Rachel: Leg crane designs

After much work trying to work out how to stabilise the crane it was decided by the group to change designs and go with a gantry style crane. These are the ideas about how to stabilise the crane:

Week Meeting

It has been decided that everyone should research on Crane legs and come up with some reasonable ideas that could work as the team wishes to take on Rachels idea and develop it further into a proposed crane, as it fits well with the specification that Sophie Latham has Provided. However if the Leg problem cannot be solved , gantry crane will have to be designed , as this perfectly fits the bill for a emergency crane.

Also at the meeting certain criteria for the main effort of the blog were discussed .

• Why the crane has been designed as it has.
• Mechanical proof of the design.
• Ideas and Innovation.
• Problem solving - Brain storms.

Proposal Specification

Project Outline
The aim of this project is to create a suitable design proposal for a portable crane to be used in disaster relief environments. The crane is to be designed specifically for disaster situations such as earthquakes and tsunamis. These kinds of disaster areas are where there are people trapped under assorted types of rubble such as concrete and steel beams. In these kinds of situations, where construction vehicles are either unavailable or cannot get to the area, the crane would be assembled and used to lift the heavier beams and pieces of rubble.
There are various factors which need to be considered such as quality versus cost and ease of use but the most influential factor, the factor that makes this crane proposal unique, is the extreme environmental conditions the crane will be expected to work in.

Specification Factors
Environmental Conditions

• The heavy rubble and general chaos of the crane site will mean that there is a risk of losing pieces of the crane (if it is transported in various pieces). To reduce this risk, it would be easier to paint the crane an eye-catching colour, preferable a bright colour, which will not only contrast against concrete and steel but will also be seen easier at night.

Costs

• The biggest customer for this crane is going to be countries with high disaster rates. A large number of these countries are third world and ruled by governments with only small budgets available. To deal with this, the crane will need to be cheap enough to be easily purchased by these countries.
• One way to tackle this is to keep the number of manufacturing methods and time used to a minimum. This will reduce man-power needed and the costs to set-up the various manufacturing processes utilised.

Quality

• The quality should be the best available without costing more than we can afford to sell it for.
• This crane will be used to move rubble under which people are trapped; this in itself is a high risk operation, one which doesn’t need the extra hazard of poor quality crane equipment. The crane will likely be pushed to its limits regularly and only with a good quality design and build will it continue to work effectively without more than routine maintenance.

Materials

• The materials used should be strong and hard-wearing whilst also of a reasonable price and quality.
• They will need to be able to function where they will come into contact with high levels of dust and air pollution.
• The materials should be readily available and legal to be used in all countries around the world.
• They should not be hazardous or need special handling requirements. Even any maintenance of the material such painting requirements or special coatings, should be easy to maintain in all countries the crane is sold to and used in.

Ergonomics

• The crane will need to be easy to use, as the rescue workers will be working under extreme pressure and will likely be distracted or not have full concentration whilst operating it.
• No one piece of the crane must exceed the legal weight that any rescue employee can carry safely on their own or with another person. This is for the safety of the rescue workers who will need to be able to carry each piece across rough terrain without damaging themselves in the process. Ideally the weight of each piece should be written on it, in a clear to view place.
• If the crane is to be designed for assembly at the site, the number of various pieces in this assembly should be kept to a minimum. This allows for the user to keep track of the various pieces easier whilst transporting. Another benefit, is the less pieces that need to be assembled, the less assembly instructions the rescue workers need to memorise and carry out every time they use it.
• The crane will need to be easy to maintain. Repair and customer care services will need to be available and all parts should be interchangeable with cheap to purchase spares in case of damage.

Customer Requested Outlines and considerations

• Minimum lifting capability of 1000Kg
• Crane reach of a minimum of 4m from central ‘pick-up’ axis
• To be easily transportable by hand, over rough terrain, for an average distance of 100m. To do this, the crane can either be designed to fold-up into itself or it can be carried onsite in pieces and assembled where it is needed.
• It must be able to either fit into the boot or on the roof rack (2m x 2m) standard Land Rover Rescue vehicle.
• The crane, when assembled on site, must be powered by either hand-crank or power-winch.

Rachel - Table of materials

Below is a table that I have made to compare the young's modulus, yield stress and ultimate stress of different materials which would be considered for the crane.

Material	Specific gravity	Young's Modulus (E)	Proof/Yield Stress	Ultimate. Stress	Price
	kg/cu.m	GPa	x 106Pa	x 106Pa	USD/Kg
Steel C<=0.3%		203
Steel C=>0.3		202
Mild Steel	7850	210	200-400	300-500	0.55
Carbon-moly steels		201
Nickle Steels Ni 2%-9%		192
Cr-Mo steels Cr ½%-2%		205
Cr-Mo steels Cr2 1/4%-3%		210
Chromium Steels Cr 12%,17%,27%		201
Alum Alloy 7075	2810	72	145	276
Aluminium	2640	68.95	30-140	60-140	2.214
Carbon reinforced plastic (50/50 fibre/matrix, unidirectional, along grain)	1700-2000	125-150			Expensive

I have tried to find out prices where possible.

I believe that the crane will have to be made out of a steel of some sort or the more expensive aluminium alloy 7075. This aluminium alloy is normally used for aeroplanes, high performance bikes and mechanical switches but it might have a use within the crane.

It might be possible to have certain parts of the crane which will not be subjected to a high stress to be made out of another material such as aluminium to save on weight.

The table will be updated and reposted if more information becomes available.

Initital Designs

As tasked from the First Meeting I was to design initial ideas for a crane that fulfils the brief.

I started this task by simply looking at the different types of cranes available. I then proceeded to initially analyse any problem that could occur if the design was placed straight into the disaster areas. From doing this it was clear that the main problem that would occur is how to secure the base of the crane. In all situations they are designed to work on level ground. This will need to be considered in the design. Also how the load is being lifted will effect how the crane works for example looking at the standard crane a huge counterbalance will be needed.

From the considered designs, ideas can be placed together to make a hybrid of all three

Once the hybrid idea was develop initial design was done.

Benefits of this Design

• If designed correctly it could have very minimal parts allowing a very quick time of construction/deconstruction. The befit with having less parts means that less people are required to carry over the 100m.
• Because the design is not actual lifting the load directly up a counter balance will not be needed.

• The design can be constructed to have supports in the large stress areas minimising any failures that could occur.

• If a effective base can be designed it removes the need for a relatively flat surface to mount on

Issues with Design

The main issues that was raised in the meeting was "is it classed as a crane" - the design does not pick the item up of the floor, however it still moves the load away from initial point.

Other Issues that was raised during the design and meetings were:-

• How can the legs be attached
• Will the beam be small enough to fit into the back of a land rover
• How hard it is to model to run stress/bending moments analysis
• Dose it fit the brief - crane?

• How is the end at load secured to ground
• How is the load removed of beam
• Will the beam be strong enough
• Each part will have to be light for carrying

These issues will be considered through further designing if decided that it is allowed to be continued with.

Further Development

Develop designs for the points noted above and carry out initial model s to test failure points.

This Design proposal was taken to the initial team meeting. It was my proposal to use a gantry crane for the project. I had came across some preliminary design failures and so we had all decided to perfect our crane ideas for another team meeting in which we would select our final design. My main problem for this idea was the weight of the horizontal beam. I had at first selected Steel as my engineering material but knew this would be far to heavy for manual lifting. Also I wanted to make the assembly much easier and quicker to build. These were factors I took away to work on over the passing week.



This was my revised crane design. I had selected Aluminium as the engineering material as it was much lighter than steel but still had the required strength for weights in the design specification. To save more weight I made the horizontal beam a t-section and also had holes punched in the upper most plate. This section of beam has no contribution to the strength and so only added weight. On the design shown the holes are Triangular whereas a more suitable shape would be circular as this would not focus stresses on the corners. The design would be held together using nuts and bolts as it is the strongest and most reliable was of assembling a rig on site.

