and testing

Asia pacific university college of technology & innovation

SHAMINI A/P PATPANAVAN @ PATHMANATHAN

SANGEETHA A/P KANARATANAM

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Crane design 2011

Abstract

This assignment requires to design a crane which will keep the boom at an angle of 45o, 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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ContentsAbstract.......................................................................................................................................................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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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

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

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make it easier to understand the forces, and torques or moments, in relation to one another and

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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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

counter-jib, and the operators cab. Or The "hammerhead “crane is a fixed-jib crane consisting of

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.

Figure 1, hammerhead crane

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Hammer head crane

Advantage Can lift up heavy materialDisadvantage

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 Easy to build 360 degree.

Weakness Only can be placed on straight surface.

Must be assemble

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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.

Figure 3

Figure 4

Unfortunately my design was over than limit of the requirement but based on my calculation

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 .

Design number 2

3 links

1 solid mast

Boom at 45 degree

About 60 g

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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

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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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 Ay

1 1.38×10−3 115 ×10−3 3 ×10−3 1.58 ×10−4 4.41 ×10−6

2 1.48 ×10−3 152 ×10−3 0.08 2.25 ×10−4 1.18 ×10−3

3 5.6 ×10−3 23.3 ×10−3 23.3 ×10−3 1.30 ×10−4 1.30 ×10−4

4 2.304×10−3 16 ×10−3 16×10−3 3.6864×10−5 3.6864×10−5

5 3.12 ×10−3 0.18 ×10−3 0.09297 5.616 ×10−7 2.9007×10−4

6 9 ×10−4 0.125 0.072 1.125 ×10−4 6.48 ×10−5

7 1.24 ×10−3 0.2008 0.016 2.489 ×10−4 1.984 ×10−5

8 1.9 ×10−4 0.0126 3.33 ×10−3 2.407 ×10−6 6.327 ×10−7

9 8 ×10−5 2.67 ×10−3 3.33 ×10−3 2.136 ×10−7 2.664 ×10−7

∑ A=0.016294

∑ Ax=9.144462 ×10−4

∑ Ay=1.7268807 ×10−3

X=∑ Ax

∑ A

=0.0561

y=∑ Ay

∑ A

=0.10598

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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 Ay

1 1.38×10−3 115 ×10−3 3 ×10−3 1.58 ×10−4 4.41 ×10−6

2 1.48 ×10−3 152 ×10−3 0.08 2.25 ×10−4 1.18 ×10−3

3 5.6 ×10−3 23.3 ×10−3 23.3 ×10−3 1.30 ×10−4 1.30 ×10−4

4 2.304×10−3 16 ×10−3 16×10−3 3.6864×10−5 3.6864×10−5

5 3.12 ×10−3 0.18 ×10−3 0.09297 5.616 ×10−7 2.9007×10−4

6 9 ×10−4 0.125 0.072 1.125 ×10−4 6.48 ×10−5

7 1.24 ×10−3 0.2008 0.016 2.489 ×10−4 1.984 ×10−5

8 1.9 ×10−4 0.0126 3.33 ×10−3 2.407 ×10−6 6.327 ×10−7

9 8 ×10−5 2.67 ×10−3 3.33 ×10−3 2.136 ×10−7 2.664 ×10−7

10 5.625×10−3 0.0375 0.0435 2.1094×10−4 2.4469×10−4

∑ A=0.021919

∑ Ax=0.02212994

∑ Ay=1.9715707×10−3

X=∑ Ax

∑ A

=1.009623

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y=∑ Ay

∑ A

=0.089948

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

Figure 10

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Figure 11

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Factor of safety:

Allowable load =100¿¿

Ultimate load=100

(155×10−3)׿¿

=53763.44pa

Factor of safety =0.05153

To find correct distance for counter weight:

To find that we should follow this rule: if l1is 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 : l1=7.5

L2=15

M1=5

M2=10

Therefore the equation is proven.

To find counter weight Cw×l1=w×l1/2

Which, cw=counter weight

W=weight for lifting

L1=length from the mast

Cw=50N

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Bonding moment

It only occurs at mast so

A=0

B=3W (L)2

32=20.54WN

C=W L2

8=27.38WN

D=3W L2

32=20.54WN

E=0

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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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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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Reference

Crane –supporting steel structure, design guide ,R.A.Maccrimmon,acres internation nigara falls, ontario

Analysis of force (c) 1998-2011 Benjamin Crowell, licensed under the Creative Commons Attribution-ShareAlike 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, Basic Notes on Factor of Safety, http://www.roymech.co.uk/Useful_Tables/ARM/Safety_Factors.html

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. Retrieved 3 June 2011.