E N G I N E E R I N G D E S I G N | By | | | |
Gun Ken Hon
*
Gun Ken Hon
*
Toni Rosinol
N1403135F
Toni Rosinol
N1403135F
Zulqarnin
U1120101c
Zulqarnin
U1120101c
Muchsin Mohd
U1123008L
Muchsin Mohd
U1123008L
| MA4001 | School of Mechanical & Aerospace Engineering50, Nanyang Avenue, Singapore 639798, Tel:65 790 5488 Fax:65 792 4062 |
Table of Contents Content | Page | 1.0 Introduction | 4 | 1.1 Background and Objectives | 4 | 2.0 Conceptual Design | 5 | 2.1 Function Analysis | 5 | 2.2 Morphological Chart | 7 | 2.3 Design Concepts | 8 | 2.3.1 Design Concept A | 8 | 2.3.2 Design Concept B | 9 | 2.2.3 Design Concept C | 9 | 2.4 Concept Evaluation | 10 | 3.0 Embodiment Design | 12 | 3.1 Stability | 12 | 3.2 Spade Design | 12 | 3.3 Mode of Transport | 12 | 4.0 Detailed Design | 13 | 4.1 Hydraulics Selection4.2 Materials Selection | 13 | 5.0 Detailed Design Calculations | 13 | 5.1 General Data | 13 | 5.2 General Calculations | 15 | 5.3 Lifting | 17 | 5.4 Tilting | 18 | 5.5 Hydraulics Selection | 20 | 5.6 Pump Selection | 21 | 6.0 Cost Estimation | 22 | 6.1 Bill of Materials (BOM) | 22 | 6.2 Purchased Parts | 27 | 6.3 Manufactured Parts | 28 | 6.4 Overall Cost Estimation | 28 | 7.0 Conclusion | 29 | References | 30 | Appendix | 31 | | | | | | | | | | | | | | | | | | | | |

1.0 Introduction

1.1 Background and Objectives

Being a densely populated island, Singapore does not have the luxury to use her land with impunity. Amidst the concrete urban jungle of Singapore, the need to consider for greenery in our country is crucial. Greenery is an important consideration for the quality of life in Singapore. we need to employ an environmentally sustainable urban planning. With the rapid urbanisation Singapore is constantly going through, we must find ways not reduce the negative impacts on the environment. Singapore is planning to increase the green space by 50ha.

Trees are a big part of our greenery. Not only do they keep temperatures cool, due to the latent heat of vaporisation from the foliage. They also help in the purification of our air through photosynthesis and also through physically acting as a filter near roads. Trees help keep global warming in check. The values of trees are more than we can fathom. With deforestation ravaging the world, Singapore must do what little it can to reduce the effect of global warming on the world.

With rapid urbanisation going on, trees turn out to be a hindrance to projects. Many companies choose to cut down the trees instead of replanting the trees, because its a cheaper alternative. companies fail to see the detrimental effects that it’ll have on the future of our environment. once a tree is cut down, replanting is not the best and viable option because it takes many years to grow a tree from a sapling. It does not have a instant effect. Hence, tree transplanting is the best option as it offers an instant and better solution.

Tree transplanting helps to transport the trees obstructing urbanisation projects to another location so that it can still serve its purpose. The tree is mechanically uprooted in one piece, minimising damage. Tree transplanting may be more expensive compared to growing saplings. Unless the value of the tree outweighs the transplanting cost.

Transplanting large trees is not often practised in Singapore. However, Singapore practises tree planting day nationwide, where small trees are planted manually by members of the society. the only drawback to this is that to plant one small tree, many hands are required. Even though this might be considered progress, this process can be optimised if we to use a tree transplanter.

There are several models of tree transplanters available. All of which serve a slightly different purpose. They all have very different designs and purposes. However, the common denominator here is the process can be further optimised and be cheaper.

Our projects aims to design a machine to move trees to new locations more efficiently than the current methods employed. we are tasked to design a machine with low-cost standard components and alternative techniques.

2.0 Conceptual Design

2.1 Function Analysis

A function analysis of our tree transplanter was conducted to study the functions it is expected to be able to undertake. This is then expanded by identifying the operations required to achieve these functions. Our group started the analysis by creating an Overall Function Analysis Diagram based of the expected inputs and desired outputs of the tree transplanter;
Tree Transplanter
Tree Transplanter

Figure 1 – Overall Function Analysis Diagram

Using the Overall Function Analysis Diagram as a guide, we identified the components and interactions that would allow our tree transplanter to convert the inputs provided into the functions necessary for it to operate.

By connecting the energy and signal flow between the various components, we compiled the full Function Analysis Chart which is as follows:

Figure 2 – Function Analysis Chart

2.2 Morphological Chart

Digging Mechanism | Conventional Excavator | Tree Spade | | Lifting Mechanism | Pulley Method | | Hydraulic Slider Method | Tilting Mechanism | Hydraulics | Spring Damper | | Counter Weights | Symmetrical Design | Lorry as Counterweight | Means of Transport | All Terrain Wheels | Caterpillar Tracks |
Table 1 - Morphological Chart

2.3 Design Concepts

2.3.1 Design Concept A

Figure 3

2.3.2 Design Concept B

Figure 4

2.3.3 Design Concept C

Figure 5

2.4 Concept Evaluation

To evaluate the tree transplanter design concepts, they were pitted against a list of criteria that gives each design a weighted rating. Each criterion and its respective weight and description is tabulated below:

Criteria | Weightage | Description | Safety | 0.33 | | High Stability | 0.16 | Stability is important as a poorly designed transplanter can topple during the tilting or digging process. | Designed for failure | 0.17 | This criterion measures the damage or safety of operators should the critical processes fail. | Physical Aspects of machine | 0.11 | | Size | 0.06 | Size determines the transplanter maneuverability on roads and pavements | Mass | 0.05 | More specifically the pressure exerted on the soil determines whether the machine can be used on soft soil. | Performance | 0.12 | | Power Requirement | 0.08 | A lower power requirement is key to cutting down costs. | Operating Speed | 0.04 | Needless to say, the operation should not take too much time. | Usability | 0.2 | | Adaptability | 0.05 | This criterion gauges the array of tree sizes the transplanter can be applied to. | X-factor | 0.15 | The improvement over other existing transplanter already in the market. | Cost | 0.2 | | Cost | 0.2 | Determines the sellability of the the product over competitors. | Manufacturing Process | 0.1 | | Simplicity | 0.07 | A simple design reduces costs and hassle in production. It also cuts down on production time. | Percentage use ofMarket Parts | 0.03 | The more market part used, there is less down time should the parts be damaged. It is also cheaper to buy off the shelf than to specially manufacture. |
Table 2 – Concept Evaluation Criteria

The concept criteria above is applied on the designed concepts. For each criterion, each concept is given a rating out of 5 with 5 being the most satisfactory and 1 the least satisfaction. The weighted rating, W.R is the product of the rating and the criterion percentage value. Finally the sum of the W.R values is taken and this gives the most suitable concept design.

| A | B | C | | Rating | W.R | Rating | W.R | Rating | W.R | Safety (0.33) | | | | | | | Stability 0.16 | 3 | 48 | 4 | 64 | 4 | 64 | Designed for failure 0.17 | 4 | 68 | 4 | 68 | 4 | 68 | Physical Aspects of Machine (0.11) | | | | | | | Size 0.06 | 4 | 24 | 5 | 30 | 5 | 30 | Mass 0.05 | 3 | 15 | 4 | 20 | 4 | 20 | Performance (0.12) | | | | | | | Power Requirement 0.08 | 3 | 24 | 4 | 32 | 3 | 24 | Operating Speed 0.04 | 3 | 12 | 4 | 16 | 3 | 12 | Usability (0.2) | | | | | | | Adaptability 0.05 | 4 | 20 | 2 | 10 | 4 | 20 | X-factor 0.15 | 3 | 45 | 2 | 30 | 4 | 60 | Cost (0.2) | | | | | | | Cost 0.2 | 4 | 8 | 2 | 4 | 4 | 8 | Manufacturing Process (0.1) | | | | | | | Simplicity 0.07 | 3 | 21 | 2 | 14 | 4 | 28 | Percentage use of Market Parts 0.03 | 2 | 6 | 3 | 9 | 4 | 12 | Total | | 291 | | 297 | | 346 |

Table 3 – Concept Evaluation Table

Based on the concept evaluation table, design concept C best meets our evaluation criteria. Hence design concept C was finalized as the design that we would like to pursue for this project.

