Mechanical Engineering

# rao shahb

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1. ## COTTER JOINT

COTTER JOINT A cotter joint is used to connect rigidly two co-axial rods or bars which are subjected to axial tensile or compressive forces . It is a temporary fastening . COTTER A cotter is a flat wedge shaped piece of rectangular cross section and its width is tapered (either on one side or on both sides) from one end to another for an easy adjustment. APPLICATIONS OF COTTER 1. Connection of the piston rod with the cross heads 2. Joining of tail rod with piston rod of a wet air pump 3. Foundation bolt 4. Connecting two halves of fly wheel (cotter and dowel arrangement) COMPARISON BETWEEN KEY AND COTTER 1. Key is usually driven parallel to the axis of the shaft which is subjected to torsional or twisting stress. Whereas cotter is normally driven at right angles to the axis of the connected part which is subjected to tensile or compressive stress along its axis. 2. A key resists shear over a longitudinal section whereas a cotter resist shear over two transverse section. __________________ DIFFERENT TYPES OF COTTER JOINTS 1. Socket and spigot cotter joint 2. Sleeve and cotter joint 3. Gib and cotter joint DESIGN PROCEDURE FOR THE SPIGOT AND COTTER JOINT To understand the design steps let take a question and solve it step by step. Q. Design a cotter joint subjected to a tensile load of 35 kN and a compressive load of 40 KN . The allowable stresses are tensile stress qt = 70N/mm2 compressive stress qc = 110 N/mm2 shear stres t = 50 N/mm2 SOLUTION STEP 1 Failure of rod in tension or compression tensile stress = tensile load / area qt=(Pt*40/(3.14*d*d) where d is the diameter of the rod from above equation we will find out the value of d and round it off to the higher integer. Now we apply the Standard shaft rule..i.e the diameter of the rod should be of the given range diameter increment in steps 1-10mm 1mm 10-24mm 2mm 24-45 mm 3mm 45-100 mm 5mm above 100mm 10mm we will make the value of the d such that it will satisfy the above table. compressive stress = compressive load /area qc=(4*Pc)/(3.14*d*d) again find the value of d ,round it off ,make according to the above table and now compare the two values of d .Take the value which is greater . STEP 2 Failure of spigot in tension across slot Pt=qt*[3.14/4*d1*d1 -d1*t] where t =d1/4 find the value of d1 and then t Emperically d1=1.2*d again find the value of d1 and choose which one is larger .. STEP 3 Failure of rod or cotter in crushing check for the condition Pt<= d1*t*qc if the above condition meet then the value of d1 and t is correct else increase the value of d1 and t to satisfy the condition .Because if the above condition is not satisfied then cotter will be get crushed due to load . STEP IV Tensile failure of socket across slot Pt=qt[3.14/4(d3*d3-d1*d1)2-(d3-d1)t] find the value of d3 from above equation Emperically , d3=1.75d choose the greater one. STEP V Crushing of cotter against collar of socket Pt=qc(d4-d1)t find the value of d4 Emperically , d4=2.4d choose the greater one . STEP VI Crushing of collar of spigot to socket Pc=(qc*3.14*(d2*d2-d1*d1))/4 find the value of d2 Emperically , d2 =1.5d choose the greater one. STEP IX Shear failure of spigot end against cotter Pt=2*T*d1*a where T=shear stress find the value of a Emperically a=0.75d choose the greater value of a STEP X Shear failure of spigot collar Pt=3.14*d*h*T find the value of h from the above equation Emperically ,h=0.75d Choose the greater value of h Step XI Double shear failure of collar of socket by cotter Pt=2*T*(d4-d1)*e find the value of e from the above equation Emperically e=0.75d Choose the greater value of e.
2. ## which university is better for studying the M. Tech of mechanical engineering?

may be IIT DELHI

its not going well.it seems that no one is interested in it...........
4. ## Team of 10 Volunteers to be formed

hi....... I am interested in this new segment.........If you think that i am worth enough for this then please reply me and also tell what I have to do?...

hi... post yaar no one is posting except me....

good night

bye see you tomarrow

just making a screw jack program in C

hi...in this thread just post any thing like what you are doing at this time ? anything like sports ,films ,games ,etc .With this thread we have to break the record of the longest thread by maximum number of posts... To err is human, but the one who rectifies is a champion. ----------------------------------------------------------------------------------------------------------- just chill

hi... we are here to share our knowledge ,ideas, and thoughts to each other. Communication will be better when both sides respond simultaneously...because it is not like a one way traffic but a two way.so it is better to share your views and just not only read but also post to make this forum the heaven for the mechanical engineers. We all are here to solve all the queries of each other and committed to provide all kind of help to 'mechanzies' aka mechanical engineers . So be ready to help fellow being with your knowledge .. and one thing more it is a platform for mechanical engineers to interact not only for technical discussions . In general talk you can discuss any thing like the current cricket match between INDIA and AUS. or the funniest thing that happened to you today.... I only request you to just post in the forum .Make it alive .Only you can make it a better place for everyone... hoping for your active participation ..... POST POST POST POST POST POST POST POST POST POST POST POST POST PS : don't post nonsense things. thanks To err is human, but the one who rectifies is a champion. ------------------------------------------------------------------ just chill
11. ## List of Softwares used by Mechanical Engineers

hi... MATLAB is also an important software for mechanical. It help in solving the difficult mathematical equations and ploting of any curve. it's official website is My link Advantages easy to use. programming software and doesn't have too many complications like in C/C++. one can easily master the software in few days.
12. ## How to make project report?

when we go to have a summer training in any company we generally take the training lightly...none of our teacher told us what we have to do there ?Which company is best for trainig? How to make the project report? What when you go for a viva then they will give you a big lecture on "What you had to do in training?" So i am just answering you about how to make a good training report. 1. Regularly go to the training with a diary to note what you have seen on that day . 2. Note the things with date and also have some photographs of the machines and workspace you have visited. 3. Now you have two options of making file. a. Either you make the report on daily bases like you write a daily report. b. Or make the report on weekly bases. What you learnt in a full week. 4. Paste the photographs you have taken from the company. 5. Never make the report from internet 'cut copy paste'. If you follow all the above steps then definitely you will get the maximum marks and your work will be original... SO hope that you like it. :wub:
13. ## Free Mechanical Engineering CAD/CAM Software

they are good ....thanks :lol: