About the NWCS Hop Equipment

Working closely with farmers, UVM Extension agricultural engineer Chris Callahan and UVM engineering students, the NWCS program developed prototypes for the following small-scale hop-related equipment.

Hop Oast

Hops are commonly harvested at 75-80% moisture by weight, but are ideally pelleted, packaged and stored only after they are dried down to 8-10% moisture. To address the needs of small-scale hop production, a modular hops oast was developed and demonstrated by UVM Extension and Borderview Farm. This oast is designed as an integrated cabinet drier that holds trays of hops. The drying is accomplished with a fan, heater and controller.

Different hop varieties can be kept separate in the oast by placing them in different trays. A total of 8 trays can be accommodated in each cabinet. Wire mesh is used as the bottom for the trays which allows air flow through the hops.

The aim of the design is to use readily available materials and common construction skills and to result in a modular and scalable oast that supports hop growers of various scales. A base module of 4’W x 4’D x 8’H makes use of standard building materials and allows for conveniently sized hop trays. All of the main structure is made with standard construction lumber and plywood. The electrical system is 220 VAC single phase and uses fairly common parts and wiring. The fan motor is 1/4 hP and the fan impeller is a 24 inch vane axial design capable of 3250 CFM at 0.7 iwc pressure rise (at 1750 RPM). The majority of air flow is circulation within the cabinet, however, in order to dry the hops the humidified air must be removed. Holes are drilled in the top of the cabinet at high pressure and low pressure areas along the impeller resulting in exhaust and fresh air intake respectively. The placement of these holes and the degree to which they are open or covered determines how much “stripping” air is pulled through the cabinet. The heating element is a 3500 Watt bent tubular heater. Although one can dry hops using unheated, ambient air, the addition of well controlled heat to the air allows for quicker drying reducing labor and maintaining higher quality hops. The components used in this oast have been selected to dry 300 lbs of wet hops from 80% moisture to 10% moisture in 8 hours with little to no labor required.

A proportional-integral-derivative (PID) controller has been used in the system. This type of controller allows the user to set a target temperature and by monitoring the actual temperature in the cabinet using a thermocouple it “zeroes” in on the set-point. This differs from a thermostatic control that would provide an “average” temperature of the set-point but with sometimes wide fluctuations above or below it. The PID controller is always monitoring the difference between the set-point and the actual temperature, the historical difference, and the rate at which this difference is changing in order to predictably adjust the heater operation to attain the desired temperature.

Plans for the UVM Modular Hop Oast including design drawings, a bill of materials, and a description of the machine are available.

Small-Scale Hop Harvester

The development of the small-scale, portable hop harvester was a project of University of Vermont Extension, Vermont Agency of Agriculture and Massachusetts Department of Agricultural Resources through the USDA Specialty Crops Block Grants Program. The intent of this project was to demonstrate the feasibility of a portable hop harvester with sufficient capacity to serve a 1 acre hop yard per day. A machine like this one is needed since relatively few hop growers in the northeast can justify the expense of a larger, stationary harvester given the limited scale of their hop production. Additionally, this project intended from the start to make all design documents available to the public for review, replication and improvement of the machine by other users.

A team of hop growers, brewers, and UVM Extension faculty and staff teamed with an engineer and a fabricator to design and develop a functional prototype of a mobile hop harvester. Two general concepts were considered; a machine that stripped vertically hung bines and a machine that stripped horizontally pulled bines. The team decided on the horizontal machine since it lent itself more to being portable (lower height). Power supply was another consideration, with the main options being electrical or hydraulic. The overall power demand estimate and need for speed control suggested that if electrical power was selected, three-phase service would be required. Combined with the fact that most of the hop yards in the group are somewhat remote and the fact that most growers would have a reasonably sized tractor with a PTO, the group chose hydraulic power.

The design requirements were developed by the design team, and the design concept was detailed by the team’s engineer. Fabrication of the prototype was largely completed by Triangle Metal Fab, Inc. in Milton, VT. Some final assembly and modification was carried out on-site at Four Star Farm (Northfield, MA) and at Borderview Farm (Alburgh, VT). The work by both of these farms in making final adjustments and, in some cases, major alterations is greatly appreciated. Plans for the UVM Small-Scale Hop Harvester, including design drawings, a bill of materials, and a description of the machine are available.

Small-Scale Hop Balers

Prototype of the very small-scale hop baler.

As part of the University of Vermont Senior Experience in Engineering Design (SEED) program, engineering students Ian Pfeiffer, Brian Pinand, Ryan Rzepka, Yuri Hudak, and John Repucci designed and built prototypes of two small-scale hops balers. Their work was conducted under the supervision of Dr. Mike Rosen, UVM College of Engineering and Mathematical Sciences. The projects were funded in part by the Vermont Agricultural Innovation Center through USDA Rural Development.

The very small-scale hop baler project developed an alternative design, aimed at producing 5 to 10 pound bales using human power, with a particular emphasis on preserving quality, safety, low cost and time efficiency. View the very small-scale hop baler design, analysis, prototype realization and test results here (pdf).

The small-scale hop baler is intended for 15 to 20 pound bales. Here the students retrofitted a log splitter to used with the baler. Small-Scale Hop Baler instructions (pdf).

Disclaimer

Please note that the associated design documents are provided “as-is” without guarantee or warranty of any kind. The purpose is to communicate the findings of a research project with the aim of developing a small scale equipment for use in the Northeastern US. The designs are based on standard practices in hops drying and other agricultural equipment operation. Descriptions of the machines are based on the first year of operation (one harvest season), during which several modifications were made. These designs should be reviewed for relevance to the user/reader’s specific location and operation. The designs of these machines do assume experienced and attentive operation teams who demonstrate safe practices when using equipment. The machines are not intended to be operated unattended or by unskilled operators. Risks of bodily injury, include, but are not limited to those that may occur as the result of various pinch points and injury due to falling from ladders/platforms during maintenance or other operations. Any deviation from the designs may create safety risks that are unknown to the designers. UVM, NeHA, their employees and their contractors do not assume liability for any actions or machine assemblies that result in personal injury or loss of property or damage to property on the part of the user of these documents or any operators of the equipment.