3.0 Embodiment Design

3.1 Stability

Our transplanter design has to be compact so that it will not take up much space when travelling on roads and when parked. In order to achieve compact dimensions, we had to narrow our design as much as possible without sacrificing on stability. However, considering we have a very symmetrical design, we have solved many issues of instability.

3.2 Spade Design

We have decided to go with the conventional spade instead of the excavator styled spade. This is mostly due to the efficiency of the conventional tree spades. The conventional tree spade is able to provide with a very symmetrical and consistent shape every single time.

3.3 Mode of transport

We have decided to use all terrain wheels instead of caterpillar tracks mostly because we want our final product to be friendly to the roads. Caterpillar tracks tend to tear up the tarmac and asphalt, even though caterpillar tracks provide for a better stability. To offset the potential problems of stability, we have decided to add an extra tyre to our final design. Hence, our final design has six tyres for optimal stability.

4.0 Detailed Design

4.1 Hydraulic Selection

The hydraulic cylinders are required for the three mechanisms, namely lifting, tilting and digging. The hydraulic is chosen from Parker as it is a well-known brand for hydraulics. Parker Hannifin Mobile CS63DC-47-82.50 S63DC Type CYL. In the calculations section below, the said model is sufficient to drive all the three mechanisms.

4.2 Material Selection

The general non negotiable requirements for this machine are: high stiffness and high strength. An extremely rough selection would be to choose among composites, ceramics and metals.

Figure 6

Figure 7

Figure 8

5.0 Detailed Design Calculations

5.1 General Data

Estimation of the Digging force
In order to start the design calculations, the force required to dig the ground is essential. From there, the appropriate hydraulic cylinders can be chosen. It is noteworthy to realize that in order to dig the ground, the pressure exerted by the tree transplanter spade is more important than the force applied to the ground. Also the path of the spade as it penetrates the ground is likely to be filled with rocks. Thus this forms the basis of the pressure estimation exerted by the spade of the transplanter.

The compressive strength of bricks and portland concrete is found to be 7000 kPa.[1] Unlike ultimate tensile strength which measures the stress required to fracture the material by pulling it, compressive strength measures the stress required to fracture the material by compression. This is clearly more appropriate in this case. Obviously the soil is not as hard as bricks, thus the pressure used in the following calculations will be only 6000kPa.

Let A be the area of the spade that penetrates the soil. A is obtained from solidworks.
A = 2(18695.87mm2) = 37391.74mm2 = 0.03739174m2
The force is applied at an angle of 75°. In reality the angle changes as the spade pierces the ground.
Thus the maximum force required to dig the ground is estimated to be F = PA = (5000k)(0.03739174) cos 75 = 48.14kN

To account for friction and other miscellaneous factors, the force shall be scaled by a factor of 1.5.
Thus the digging force is 48.14(1.5) = 72.2kN per spade.

In comparison, the force required by the bucket excavator is about 5kN [2]. Thus the digging force used here is a relatively good estimate as the spade is much bigger and it also goes much deeper. In addition, there is a possible requirement to penetrate the rocks that may be present in its path.

Estimation of the Tree’s weight
The tree’s weight is an important parameter in order to proceed with the calculations. It is required especially for the lifting and tilting mechanism calculations. From [3] the mass of the tree can be estimated from the following algorithm:
0.38315 (D2H)0.92045 where D is the diameter of the tree, H is the height of the tree.
To obtain the maximum weight, H is maximized.
Take H = 3.5m = 137.795 inches, D = 0.15m = 5.905 inches
Using the above algorithm, Tree’s mass is 95.24 pounds = 43.2kg
So tree’s weight is 423.8N.
In addition the soil encasing the root needs to be calculated. The dry density of soil from wikipedia is between 1 to 1.6g/cm3.[4]
Assume the wet density of soil is 2.3g/cm3 = 2300kg/m3. Estimate the root ball to be a hemisphere, with diameter 1.5m and the depth 0.5m.
Volume of root ball is (4/3)πr3 = (4/3)π(0.753) = 1.767m3.
Then the mass of the root ball = 2300(1.767) = 4064kg.
Weight of root ball = 39.872kN
Note that within the root ball, the roots are present i.e. it is not made up of soil completely.
Thus a factor of 0.9 is taken.
So weight of root ball is reduced to 35.88kN
Finally the weight of tree inclusive of root ball = 35.88+0.423 = 36.3kN

5.2 General Calculations

In this section, the general force and moment balance on the entire vehicle is calculated.

