Design Of Fly Wheel And Modified Cam For Manually Energized Black Smith Forge Hammer For Rural Artisans

Transcription

1 Design Of Fly Wheel And Modified Cam For Manually Energized Black Smith Forge Hammer For Rural Artisans A. R. Sahu and U. D. Gulhane Department of Mechanical & Production Engineering B. D. College Of Engineering, Sewagram Wardha.(M. S.) ABSTRACT: The authors had developed cam operated flywheel driven blacksmith forge hammer for rural artisans for an NGO Center of Science for Villages Dattapur, Wardha (M. S.). The machine utilizes the energy stored [7] in deflected spring for forging the small components specially agricultural tool and implements. The deflection is obtained by a modified semicircular cam. The initial work with a semicircular cam [4,5] has been presented and published [1]. This paper presents the design of flywheel and modified semicircular cam, which made the machine convenient for rural blacksmiths. INTRODUCTION: In India, large amount of agricultural tools or implements are still manufactured in villages. Various local artisans such as carpenters, blacksmiths, fabricators are performing these jobs. The authors with the help of an NGO identified forging as the most critical activity, which should be automated up to certain level. The automation may be in the form of forging machine. As a first step the simple machine has been designed fabricated and tested. The hand lever was provided for deflecting the leaf spring. For small sized and less in quantity jobs the hand lever operation was found suitable but for large quantity fabrication the operation was time consuming and strenuous. The author further modified the machine by incorporating a flywheel. The developed machine utilizes human energy for energizing the flywheel by pedaling. The flywheel is designed in such a way that its stored energy will be utilized for deflecting a leaf spring. The strain energy stored in the deflected spring is released in the form of an impact of a forging tool on the work piece, which is heated red hot in the blacksmith s furnace. The major advantage obtained in the modified machine is its continuous hammering. The machine designed 40 to 50 strokes per minute rate. The only shortcoming the machine has, the requirement of suitable fixtures and dies for holding the work pieces and fabricating the desired size.

2 Flywheel Leaf Spring Pedeal Drive Cam Machine diagram, Fig No. 1 DESIGN OF FLYWHEEL: The flywheel is incorporated to provide the necessary inertia required for deflecting the metal plate. In the original system the handle was provided for deflecting the spring plate. In the modified version the system is driven by pedal and chain drive (fig No. 1). The following considerations have been made for the design. 1. An average worker lifts hammer of 5 kg and strikes it on the job from an approximate height of 1.2 m. 2. Energy generated from it is 120 Nm. 3. The spring plate is assumed simply supported. 4. The pedal is operated at the speed 40 to 50 rpm. 5. The flywheel is rotating 160 to 200 rpm through a chain drive. 6. The flywheel supplies energy 40 to 50 strokes in one minute. 7. Drive efficiency is 80% 8. The flywheel supply whole energy 9. Speed fluctuation 2% 10. Maximum diameter of flywheel 700mm.

3 With the above considerations the flywheel mass is decided on the basis of maximum strain energy stored in the leaf spring. The fig. No.2 shows the deflection of metal plate at different points. The deflection at C is obtained by the follower motion. 69mm 46 mm A B C D l 1 l 2 l 3 Deflection of a spring plate, Fig No 2 Strain energy stored E 1 = V R ; V = L t b ; R = σ max 2 /18E σ max = M/Z ; M = F x l 2 ; Z = 1/6 bt 2 σ max = MPa E = MPa E 1 = 79.3 Nm This amount of energy is to be supplied by flywheel which is rotating 160 to 200 rpm. Maximum fluctuation of energy E = 79.3 / 0.8 = E = mk 2 ω 2 C s, k = 0.35m, ω = 2πN/60, N = 160 rpm m = kg. A 20 kg flywheel is selected. The flywheel is checked for all induced stresses and found satisfactory. The arrangement of flywheel along with chain drive is shown in fig. No 1.

