Crane design and testing SHAMINI A/P PATPANAVAN @ PATHMANATHAN SANGEETHA A/P KANARATANAM
Asia pacific university college of technology & innovation
Crane design
2011
Abstract o
This assignment requires to design a crane which will keep the boom at an angle of 45 , hold up a mass of 10 kg being loaded on the boom, and also to find an appropriate counter weight which will keep the crane from tipping over but not exceed half of the load .we are allowed to use as many links in the design but it must have at least two links and the carne should not be more than the dimension 50x50x30(all in cm) and the most importantly the weight of crane must be 40g and below .balsa wood is the material that has been used for building this crane. For more understanding of the applied mechanic topic we were advised to complete the free body diagram, force analysis of the crane as well as centroid and some brief description and discussion to achieve the aim of the given project.
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Crane design
2011
Contents Abstract ......................................................................................................................................................... 1 Introduction .................................................................................................................................................. 3 Problem definition ........................................................................................................................................ 5 Design development ..................................................................................................................................... 7 Design Development – Force Analysis .......................................................................................................... 9 Center of mass of the crane without the counter mass ........................................................................... 9 Center of mass of the crane with the counter mass ............................................................................... 10 FBD .......................................................................................................................................................... 11 Factor of safety: ...................................................................................................................................... 13
To find counter weight ............................................................................................................................ 13 Bonding moment .................................................................................................................................... 14 Discussion.................................................................................................................................................... 15 Conclusion ................................................................................................................................................... 16 Reference .................................................................................................................................................... 17
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Crane design
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Introduction As we live our life in tall and huge skyscraper without showing any interest to know how they build and even asking our self how these heavy material have been lifted to 30 floors up, engineers are working hard on the same concept but the different is that they know answer of question and that is the reason they are working. the answer is simple of course crane is the machine that lift heavy material up and help human to build these skyscrapers . A crane is a type of machine, generally equipped with a hoist, wire ropes or chains, and sheaves, that can be used both to lift and lower materials and to move them , but crane is not new to this world actually The first construction cranes were invented by the Ancient Greeks and were powered by men or beasts of burden, such as donkeys. These cranes were used for the construction of tall buildings. Larger cranes were later developed, employing the use of human tread wheels, permitting the lifting of heavier weights. In the High Middle Ages, harbor cranes were introduced to load and unload ships and assist with their construction – some were built into stone towers for extra strength and stability. The earliest cranes were constructed from wood, but cast iron and steel took over with the coming of the Industrial Revolution. Having idea of building crane has been developed by human kind for centuries and even now it has not stopped but what are the knowledge and information that is necessary to do this? How can we make sure that crane overcome three major considerations in the design of cranes (lift the weight, not topple, and rupture)? Aim of this project is to design an wooden crane and to be able to lift up to 10kg to achiving this aim I am going to study on different model of cranes ,doing force analysis and Free body diagram (FBD)and also I am finding The centroid of the crane by presenting my idea and design of crane. What is FBD? A free body diagram (FBD), also called a force diagram is a pictorial c i n a h c e m d e i l p p A
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representation often used to analyse the forces acting on a body of interest. A free body diagram shows all forces of all types acting on this body. Drawing such a diagram can aid in solving for the unknown forces or the equations of motion of the body. Creating a free body diagram can make it easier to understand the forces, and torques or moments, in relation to one another and
Crane design
2011
suggest the proper concepts to apply in order to find the solution to a problem.and finnaly at the end there would be attached of all photo of the carne that has been taken and I also attached the video of the my crane testing for more reference .
