Pull-Type Hazelnut Combine Development

Progress report for FNC23-1362

Project Type: Farmer/Rancher
Funds awarded in 2023: $30,000.00
Projected End Date: 01/31/2025
Grant Recipient: Happy Roots Farm
Region: North Central
State: Wisconsin
Project Coordinator:
David Bohnhoff
Happy Roots Farm
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Project Information

Description of operation:

Bohnhoff and Ronsheim: Self-employed hazelnut farmers and board members of the American Hazelnut Company (AHC). Ronsheim also serves as AHC treasurer and manages AHC oil and flour production.
Bashaw: Owner of Pendragon Specialties, LLC – an agricultural machinery manufacturer in East Troy, WI.
Osterhaus: Research Program Manager, UW-Madison Department of Agronomy.

Bohnhoff: Primary designer, parts procurement and fabrication, machine assembly and testing, report preparation.
Ronsheim: Machine testing/demonstration, primary data collection, field day organizer.
Bashaw: Green cluster husker design, parts procurement and fabrication, machine testing.
Osterhaus: Design consultation, parts procurement.

Bohnhoff: Happy Roots Farm - a 14 acre fruit, nut and vegetable operation in Sheboygan County. Primary crops are apples (850 trees) and hazelnuts (3.5 acres); also organically grown pears, peaches, plums, cherries, mullberry, elderberry, aronia and numerous vegetables. Hazelnut acreage includes separate research plots of WI-MN hybrid selections, new Rutger’s releases, and OSU cultivars.
Ronsheim: Blue Mound Hazelnuts, LLC – a 30 acre permaculture operation in Iowa County that includes a 10 acre woods (mostly walnut, bitternut hickory and oak) and six-acres of hybrid hazelnuts. The hazel planting has been the center of UW-Madison hazelnut field harvesting research for the past 3 years.

BACKGROUNDS (Education/Past Employment/Skills):
Bohnhoff: BS, MS and PhD Agricultural Engineering. Former dairy farmer. Former agricultural equipment design engineer for Gehl Company. Former UW-Madison engineering professor (30 years) with hundreds of technical publications. Licensed WI professional engineer. Heavily involved in hazelnut related research over past 8 years. Designed and fabricated roller sorter, drum sorter, tilt bed sorter and aspirator for UMHDI Hazelnut Processing Accelerator in Ashland, WI.
Ronsheim: BS Physics and PhD Materials Science. Formerly in microelectronics R&D for 35 years with AT&T Bell Labs, IBM Microelectronics, and National Semiconductor.
Bashaw: BS Soils and Agricultural Engineering. Managed organic farm (9 years). Owned and operated Pendragon Farms (10 years). Designed and built mobile lay-down produce harvesters, rotary weeders, and numerous hazelnut processing machines including a cracker, husker, aspirator, and roller sorter for New Forest Farms and drum and tilt-bed sorters for the UMHDI Hazelnut Processing Accelerator.
Osterhaus: BS Agricultural Engineering Technology. R&D Product Evaluation Engineer for Knight Manufacturing, Meyer Manufacturing, Kuhn North American (34 years). As an independent contractor, has designed and built a water wheel planter, plastic mulch layer, aronia harvester, milkweed pod harvester, and milkweed fiber extraction machine. Operating own corn breeding/improvement program for past 6 years.


Over 99% of the hazelnuts produced in the United States are grown as a monoculture crop in the Willamette Valley of Oregon. Nuts in Oregon are allowed to fully ripen and fall to the orchard floor, where they are windrowed and swept up using special equipment. To facilitate this practice, the orchard floor is frequently tilled and press-rolled to maintain a flat, bare surface that's void of rodent holes. These flat surfaces are subject to both wind and water erosion and are completely void of bio-diversity. Harvesting hazels in the Oregon manner is not possible in the Upper Midwest given the sloping topography in much of the area - sloping land that requires maintaining a vegetated orchard floor. To: (1) facilitate harvest on sloping terrains, (2) minimize nut predation by animals, (3) eliminate nut contamination via orchard floor contact, and (4) reduce harvest costs, hazel farmers in the Upper Midwest have opted to mechanically remove and collect hazelnut clusters from plants before they are fully abscised by the plant and fall to the ground. To do this efficiently and effectively (and thus drive more cropland toward a more sustainable perennial cropping alternative) requires equipment specifically designed for hazelnut harvesting.