Force/Moment Balance
Basic Information:
Recall from the above section that the force per spade is 72.2kN.
The mass of the trailer together with the truck is approximately 11340kg.
Thus it’s weight is 111.2kN.
The vehicle has 6 wheels, 3 on each side.
There are 4 spades however the spades enters the soil 2 at a time. The spades enter in opposing directions. This is to provide stability. The following figure shows the forces when the first two spades are digging(obviously without the tree):

Pivot
72.2kN
72.2kN
0.4m
1.5m
0.4m
111.2kN

Pivot
72.2kN
72.2kN
0.4m
1.5m
0.4m
111.2kN

For simplification, the pivot is taken to be at the centre of the two wheels i.e. a single entity.
Assume that the weight is evenly distributed.
From symmetry, the force can be determined easily.
Force on rear wheels = 111.2/2+72.2 = 127.8kN
Force on each rear wheel = 127.8/2 = 63.9kN
Force on front wheels = 111.2/2+72.2 = 127.8kN
Force on each front wheel = 127.8/4 = 31.95kN

The figure below shows the forces when the next pair of spades are in action (without the tree):

Pivot
111.2 kN+72.2kN+72.2kN
1.75m
1.5m
1.75m

Pivot
111.2 kN+72.2kN+72.2kN
1.75m
1.5m
1.75m

Similar to the above, the forces can be determined by symmetry:
Assume that the weight is evenly distributed.
Force on rear wheels = 111.2/2+72.2 = 127.8kN
Force on each rear wheel = 127.8/2 = 63.9kN
Force on front wheels = 111.2/2+72.2 = 127.8kN
Force on each front wheel = 127.8/4 = 31.95kN

Note that during the whole operation, whether the first pair or the last pair of spades are operating, the reaction forces on the wheels are the same.

5.3 Lifting Calculations

In this section, the force required to lift the tree is determined.
Recall the weight of the tree including the root ball is 36.3kN.
The weight of the equipment that holds the tree and is required to be lifted is 5.65kN.
Total weight to be lifted is 36.3+3.5 = 41.95kN.
Thus force required to lift the tree is 41.95kN at constant speed.
Taking into account air resistance and friction, a factor of 1.3 is scaled to the force.
Finally the force to lift the tree together with the root ball is L = 1.3(41.95) = 54.5kN at constant speed.
Lifting is done using hydraulics.
It is sufficient to use the same hydraulic as those used for digging the ground. This can be found in the hydraulic section calculations.

5.4 Tilting Calculations

The force/moment balance is determined in this section. The working principles of the tilting mechanism is explained as follows. Using the hydraulic at maximum extended position, the tree stands in its vertical position. A small moment is applied, and the tree will ‘fall’ resisted by the cylinder. Thus, the force to tilt the tree is simply the force that pushes the hydraulics to its retracted position. This is easy.
The main concern is the hydraulic’s ability to extend pushing the tilted tree to its vertical position. The tree rests at 45° above horizontal.

W
W
R
R

θ θ d x W
W
R
R

θ θ d x The picture on the left shows the tree fully tilted at 45°. And the figure on the right shows the process of the hydraulic pushing to tilt the tree. Note that the hydraulic is not directly in contact with the tree. R is the force exerted by the hydraulic, It is applied at a constant angle above the horizontal. W is the weight of the tree and body of the transplanter that tilts. θ is the angle of inclination. d and x are the distances shown as above.
To determine the force required by the cylinder, the maximum value of R is required. Since θ vary from 45° to 90°, R must change.
Using balance of moments,
Wd cos θ = Rx cos (θ-45)
R = (Wd/x)(cos θ/cos(θ-45))
W, d, x are constants.
To obtain the maximum value, the graph of R against θ is plotted. For the domain of θ from 45 to 90, the maximum value of R = Rmax is obtained when θ = 45°.
Thus if the hydraulic cylinder can apply a force of Rmax, then we can use Rmax as a basis to select the hydraulic.
The specifications of the system above is as follows:
W = 73kN, d = 2.5m, x = 3.5m, θ = 45°.
Rmax = (Wd/x)(cos θ/cos(θ-45)) = 36.9kN
Considering friction, a safety factor of 1.3 is used.
Thus Rmax = 1.3(36.9) = 47.9kN

