The Watanabe stone rake range covers two distinctly different operational scales. The EP-EW-4000 (75 HP, 3.6 m working width) is the right tool for Korean family farm and small commercial operations: annual frost-heave maintenance on established potato and vegetable fields, pre-planting clearance on small ginseng plots, and orchard inter-row surface stone management. For these applications — typically below 50–80 hectares of annual stone clearance — the EP-EW-4000 delivers adequate throughput and operates on the same 75 HP tractor as the planting and cultivation equipment.

The BlackBird Rock Rake is an entirely different scale of implement. At 9.5 metres working width — more than 2.6 times the EP-EW-4000’s working width — and with a 300 HP minimum tractor requirement and 1000 RPM PTO operation, the BlackBird is designed for large-scale land clearing contractors, agricultural development projects, government land improvement programs, and commercial farm operations above approximately 100 hectares of annual clearance. Its rear-hitch coupling system for the THOR 3.0 stone crusher — which allows both machines to operate simultaneously on one tractor — further distinguishes it as a system machine for maximum single-pass efficiency on large open terrain.

This guide explains the BlackBird’s specifications, how its coupling system with the THOR 3.0 works, which Korean operations genuinely benefit from this scale of equipment, and how it fits within the broader Watanabe land clearing range alongside the EP-EW-4000 for the lower-scale applications.

BlackBird Rock Rake — Confirmed Specifications

All BlackBird specifications from the Watanabe official product brochure:

Scale Context — BlackBird vs EP-EW-4000

The BlackBird + THOR 3.0 Coupling System — Single-Pass Rake-and-Crush

The most operationally significant feature of the BlackBird is its rear hitch coupling system that allows the THOR 3.0 stone crusher to be connected directly to the BlackBird’s rear frame — creating a combined three-machine single-pass operation: the BlackBird rakes stone windrows ahead, and the THOR 3.0 (towed behind the BlackBird, both pulled by the same 300+ HP tractor) crushes those windrows in the same forward movement.

How the Coupling Works

The BlackBird’s rear frame includes a drawbar hitch point designed to accept the THOR 3.0’s Drawbar Kit connection. In this combined configuration:

The 300+ HP tractor provides the motive force for all three components (tractor + BlackBird + THOR 3.0 in tow), PTO power at 1000 RPM for the BlackBird’s tine drive, and PTO power for the THOR 3.0’s rotor drive via the second PTO connection from the THOR’s own drive shaft running from the tractor rear PTO through the BlackBird’s frame.

The BlackBird sweeps a 9.5 m wide strip of the field at each forward pass, concentrating surface stones and vegetation into windrows along the centreline of the swept strip — exactly where the THOR 3.0 will travel.

The THOR 3.0, towed behind the BlackBird, encounters the concentrated windrow of stones that the BlackBird has deposited in the centre of the raked strip. Rather than processing dispersed surface stones — as the THOR 3.0 would do in standalone operation — it processes the concentrated windrow. This concentrated windrow processing approach is more efficient per unit of crushed stone volume than dispersed-surface processing: the THOR’s rotor contacts stone material continuously along the windrow centreline rather than intermittently across a dispersed surface.

Coverage Rate of the Combined System

The combined BlackBird + THOR 3.0 system covers the BlackBird’s 9.5 m working width in a single forward pass. At a typical combined system working speed of 2.0–3.5 km/h (slower than the BlackBird alone because the THOR 3.0’s working conditions — processing concentrated windrows — determine the forward speed), the theoretical pass coverage rate is 1.9–3.3 hectares per hour. Accounting for headland turns on open flat terrain — a 300 HP tractor with two large trailing implements requires significant headland clearance — productive daily coverage on a 10-hour working day is typically 15–25 hectares of cleared ground.

For a land clearing contractor operating a 300-hectare seasonal contract, the BlackBird + THOR 3.0 combined system completes the rake-and-crush step in approximately 12–20 productive days (depending on stone density and field logistics). An EP-EW-4000 + THOR 2.4 combination on the same 300-hectare area would require approximately 40–60 days for equivalent coverage — the BlackBird system’s throughput advantage at large scale is substantial.

When the BlackBird Is the Right Choice — and When It Is Not

The BlackBird IS the right tool for:

Large land clearing contractors with seasonal contracts above 100 ha. Korean land development contractors working government 농지 개량 (farmland improvement) contracts, rural infrastructure projects, and large commercial land conversion projects routinely encounter contracts of 100–500+ hectares of annual clearance. At this scale, the BlackBird + THOR 3.0 system’s daily coverage rate is the operational requirement — the EP-EW-4000 + THOR 2.4 combination simply cannot maintain the throughput needed to complete these contracts within seasonal timelines and contractor scheduling commitments.

Large commercial farms above 100 ha clearing area. Korean commercial grain, potato, and vegetable farms at 100+ hectares of annual stone clearance requirement — concentrated in the plains of South Gyeongsang, the highland development zones of Gangwon-do, and the reclamation areas of Chungcheongnam-do — face the same throughput constraint as contractors. The narrow spring preparation window before planting requires that the full clearance area be completed within 3–4 weeks, which the BlackBird system can achieve on open terrain where the EP-EW-4000 combination cannot.