Project Objectives:


For the past decade, a handful of growers in the Upper Midwest have used old over-the-row (a.k.a. straddle) blueberry harvesters to mechanically remove and collect hazelnut clusters from plants. Use of these harvesters, along with research recently conducted at UW-Madison with aronia, olive and blueberry harvesters, has demonstrated that hazelnut clusters can be effectively removed by a variety of mechanical shaking devices. At the same time, use of these harvesters has shown they can't adequately handle tall hazel plants, frequently get plugged by dead branches also shook from the plants, and require low-boy trailers for over-the-road transport.  Additionally, these harvesters only remove and collect hazelnut clusters; they don't remove nuts from the clusters [Note: a hazelnut cluster consists of one or more hazelnuts each surrounded by an involucre (a.k.a. husk)]. Instead, clusters are transported to a facility where they are dried, and the nuts then removed from their clusters using specialized husking equipment. 

The solution to the current mechanical harvesting shortcomings is to design a harvesting machine specifically for hazelnuts that is easily transportable.  In addition to removing clusters from plants, this harvester would also contain a threshing mechanism (a.k.a. a green cluster husker) for freeing nuts from their husks, as well as a system for separating out the nuts (from husks and other debris) and transporting them to a storage bin on the machine.  Given that this machine would COMBINE reaping, threshing and winnowing operations, it is herein refereed to as a hazelnut COMBINE.

In addition to a green cluster husker and nut cleaning system, the proposed combine would contain a low-cost collection platform that eliminates “stick plugging” issues, and a unique frame with adjustable shaker mechanisms that (1) enable the harvest of taller plants and (2) facilitate long-distance, over-the-road transport without reliance on a low-boy trailer.

The money secured from this grant would be solely used to pay for a portion of the raw steel and components needed to build the combine.  Additional material/supplies, travel costs, and all labor for the design, fabrication, assembly and testing of the combine will be donated/covered by team members.  The UW-Madison Biosystems Engineering shop will be relied on for parts fabrication when needed (see letter of support).

It is important to note that team members Bohnhoff, Bashaw and Osterhaus are agricultural engineers, each with a long history of successful product development.  Each has not only designed several different pieces of agricultural equipment, but each (without any outside help and often on a shoe string budget) has used their machining, sheet metal fabrication and welding skills to build the machines.  It is an awareness of, and an appreciation for each other’s engineering talents and fabrication skills, combined with their farming experiences and mutual interest in sustainable crop production (which they share with Ronsheim), that has brought them together over the past few years.  It is an association that will enable attainment of the following objectives at minimal cost.


  1. Fully detail a hazelnut combine harvester using CAD software.  Produce a complete set of shop drawings for machine fabrication. (March 2023 – March, 2024)
  2. Test an improved green cluster husker with cleaning system (February, 2024)
  3. Fabricate the combine (April- August, 2024)
  4. Field test hazelnut combine (September-October, 2024)
  5. Push technology transfer (November-December, 2024).



Click linked name(s) to expand/collapse or show everyone's info
  • John Bashaw - Producer
  • David Bohnhoff - Producer
  • Timothy Osterhaus - Producer
  • Paul Ronsheim - Producer


Materials and methods:

Development of a complex piece of machinery like a hazelnut combine begins with the establishment of major design specifications that control/limit design options.  For example, major design specifications for this project included a maximum height in the transport position of 10.5 feet, the ability to transport the machine on a deck-over trailer with a width of 8.5 feet or less, the ability to quickly transfer a bin of nuts into hopper trailers with sidewall heights up to 11 feet, a picking tunnel width of 5 feet, and the flexibility to harvest hazelnut plants at a variety of plant heights.  Guiding design principles (i.e., design selection criteria) for this project (in overall order of importance) were/are (1) functionality and compatibility (i.e., how the does a particular option fit with other systems on the machine), (2) safety, (3) cost, (4) KISS (Keep it Simple, Stupid) which is related to cost, (5) interchangeability/flexibility, (6) repair-ability by owner, and (7) ease of maintenance.

Self Propelled vs Pull-Type Combine

The first major decision on this project came after initial brainstorming and evaluation of existing fruit harvesting equipment.  This decision was to develop a self-propelled combine instead of a pull-type unit as implied by the title of this SARE grant.  The reason a pull-type unit was initially proposed was largely because it was felt that adding a power unit (i.e., engine) and wheel drive system to the harvester would significantly increase cost.  Additionally, we also had picked hazelnut clusters with the Johanna 4 (a pull-type aronia harvester) without major problems.

