tree shear design樹(shù)剪的設(shè)計(jì)

1、<p>　　Redesign of a Tree Shear</p><p>　　Clint CosgroveMatt Lemmons</p><p>　　Kevin TaylorLance Klement</p><p>　　Redesign of a Tree Shear</p><p>　　Clinton Travi

2、s Cosgrove</p><p>　　Matthew Lynn Lemmons</p><p>　　Kevin DuJuan Taylor</p><p>　　Lance Paul Klement</p><p>　　Biosystems & Agricultural Engineering</p><p>

3、;　　Oklahoma State University</p><p>　　Advised by Dr. Paul Weckler</p><p>　　_____________________ ______ _____________________ ______</p><p>　　Clinton Travis Cosgro

4、ve Matthew Lynn Lemmons</p><p>　　Biomechanical Option Biomechanical Option</p><p>　　May 2007 Graduate December 2007 Graduate <

5、;/p><p>　　_____________________ ______ _____________________ ______</p><p>　　Kevin DuJuan Taylor Lance Paul Klement</p><p>　　Biomechanical Optio

6、n Environmental Option</p><p>　　May 2007 Graduate May 2007 Graduate</p><p>　　_____________________ ___

7、___ _____________________ ______</p><p>　　Dr. Paul R. Weckler Steven L. Fowler</p><p>　　Senior Design Advisor Sr. ASABE

8、 Student Club Advisor</p><p>　　Submitted on April 30, 2007</p><p><b>　　Abstract</b></p><p>　　The Vassar Company is a manufacturer of farm and ranch equipment in Perkins,

9、 Oklahoma. The company makes an economical tree shear for use by either a skid steer loader or a tractor. Recent competitors’ machines introduced into the market have led Vassar to request a redesign of their current tre

10、e shear from Clam Lake Engineering. The redesign accommodated new options and reduced the number of fabricated parts. After extensive testing, computer-aided modeling, and consultation, Clam Lake Engineer</p><

11、h2>　　Acknowledgements</h2><p>　　Jack Vassar—Vassar Farm Equipment Company, Owner</p><p>　　Larry Kimmel—Vassar Farm Equipment Company, Sales Manager</p><p>　　Dr. Paul Weckler—Okla

12、homa State University Biosystems & Agricultural Engineering Assistant Professor and Senior Design Advisor</p><p>　　Wayne Kiner—Oklahoma State University Biosystems & Agricultural Engineering Laborato

13、ry Manager</p><p>　　H. Clay Buford, P.E.—Design Consultation </p><p>　　Table of Contents</p><p>　　Problem Statement1</p><p>　　Statement of Work2</p><p>　

14、　New Features2</p><p>　　Rotation3</p><p>　　Frame Design3</p><p>　　Flush Cutting4</p><p>　　Limitations5</p><p>　　Literature Review5</p><p&g

15、t;　　Engineering Specifications6</p><p>　　Dimensions6</p><p><b>　　Forces7</b></p><p>　　Other Considerations7</p><p>　　Preliminary Design Concept8</p&

16、gt;<p>　　Rotation8</p><p>　　Flush Cutting9</p><p>　　Improved Frame Designs10</p><p>　　Stress Analysis13</p><p>　　Determination of Final Design14</p>

17、<p>　　Rotation15</p><p><b>　　Frame16</b></p><p>　　Flush Cutting17</p><p>　　Manufacturing18</p><p><b>　　Issues19</b></p><p&g

18、t;<b>　　Costs19</b></p><p>　　Testing19</p><p>　　Final Recommendations23</p><p>　　Appendix A. Gantt Chart25</p><h2>　　Table of Figures</h2><p&g

19、t;　　Figure 1: Current SS-4 tree shear2</p><p>　　Figure 2: Vassar SS-4 tree shear frame3</p><p>　　Figure 3: Ram Angle4</p><p>　　Figure 5: Initial Double Plate C-Shape Frame11<

