diameter upward — as the drum rotates and the tractor advances. Smaller stones and soil particles pass between the tines and return to the field. Stones above the tine gap threshold are carried rearward by the tine rotation.

Stone transfer and windrow deposition: Captured stones are transferred by the tine drum into the machine’s collection pan and then discharged laterally to form a windrow. The windrow accumulates alongside the machine’s working path as the tractor advances. EP-EW-4000(T) models include discharge to the rear for collecting stones directly behind the machine path, which the following CT-2100 picker then collects.

Intact stone collection: Unlike the stone crusher, the rake does not fracture the stones it gathers. Stones arrive at the windrow in the same size and form they were on the field surface. This is both the rake’s advantage (no crushing required for light stone conditions) and its primary limitation (stones above approximately 40–60 Kg cannot be effectively moved by the rake’s tine mechanism).

Eight Korean Farm Applications Where the Rake Is the Right Tool

EP-EW-4000T rock rake variant — rear discharge configuration for direct CT-2100 follow-up picking

Annual frost-heave maintenance on established highland fields. Korean highland fields experience regular frost-heave that pushes small-to-medium stones to the surface each winter. If the heaviest stones are below 40–50 Kg, the EP-EW-4000 handles the annual maintenance pass alone — no stone crusher needed. The rake is the efficient annual maintenance tool where the previous season’s crusher pass left no stones above 40–50 Kg embedded in the field.

Pre-crusher assessment pass. On fields where stone density and size are unknown — first-time clearance, newly acquired land — a rake pass before the stone crusher identifies which zones of the field contain stones manageable by the rake alone (light stone zones), and which zones contain heavy embedded boulders requiring the THOR. Zone-based clearing then deploys the THOR only in heavy-stone zones, saving THOR operating hours on light-stone areas.

Post-crusher surface cleanup. After the THOR stone crusher pass, all stones have been fractured to below 30–40 cm maximum dimension — well within the rake’s manageable size range. An EP-EW-4000 pass after the THOR windrows the crushed fragments into concentrated rows that the CT-2100 picker can collect more efficiently than picking from diffuse surface scatter. The rake-then-CT-2100 sequence is often more productive than CT-2100 picking directly from diffuse crusher scatter.

Orchard alleys between tree rows. In Korean fruit orchards (apple, pear, persimmon), the between-row alleys maintain surface stone coverage that reduces erosion and weed competition. Periodic rake-and-collect passes remove surface stone accumulation from alleys without disturbing the orchard tree root zone. The 75 HP requirement and 3.6 m working width are compatible with most Korean commercial orchard alley dimensions. The crusher’s higher HP and broader stone fracturing action is rarely necessary in established orchard alleys where stone size is self-limiting by the orchard surface management history.

Jeju Island annual basalt surface management. Jeju Island’s volcanic basalt fields experience continuous surface emergence of small-to-medium basalt fragments through annual freeze-thaw cycles and weathering. Many Jeju operations where the crushing pass has already reduced large basalt outcrops in previous seasons now require only an annual rake pass to maintain the surface. The EP-EW-4000 handles Jeju basalt fragment management efficiently at 75 HP — a lower operating cost than THOR crusher deployment for stone conditions that no longer require crushing.

Ginseng field annual maintenance (between planting rotations). Korean ginseng fields cleared to zero-stone standard with THOR+CT-2100 before planting require zero-stone maintenance over the 6-year growing period. Annual EP-EW-4000 passes through ginseng field alleys remove frost-heave stones that re-emerge during the growth period before they can contact the developing root system. This annual maintenance with the 75 HP rake is significantly more cost-effective than deploying the full THOR+CT-2100 system for small annual frost-heave volumes.

Highland vegetable field preparation (light stone season). Korean highland vegetable production areas — highland Chinese cabbage (배추), Korean radish (무), and other summer vegetables in Gangwon-do — face annual frost-heave stone management similar to potato fields. In years where frost-heave stones are predominantly below 40–50 Kg, the EP-EW-4000 annual rake pass handles field clearance without requiring the stone crusher deployment, reducing clearance preparation cost in lighter stone years.

Mountain farm access track surface stone maintenance. Korean mountain farm tracks accumulate surface stones from frost-heave and bank erosion. Annual EP-EW-4000 passes along track margins gather surface stones from the track surface into roadside windrows — clearing the track without the road-building process that the THOR crusher is better suited to. For established tracks where surface stones are surface-level only (not embedded), the rake maintains track surface quality efficiently at the 75 HP operating cost.