After some digging, we became concerned about side-draft issues with an over-the-row pull-type unit (note here that the Johanna 4 we tested was not an over-the-row harvester).  Side draft is the tendency of an implement to move or be forced in a direction at right angles to the direction of forward motion.  Such movement increases the greater: (1) the trailing implement is offset to the side of the tractor, (2) the force at which the crop and/or soil pushes back on the trailing implement, (3) the rolling resistance of the trailing implement, and (4) the incline of the land on the side of the tractor to which the implement is offset.  In the case of straddle harvesting of hazelnuts, soil/crop pushback occurs when the plants are forced into the tunnel, plants scrape along the sides of the tunnel, plants strike the shaking system, plants force the collector plates open, and the machine frame strikes the ground. The only effective way to counter side-draft when it is affecting a pull-type implement is to power (i.e., drive) the wheels of the trailing implement.  The drawback of this approach is that a certain amount of energy gets wasted, and perhaps a bit of turf gets torn up (and unnecessarily so) when tractor ground speed and the ground speed of the driven pull-type implement do not independently match.

Given that any pull-type hazel combine will likely require one or more hydrostatically-driven wheels to prevent side-draft, the cost advantage of a pull-type harvester over a self-propelled is measurably reduced.  Other advantages of a self-propelled over a pull-type combine include:

  1. Maneuverability.  A pull-type unit requires a much wider headland to align the harvester with a plant row prior to engaging the crop.  Self-propelled units can be designed with a very tight turning radius.
  2. Horsepower.  A pull-type hazel combine will likely require a tractor with at least 70 hp (with 100+ much more preferred).  Not all farmers have such a tractor.
  3. Orchard Suitability.  Most tractors are not suitable for orchard conditions as the ideal tractor for a pull-type hazel combine would have a lower profile, feature turf tires, and be narrow enough to move between hazel rows without damaging the plants or the tractor.
  4. Transport. A self-propelled piece of equipment is typically easier to load on a transport trailer than a large, offset pull-type harvester.
  5. Operator View.  A self-propelled combine can be designed so that the operator is ideally located for proper maneuvering of the unit.  This is likely to be at a location that is at the front of the machine and at a low enough position to see the base of each plant entering the harvester.
  6. Control Accessibility.  Controls for pull-type units are either on the harvester where they are not accessible to the operator, and/or in a box that must be clamped to the tractor when hitching up to the harvester.  It follows that such controls are not ideally located for operator use/comfort like they would be in the compartment of a self-propelled machine.
  7. Alley Cropping.  When other crops are grown between rows of hazels, it is highly desirable to minimize/avoid driving on these crops.  Eliminating a tractor likely minimizes the width and/or number of wheel tracks associated with harvest.

Wheel Numbers

Once the decision to switch to a self-propelled harvester was made, the advantages and disadvantages of a 3- versus a 4-wheel harvester were examined.  Three principle factors led to a decision to go with a 3-wheeled machine (1 front, 2 rear): simplicity, cost and maneuverability.  Simplicity is associated with the realization that three points determine a plane, and thus when you have three wheels, each of them is in contact with the ground regardless of what surface you are on.  With a 4-wheel machine, you must add special linkages, connections and/or suspensions to keep all four wheels on or near the ground, especially when traversing rough terrain.  Not only are these special linkages, connections and/or suspensions costly, they get more complex when design specifications include the ability to independently raise/lower each wheel.  With respect to cost, we were told during a 2022 visit to a fruit harvester equipment manufacturer in Oregon that the cost for them to go from three to four wheels on a particular harvester was around $30,000.  As far as maneuverability is concerned, suffice it to say that it’s much easier to obtain a tight turning radius with a single, driven, steerable wheel than with two, driven, steerable wheels.

Wheel Orientation

Each hydrostatically driven wheel requires a planetary gear hub, a hydraulic drive motor to turn the planetary, and associated hydraulic hoses/plumbing.  On every known fruit harvester in existence, these items are on the inside of the wheel, that is, on the side of the wheel that does not face the outside of the machine.  Also on the inside of the wheel on these fruit harvesters are the components and structural framework required to raise and lower the wheel.  The space that is taken up by these items (specifically, the drive motor, associated hydraulic hoses/plumbing, and the components and structural framework required to raise and lower the wheel) forces the wheel outward from the picking tunnel.  When the width of this space is in the neighborhood of one foot, the minimum side-to-side distance between the tires on opposing sides of a harvester with a five foot wide picking tunnel and 3 or so inch wide tunnel walls would be 7.5 feet.  This wheel spacing presents a problem when the goal is to transport the harvester on a trailer with a width no greater than 8.5 feet.

To address the wheel spacing issue, a decision was made to flip the wheels 180 degrees; that is, to position wheels so that the drive motors and wheel raising/lowering components are outside the wheels.  This enables the tires to be placed within a couple inches of the picking tunnel sidewalls, and also provides better service access to hydraulic drive motors and wheel raising/lowering components.  The downside of this is that to change tires requires (A) wheel access through the picking tunnel walls, or (B) that the machine be raised up high enough (and then blocked in place) to provide wheel access below the picking tunnel and the attached cluster collection platform.  Of these two design options, raising the machine for tire changes was felt to be the most attractive.

Machine Raising/Lowering

Incorporating the ability to independently raise and lower each wheel was one of the initial design specifications for the hazelnut combine for three primary reasons.  First, it enables the machine to be leveled on sloping terrain.  Such leveling not only provides stability, but it also helps ensure that the picking tunnel remains parallel to the vertical axis of the plant, which in turn, provides more uniform shaking.  Second, it enables the machine to be raised for the harvest of taller plants.  Without the ability to raise the machine in the field, the harvestable height of plants is largely restricted by over-the-road transport height limitations.  Third, the machine can be raised to keep the collection platform frame from plowing through material surrounding the base of plants. This is needed in fields where plants has been planted into soil mounds, or where mulch has been added around the base of plants.

For commercially-available fruit harvesters with the ability to independently raise/lower wheels, the maximum lift ranges between 24 and 30 inches.  For our machine, it was decided that maximum lift height would be determined by tire height to enable the wheels to be removed from under the picking tunnel when the machine was fully raised.  With this in mind, attention was turned to tire selection.

Tire Selection

Tire selection is tied to a design goal of minimizing soil compaction and other damage to the orchard floor.  This goal is largely obtained by (1) minimizing overall machine weight, (2) using flotation tires (i.e., tires designed to provide a larger footprint for weight distribution), and (3) incorporating a tire tread design that balances traction needs with the need to minimize surface damage and/or deformation.  Under the assumption that the self-propelled combine (as it was being planned) could weigh as much as 14,000 lbs when loaded, we searched for flotation tires with a load rating of at least 5000 lbs, a tread more common to turf tires (TRA code R-3), and a maximum diameter of 30 inches.  The maximum 30 inches diameter was selected to avoid having to raise the machine more than this to change wheels. 

After scouring agricultural tire data, it became apparent that common flotation tires with diameters under 30 inches have, at best, load ratings approaching 3000 lbs.  A BKT tire representative was contacted for tire selection assistance and they suggested their RIDEMAX FL 693 M which is a 10-ply radial tire designed for agricultural trailers and tank trucks used mainly for on-the-road transport.  The tire has an overall diameter of 31.5 inches, a static loaded radius of 13.5 inches, a section width of 15.7 inches, and a load rating at 5 mph of 5020 lbs at 35 psi and 9640 lbs at 87 psi. At an operating speed of 45 mph the tire has a load rating of 2550 lbs at 35 psi and 4888 lbs at 87 psi. Tire size is listed as 400/45 R 17.5.  This tire has a hybrid tread that is somewhat characteristic of a turf tire, but with a bit more traction and self-cleaning capabilities.  A set of three RIDEMAX FL 693 M tires have been purchased, and special rims will be fabricated to match the planetary gear hubs that will be used.  Once the tires have been installed on the completed harvester, a local tire specialist will determine (via visual observation) the proper inflation pressure for each tire in order to maximize traction and minimize soil compaction and other damage to the orchard floor.


The decision to move to a self-propelled machine brought with it the need for a powertrain; in this case, an engine, variable-speed hydrostatic pumps, wheel drive motors, and planetary gear hubs. On-line searches and visits to salvage yards were conducted in an attempt to locate a used machine that contained all these elements.  On-and-off searching for a couple months (primarily focused on self-propelled windrowers and swathers) failed to turn up a reasonably priced machine. On a suggestion from Tim Osterhaus, a visit was made to Scott Hacker Equipment in Lexington, Illinois -- a company specializing in used corn detasselers.  There we purchased a self-propelled unit produced by Louks Manufacturing Company of Gilman, Iowa (now defunct).  From this unit we salvaged a Ford 300 Industrial In-Line 6 engine, two Danfoss Series 40 M46 variable-speed axial piston pumps, and four Auburn Model 6 Power Wheel® planetary gear drives with Eaton hydraulic motors.  At an engine speed of 2000 rpm, each M46 piston pump has a maximum output of 24 gallons per minute.  On the Louks detasseler, one of these pumps was fully dedicated to propulsion (i.e., the four wheel-drive motors), and the other pump could be switched from providing propulsion (i.e., it was used to double the ground speed of the detasseler) to powering the detasseling motors.


