MILESTONES & DELIVERABLES

Purpose

Concerns have been raised by both our advisors and team members regarding the success of brushes in separating leaves from the stalks during harvesting and collection. Our group conducted research regarding the characteristics of various rubbers and bristle brushes to determine which material would be most successful in terms of the goals of the project. Research focused on various rubbers, such as neoprene and polyurethanes, as well as bristle brushes. From our findings, bristle brushes have a larger coefficient of friction and can be purchased in a variety of sizes. Rubber is more cost effective, however it has a lower coefficient of friction, is not available in a variety of sizes, and have been shown to erode over time. Significant testing will be conducted with the rollers once purchased to find the optimal speed, separation distance, and contact area to maximize harvesting.

Stalk-Cut Tobacco Stripper Development – Morrison and Yoder, ASAE

• Used 2 counterrotating rubber wipers to strip tobacco leaves from the stalk

  • • 4.75” wide, 0.375” thick neoprene rubber at 65 durometer hardness

    • Slits cut 0.125” deep, 1” long at 10” intervals which were successful in making close contact with the leaves

• Found the 65-durometer neoprene rubber eroded over time and replaced it with 70 durometer polyurethane rubber

• Suggested using steel with spring reports as steel is easy to fabricate, more durable, and requires less maintenance

• Conducted a kinematic study in which they found more contact with the stalk yielded more successful results (more leaves stripped)

Design, Fabrication, and Performance Evaluation of Indigenous Sugarcane Leaf Stripping Machine – Ikram, K., Ahmad, M., Ghafoor, A., Tanveer, A., Pakistan Journal of Agriculture Science

• Used both continuous and discontinuous rubber rollers as intake rollers for their sugarcane leaf stripper

  • • The continuous rubber roller used thin mild steel bars with rubber on the edges to prevent scratching and damaging the stalk

    • The second roller used rubber squares attached to springs, also to prevent damaging the stalk

• Elected not to use metallic material as metal can damage the stalk or leaves

• Found that 92 N to 750 N of force should be applied to the stalk to remove leaves but not crush the stalk

• Cleaning roller – primary component used to remove leaves – was made of tire ply as it was affordable and locally available

  • • Tire ply has a typical coefficient of friction between 0.4 and 0.7

• A spiral was needed on the cleaning roller to rotate the stalk in the machine and increase the striking force of the cleaning roller

• A rotational speed of 1033 rpm for the cleaning roller was found to yield the best results

Modelling Bristle Brush Behavior in Rotating Brush Duct Cleaning – Holopainen and Salonen, Helsinki University of Technology

• Bristle brushes typically operate at speeds between 300 and 1000 rpm

• The thickness of bristles ranges from 0.3 mm to 1 mm

• Increased rotational speed leads to increased bristle deflection and a higher coefficient of friction (up to ~8000 rpm)

• Higher speeds increase the torque

• The average coefficient of friction is 0.7, which is higher than that of nylon (0.5)

  • • Speed has little effect on the coefficient of friction of the brush rollers

Case Study: Agriculture Brushes Are Built for the Harvest and Beyond

• Cylindrical brushes mimic a human hand and fingertips used for scraping and plucking

Mechanical Properties of the Sheath of Sugar Cane - Xiangwei Mou, Qingting Liu, Yinggang Ou, Meimei Wang, Jianming Song, ASABE

• Data taken for moister content of 45-70%

• Longitudinal tensile strength- 28 MPa

• Transversal tensile strength- 0.9 MPa

• Punch and die shear strength- 7.13 MPa

Jenkins Brush Company

• Brush data for nylon and polypropylene are supplied

• Polypropylene produces higher tensile strength but less bend recovery

Commutation Characteristics and Brush Wear of DC Motor at High Rotation Speed - Koichiro Sawa, Masayuki Isato, Takahiro Ueno, Nippon Institute of Technology

• As rotation speed increases brush wear increased significantly

• This will be accounted for to find the optimal brush speed for conservative wear and effective harvesting

Rubber and Durability - Fournier Rubber & Supply Co.

