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Rakes and mergers

Ronald T. Schuler Published on 01 April 2011

Hay and forage producers have a wide variety of equipment options for raking and merging swaths or windrows.

Selecting the proper equipment and operating it correctly will ensure high-quality hay and forage with a cost effective harvesting system.

Numerous studies have provided results on equipment performance and selection that fit specific forage harvesting systems. Rakes/mergers are often used for four purposes:

1. Creating a narrow swath in windrow sufficiently narrow to meet the width of the harvester or baler pickup

2. Merging swaths together to match the windrow density with the harvester or baler capacity

3. Inverting the crop to allow wet forage on the bottom of the swath to be exposed to sun and wind for faster drying

4. Moving the swath from wet to dry ground

Machines available
The machines include rakes (wheel, parallel bar and rotary), mergers and tedders/inverters.

Each of these machines has strengths and weaknesses which allow the producers to select a machine that best fits their production system needs.

Wheel rakes are not powered directly by the tractor PTO or hydraulic system. Rather, forward motion of the tractor and the engaging of the rake wheels in the crop and/or soil to drive the rake wheels.

These machines may have difficulty moving wet, heavy swaths or windrows.

As a result, wheel rakes are frequently limited to raking drier crops that will be harvested as dry hay. These rakes are known for gently handling the swaths. The rake wheels are supported with springs having adjustable tension.

Excessive tension may cause the wheel to float over the crop and leave some crop behind. Inadequate tension will cause more rapid tooth wear and greater contamination of the forage with soil, rocks, and other debris.

The twin or double rake design has become more popular to meet the needs of large hay production systems. Rake widths in excess of 36 feet are available which permits the merging of two passes of an 18 foot mower-conditioner.

The wheel rake is the lowest cost rake and these machines can have features such as, larger diameter rake wheels, more teeth per wheel, and hydraulic controls versus manual folding and width adjustments.

Parallel bar rakes were the most popular rake years ago. Because of costs and limited widths, these machines are less available.

Twin frame rakes are available for the larger production systems but they are more costly than wheel rakes and are more limited with respect to raking widths which do not exceed 30 feet.

Rotary rakes were introduced into the U.S. in the 1980s and sales have slowly increased since. Single rotary rakes are most popular but multiple rotor rakes are readily available.

The two primary features that differentiate single rotor rakes are the rotor diameter and the number of arms. Larger diameter rotors and more arms will increase the capacity.

Standard twin rotor rakes are typically designed to sweep two swaths toward the center forming a single merged windrow. The distance between the two rotors, and hence the coverage width, may be adjustable.

These rotors are not directly side by side so that one rotor leads the other. Some twin rotor rakes can be adjusted so that all hay is moved in the same direction.

This allows merging to the side of the machine, rather than the center, so that when the next pass is made, another merged windrow is laid beside the first. This may be done to meet the capacity of a large self-propelled forage harvester.

These machines would typically be used to merge crop for large self-propelled forage harvesters. Rotary rakes have a deserved reputation for creating a well-formed, fluffy, less roped windrow that allows good air circulation and good crop drying.

For this reason, these rakes are becoming increasingly popular to merge the crop for large square balers because of the need to get hay very dry in these large bales.

Care must be taken with this rake not to sweep the ground too aggressively to minimize soil and rock contamination of the windrow.

Another important adjustment is the rotor to ground speed ratio. The correct combination of tractor gear and engine speed must be found so that the crop is completely swept into the windrow, but the rotor is not turning so fast that leaves are shattered from the stem.

Rotary rakes are the most expensive rake type discussed because they require the heavy frame, and the cam-actuated gearbox that drives the rotor is more complicated and expensive. The cam/gearbox can be quite expensive to repair if failure occurs.

As forage harvesters have increased in capacity, the need has grown for merging more swaths into a single windrow.

The major difference between the rakes and mergers is that the mergers lift the crop onto a belt conveyor that is used to move and deposit the swath into the desired location so the crop is never dragged along the ground.

The merger can be used for either silage or dry hay although its primary use is silage. Most machines can deposit the crop to the left or right simply by changing the direction of the hydraulically driven belt conveyor.

Most merger manufacturers have single merger systems but double and triple mergers have become available. The double merger picks up two swathes and places them on a third swath.

With this merger, the operator can return on the other side of the merged swathes and place two more swathes on the three. One manufacturer has a 30 foot wide continuous pickup, which can pick up a wide range of swath widths.

If a 30 foot mower conditioner with three ten-foot sections, which creates three swaths, is available, this machine would be capable of picking up the three swaths and is considered a triple merger.

Another example of a triple merger is one capable of picking up three swathes and depositing them on a fourth. Another manufacturer mounts a single merger on the front of the tractor which tows a double merger.

The merger on the front of the tractor picks up a swath and lays it on the adjacent swath. The double merger towed behind the tractor picks up three swaths (a single swath and the double swath) and lays them on a fourth swath.

Before purchasing a merger, the compatibility of the mower-conditioner width, merger pickup width and the forage harvester or baler pickup width should be checked. For the double and triple mergers the spacing of the pickups should be easily adjustable using hydraulics.

Tedders and Inverters
Windrow inverters pickup one windrow and lay it on the ground up side down. They are configured quite similar to windrow mergers with a conventional or belt-type pick-up, cross-conveyor belt and inverter shield at the conveyor output.

The primary differences between a merger and inverter are that the inverters have a narrow pick-up that can only accommodate a narrow windrow and the inverter is lighter-duty than a merger.

The inverter is not intended as a merging device. Rather, the inverter is intended to move an already formed windrow off of wet ground and invert it for faster drying to dry hay moisture.

Two types of machines are available, rotary and parallel bar. Rotary tedders are used to spread crop into a swath potentially as wide as the cut width of the mower-conditioner.

This not only aerates the swath, but more importantly it allows all the sunlight that is striking the field to be used to dry the crop. The parallel bar tedder fluffs the swath and minimal impact on the swath width.

Tedding is an aggressive action and is acceptable for grasses where leaf loss is less of a concern. But for alfalfa there is concern that tedders will cause unacceptable leaf loss, especially if the tedding is done when the crop is partially dry and the leaves are brittle.

Tedding adds an additional step in the haymaking process: cutting, tedding, raking and baling.  FG

References omitted due to space but are available upon request.

—Excerpts from revision of ‘Equipment to Rake and Merge Hay and Forage’, Wisconsin Forage Council

Ronald T. Schuler
Extension Agricultural Engineer
University of Wisconsin