Between 2018 and 2022, four different mechanical harvesters were used by UW-Madison researchers to remove hazelnut clusters.  Based on an evaluation of their performance, it was felt that a rotary shaker system would be the best shaker system to install in a prototype hazelnut combine, this since rotary shakers have the ability to reach into a plant and make contact with almost all branches regardless of branch orientation.  This capability is of increased importance given the fact that the machine will be used to harvest plants that will differ in height, width, shape and branch structure because of differences in genetics and/or the manner in which they have been managed (i.e., grown naturally as bushes, maintained as single-trunk trees, or pruned to something in between these two extremes).

From a design perspective, rotary shakers are relatively complex, with designs optimized through years of use and experimentation.  In full realization of this, Littau Harvester of Stayton, Oregon was approached about providing one of their vertical axis, freewheeling rotary shaker systems for the hazelnut combine. For the past couple years, Littau has successfully harvested hazelnuts near their manufacturing facility with their over-the-row harvesters, proving the ability of their shakers to remove hazelnut clusters.

Littau recommended two of their shaker systems: the HHDX unit with an overall height of 88 inches and the TF-14 system with an overall height of 116 inches.  These heights include the framework that enables the entire shaker assembly to be pushed outward to avoid snapping a shaking rod when its end makes direct contact with a trunk or large branch.  The shorter HHDX shaker was selected with the plan that it would be installed with a hydraulic system that could rapidly raise and lower the shaker assembly one to two feet.  With young, bushy plants, it is advantageous to run the shaker as close to the collection platform as possible.  As plants grow, it’s advantageous to move the shaker up with the plant canopy, and thus away from the base of thicker shoots/trunks where there are fewer nuts, and contact with the shoots/trunks are more likely to dampen shaking and damage shaking rods.

The diameter of a HHDX shaker (sans support frame) is 61.5 inches, and in Littau machines, the left and right shakers are set up with a minimum and maximum tip-to-tip gap of 1 inch and 20 inches, respectively.  This equates to a maximum “shaker system width” of 20 + 61.5*2 = 143 inches.  To accommodate this width, along with 2.5 inches of machine framing on the outside of each shaker, a minimum overall machine width of 148 inches is needed.

Cluster Collection System

Material removed by shakers in over-the-row harvesters falls onto a collection platform.  This platform consists of two sets of collector plates - one set on each side of the picking tunnel.  Each plate rotates independently toward the rear of the machine as it is pushed backward by a passing plant.  As the plant passes, the plate snaps back into its original position, thereby closing up the area in front of the plant and minimizing loss of crop to the orchard floor.  In their non-rotated (i.e., closed) position, these plates are angled upward toward the center of the picking tunnel.  This slope, as well as the opening and closing action of surrounding plates, and the wiping action of passing branches, moves the crop off a plate and to the side of the picking tunnel where it is conveyed to storage. 

Two fundamentally different methods are used to produce the rotational action of a collector plate.  The traditional method is to attach a pivot pin to the collector plate.  This pivot pin passes through a sleeve that is welded into the frame in such a way as to achieve the initial desired collector plate angle and the plate’s plane of rotation. A tension spring is used to snap the collector plate back into position after it is no longer in contact with a plant. A more recent method of obtaining the rotational action of a collector plate involves the use of a molded mount that consists of a rubber block adhered between two metal plates.  One metal plate is rigidly attached to the collector plate and the other is rigidly attached to the frame.  The rubber block acts both as the plate’s center of rotation and as a torsional spring.  The plan was to use molded mounts in the hazelnut combine, however the mount is expensive and in laboratory tests conducted with the mount, plate rotation appeared limited to 45 degrees.  The less rotation a plate has, the longer the plate must be to properly perform its job.

Conveyance of soft fruits to storage is accomplished with either flat (generally ribbed) belts or bucket conveyers.  Bucket conveyors have an advantage over ribbed belts in that they can move more product per conveyor length, and they can move product up steeper slopes.  Conversely, they generally have more moving parts and a higher initial cost.  Bucket conveyors are essential where an easily damaged product must be moved vertically upward for processing, storage, and/or transport to the opposite side of the machine. 

As hazel plants age, a greater number of old and broken branches are knocked off by shakers.  During harvesting research, machines that utilized bucket conveyors to move material from the collector plates to the rear of the machine and then straight upward, would frequently experience a build up of sticks at the horizontal to vertical transition of the conveyors.  Plugging with sticks was also a problem in machines with belt conveyors where the conveyors passed through narrow openings or where the conveyors had a combination of a low side and a steeper slope.

To simplify design, lower overall machine costs, and combat problems with sticks, a decision was made to employ screw conveyers to move material from the collector plates to the rear of the machine.  Screw conveyors are routinely used to move cereal grains, shelled corn, soybeans, coffee beans and other more resilient crops.  A single rotating auger is the only moving part.

A hand-cranked conveyor featuring a 9-inch diameter auger was assembled to test the ability of a screw conveyor to move hazelnut clusters loaded with sticks.  Welded to a 4.5 inch diameter opening in the end and side of the conveyor was a tube through which clusters were vacuumed out of the conveyor.  The end of the conveyor was left open.  For testing, the conveyor was loaded with a mix of hazelnuts and sticks. Vacuum was generated with a Hasatsan H2200 hazelnut harvester.  The entire system worked extremely well.  Sticks were either broken up by the auger or they road along the top of the auger until they fell off the end of the conveyor. 

The Hasatsan H2200 uses a 20 inch diameter fan spinning in a 28 inch diameter housing at a typical operating speed of 3000 rpm.  The current plan is to incorporate a similar fan into the prototype hazel combine to draw hazelnut clusters from the rear end of the screw conveyers into a vacuum chamber at the top of the machine.  Located inside this chamber will be an auger that drops clusters into an air-lock that then feeds the clusters into the threshing unit.

Nut Extraction System

The nut extraction system consists of three major units operations: a thresher, a winnowing chute, and a drum-in-drum sorter.  Details of the threshing unit will be decided once experiments on the latest John Bashaw designed husking unit have been completed.  Material discharged from this threshing unit will drop into a chute of upward moving air generated by a winnowing fan with an adjustable rotational speed.  Material moved upward because of its higher specific surface area will be discharged out of the back of the machine.  Material dropping down in the upward moving airstream will enter a drum-in-drum sorter.

The drum-in-drum sorter will be identical to the drum-in-drum sorter used in the Hasatsan H2200.  Additionally, the manner in which the Hasatsan H2200: (1) uses air to move nuts from the drum-in-drum sorter to the storage bin, and (2) refeeds partially husked material back into the thresher, will also be utilized.

Dump Bin

Because of the time and cost associated with over-the-road transport of produce, the farming industry has moved, at the farm level, to the bulk handling of agricultural produce via semi-trailers and other large containers.  This trend is no different in the Oregon hazelnut industry.  As of January 2023, 42 self-propelled Monchiero nut harvesters were being used in the Willamette Valley of Oregon to collect hazelnuts.  The Moncheiro harvesters sweep nuts off the orchard floor, separate the nuts from most of the dirt collected with the nuts, and then convey the nuts into a dump bin at the rear of the machine.  This bin is emptied by first raising up the bin, then backing the harvester up to the receiving vessel (or driving the receiving vessel under the raised bin), and then dumping the bin.  One shortcoming of the Monchiero units is that it can not dump in taller trucks/trailers.  This shortcoming resulted in the special development of a 215 cubic foot, low-profile dump cart by Hillco Technologies, Inc. of Nezperce, ID.  This dump cart, with a maximum dump height of 14 feet, is used to transfer nuts from the Monchiero unit to taller trucks/ trailers.

It is fully anticipated that hazelnuts grown in the Upper Midwest will be handled at the farm level in the same way as cereal grains, shelled corn and soybeans; that is, they will be moved via semi-trailers and large gravity wagons to local agricultural marketing cooperatives or special receiving stations where they will be dried, temporarily stored and then moved to a processing facility. 

To facilitate quick bulk handling, the hazelnut combine will be fitted with a storage bin that can dump at a maximum height of 11.5 feet when the machine is fully lowered, and at a maximum height of 14 feet when the machine is fully raised.  So as not to affect machine stability, the bin will be located between the shaker and the rear wheel on the same side of the machine as the front wheel.  The bin can be raised to any desired height and then dumped.  Dumping is out to the side so that the machine can be driven alongside the receiving vessel, or the receiving vessel can be driven alongside (parallel to) the combine.