• Neoprene rubber

  • • low susceptibility to burning, corrosion and degradation

• Polysiloxane

  • • bio compatibility and resistance to extreme temperatures (important for the temperature during harvesting)

• Styrene-Butadiene Rubber (SBR)

  • • Superior hardness and durability

Discussion

A coefficient of friction between 0.5 and 0.75 is needed to successfully remove the sorghum leaves from the stalk. Both tire ply and bristle brushes have satisfactory coefficients of friction (0.7), while polyurethane and neoprene rubbers have low coefficients of friction that will not be suitable (0.25 and 0.1, respectively).

The sheave strength measurements indicate that the optimal way to remove a leaf from a plant like sorghum is to pull both radially and upward. Our current design utilizes the rollers to pull radially and the harvester and brushes to allow the upward force to be applied to the leaves.

Our team is focusing on the following harvesting methods as potential templates for our final design and prototype – cotton picker, sugar cane harvester, forage equipment, and corn snapper head. We conducted research on the process, pros, and cons of each method and how they apply to our project specifically.

We had originally included bean pickers and tea leaf harvesters as potential harvesting methods that could be modified to harvest sorghum; however, they were removed from consideration. The bean picker functions at a much lower height than is desired, and the tea leaf harvester removes the stem and the leaf rather than just the leaf.

Cotton Picker

Process

Cotton plants go into the head in individual rows. The cotton then meets 2 spinning drums with rotating spindles on the outside. These spindles are threaded to grab the cotton fibers and pull them from the plant while leaving the remainder of the plant in the field. The cotton is blown upward into a collection basket.

Advantages

• Removes the desired part from the plant leaving the rest behind

• Drum application could be useful

• The process of blowing the cotton into a basket could potentially be applied to sorghum leaves

Disadvantages

• Spindles will need to be modified or substituted for a leaf application

• Possibly needs a different sort/thrashing method

• Spindles and drum assembly is somewhat complex

• May face challenges in reaching leaves on the front and rear of the stalk and bending the plants to reach the upper leaves

Additional thoughts

Pieces of the cotton picker can be modified to meet our needs, such as:

• Drums in a different orientation with different stripping devices installed

• Hedge trimmer type blades (oscillating)

• Blades which rotate/swing/oscillate vertically

Sugar Cane Harvester

Process

Sugar cane stocks enter the head of the harvester. The stalks are cut at the base then rotating arms inside the machine strip the leaves off the plant and the stalk is cut into sections. A conveyer arm transfers the stalk pieces to a tractor pulling a large hopper-style trailer.

Advantages

• Removes leaves from stalk

• Sugar cane is similar in size and shape to sorghum, thus less modifications are needed

Disadvantages

• The leaves from the sugar cane are ejected out of the machine and dispersed back on to the field

• Entire system rather than just a head or attachment

• Expensive and targeted system

Additional thoughts

The sugar cane harvester could be a viable option if we could find a way to modify the machine to wear it keeps the leaves and disperses the stalks. Since the sugar cane is similar in size and shape to the sorghum plant the harvester would require minimal modifications. The leaves are cut up in the sugar cane harvester, however the sorghum leaves do not need to remain intact for RedLeaf’s purposes.

Forage Equipment

Process

Typical application is to chop whole stalks of corn including the grain into a feed. Corn stalks enter the front of the head and are grabbed by a mechanism and cut. The cut stalk is then moved into the feedrolls where it is then sheared into smaller pieces. It can then be run through a set of rollers to grind the mixture into a finer blend. A set of paddles forces the chopped forage out of a chute and into a wagon or truck that runs along the side of the machine or is towed behind.

Advantages

• Easy to bring the stalk in

• Would blow the blend into a wagon for easy transportation

Disadvantages

• The leaves will be mixed with the stalk and grain, require postprocessing

• Requires a separator which forage harvesters don’t have

Additional thoughts

The forage harvester could work but would require postprocessing to sort the leaves from the rest of the biomass. As our goal is to eliminate the need for postprocessing and develop a one step process, this equipment may be unusable. It seems like a worse form of a combine given that a combine will include a separator.