20、/p><p>　　Figure 6: Double Plate Frame Design with Flange Rotation11</p><p>　　Figure 7: Single Plate C-Frame Alternate Design12</p><p>　　Figure 8: ANSYS frame analysis13</p>&

21、lt;p>　　Figure 9: Hand checked FEA cross sections14</p><p>　　Figure 10: Redesign of Vassar SS-4 tree shear15</p><p>　　Figure 11: Rotation Cylinder15</p><p>　　Figure 12: DOM Tub

22、ing for Rotation16</p><p>　　Figure 13: Double Plate C-Frame Final Design17</p><p>　　Figure 14: Assembled Tree Shear18</p><p>　　Figure 15: Blade Carrier Being Cut Out on Vassar Fl

23、ame Table18</p><p>　　Figure 16: Cut test post20</p><p>　　Figure 17: Testing Shear on Blackjack Oak21</p><p>　　Figure 18: Testing Shear on Eastern Red Cedar21</p><p>

24、;　　Figure 19: Testing Shear Rotation22</p><h2>　　Problem Statement</h2><p>　　A recent explosion in the number of Eastern Red Cedar trees in the region around Oklahoma has led many landowners an

25、d farmers to research different control methods against this exponential growth. Many options exist, such as controlled burning, manual removal with chainsaws, or tractor-powered tree saws. Tree shears provide an alterna

26、tive to burning or sawing. </p><p>　　Most tree shears work with basic mechanical principles. One or two hydraulic cylinders close blades in a scissor-like motion to sever trees. Various products on the marke

27、t have adapted this design for different uses, such as rotational movement, tree cutting, and tree moving. Tree shear manufacturers are being forced to increase the capabilities of their products in order to remain compe

28、titive.</p><p>　　Vassar Farm Equipment requested a redesign of their current tree shear from Clam Lake Engineering (CLE). The new design should be more efficient, competitive in cost, and more appealing to t

29、he consumer than the previous models. The current 10 inch capacity shear produced by Vassar Farm Equipment is shown below in Figure 1.</p><p>　　Figure 1: Current SS-4 tree shear</p><h2>　　Statem

30、ent of Work</h2><p>　　Clam Lake Engineering contacted The Vassar Company and was provided with requirements for the new tree shear design. The new design started with a definition of the project. To help def

31、ine the project parameters, CLE split the details into two sections: New Features and Limitations.</p><h3>　　New Features</h2><p>　　The Vassar Company communicated several new features they feel

32、 would make their tree shear competitive. These included ideas that focused on the consumers’ needs, reduced the manufacturing costs, and improved the overall capabilities of the shear. After visiting with Larry Kimmel,

33、manager, and Jack Vassar, owner, the new features of the Vassar tree shear were defined as: rotational capabilities, a more efficient frame design, and the capability to make flush cuts.</p><p><b>　　Ro

34、tation</b></p><p>　　Vassar expressed the need for rotation for the purpose of trimming large limbs. The capacity of the shear was limited to 10” because Vassar felt cutting branches over 10” in diamete

35、r would present the potential of injury from falling objects. The company also requested, but not required, that the design be manually operated, because most client vehicles operate with only one remote hydraulic circui

36、t. Vassar did not apply any other requirements to the rotation feature. Therefore, the type of rota</p><h4>　　Frame Design</h2><p>　　Figure 2: Vassar SS-4 tree shear frame</p><p>　　

37、The Vassar Company produces the current shear frame from eleven pieces of heavy gauge steel ranging from 0.375” to 1.25” in thickness, as shown in Figure 2. The company felt that this was an excessive number of pieces, c

38、onsidering the production process for the frame. Therefore, the company requested that many of these pieces be merged into larger pieces. Simplifying the frame included two major changes: minimizing parts and reshaping t

39、he frame to align the cylinders with the blades. The current</p><p>　　Figure 3: Ram Angle</p><h4>　　Flush Cutting</h2><p>　　Vassar requested the new tree shear design to incorporate