Below shows the type of t-section I would have integrated into my design.

Initial Crane Design

As tasked last Tuesday, i was to design a crane based on engine cranes currently on the market. Most of the designs currently on the market do not have a counter weight but instead use long legs , so the centre of gravity is never past these legs and the crane does not topple. Most of the research shows that many have telescopic booms, and a hydraulic lift system and are easily foldable. The cost of these cranes are fairly low as most of the materials used are steels and the shapes of the steel sections are mostly standard, box section beams. However to adapt this design my

earthquake environment some changes were made.

• Multiple legs to make sure the C of G was never going to topple the crane.
• Adjustable legs to allow for uneven ground and to gain a flat base.
• A swivel crane made from tubular steel so it could be swung round.
• Hydraulic car jack, to allow for lifting.

There are however many different ways of designing a engine hoist like crane, the Swivel beam need not be vertical , the hydraulic system could be connected to the base as not to strain the swivel beam, the legs could be like spider legs allowing for more adaptation to the environment.

My initial plan of constructing a mechanics model of the crane.

These pictures are in the wrong order, it should be reversed.

These are my design ideas for the basic design I was given.

The first idea I started with was a portable version of the hand operated crane with a triangular shaped boom. The problems I found with this design was making it portable was very difficult and a hand operated winch system with pulleys might not have been the most effective as the pulleys could get jammed and the rope system was complicated.

So I switched to the idea of a telescopic beam with a simple powered winch. This design could be disassembled in half and transported in this fashion. It has a simple screw system to change the pitch of the boom and it also features a pivot so the load can be moved. It has extendible legs for balance.

Initial crane Design

Above is my initial Crane Design. Looking at the proposal specification i tried to keep my initial design simple, this makes it easier to manufacture, assemble and maintain.
The above Gantry style crane has numerous features that make it ideal for the task it is being designed to work with, these are as follows:

• The crane would be made out of a lightweight, yet tough, material such as an aluminium alloy.
• There are rubber feet on the bottom of each of the four legs to help the crane grip when in use. Another advantage to using these rubber feet is that, it's the easily replaceable rubber feet that wear over time, not the bottom of the aluminium crane legs.
• The length of the I-beam along the top is a length of 4m, allowing for the specified travel span.
• The 4m long I-beam can be split in the middle to allow for easier portabillity.
• The legs will be a hollow form of bar stock that will be lightweight and cheaper to buy without losing any vital strength.
• The crane can be easily taken apart and re-assembled on-site, thus making it very portable without excess parts to carry (minimal components involved).

Discussion of ideas

The following pictures include the general mind-mapping that took place regarding the meeting on Tues 9th March where we discussed basic design criteria and some initial ideas based on crane research. Please click on a picture to see an enlarged view.

Post: Alec Kingsnorth

Project Management

Group F -Notice of interest

Project Manager- Alec Kingsnorth

Finance Officer- Sophie Latham

Chief Designer- Mark Lobato

Stress Analyst-Michael Kiriakou

Materials Specialist-Rachel Liddiard

Gantt Chart

Day 2

Today in our team meeting we established individual roles. We have decided that to start the project each team member will bring forward a design proposal by next Tuesday the 16th. We will have approached our proposals with cost, stress analysis and materials in mind. This way as a group we can accumilate our ideas and form a amalgamation of ideas to create a suitable crane design.

Update 8th March

All group members are researching different crane types.. We are meeting as a group on Tuesday the 9th to discuss different designs and materials and a final establishment of member roles in the group project..

Designs and roles for different group members will be posted March 9th.

Michael K Kiriakou

Day 1

Blog has been created.

We are dicussing roles that individual team members will take over the weekend.

Michael Kiriakos Kiriakou