Corn Snapper Head

Process

A pair of spinning rolls pull the corn stalks down through the head. Just above those rolls metal plates pop the ear off the stalk. Gathering chains push the ears to the back of the head where an auger funnels the ears to the center of the head and into the front of the combine to begin the grain separating process.

Advantages

• Head rather than an entire system which is less expensive and minimizes modifications

• Clear multiple rows at a time

• Designed to separate the corn from the stalk

• Meets the design constraint of maintaining consistent spacing

• Corn is similar in height and shape to sorghum

Disadvantages

• Differences in toughness of sorghum leaves vs corn

• May need to modify the collection method since leaves are much smaller and less dense than corn

Additional thoughts

The corn snapper head meets many of our requirements. Since it is just a head it can be easily modified and is less expensive then purchasing an entire system. Corn is similar in size to sorghum so we would just need to modify the head to remove and collect leaves instead of corn.

Research was conducted regarding leaf strength, plant height, stalk width, and leaf count.

Leaf Strength:

The leaf strength was measured in terms of the force (lb) required to pull the leaf from the stalk. The pull force was measured in four directions: up, down, sideways, and out. The average pull forces were 8.62 lb (up), 5.36 lb (out), 4 lb (sideways), and 1.89 lb (down). This data was used to determine the friction coefficient for the roller material.

Stalk Width:

Stalk width was measured and used to determine roller spacing.

Leaf Count:

The amount of leaves ranged from 6 to 14 per plant with an average of 11 leaves per plant. The amount of leaves per plant was used to calculate power per leaf.

Figure 1. Project timeline.

Our project has been broken down into sections to better monitor project progress. We have completed our gantt chart, project breakdown, website URL (sites.google.com/view/sorghumleafharvesting), and have conducted research regarding various harvesting methods. We are currently beginning the preliminary design and testing stages. By December 17^th we will have a CAD package, final report, poster, and completed website prepared.

CONCLUSION

We look forward to working with RedLeaf on this project. We are confident that we can come up with a solution to help solve your problem.

If you have questions on this proposal, feel free to contact us at your convenience by email at bae.redleaf@gmail.com.

Thank you for your consideration,

The Design Team:

John Wesche

Kiley Power

John Mann

Nick Rydz

Design #1 consists of two horizontal and parallel rollers mounted on the corn head which are counter-rotating upwards. Issues with this design included stripping leaves from smaller diameter stalks, collecting leaves once they are stripped, and conveying the leaves into the auger.

Design #2 uses parallel rollers in a vertical orientation which counter-rotate inward towards the auger of the forage harvester. The concern with this design was that the contact with the plant would be minimal and the plant may get pulled through with little to no leaves removed.

Design #3 uses two hard, commercial grade rubber plates to grasp the stalk tightly as it is pulled down by the corn head. The leaves would be sheared off by the friction from the rubber plates. This design could have issues handling different stalk diameters, as well as collecting and conveying the leaves once removed.

Design #4 also consists of two counter-rotating rollers mounted to the corn head. However, in this design those rollers are tapered inward which allows them to handle a variety of stalk sizes. The rollers are also tilted slightly upward to aid with collecting and feeding the leaves into the auger of the forage harvester. Conveying is still an issue with this design and ensuring once the leaf is removed it will be collected is also an issue.

Design #5 uses a single large roller over top of a stripper plate to wedge the stalk between them while the roller strips the leaves and pushes them towards the forage harvester. The issue with this design is ensuring that the sorghum plants are fed to go between the roller and stripper plate. If the plants are unlikely to slide between the two, then the leaves would not be stripped.

Final Design: The final design is a combination of designs #1 and #4. This design uses two counter rotating rollers which are adjustable to be angled upward and tapered if needed. In addition to this, two extra gathering chains have been added above the rollers to aid the stalks to engage the rollers. These extra gathering chains will also assist in conveying the leaves into the auger of the forage harvester. A hood will be added to prevent cross winds from blowing harvested leaves off of the machine.