New Bunching Saw Goes Beyond Durability Requirements

Prentice is introducing the SH-56B, a new high capacity bunching saw built with the durability and performance to match the new Prentice C Series wheel feller bunchers.

“We made sure this head could live up to the increased capabilities of the new C Series wheel feller bunchers,” said Matt McDonald, Caterpillar Forest Products product performance engineer. “We went above and beyond basic durability requirements with tapered roller bearings and new abrasion-resistant materials. And we maximized performance by incorporating our patented Strait Grip bunching finger that keeps bunches tightly compressed and straight.”

The SH-56B meets the most demanding production requirements in both first and second thinning applications, handling high volumes of small stems, mixed stems and large single stems. The expanded accumulating pocket provides high capacity small wood harvesting while the 56 cm (22 in.) single cut capacity lets you tackle larger timber when needed.

Durability

Primarily due to added guarding, thicker plates and other durability features, the SH-56B is over 600 lbs. heavier than the heads it replaces, the SH-50 and SH-56.

“A limiting factor on previous heads was the stability of the carrier. In the new C Series, the engine is at the back of the machine for better weight distribution and balance between the front and rear axles. The machine is extremely stable. As a result, we were able to substantially beef up the structure of the head, because the carrier can handle it,” McDonald said.

Tapered roller bearings

The patented tapered saw shaft and bearing design, in service since 1999, is field proven to be reliable in the center hitch of Cat tractors. Incorporating a similar design in the SH-56B reduces the impact on the hydraulic system and on the structure from the continual shock loads created in high cycle applications. Sealed upper and lower bearing chambers are individually lubricated and vented from the bottom up.

The SH-56B is the first and only saw in the industry to feature tapered roller bearing joints in both the upper and lower high cycle pin joints of the gathering arm and bunching finger.

Abrasion-resistant materials

Abrasion-resistant materials are used extensively in the saw housing, carry plate and discharge chute structures to maximize durability. An additional layer of replaceable abrasion-resistant material reinforces areas that take the most abuse.

“This really helps extend the life of the saw by protecting the primary structures,” McDonald said.

Saw base

The SH-56B has a larger diameter disc than the SH-50 for an increase in single cut from 20 in. to 22 in., but the width of the head remains the same. “Even though we went to a larger diameter disc to give us more cut, we didn’t have to increase the width of the head,” McDonald explained. “We still have a nice tight package for first thinning applications.”

Compared to the SH-56, the disc is extended out further from the frame. “On the SH-50 the disc was positioned closer to the back of the frame. We had customers in thinning applications looking for a little more reach. We were able to move the disc out and give them more reach because of the stability of the C Series,” McDonald said. “Moving the disc also provided more space for a more substantial structure in the base to support the gather arm cylinder.”

The robust box section saw base transfers loads into the lift arms — not through the welds. A small cutout acts like a spring and allows the carry plate to flex a on a microscopic level so less load is transferred through the welds.

The large discharge chute quickly exhausts chips and debris from the saw housing, reducing wear and enhancing disc recovery time to improve fuel efficiency. Additional design changes to the saw housing shed debris from the top of the disc and safely direct it toward the ground to improve saw performance, eliminate plugging and greatly reduce wear.

From front to back, all guards that protect hoses and the saw motor have been beefed up to prevent debris build-up and damage from high capacity bunching.

Hydraulic hoses are encased in rubber tubing with two bolt-on guards holding them neatly in place, so no hoses are exposed at the base of the head. The bulkheads are easily removed when servicing is required. Of the eight hoses, six are identical and two are identical. All are the same diameter and use the same fittings.

Gather arms

With a bunching capacity of 0.69 sq m (7.4 sq. ft.), the SH-56B can handle single and multiple large stems. The large torque tube design of the gather arm supports loads that can twist or bend the arm of less rigid saws. Substantial structures were developed to support the high cycle gather arm, including a flared lower joint.

“Think about trying to hold onto the base of a soda can while someone pushes on it. You have to hold pretty tight. But if it is a paint can, you have a lot more to hold on to and can better resist the force pushing on it. Same principle applies to the flared gather arm joint.” McDonald explained.

Strait Grip finger

The innovative Strait Grip bunching finger tucks trees into the accumulating pocket, keeping the tops together and creating tight bunches. Ideal for first and second thinnings, this innovative bunching technology allows the operator to cut, bunch and control more wood before piling. Other saw designs don’t keep the treetops together, forcing the operator to drop the load before reaching full capacity.

“The bunching finger is the most powerful in the industry and keeps bunches tightly compressed and straight — no jackstrawing,” McDonald said. “Besides providing excellent productivity, it optimizes skidder and loader efficiency because the stems are well organized and straight.”

Tower

The tower is a robust box section type design. The 107 in. height provides excellent stem control and the twin tower frame gives the operator direct-line visibility. For working in big timber, performance is similar to a center post head because the top is designed so there is no way for a large tree to get caught in the pocket. “The no-pinch-point tower prevents stems from getting caught in the pocket, as is the case with other high capacity bunching saws,” McDonald said. “And it carries the load within the lift arms for maximum control.”

Compatibility

The SH-56B can be matched with all new C Series models, the Prentice 2570C and 2670C wheel feller bunchers.

Prentice SH-56B Bunching Saw photo
Prentice is introducing the SH-56B, a new high capacity bunching saw built with the durability and performance to match the new Prentice C Series wheel feller bunchers.