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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 blacksmiths furnace. The major advantage obtained in the modified machine is

its continuous hammering. The machine designed for @ 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.

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Pedeal Drive

Flywheel

Cam

Leaf Spring

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 of @ 40 to 50 rpm.

5. The flywheel is rotating at @ 160 to 200 rpm through a chain drive.

6. The flywheel supplies energy for @ 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 is @ 700mm.

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With the above considerations the flywheel mass is decided on the basis of maximum strain

energy stored in the leaf spring. Thefig. 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

350 350 350

l1 l2 l3

Deflection of a spring plate, Fig No 2

Strain energy stored

E1 = V R ; V = Ltb ; R = max2/18E

max = M/Z ; M = F x l2 ; Z = 1/6 bt2

max = 510.48 MPa

E = 211103

MPa

E1 = 79.3 Nm

This amount of energy is to be supplied by flywheel which is rotating at @ 160 to 200 rpm.

Maximum fluctuation of energy

E = 79.3 / 0.8 = 99.12

E = mk2

2Cs, k = 0.35m, = 2N/60, N = 160 rpm

m = 14.41 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.

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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.

r

Old Cam Modified Cam

Cam

F

F

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 clutch @

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

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OBSERVATION TABLE:

L/d Ratio Deflection per revolution

s

50/16 1.7 mm

40/16 1.0 mm

40/11 1.7 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 E1 = 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 responsiblefor this deformation will be a reaction offered by the billet or a work piece which is heated

red hot having its ultimate strength reduced to @ 250 MPa.

F = E1

For E1 = 79.3 Nm and = 69 mm the force obtained is

F = 2298.5 N

Deformation of billet for the billet size d = 16mm and l = 50mm

ut A s = E1

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.

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NOMENCLATURE:

Bending stress Mpa

E Youngs Modulus Mpa

R Proof Resilience Mpa

V Volume mm3

L Length of spring plate mm

t Thickness of plate mm

b width of plate mm

E1 Strain Energy Nm

F Force on the follower N

m Mass of flywheel Kg

K Radius of gyration m

Angular velocity rad / s

Cs Coefficient of fluctuation of speedE Maximum fluctuation of energy Nm

A Cross Section area of plate mm2

d Diameter of billet mm

l length of billet mm

ut ultimate strength Mpa

s Deformation of billet mm

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 inMechanical Engineering , REC, Kurukshetra, March 7-8, 1997

2. 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

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To,

Dr. S. K. Saha,The Organizing Secretary

NaCoMM- 2003

Dept. of Mech. Engg., IIT Delhi

Hauz Khas,

New Delhi 110016

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 2003. This paper is also e-mailed to NaComm2003@yahoo.co.inon 13 September 2003Kindly acknowledge the receipt of the same.

Thanking you,

Yours truly,

Prof. A. R. Sahu, Prof. U. D. Gulhane

Mech. & Prod. Engg. Deptt. BDCOE, Sewagram

Email: anilrsahu@yahoo.com, : radheya3@rediffmail.comDate: 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.)

mailto:NaComm-2003@yahoo.co.inmailto:anilrsahu@yahoo.commailto:radheya3@rediffmail.commailto:radheya3@rediffmail.commailto:anilrsahu@yahoo.commailto:NaComm-2003@yahoo.co.in