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Crane design
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Problem definition There are 3 different kind of crane which are overhead crane mobile crane and fix crane each kind of crane is existing of other design , I have choose fix crane for my assignment so in the fix category they are tower crane , self-erecting crane, hammer head crane and so on Let’s have closer look at each crane for example Tower cranes are a modern form of balance crane that consist of the same basic parts. Fixed to the ground on a concrete slab , tower cranes often give the best combination of height and lifting capacity and are used in the construction of tall buildings. The base is then attached to the mast which gives the crane its height. Further the mast is attached to the slewing unit (gear and motor) that allows the crane to rotate. On top of the slewing unit there are three main parts which are: the long horizontal jib (working arm), shorter fixed -jib crane consisting of counter-jib, and the operators cab. Or The "hammerhead “crane is a fixed-jib a steel-braced tower on which revolves a large, horizontal, double cantilever; the forward part of this cantilever or jib carries the lifting trolley, the jib is extended backwards in order to form a support for the machinery and counter-balancing weight. These cranes are generally constructed in large sizes, up to 350 tons. The ability of the hammerhead crane is to lift heavy weights. Of course each kind of crane has its different benefits as well as weakness ,for example hammerhead crane is both too expensive and heavy to build and there are some special places that it can be used so it would be better if we try to build other crane that need less metal ,so they are some limitation for using hammerhead like it can only be fix in one place, it usually be used in ships factory so it wont be good idea if we want to use that for other purposes.
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Figure 1, hammerhead crane
Crane design
2011
Hammer head crane Advantage Disadvantage
Can lift up heavy material Too heavy and expensive to build Only can be used in ship industry
another example could be tower crane as we all know tower crane is used to build tall structure like skyscrapers and I am of the opinion that tower crane is the most useful crane cause it does have the ability to rotate 360 degree and can lift up material from ground and main importantly we can increase the height by adding other parts to the mast however on the other hand it needs to be assemble and it take lots of energy and time (I have attached a video from YouTube for more understanding).
Figure 2,tower crane
Tower crane
advantage
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Weakness
Easy to build 360 degree. Only can be placed on straight surface. Must be assemble
Crane design
2011
Design development After I studied about crane and find out how they are working I decided to build my wooden crane based on this design.
Design number 2 3 links 1 solid mast Boom at 45 degree About 60 g
Figure 3
Figure 4
Unfortunately my design was over than limit of the requirement but based on my calculation c i n a h c e m d e i l p p A
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other than this size and weight would have made my crane weak and put it in danger of breaking and not be able to carry 10 kg . Based on studies if a crane want to survive a test it must has strong both base and mast so I use the final thick available balsa wood and for the base I used medium thickness. There is a old
Crane design
2011
story that help to build my boom and the secret that I used is that I attached two wood tougher so this made them stronger and unbreakable as what story told. I have used 3 links but honestly the 2 upper links were not that necessary to use because the 3
rd
links that is connected to both boom and mast (under boom) is enough to support the boom but using at least 2 links was in assignment requirement.
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Crane design
2011
Design Development – Force Analysis Center of mass of the crane without the counter mass Based on the figure 5 in next page I have find these result. number
Area
x
y
Ax
1
1.38
115
3
1.58
2
1.48
152
0.08
2.25
3
5.6
23.3
23.3
1.30
4
2.304
16
16
3.6864
3.6864
5
3.12
0.18
0.09297
5.616
2.9007
6
9
0.125
0.072
1.125
6.48
7
1.24
0.2008
0.016
2.489
1.984
8
1.9
0.0126
3.33
2.407
6.327
9
8
2.67
3.33
2.136
2.664
∑ ∑ ∑
=0.016294
=9.144462
=1.7268807
∑ ∑ ∑ ∑
X=
=0.0561 c i n a h c e m d e i l p p A
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y=
=0.10598
Ay 4.41 1.18 1.30
Crane design
2011
Center of mass of the crane with the counter mass
Base on the figure5 in the next page I have find these result.