Nuts are blown into the bin through a hole near the very top of the bin side.

Hydraulic System

The combine will be powered by three hydraulic pumps.  One Danfoss Series 40 M46 pump operating in a closed loop system will be fully dedicated to turning the three drive wheels, the second Danfoss Series 40 M46 pump operating in a closed loop system can be switched between (A) powering the material transport fan motor during harvest, and (B) powering the drive wheels for an increase in ground speed during non-harvest activities.  The third pump, with an output of 30 gallons per minute and operating in an open loop system, will be used to power the two shaker motors, three screw conveyer motors, the airlock motor, the thresher motor, the winnowing fan motor, the steering motor, and the drum-in-drum sorter motor.  The third pump will also be used to power all hydraulic cylinders.  This includes the three cylinders used to raise/lower each of the three wheels, a dump bin lift cylinder, dump bin tilt cylinder(s), shaker raise/lower cylinders, a cab lift cylinder, and the two cylinders used to change the frame between transport and harvest modes.

Movement of all cylinders will be electronically controlled from the operator cab, and all motors powered by the third pump (except the steering motor) will be switched on and off from the cab.  The speed of pumps 1 and 2 will also be controlled from the cab.  Exactly what method will be employed to control the volume of flow to motors powered by pump 3 has not yet been finalized.

The hydraulic oil reservoir will sized to hold a minimum of 60 gallons of oil.  Hydraulic oil coolers and filters have not yet been sized/specified.

Operator Compartment

The 3-wheeled machine has been laid out with the single front wheel (which is both driven and steerable) located on the right side of the machine, and with the operator compartment located in the front left of the machine (i.e., directly across from the front wheel). 

Many over-the-row harvesters place the operator atop the machine, directly above the plant row.  While this location provides an ideal line-of-sight for the harvest of shorter crops like grapes and blueberries, it can be a problematic location when harvesting taller plants.  During some of the hazelnut harvesting trials conducted at UW-Madison, plants were so tall that the operator’s view forward from atop the machine was completely blocked, forcing the driver to rely on a person walking alongside the harvester for steering adjustments.  To this end, to properly align an over-the-row harvester for closely spaced plants, the machine must have auto-steer and/or the operator must be able to see the base of the bush or tree as it enters the picking tunnel.  Suffice it to say that the latter is difficult unless the operator is positioned below the plant canopy.  Two other reasons for not placing an operator compartment with a roll-over-protection structure (ROPS) atop a harvester are (1) it restricts picking tunnel height if it can not be lowered for over-the-road transportation, and (2) it requires up-and-down climbing.

The ideal vertical location for an operator compartment for nut harvest is believed to be as close to the ground as possible such that there is an unrestricted forward view under the plant canopy when harvesting single-truck trees.  Multi-shoot plants with branches that extend or sprawl outward from the plant base are likely to partially or wholly block the forward view, but should not interfere with the operator’s side view of plants entering the picking tunnel.

To enable the operator compartment to be as close to the ground as possible, a hydraulic cylinder on the prototype combine will be dedicated to raising and lowering the compartment.  When fully extended, this cylinder will allow the compartment to continually ride on a pair of spring-loaded caster wheels, even when the rest of the machine is raised and lowered.  In addition to providing a more cushioned ride, this feature helps dampen the compartment from machine vibrations, and ensures that the mass of the compartment and operator do not negatively impact harvester stability.  This same cylinder can be retracted to move the compartment upward, to give the operator a view over the top of smaller plants.  In such raised positions, the compartment will not be as well isolated from machine vibrations.

Since: (1) space limitations require the operator compartment and front wheel to be on opposite sides of the machine, and (2) stability needs require the dump bin to be on the same side as the front wheel, it follows that the operator compartment and bin will be on opposite sides of the machine.  This means that the operator can not directly observe bin movement during unloading.  For this reason, an LCD display attached to four different cameras will be mounted in the operator compartment.  One of these cameras will be used to monitor bin movement.  It is not yet known where the other three cameras will mounted.  Options include a back-up camera, a camera to monitor nut level in the dump bin, a camera monitoring the rear end of the screw conveyers (i.e., point where clusters are sucked out of the conveyors), a camera monitoring the drum-in-drum sorter and aspirating chute, and a camera pointed forward atop the machine.