40、 flush cut capabilities. Their customers have voiced the desire for flush cut capabilities several times, so that equipment can be driven over the stump without inflicting damage upon the tires. Larry Kimmel, sales manag

41、er for Vassar, stated that the current shear allowed flush cutting, but the process included driving the shear below ground level and cutting the trunk of the tree below the ground. This disturbed the topsoil and increas

42、ed </p><h3>　　Limitations</h2><p>　　Several factors dictated the design of the new Vassar tree shear. Clam Lake Engineering realized the limitations set forth and applied the limitations to eval

43、uate solutions. Vassar set some of the constraints which the new design followed, along with those imposed by CLE:</p><p>　　Weight of new design Model SS-4 was to be below 1200 lbs</p><p>　　The

44、new design must have a brush guard </p><p>　　The new design must be competitive in cost</p><p>　　Operation of the new design must be performed by one hydraulic circuit</p><p>　　The

45、shear must remain easily maintainable</p><p>　　The new design must conform to the set hydraulic pressure of 2000 to 3000 psi</p><p>　　Hydraulic cylinder bore should be the same as previous desig

46、ns </p><p>　　CLE produced the list of limitations above to aid in the design process of a new tree shear. The weight limitation was set forth by the skid steer capacity. The Vassar Company asked that the tot

47、al weight of the shear be no more than 1,200 pounds, which would allow the shear to be an attachment for smaller capacity skid steers. </p><h2>　　Literature Review</h2><p>　　Clam Lake Engineerin

48、g focused on patent searching and reviewing the designs of other manufacturers for the literature review portion of this project. The team found six patents and considered them before proceeding with the design process.

49、These are available in the CLE fall progress report (Cosgrove et al, 2007) </p><h2>　　Engineering Specifications</h2><p>　　Based on requirements from The Vassar Company and CLE’s engineering exp

50、erience, the following specifications must be met by the new tree shear. For clarity, the specifications have been broken into three sections: Dimensions, Forces, and Special Considerations. The Dimensions section descri

51、bes the physical shape of the tree shear and how its dimensions impact its functionality. The Forces section covers the loads imposed on the shear during the tree cutting process as well as the forces on the r</p>

52、<h3>　　Dimensions</h2><p>　　The new tree shear should be large enough to cut down a 10” tree, yet small enough to be mounted to a 40-60 horsepower skid-steer loader. Vassar’s current SS-4 shear has a 1

53、0” capacity, determined by the distance from the tip of the blade to the blade carrier. The length of the implement should also be minimized in order to shorten the moment arm acting on the loader. If the new shear becom

54、es too long, the center of gravity could move out far enough to tip over a small skid-steer loader. The she</p><p><b>　　Forces</b></p><p>　　The primary forces acting on the tree shea

55、r are the shearing forces imparted on the tree by the hydraulic rams. The maximum ram forces have been estimated by multiplying the maximum rated hydraulic pressure of 3000 psi by the bore area of the 4” rams, giving a c

56、olumn load on the cylinder of 37,700 lbs. The resulting force on the blades was larger than the cylinder force when the moment arm the cylinder operated on was taken into account. </p><p>　　The force require

57、d to shear a tree was estimated using a nomograph created by Rodger Arola (1972). The specific gravity of the wood is required to use the nomograph, which was determined to be 0.48 for Eastern Red Cedar (Forest Products

58、Laboratory, 1999). Therefore, a required shearing force of 59,000 lbs was calculated. This was less than the calculated blade force of 62,000 lbs at maximum pressure. Vassar’s previous experience with this cylinder also

59、indicated that it should be more than adequ</p><h3>　　Other Considerations</h2><p>　　The mechanisms of operation, cost, and safety of the operator were incorporated into the special consideratio

60、ns of the new design. These also included the angle of rotation and features of the rotation mechanism. </p><p>　　After considering the hardware required for rotation, the members of CLE agreed that the opti