number
Area
x
y
Ax
1
1.38
115
3
1.58
2
1.48
152
0.08
2.25
3
5.6
23.3
23.3
1.30
4
2.304
16
16
3.6864
3.6864
5
3.12
0.18
0.09297
5.616
2.9007
6
9
0.125
0.072
1.125
6.48
7
1.24
0.2008
0.016
2.489
1.984
8
1.9
0.0126
3.33
2.407
6.327
9
8
2.67
3.33
2.136
2.664
10
5.625
0.0375
0.0435
2.1094
2.4469
∑ ∑ ∑
=0.021919
=0.02212994
=1.9715707
∑ ∑ ∑ ∑
X=
=1.009623 c i n a h c e m d e i l p p A
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y=
=0.089948
Ay 4.41 1.18 1.30
Crane design
2011
FBD In the next following pages I am going to present the (FBD) of the crane. (figure6,7,8,9
Figure 7
Figure 8
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Figure 9
Crane design
Figure 10
Figure 11
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Crane design
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Factor of safety:
{ }
Allowable load =
Ultimate load=
=53763.44pa Factor of safety =0.05153 To find correct distance for counter weight: To find that we should follow this rule: if l 1is the distance from the first mass to the fulcrum and l2the distance from the second to the fulcrum, then: M1l1=m2l2 So based on figure 5 :
l 1=7.5 L2=15 M1=5 M2=10
Therefore the equation is proven.
To find counter weight Cw×l1=w×l1 /2 c i n a h c e m d e i l p p A
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Which, cw=counter weight W=weight for lifting L1=length from the mast
Crane design Cw=50N
Bonding moment It only occurs at mast so
A=0
B=
C=
D= c i n a h c e m d e i l p p A
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E=0
=20.54WN
=27.38WN
=20.54WN
2011
Crane design
2011
Discussion At the end I have achieve the project aim by understanding all force and formula and also by finding the counter weight and bounding moment also by building the crane and testing it . I think in the building a crane we should always use higher factor of safety I mean for example if we want to pick 20 kg we should build the crane strong enough to be able to carry about 25 kg , so in that case it would never fail. I have tested my crane and unfortunately it fails at 10 kg weight, the mast took off when the last force was taking on it. they are some important concept that break the crane , first of all the quality of the wood, as you can see in the figure12 the part of mast that is connected to both triangle are cracked exactly from the middle and I am of the opinion that the main and most important reason that failed the testing is wood quality .
Figure 12
Another reason could be the factor of safety which is too low and also it has been calculated after testing, but most importantly is that mast was under too much of pressure and finally it could take it more and break but still I am of opinion that wood is the main reason.
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Crane design
2011
Conclusion In conclusion, crane is the most necessary part of our life now days and for an engineer that he or she may want to design one in the future is important to know how does the crane work ? and what are the factors that may put the crane in danger, actually I have achieved the aim of this project by building a crane and also by finding all relative formula to the crane which necessary to know for building a crane however my crane fail at 10 kg and could not be used after all, but I have found the reasons and also learned how to prevent it to happen next time. When I was calculating to find moment I relies that mast of crane is under too much of presser and I decided for next time make the mast stronger that this time. I wish u enjoy reading my project and thanks a billion.
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Crane design
2011
Reference Crane – Crane – supporting supporting steel structure, design guide ,R.A.Maccrimmon,acres ,R.A.M accrimmon,acres internation nigara falls, ontario Analysis of force (c) 1998-2011 Benjamin Crowell, licensed under the Creative Commons Attribution-ShareAlike license. license . Photo credits are given at the end of the Adobe Acrobat version., http://www.lightandmatter.com/html_books/lm/ch05/ch05.html Roy Beardmore , Beardmore, Basic Notes on Factor http://www.roymech.co.uk/Useful_Tables/ARM/Safety_Factors.html
of
Safety,
Center of mass, http://hyperphysics.phy-astr.gsu.edu/hbase/cm.html Croucher, Martin (11 November 2009). "Myth of ‘Babu Sassi’ Remains After Burj Cranes Come Down".. Khaleej Times. Down" Times . Retrieved 3 June 2011.
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