Presentation on theme: "BY ROBERT G. SPERRY M.S. GRADUATE JOHN H. WILHOIT EXTENSION ASSOCIATE PROFESSOR DAVE ASH ENGINEER AID BIOSYSTEMS AND AGRICULTURAL ENGINEERING, UNIVERSITY."— Presentation transcript:
BY ROBERT G. SPERRY M.S. GRADUATE JOHN H. WILHOIT EXTENSION ASSOCIATE PROFESSOR DAVE ASH ENGINEER AID BIOSYSTEMS AND AGRICULTURAL ENGINEERING, UNIVERSITY OF KENTUCKY 2012 DEVELOPMENT AND EVALUATION OF A BURLEY TOBACCO MECHANICAL STRIPPING CONCEPT UTILIZING STRING TRIMMERS
Harvesting (48-60 wk*hr/ac) and stripping (51-73 wk^hr/ac) are by far the biggest labor requirements OperationsLabor Required, Conventional (hours/acre) Labor Required, Enhanced (hours/acre) Plant Production62 Field Prep. & Cult.22 Transplanting11 Topping88 Cutting26 Load & Haul88 House2614 Cure33 Bulk & Load12 Strip & Bale7351 Load & Market22 Total197159
Grading Based on stalk position Each grade takes up a length of stalk Leaves for each grade stripped off by hand seperately
Manually stripping tobacco is very labor intensive
New Method Combining major elements of proven systems Straight line conveyors Plants conveyed at even spaces Grading based on stalk position ● Using new tobacco stripping technology String trimmers to remove leaves Flexible brushes to align leaves
Basic configuration of stripping machine concept
Leaf Alignment Brushes used for aligning and holding leaves Cams open brushes to allow stripped leaves to fall
Leaf Alignment Brushes used for aligning and holding leaves
Objectives Develop a mechanical system for removing a single grade of burley tobacco from the stalk utilizing string trimmer technology. Determine the best combination of motor speeds and string lengths for optimal stripping efficiency. Strip tobacco leaves into three appropriate grades based on stalk position and linear progression along the length of the machine using multiple string trimmers. Evaluate the stripped leaves for damage due to shredding by classifying potential losses.
Coverage 5 in. string (7 in. radius)7 in. string (9 in. radius)9 in. string (11 in. radius)
Single Grade Testing Procedure String length (in.) Motor speeds (rpm) 5 3000340038004200 72800 300032003500 92200 250028003000 5 in. String7 in. String9 in. String Strip first 14 in.Strip first 12 in.Strip first 10 in. Leave 10 in.Leave 14 in.Leave 18 in. Strip the rest
Resulting Efficiencies Motor Speed (rpm) 3000340038004200 Trial 149.974.492.096.7 Trial 273.442.291.891.6 Trial 362.166.294.884.8 Average61.860.992.991.0 5 IN. STRING LENGTH Motor Speed (rpm) 2800300032003500 Trial 186.495.291.084.8 Trial 296.197.296.493.2 Trial 382.694.791.792.3 Average88.495.793.090.1 7 IN. STRING LENGTH Motor Speed (rpm) 2200250028003000 Trial 168.595.595.899.3 Trial 279.192.397.096.2 Trial 353.394.295.295.6 Average67.094.096.097.0 9 IN. STRING LENGTH
Machine Stripping 3 Grades Flyings are removed by hand Lug, leaf and tip are removed with string trimmers 7 in. string length used for proper coverage and grading on 44 in. plant
3 Grade Machine Stripping Results Plant Efficiency (%) Average Efficiency 1 94.6 97.0% 2 98.0 3 94.1 4 98.3 5 96.7 6 97.8 7 98.0 8 99.8 9 95.8 Note: The stripping efficiency results for plant 10 contained an error and were left out.