61、mum angle of rotation was 90º from horizontal. A 90º rotation simplified the mechanism required for either manual or hydraulic rotation. CLE concluded a rotation angle larger than 90º would require costly

62、mechanisms and higher manufacturing costs.</p><p>　　Safety of the operator while using the shear is also a major concern to both CLE and Vassar. While considering designs CLE noted that the location of the c

63、enter of gravity of the shear would be critical. Loader capacity was based on the center of gravity of a load in the bucket, so any load center of gravity deviating from the center of gravity of a load in a bucket is a s

64、afety issue. A safety consideration concerning rotation was accessibility to the rotation mechanism, particularly mechanisms </p><h2>　　Preliminary Design Concept</h2><p>　　After considering the

65、 requirements the new tree shear must fulfill, Clam Lake formulated new designs. Design considerations were based on the criteria discussed in the preceding Engineering Specifications section. CLE’s solution to the probl

66、ems of rotation, flush cutting, and improved frame design are discussed below. </p><p><b>　　Rotation</b></p><p>　　The main issue facing CLE was rotation. For the pivot point of the s

67、hear, CLE initially considered a shaft and bearing construction, but it was determined that large diameter bearings were too high in cost. Another proposed new idea involved using two pipes with bearings between them. Th

68、e proposed idea was to utilize severed round stock or commercially produced bearings if available. After consulting H. Clay Buford, P.E., CLE considered drawn over mandrel tubing (DOM tubing) placed within anothe</p&g

69、t;<p>　　Next, CLE focused on the mechanisms that would be needed to drive the rotation system. Initially, both hand and hydraulic actuators were considered. Through further discussion of the problem with Larry Kim

70、mel, it was determined that a hand-move system was preferred. The hydraulic system, therefore, was put on hold while the team determined more efficient hand-move designs. After exploring several hand-move options, such a

71、s a moveable flange (Figure 6) and a worm gear, CLE elected to omit any man</p><p>　　One option for hydraulic rotation was a rack and pinion arrangement. A hydraulic cylinder would move a straight rack horiz

72、ontally over a pinion mounted to the frontal section. The idea of one large gear powered by an electric or hydraulic motor turning a small gear was also considered. Lastly, the team also proposed using a single hydraulic

73、 cylinder, connected to both the shear head and the frame. This arrangement was determined to be optimum due to its simplicity and affordability.</p><h3>　　Flush Cutting</h2><p>　　New concepts g

74、enerated needed the ability to perform flush cuts. Flush cutting refers to the ability to shear a tree trunk flush with the ground level and leaving no portion of the stump above the surface. After modeling the system in

75、 Pro-E, CLE began to explore different options that would lower the blades. Designs generated by CLE incorporated flush cutting capabilities in two ways, depending on the shear head frame design. If the blade assembly wa

76、s placed between two plates, then the blade le</p><p><b>　　.</b></p><p>　　Shortening the blade places the bottom face of the blade flush with the bottom surface of the shear, but the

77、 shear is not truly flush. The bolt heads holding the blade protrude from bottom of the shear. CLE considered countersinking bolts or threading the blades to remedy the problem, but ultimately decided the thickness of th

78、e bolt heads was negligible. </p><p>　　An issue also related to flush cutting was the increased torsion on the blade carriers. As seen in Figure 4, obtaining flush cut requires an increasing of the distance

79、between the blade and the centerline of the cutting cylinders. To compensate for the increased torsion produced by this alignment, CLE increased the torsion capacity requirement of the redesigned blade carriers.</p>

80、;<h3>　　Improved Frame Designs</h2><p>　　After analyzing the loads involved, setting the design criteria, and considering safety factors, CLE began with a collection of preliminary design concepts. CL

81、E did not perform detailed analysis of each concept until the group decided on a final design.</p><p>　　The first concept, shown below in Figure 5, was a four piece frame, with the cylinders placed at a perp

82、endicular angle from the cutting edge of the blades. Rotational ideas for this design were put on hold until all designs were considered. As seen in the drawing, the hydraulic cylinders extend lower than the bottom plane