When the Rake Is NOT the Right Tool — Use the THOR Crusher Instead

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Large embedded stones above 40–60 Kg. The rake’s tine mechanism cannot move large embedded stones. Attempting to rake a field where stones above 40–60 Kg are present results in tine deflection, reduced effectiveness on those stones, and potential tine damage. Large embedded stones require the THOR crusher.

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Road building applications. Road base construction requires angular crushed aggregate — the crushed product of the THOR. The rake only gathers and moves stones; it does not fracture them into road base aggregate. The rake is not a road construction tool.

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First-time clearance of heavily stoned land. Land conversion from forest, scrubland, or long-fallow to agricultural production typically has heavy embedded stone concentrations with individual boulder weights of 100–500+ Kg. The rake cannot address this stone population — the THOR crusher is required for initial clearance, with the rake deployed for subsequent annual maintenance after the initial clearance reduces stone size to within the rake’s operating range.

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Silviculture and stump processing. The rake’s tine mechanism does not process stumps or woody root systems. Forestry and silviculture clearing applications require the THOR FLM stone crusher, not the agricultural rake.

Rake vs Crusher — Simple Decision Guide for Korean Farmers

THOR stone crusher and CT-2100 rock picker — the system for heavy stone conditions; EP-EW-4000 rake for light surface stone

Answer these three questions:

Q1: Is the largest stone in my field below 40–50 Kg?

Yes → Rake is viable. No (stones above 50 Kg present) → THOR crusher required first.

Q2: Are the stones embedded in the soil, or sitting on the surface?

Sitting on surface → Rake handles them. Embedded (frost-heave emerging) → check size. Deeply embedded (original geological position) → THOR crusher required to fracture before rake can gather.

Q3: Do I need to crush stones for road base aggregate?

Yes → THOR crusher only. No (collecting for removal or windrow) → Rake is appropriate.

Decision result: If Q1 = Yes + Q2 = Surface + Q3 = No → EP-EW-4000 rake is the correct tool. If any answer is opposite → THOR crusher is required, rake may be supplementary.

Productivity and Seasonal Planning — Getting the Most from the EP-EW-4000

The EP-EW-4000’s 4–6 km/h working speed and 3.6 m working width make it one of the fastest stone clearing machines per working hour of any machine in the Watanabe range. This speed advantage is the rake’s primary operational strength: it can survey and clear a field quickly, allowing rapid identification of which zones require the THOR crusher follow-up and which are adequately cleared by the rake alone.

Integrating the Rake into the Korean Highland Spring Calendar

The optimal position of the EP-EW-4000 rake in the Korean highland potato spring preparation calendar is immediately after soil thaw confirmation and before the PSW-3200 rotavator tillage. The sequence:

Day 1

EP-EW-4000 rake pass — full field at 4–6 km/h. Windrow surface frost-heave stones. Mark heavy-stone zones where boulders above 40 Kg are present.

Day 1–2

CT-2100 rock picker collects the rake windrows. Simultaneously: THOR 2.4 crusher processes the heavy-stone zones identified during the rake pass.

Day 2

Second rake pass over THOR-crushed zones → CT-2100 collects crushed aggregate windrows.

Day 3+

PSW-3200 rotavator tillage on cleared field — stone-free seedbed confirmed before tillage begins.

This sequence uses the rake’s speed advantage (covering the full field in Day 1 to identify zones) while deploying the THOR crusher efficiently — only on zones that actually need it. Operations that skip the rake assessment pass and apply the THOR across the full field pay for THOR operating hours on light-stone zones that the rake alone could handle at 75 HP rather than 180 HP.

Tine Maintenance — What to Check and When

The EP-EW-4000’s picking tines are the primary wear component. Unlike the THOR’s carbide teeth (which require careful monitoring and individual replacement at defined wear thresholds), the rake’s tines have a more gradual wear profile — they wear progressively and the machine continues to function until wear is significant enough to reduce picking effectiveness.

Start of season inspection

Visually inspect all tines for: tip shortening (worn tip shorter than a new tine by 15mm+); bent tine body (impact with large boulder during previous season); cracked or chipped hardened steel tips. Replace individual tines as needed. Confirm all tine mounting bolts are torqued to specification before the first operational pass.

In-season monitoring

Check tine condition every 30–40 operating hours during peak season use. A useful field test: park the machine on flat ground, rotate the drum by hand, and visually check tine tip height consistency — worn tines will be noticeably shorter than new tines in the same drum section. Uneven tip heights produce uneven stone capture efficiency across the drum width.