4 CAM MODIFICATIONS: The cam follower arrangement is designed for applying the necessary force for deflecting the spring plate to the desired value i.e. 46mm. In the original machine semicircular cam was selected and for frequent operations with hand lever it worked properly but for continuous operations the impacts of follower on cam were causing extra stresses on follower stem and other moving parts. In the modified design (Fig. No.3 ) a slight change in cam contour reduced the problem to the higher extent. Since the cam is operating at considerably low speed the dynamics of cam is designed only for static and impact loading. F Cam F r Old Cam Modified Cam Cam Diagram, Fig No. 3 PERFORMANCE EVALUATION: The performance of the machine was tested on mild steel billets of various sizes and the following observations were noted. The billets were heated to red-hot. 1. Once the flywheel is energized fully and connected to camshaft through 46 strokes were obtained most of the time. All our design calculations are based on 46 strokes per minute rate. 2. The deformations in the billets were tabulated. 3. The actual deformations were compared with the theoretical calculations

5 OBSERVATION TABLE: L/d Ratio Deflection per revolution s 50/ mm 40/ mm 40/ mm Sample calculation: The strain energy stored in the deflected spring would be responsible for providing necessary impact on the work piece. This energy as per calculations is E 1 = 79.3 Nm. This energy is converted in to the work done on the work piece for its deformation. The deformation is in the form of reduction in length of the work piece. The force responsible for this deformation will be a reaction offered by the billet or a work piece which is heated red hot having its ultimate strength reduced 250 MPa. ½ F δ = E 1 For E 1 = 79.3 Nm and δ = 69 mm the force obtained is F = N Deformation of billet for the billet size d = 16mm and l = 50mm ½ σ ut A s = E 1 s = 2.25 mm/stroke The calculated deformation is totally based on the ultimate strength at the plastic stage of the material but the temperature of billets drops suddenly increasing the strength considerably which causes actual deformation less than the theoretical one. But if the same is compared with the manual operation for one minute forging the machine has given very good deformations. CONCLUSION: As per the testing conducted on the machine, it is estimated that the required amount of energy for hammering is continuously obtained by introducing the flywheel, so maximum work is done in minimum period of time but to make the machine more efficient, it is required to make some changes such as fixtures, dies etc. The machine has been found useful and it has a scope in future with some modifications.

6 NOMENCLATURE: σ Bending stress Mpa E Young s Modulus Mpa R Proof Resilience Mpa V Volume mm 3 L Length of spring plate mm t Thickness of plate mm b width of plate mm E 1 Strain Energy Nm F Force on the follower N m Mass of flywheel Kg K Radius of gyration m ω Angular velocity rad / s C s Coefficient of fluctuation of speed E Maximum fluctuation of energy Nm A Cross Section area of plate mm 2 d Diameter of billet mm l length of billet mm σ ut ultimate strength Mpa s Deformation of billet mm δ Deflection of plate mm REFERNCES: 1. Sahu A. R. & Gulhane U. D., Design of Cam Operated Blacksmith Forging hammer for Rural Artisans, National Conference on Recent Advances in Mechanical Engineering, REC, Kurukshetra, March 7-8, Sony, A. H., Mechanism synthesis and Analysis, McGraw-Hill. 3. Tao, D.C. Applied linkage synthesis, Addisen-Wesley. 4. Routhbort, H. A. Cams, Wiley. 5. Shigley, J.E., Uicker, J., Theory of Machines and Mechanisms, McGraw-Hill. 6. Shigley, J.E.,Mische,C., Standard Hand Book of Machine Design, McGraw-Hill. 7. Shigley, J.E., Mechanical Engineering Design, McGraw-Hill 8. Rattan, S. S., Theory of Mechanics, Tata McGraw-Hill. 9. Shiwalker, B. D., Machine Design Data Book. 10. P.S. G. College of Technology, Coimbatore, Design Data. 11. Sinha, Post Graduate Thesis report, V R. C. E., Nagpur

7 To, Dr. S. K. Saha, The Organizing Secretary NaCoMM Dept. of Mech. Engg., IIT Delhi Hauz Khas, New Delhi Dear Sir, Please find enclosed herewith two copies of full length paper entitled Design Of Fly Wheel And Modified Cam For Manually Energized Black Smith Forge Hammer For Rural Artisans coming under Rural Machines And Mechanisms category of your NaCoMM This paper is also ed to on 13 September 2003 Kindly acknowledge the receipt of the same. Thanking you, Yours truly, Prof. A. R. Sahu, Prof. U. D. Gulhane Mech. & Prod. Engg. Deptt. BDCOE, Sewagram : Date: 13 September 2003 Address for Correspondence: Prof A R Sahu Sr. Lecturer, Department Of Mech. & Prod. Engg. B D COLLEGE OF ENGINEERING, SEWAGRAM (M. S.)