By far and away the most difficult and critical harvester design element is that of the frame.  No other element controls the overall cost of the machine more than the frame.  If elements of the frame are over-designed, or a portion of the frame geometry is not efficiently structured, the frame will have excess mass.  Frame mass is directly proportional to its cost.  In general, when you double the mass of a frame, you double its costs.  Additionally, the more mass a frame possesses, the larger and heavier must be the tires and the greater the power required to propel the machine (which in turn can drive the need for a heavier and more expensive powertrain).  Soil compaction and damage to the soil surface also increase with frame mass, and heavier machines are generally more difficult and expensive to transport.

As planned, the hazelnut harvester has six major elements that add to frame complexity:

  1. Large picking tunnel.  The only way to tie one side of an over-the-row harvester to the other side is via framing members that cross over the top of the picking tunnel.  The higher the top of the picking tunnel, the further this cross framing is from the ground, and the greater the total bending moment induced in the cross framing by forces working to change the spacing between the separate halves of the machine.
  2. A more open front structure.  Most over-the-row harvesters have a fully enclosed picking tunnel.  The top of this tunnel will bend tall plants before they reach the shakers, and also dampen the vibration of the plants as they move through the shakers.  A primary design objective is to eliminate this contact as much as possible until plants have moved past the shakers.  This requires that the top of the tunnel and any framing across the front of the machine be removed or moved upward so as not to contact plants.  For the hazelnut combine, it was decided to hinge the front cross-framing assembly so that it could be hydraulically raised for harvest and lowered for transport just by flicking a switch in the operator compartment.
  3. Three-wheels.  An over-the-row harvester with three wheels has two wheels on one side of the row and one on the other.  This asymmetric machine support induces front-to-back torsion in the overall frame due to the mass in the corner of the machine without wheel support.  To help minimize this torsion, the operator compartment (which occupies the space that would normally be occupied by a fourth wheel) will be lowered to the ground where it will be supported by its own caster wheel during harvest.
  4. Machine lift system.  When each wheel on the combine is completely lowered, the harvester will be raised 32 inches.  This increase in height adds to the total bending moment that can be potentially induced in the framing system crossing over the top of the picking tunnel.  Additionally, the bending moment induced in the vertical support attached to a wheel, will increase linearly with an increase in the distance the wheel is lowered. 
  5. Large rotary shakers.  No fixed framing members can cross through the area occupied by rotary shakers that are free to move-side-to-side and that are designed to be raised and lowered while in use.  This means that all structural framing must be located under, outside, and above the shakers.
  6. Side dump bin. To utilize a side dump bin, there can be no fixed framing member outside or above the bin as these members would interfere with the ability to raise and tilt the bin, respectively.  The inability to utilize the area outside and above the bin, complicates frame design from the standpoint that the bin is right behind the right shaker, and the only place to place framing is above, below and on the very outside of the shaker.

The frame must be designed to support all unit operations, the powertrain, and the hydraulic systems.  This equipment must be located and supported in such a way that it’s accessible for service/maintenance.  Also, room must be provided for the safe routing of numerous hydraulic hoses and electrical lines.

Incorporated into the frame will be a system for holding the machine in an elevated position after it has been raised up on its wheels.  Once the machine is locked in this elevated position, tires can be changed, or they can be fully retracted.  When fully retracted, a transport trailer can be backed under the combine.  Plumbed into the hydraulic system that powers the wheel lift cylinders will be a set of hoses and quick-connect couplings that can be used to remotely power lift cylinders in the event that the combine is dead (i.e., the machine can not be started to power the hydraulic pump connected to the wheel lift cylinders).

The combine frame is being modeled and analyzed using Visual Analysis, a software program developed by Integrated Engineering Software, Inc.  Visual Analysis utilizes “natural” two-node frame elements with 6 degrees of freedom (DOF) per node to model and analyze 2-D and 3-D frames.  The program is largely used by civil engineers to design building frames.  The advantage of using a tool like Visual Analysis is that members can be quickly resized, added or removed from a model and the model reanalyzed in seconds to determine the impact of the change.

Detailed Working Drawings

Once structural analysis of the frame has largely been completed, the combine will be detailed using Onshape, a computer-aided design (CAD) program that is delivered over the Internet and makes extensive use of cloud computing.

Research results and discussion:

As the hazelnut combine is still in the design phase, their are no testing/performance results to report at this time 

Participation Summary
3 Farmers participating in research

Educational & Outreach Activities

Participation Summary:

Education/outreach description:

This harvester is still in the development state, thus education and outreach activities have not commenced 

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.