Leaf Damage Small pieces make up 5.6% of total weight removed
Particle Distribution Plant Stripping Efficiency (%) Whole Leaf Particles (%) Particles larger than 1x1 in. but smaller than whole leaves (%) Particles 1x1 in. and smaller (%) 197.6 220.127.116.11 295.7 18.104.22.168 392.5 22.214.171.124 499.3 126.96.36.199 597.2 188.8.131.52 699.8 89.75.05.3 799.7 184.108.40.206 893.9 220.127.116.11 994.8 91.34.3 1098.4 18.104.22.168 Average96.9%90.1%4.3%5.6%
Conclusions Significant difference in efficiency for faster speeds at given string length Results for 3 grade stripping with 4 th grade stripped by hand showed 97% efficiency Particle size distribution test results showed 5.6% by weight pieces smaller than 1 in. x 1 in. With modifications, the current setup could be turned into a fully operational field prototype with the potential to significantly reduce stripping labor requirements.
Potential Productivity Conveyor Speed was timed: 2.73 s/plant (cups holding plants spaced 24 in. apart) With two people hand-stripping flyings and feeding machine, each person would process 1 plant/5.5 s Potential productivity: Assume 85% field efficiency Approximately 1100 plants/hr 370 lb/hr Approximately 3,000 lbs per 8 hour day Approximately 1.25 acres stripped per day (depending on yield) With 4 person crew stripping rate is 26 wkr*hr/ac Conventional hand stripping 51-73 wkr*hr/ac
Cost and Payback Labor costs for crew of workers are $10-15 per hour per worker Potential savings with this machine $5,000/year for 20 acre crop at $10/hr labor rate At $15/hr, savings could be $7,500/year If machine cost $10,000, pay back period could be 1.5 to 2 years, twice that if cost is $20,000
Further work needed to develop operational prototype Automatic opening and closing of stalk-holding cups for faster loading Automatic ejection of stalks from stalk-holding cups Automatic opening of brushes to eject detached leaves Shielding between grades Possible conveyor speed variations More detailed look into the power requirements and usage Investigate issue of foreign matter (from plastic string) in tobacco
Modifications Made for 2011-2012 Season Automatic opening and closing of stalk-holding cups for faster loading Automatic ejection of stalks from stalk-holding cups Automatic opening of brushes to eject detached leaves Shielding between grades Possible conveyor speed variations More detailed look into the power requirements and usage Investigate issue of foreign matter (from plastic string) in tobacco
Modifications to Stalk-Holding Cups A cam opens spring-loaded cups over an 18 in. distance at the front end of the machine to facilitate continuous loading
Modifications to Stalk-Holding Cups Another cam at the end of the machine opens the cups again as for ejecting the stalks after stripping
Ejection Wheels Rotating rubber wheels grasp stalks as they come around to ensure that they are ejected from the cups
Modifications to brushes Bristle brushes have been replace by sheet rubber, and they pivot to open in between every plant so detached leaves can fall instead of being pushed into the string trimmers.
Results of Preliminary Tests Conducted in 2012 Tests conducted with additional string trimmer added for stripping tip grade, to better handle taller plants. Tip grade was stripped first rather than last. Trials 3 and 4 conducted at higher motor speeds.
Results of Preliminary Tests Conducted in 2012 Note low stripping efficiencies for a few plants that reduced average efficiencies. Based on observations, the cause was usually a stalk that was poorly seated in the cup so that the string trimmers caused the stalk to bend over significantly.
Further work needed for reliable operational stripping To achieve stripping efficiencies comparable to hand stripping (95%- 100%), the machine needs to effectively strip nearly every single plant. The key to such reliability seems to be that the stalk ends be securely seated in the cups so that the stalks remain vertical as they pass all of the string trimmers. Further work is needed to determine optimum string trimmer placement to give full stripping coverage for a range of stalk heights. Once reliable operational stripping is achieved, efforts will be directed at working out shielding for grade separation and assessing grading accuracy. Efforts will also be directed at assessing foreign matter in the tobacco (from the plastic string), and developing methods for minimizing it if necessary.