83、 of the blades. This prevents the design from achieving a true flush cut shear as Vassar requested. For this reason, CLE moved on to alternative designs. </p><p>　　Figure 5: Initial Double Plate C-Shape Fram

84、e</p><p>　　Figure 6 illustrates a second design concept consisting of three shear frame pieces. As the figure shows, in the closed position the cylinders are at a perpendicular angle to the cutting edge of t

85、he blades. CLE also incorporated rotational capabilities into this design. After CLE presented the alternative design, Vassar had concerns about the angle of the cylinders. CLE was also concerned about the amount of tors

86、ion on the blade carriers. As seen in the drawing the blade carriers consist of a si</p><p>　　Figure 6: Double Plate Frame Design with Flange Rotation</p><p>　　A four piece frame design is shown

87、 below in Figure 7. As with the design in Figure 5, rotational capabilities for this concept were not considered until the group agreed on a final solution. The design met the flush cutting capabilities and reduced the n

88、umber of parts. A major issue with the design was the single piece blade. As shown the hinge pins on the blade carriers in this design are supported by a single plate, creating a cantilever pin. The plate supporting the

89、pin would require more mat</p><p>　　Figure 7: Single Plate C-Frame Alternate Design</p><p>　　A common feature among each of the preceding designs was the angle of the cylinders to the shear blad

90、es. When the blades were closed, the cylinders were at a 90º angle to the blades to maximize the force. At this point in the design process, Vassar expressed concern about the possibility of the cylinders shifting p

91、osition on the blade carriers due to the angle. This concern of “l(fā)ocking up” furthered CLE’s decision to change the possible designs to include ram angles less than 90°.</p><h2>　　Stress Analysis</h2

92、><p>　　After formulating design concepts for the shear frame CLE examined each concept using a computer generated stress analysis. CLE utilized ANSYS Workbench to evaluate concepts through finite element analy

93、sis (FEA). Geometries from Pro/ENGINEER were imported directly into ANSYS. The finite element model allowed CLE to identify stress concentrations and modify the design to compensate for the high stress regions. An area o

94、n the frame that CLE was concerned with was between the hinge points of the b</p><p>　　Figure 8: ANSYS frame analysis</p><p>　　Finite element models were analyzed in detail by CLE. Conformation

95、of the models was done by assuming static loading. Stresses were calculated by hand at the cross sections shown in Figure 9 to confirm CLE’s findings in ANSYS. These hand calculations showed that ANSYS was typically more

96、 conservative than CLE’s stress estimates.</p><p>　　Figure 9: Hand checked FEA cross sections</p><h2>　　Determination of Final Design</h2><p>　　Figure 10 illustrates the final desig

97、n that CLE chose. The design met the needs of Vassar. Clam Lake Engineering utilized Pro/ENGINEER to formulate these new designs. The Pro/ENGINEER drawings will also be valuable to the Vassar Company in the future, shoul

98、d they choose to change any aspects of the shear.</p><p>　　Figure 10: Redesign of Vassar SS-4 tree shear</p><p><b>　　Rotation</b></p><p>　　The rotation mechanism chosen

99、is a 2” cylinder with an 8” stroke mounted to the frame that attaches to the right side of the shear, as seen in Figure 10. The problem of having only one hydraulic remote to run both the shears and the rotation cylinder

100、 was overcome by installing a 6-way, 2-position hydraulic valve on the back of the shear. This will enable a user to switch between the rotational cylinder and the shearing cylinders with the flick of a switch. It will a

101、lso enable Vassar to offer a n</p><p>　　Figure 11: Rotation Cylinder</p><p>　　CLE intended to use DOM tubing for the prototype of the final design. When visiting with Vassar, Mr. Kimmel informed

102、 the team the company uses 4.5” O.D. seamless pipe with a 0.5” wall. Due to the small quantity of DOM tubing required for the prototype, the seamless pipe Vassar had in-house was used as the collar for rotation. The shaf