Replacement tines for the EP-EW-4000 are stocked by Korea Watanabe in Ansan-si, Gyeonggi-do, with next-day domestic dispatch available during the operating season. Stock 5–10% spare tines on site for each full field operation — having spare tines eliminates the wait for delivery if tine damage is discovered mid-operation.

EP-EW-4000 vs BlackBird — Single Rake or Tandem System?

The EP-EW-4000 (3.6 m, 75 HP) and the BlackBird (9.5 m, 300 HP minimum) address very different scale requirements. The EP-EW-4000 is a standard-tractor single-machine solution for individual farm operations up to 20–30 ha requiring efficient stone windrowing. The BlackBird is a large-scale system combining multiple rake sections into a 9.5 m working width, designed for large farms and land clearing contractors covering 50+ ha in a season. For most Korean highland farm-scale operations (2–30 ha), the EP-EW-4000 is the appropriate and cost-efficient choice. For operations at commercial contract clearing scale, the BlackBird’s throughput advantages justify its 300 HP requirement and higher machine cost. Contact Korea Watanabe to confirm which configuration fits your specific annual area and tractor availability.

Frequently Asked Questions

What is the EP-EW-4000(T) variant — how does it differ from the standard EP-EW-4000?

The EP-EW-4000(T) variant is a rear-discharge configuration that deposits windrowed stone directly behind the machine’s working path rather than to one side. This rear-discharge format is optimised for the sequence where the EP-EW-4000(T) travels a field row and the CT-2100 rock picker follows directly behind it in the same pass — the rear windrow is positioned exactly where the CT-2100’s picking mechanism can collect it. The standard EP-EW-4000 produces a side windrow, which the CT-2100 collects in a separate pass. The (T) variant is more efficient when the CT-2100 is available as a following machine in the same field session; the standard is more efficient when the rake and picker operate in separate passes or separate days. Confirm which variant is appropriate for your planned rake-and-pick sequence when ordering.

What is the working speed of the EP-EW-4000 — how many hectares can it cover per day?

The EP-EW-4000 operates at 4–6 km/h forward speed for effective stone capture. At 3.6 m working width and 5 km/h average, the theoretical coverage rate is approximately 1.8 ha/hour. Accounting for headland turns, windrow inspection, and speed reduction on areas of denser stone concentration, effective productive coverage is approximately 1.2–1.5 ha/hour or 10–12 ha per 8-hour productive day. On established highland potato and vegetable fields where annual frost-heave is the primary stone source, a 15-hectare farm can complete the annual EP-EW-4000 rake pass in approximately 1–1.5 productive days, significantly faster than the same area would take with a THOR crusher pass (which operates at 0.5–2.5 km/h).

Does the rake damage soil structure or disturb the seedbed?

The EP-EW-4000 tines penetrate approximately 5–8 cm into the surface — shallower than the CT-2100 picker (8–12 cm) and far shallower than the PSW-3200 rotavator (25–30 cm). Surface disturbance from the rake pass is minimal and concentrated in the shallow surface zone where stones are present, not in the cultivated root zone below. For the standard Korean highland potato preparation sequence (stone clearance → rotavator tillage → furrowing), the rake pass preceding the rotavator tillage creates no seedbed disruption issue — the rotavator incorporates the slight surface disturbance into the full tillage depth. For established crops where a rake pass is done mid-season (ginseng alley maintenance, orchard alley cleaning), the minimal surface disturbance does not affect the established root zone below 15 cm.

Is the EP-EW-4000 eligible for Korean agricultural machinery subsidies?

The EP-EW-4000 rock rake (돌 갈퀴기, 스톤 레이크) is classified under the 농지 정비 기계류 (farmland improvement machinery) category in the Korean agricultural machinery purchase support program — the same category as the stone crusher and rock picker. Eligibility for the current year must be confirmed with your regional agricultural technology center (농업기술센터). Korea Watanabe provides technical specification documentation for EP-EW-4000 subsidy applications. The rake’s lower machine cost relative to the THOR crusher means the subsidy represents a proportionally larger fraction of the purchase price — making the subsidy application particularly worthwhile for farmers purchasing the EP-EW-4000 as their primary stone management tool.

Stone Condition + Crop + Scale → Rake, Crusher, or Both?

Describe your field conditions (typical largest stone weight, surface vs embedded, annual vs first-clearance) and target crop — we confirm whether the EP-EW-4000 alone, THOR+CT-2100, or the combined three-machine sequence is the correct system for your Korean farm. EP-EW-4000 in Korea local stock, Ansan-si, Gyeonggi-do.

Editor: Cxm

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