5.5 Hydraulics Calculations

In this section the calculations for the hydraulics is done in conjunction with data of hydraulics selected from Parker. A single acting telescopic cylinder consisting of 3 cylinders is selected for this application. The use of hydraulics is for the lifting, tilting and digging the ground. Comparing Fdig (digging force), L (lifting), R(tilting force), the force required to dig the ground, Fdig is the largest. Thus the hydraulic calculation is done with the digging force as basis. The same hydraulic cylinder is used for the lifting, tilting and digging mechanism. From the calculations below, the weakest powered telescopic cylinder available from Parker is sufficient to drive the digging mechanism. Thus for tilting and lifting, the same cylinder is used.
Data of the cylinder:
Stroke: 82 inch=2.08m
Diameter: 3.75 inch, 4.75 inch, 5.75 inch corresponds to 0.09525m, 0.12065m, 0.14605m respectively.

Recall Fdig = 72.2kN is the digging force per spade. Given that each cylinder has to exert a force of Fdig at all points during its stroke, the required pressure, Pdig for the digging operation can be obtained:

It is sufficient to use the smallest area to obtain the max pressure:
Acylinder = π(0.09525/2)2 = 0.007126m2 Pdig = Fdig/Acylinder = 72.2k/0.007126 = 10.13MPa

Thus we select the cylinder with the available pressure: 2000 PSI = 13.79MPa to satisfy the pressure requirement. Thus this hydraulic is sufficient to provide the digging force.

The allowable time for the extension is 8s.
The allowable time per cylinder is 8/3 = 2.667
The stroke per cylinder is 2.08/3 = 0.693m therefore the flow rate is:
Qmax= AcylinderStroke/2.667 = π(0.14605/2)2(0.693/2.667) = 4.35(10-3)m3/s = 261.19 lpm

The capacity for the pump should be QP = 1.2Q = 313.4lpm
In the next section, the pump required to develop the above flow rate is selected.

5.6 Pump Calculations

In this section the calculations for the pump to drive the hydraulics is done with respect to data from Parker.
The pump chosen has the following specifications:

Dp=81.95cm3/rev, 109.79cm3/rev, 140.92cm3/rev, 196.64cm3/rev, 262.19cm3/rev
Np=2550 RPM, 2450RPM, 2300 RPM, 2100 RPM, 1800 RPM respectively
Pressure up to 6000 PSI for continuous use

The flow rate is given by QP = DPNPηv where ηv is the volumetric efficiency taken to be 0.9
The pump with the following characteristics: Dp = 196.64cm3/rev, Np = 2100 RPM is minimum to drive the hydraulic.
QP = DPNPηv = 371.6 lpm

The size of the reservoir is 3QP = 3x371.6 = 1114.8lpm

The size of electric motor required to drive the pump is:
(lpm)(bar)/(600O) = 371.6(137.9)/(600x0.81) = 105.4 kW where O the overall efficiency is taken to be 0.81

The drive torque at pump shaft is TP = DPPP/(2ηTπ) = 196.64x10-6(13790000)/(2x0.9xπ)
= 479.5Nm where ηT the torque efficiency is taken to be 0.9

So the pump is sufficient to drive the hydraulic.

6.0 Cost Estimation

6.1 Bill of Materials (BOM)

The following figures display the exploded diagrams of various sections of the transplanter. These diagrams break up the transplanter into separate components, hence showing the various parts required. From these, a BOM was created to list all the assemblies, parts and the respective quantities needed to manufacture it.