Operations where a 300+ HP tractor is already in the equipment fleet. The BlackBird’s 300 HP minimum requirement means it is only practical for operations that already have a tractor of this power class, or that can justify a new tractor purchase at this power level based on total machine utilization. Adding the BlackBird to an existing 230 HP THOR 3.0 tractor fleet requires a tractor upgrade — the economics of that upgrade should be evaluated alongside the BlackBird’s productivity benefit.

Open terrain with row lengths above 200 m. The combined BlackBird + THOR 3.0 system has a large turning envelope at headlands — the tractor pulling both a 9.5 m trailing rake and a 3.0 m stone crusher requires significant headland space. On fields with row lengths below approximately 150–200 m, headland turning time represents an excessive fraction of total working time and reduces the effective coverage rate advantage of the BlackBird system versus smaller equipment. The BlackBird delivers its full efficiency advantage on large, open fields with long rows — not on terraced, irregularly shaped, or short-row highland fields.

The BlackBird is NOT the right tool for:

Standard Korean family farm operations below 50 ha. For operations below approximately 50–80 hectares of annual clearance, the EP-EW-4000 (75 HP, 3.6 m) provides adequate throughput at dramatically lower capital cost, lower tractor HP requirement, and greater flexibility on the irregular, short-row terraced field geometries of Korean highland family farms. The BlackBird’s investment — including the 300 HP tractor requirement — is not justified by the throughput benefit at this scale.

Orchard inter-row and narrow row applications. The BlackBird’s 9.5 m working width cannot enter orchard rows or narrow terrace field configurations. The EP-EW-4000 at 3.6 m is the appropriate rake for Korean orchard and narrow-row applications. No large-format rake can substitute for the EP-EW-4000 in these constrained-geometry applications.

Operations on steeply sloped terrain. The BlackBird + THOR 3.0 combined system — a large tractor pulling approximately 13 metres of trailing equipment — requires substantially more turning radius and has different slope stability characteristics than a single tractor-implement combination. For operations on slopes above 15%, the more compact EP-EW-4000 + THOR 2.4 combination is more appropriate. The BlackBird’s efficiency advantage is specifically on open, relatively flat terrain with long row lengths.

The Complete Large-Scale System — BlackBird + THOR 3.0 + CT-2100

For large-scale operations that require complete stone removal — not just crushing — the BlackBird + THOR 3.0 combined system produces crushed aggregate that is then collected by the CT-2100 steenrapper in a subsequent pass. The three-machine large-scale sequence:

Tractor Requirements for the BlackBird System

The 300 HP minimum tractor requirement for the BlackBird combined system (BlackBird + THOR 3.0) reflects the combined power demand of both implements at working load. The breakdown:

BlackBird alone: The BlackBird’s tine rake mechanism draws PTO power for its own drive system at 1000 RPM. The drawbar pull for towing the BlackBird at working speed and depth adds to the tractor’s tractive demand. 180–230 HP would handle the BlackBird alone on most soil conditions.

THOR 3.0 added: The THOR 3.0 requires 230 HP minimum for its own rotor operation at 1000 RPM PTO. With the BlackBird drawing a portion of the tractor’s PTO output simultaneously, the minimum tractor HP for the combined system rises above the THOR 3.0’s standalone 230 HP requirement. The 300 HP minimum for the combined system provides adequate power for both implements to operate at full rated performance simultaneously without power-starving either machine.

Compatible 300+ HP tractors in the Korean commercial sector: John Deere 8R series (8R 280, 8R 310); New Holland T8 series; Case IH AFS Quadtrac (where large-scale open terrain makes articulated tractor appropriate); Fendt 900 Vario series (930–936 Vario); CLAAS AXION 900 series. These are large-format agricultural tractors not commonly found in Korean family farming operations — the BlackBird system is specifically for professional contractor and large-scale commercial operations with appropriate equipment. Confirm the specific tractor model’s rear PTO capacity and drawbar rating for combined front-and-rear implement operation before configuring the BlackBird + THOR 3.0 system.

For Most Korean Operations — The EP-EW-4000 Is the Right Rock Rake

This guide would be incomplete without a clear statement: the majority of Korean agricultural stone rake applications are correctly served by the EP-EW-4000 steenhark (75 HP, 3.6 m), not the BlackBird. The scale of Korean family farms and mid-size commercial operations — typically 2–50 hectares of annual stone clearance — is precisely the range where the EP-EW-4000’s lower HP requirement, lower cost, greater terrain flexibility, and compatibility with Korean highland field geometry makes it the appropriate choice.

The BlackBird’s 300 HP requirement and large working width are advantages only when the operational scale, field geometry, and seasonal throughput requirements genuinely require them. Purchasing a BlackBird for an operation below 100 hectares annual clearance results in a machine that is underutilized relative to its capital cost and that requires a tractor larger than the rest of the operation’s equipment fleet requires. Purchasing an EP-EW-4000 for an operation above 100 hectares annual clearance results in a throughput bottleneck that prevents completing the seasonal clearing program within the available weather window.

The correct selection boundary between EP-EW-4000 and BlackBird is approximately 80–120 hectares of annual stone rake clearing area on open terrain — with field geometry, row length, terrain slope, and available tractor HP all influencing where exactly the transition is economically justified for a specific operation. Korea Watanabe can assist with this throughput analysis based on your specific field parameters and seasonal clearance requirements.

Frequently Asked Questions — BlackBird Rock Rake

Editor: Cxm