Figure 20 – Exploded Spade and Frame Components

Figure 21 – Exploded Tilting and Lifting Components

Figure 22 – Exploded Digging System Components

Table 15 – Bill of Materials (BOM)

Item No | Part Number | Qty | Cost Estimation | 1 | halfring | 1 | 6000 | 2 | leftring | 1 | 4000 | 3 | rightring | 1 | 4000 | 4 | Digger without support | 4 | 7000(4)=28000 | 5 | frame | 4 | 4000(4)=16000 | 6 | Platform | 1 | 16000 | 7 | lift Frame | 1 | 3600 | 8 | Lift base | 1 | 700 | 9 | Long Piston Small | 1 | 4000 | 10 | Piston stand holder | 1 | | 11 | Long Piston Big | 1 | | 12 | Small Piston Tip | 1 | 3000 | 13 | Short Piston Big | 1 | | 14 | Short Piston Small | 1 | | 15 | Big Piston Tip | 1 | 400 | 16 | Piston Stand Holder Pin | 1 | 300 | 17 | Piston stand holder pin lock | 1 | 300 | 18 | Quick Pin | 1 | 300 | 19 | Hydraulic Cylinder (Spade) | 4 | 3000(4)=12000 | 20 | Wheels | 6 | 8000(4)=32000 | 21 | Brakes | 6 | 2500(6)=15000 | 22 | Brake Lighting | 2 | 1500(2)=3200 | 23 | Wiring | 1 | 4500 | 24 | Hydraulic Pump | 6 | 1600(6)=9600 | 25 | Operation Lighting | 1 | 500 | 26 | Emergency Stop | 1 | 16,000 | | Total | | $179,200 |

6.2 Purchased Parts
A multitude of the parts are purchased. This will be easy for replacement should any parts are spoilt. The machine would also have less downtime when the parts are spoilt.

Part | Quantity | Long Piston Small (Parker) | 1 | Piston stand holder (Misumi) | 1 | Long Piston Big (Parker) | 1 | Small Piston Tip (Parker) | 1 | Short Piston Big (Parker) | 1 | Short Piston Small (Parker) | 1 | Big Piston Tip (Misumi) | 1 | Piston Stand Holder Pin (Misumi) | 1 | Piston stand holder pin lock (Misumi) | 1 | Quick Pin (Misumi) | 1 | Hydraulic Cylinder (Spade) (Parker) | 4 | Wheels (Dunlop) | 6 | Brakes (Mitsubishi) | 6 | Brake Lighting (Hitachi) | 2 | Wiring(Mitsubishi) | 1 | Hydraulic Pump (Parker) | 6 | Operation Lighting (Panasonic) | 1 | Emergency Stop (Panasonic) | 1 |
Table 16 – List of Purchased Parts

6.3 Manufactured Parts

Some components must be manufactured. This is because to protect the secrecy or knowledge of the product, not everything should be purchased. Furthermore some components are specialized, thus not available on the market.

Material | Part | Quantity | Stainless Steel | lift Frame | 1 | | Lift base | 1 | Mild Steel | platform | 1 | | halfring | 1 | | frame | 4 | | leftring | 1 | | rightring | 1 | | Digger without support | 4 |
Table 17 – List of Manufactured Parts

6.4 Overall Cost Estimation

The total cost of the machinery (trailer only) not inclusive of the truck costs $179,200. The actual design cost would be $95,000. Including the assembly process of about $130,000, the final cost is estimated to be $404,200. The selling price of this equipment would be $970,000.

7.0 Conclusion

Figure 22 – Overall Transplater Design

The objective of this project was to design a better and more efficient tree transplanter than what is available on the market currently.

Our group came up with a trailer designed transplanter that is very mobile and light. We believe that our transplanter can serve better due to a better stability and range of tree sizes it can be applied to.

Throughout the project, our group has learnt to appreciate the fundamentals of engineering design. This course has taught us to analyse problems in a more detailed and logical manner as well as to understand the relationship between various components in design. The skills learnt during the duration of this design project will be of great use in future engineering related tasks.
References

[1] compression and tension strengths of some common materials (n.d.). Retrieved March 10, 2015, from http://www.engineeringtoolbox.com/compression-tension-strength-d_1352.html

[2] Evaluation of bucket capacity, digging force calculations and static force analysis of mini hydraulic backhoe excavator. (2012.). Retrieved March 12, 2015, from http://www.mdesign.ftn.uns.ac.rs/pdf/2012/no1/059-066.pdf

[3] Tree Weighing (n.d.). Retrieved March 12, 2015, from http://www.ncsec.org/cadre2/team18_2/students/science.html

[4] Bulk density. (n.d.). Retrieved April 3, 2015, from http://en.wikipedia.org/wiki/Bulk_density

Appendix

Figure A – Hydraulic Piston

Figure B – Hydraulic Pump