Machining Cost

One of the questions that needs to be answered is how much it is going to cos to make the crane. The beam is of a standard design and can be purchased pre-made and cut to the required length. However the legs must be specially made and a machining cost must be evaluated.

First and foremost we must look at the different types of tools that could be used to cut the aluminium into the specified dimensions.

High Speed Steel

This material was invented in the 19th century and was a massive improvement on the standard cutting tools of that time since they can function under higher speeds and hotter temperatures than standard steel tools. Out of all the tools researched this has the lowest range of cutting speeds, however it is still able to cut aluminium to a rough finish, but the life of the tool is significantly small when cutting this material. However the material is the cheapest type of tools looked at.

Cast Alloys

This material is a standard base metal (e.g. iron) which has been augmented with an alloying element (e.g. nickel, tungsten, chromium etc.). The reason for doing this is to improve the metals strength and reaction to heat. This group of cutting tools can operate at higher cutting speeds and temperatures than High Speed Steel, and the tool life is significantly higher. The price of these tools are also quite reasonable.

Carbides

Strong metal such as titanium are part of the this group of materials, and are used in some of the most extreme situations, for example they are used to construct the fuselage of space shuttles which are put under the most extreme temperature any material could be put through. In relation to cutting tools, this material is second only to certain ceramics in cutting speed and operating temperatures. The pieces are highly expensive though.

Price for Cast Alloy cutting tools = approx £20.00 (set of 11 cutting tools)

source: axminster tool centre

Ceramics

As mentioned before this the type of cutting tool that is second to none. Ceramic is the name given to most crystalline oxide structures, such as silicon carbide, saolin, titanium carbide. The strength of this material has been proven through the use in space shuttle re-entry shields, military ballistic vests, and heavy duty abrasives. Yet, as said with the carbides ceramics are very expensive to produce so the tool prices are very dear, but the tool life balances that out quite well.

By looking at this research it can be said that for the current project using Cast Alloy tools would be the most beneficial to the production of the cranes.

area of aluminium = 1.88 m^2

cutting speed = 1.1-1.8 m/sec (66-108 m/min)

life of cutting tool when cutting to a finished result = approx 175 mins

cost per cutting tool = £20/11 = £1.82 per tool

tool cost = £1.8/175mins = £0.01/min

minimum wage of machine operator = £6/per hour = £0.1/min

Machining Cost = Co x tm

Co = operator wage + overhead

overhead = life of tool + material able to be cut by tool per minute

tm = amount of time needed for task to be completed

Machining Cost = £241 per/min

This is quite a reasonable cost seing as the amount of material that can be machined within a minute will make up multiple kits.

source of calculations: Handbook of Material Selection, Myek Kutz, 2002 edition, published by John Wiley & Sons New York.

other sources:

http://en.wikipedia.org/wiki/Ceramic_materials

http://en.wikipedia.org/wiki/Carbide

http://www.thefreedictionary.com/alloy+cast+iron

http://www.wisegeek.com/what-is-high-speed-steel.htm

Abdi Elmi - Initial Crane and Finance research

Crane Research

Through net research ive found quite a few portable cranes that are manufactured and mass produced by companies such as : Abus Cranes , Spanco Inc, Contrx Cranes etc.
The most ideal crane most of these companies supply is the Jib crane:From our first few meetings we've identified flaws to this design in out particular situation (such as the platform and the mobility) and we're planning to go for quite a different design.

Finance

Ive done some research on manufacturing finance (via previous lecture notes). Some equations essential to finding the manufacturing cost of the crane parts is shown below :
Manufacturing Cost(Mi) = Material Cost(Mc) +( Processing Cost(Pc) * Cost Coefficient(Rc))
[Mi=Mc+(Pc.Rc)]

Material Cost(Mc) = Total volume of material to produced part(v) * Cost of material per unit volume (cmt)
[Mc=V.Cmt]

The material we discussed so far in using is an Aluminium alloy, but that ofcourse is subject to change.
Manufacturing costs will alter depending on the method of manufacturing and the individual shape complexity, but that will be something we will discuss in the near future.

Mark Hawkins - Design Inspiration

The main focus of this initial research phase was to consider preexisting portable crane designs, and assess their pro and con. This should allow better understanding of crane design for future design phases.

The first style of crane that I considered was a gantry style crane. The example to the left shows a "Hasemer and Feltes Aluminium Gantry Crane" which seems to meet most of the project brief criteria.

The main issues with this particular style of crane is firstly that on the loose and uneven post earthquake ground, the struts may not be adjustable enough to keep the winch guide stable and horizontal.

Also, in order for this crane to move debris a minimum of 4 metres from any point of lift, the winch guide beam would have to be 8 metres long. This would cause the whole structure to become very unstable in the likely event of aftershocks. For more information on this preexisting design please visit http://www.ghequipment.com.au/products/cranes/portcranes.htmcranes/portcranes.htm

The next type of crane considered were overhead cranes, as depicted to the right. This type of crane has several advantages over the gantry style crane as its much wider base would make it far more resilient to aftershocks. This design could also be fitted with adjustable legs to allow it to be positioned on uneven surfaces.

The main disadvantage of this crane is that it would have to be 8 metres square to meet the required design criteria. This would make such a crane very difficult to transport by hand over rough terrain, and would not fit inside the back of a standard 4x4 vehicle. For more information on this crane, please see

http://www.low-cost-cranes.com/jib-cranes-350.html

The final style crane that I researched was the portable jib crane as shown to the left and right. The main advantage of this style of crane is that it is rotary and thus may move an object through 180 degrees. This means that the length of the crane arm is minimised, as is the overall size of the crane. However, the main disadvantages of this crane are that in order to remain stable; the base either needs to be significantly counterbalanced with a heavy weight, or the legs need to spread across the ground meaning it can only be placed on a flat surface. Details of the particular crane depicted here can be found at http://apexlifting.tradeindia.com/Exporters_Suppliers/Exporter18134.292868/PORTABLE-JIB-CRANE.html

This research has shown the three main types of crane that I believe would be appropriate to meet the design brief. Each of these preexisting designs has advantages and disadvantages, so the next step is to use the basic principles discovered here in crane design; and create a new, unique, and innovative alternative to be used in earthquake disaster relief operations.

Sandra Donohoe - Initial concept

The main objective for this section was to draw inspiration for a new design by studying the current market.



If these models were to be considered as the foundation for the principal design, certain factors would need further investigation, including:

• Non-collapsible side frames.

• Design a product where the glide rail has a minimum internal width of 4m.

• Weight and height of each part/piece (dependent on material) as they would need to be carried quickly over 100m to the site.

• Aluminium alloy could be used for certain sections due to its high strength to weight ratio (one of the examples given contained a combined total weight of 100kg).

• Material used for cables and ropes (i.e. stainless steel).

• Each piece needs to have restricted dimension sizes in order to be transported by a 4x4 vehicle (some models can quickly fold into 7 pieces).

• Assembly needs to support a minimum load of 1000kg.

• Powered winch can be used to rapidly lift the load.

• Pin type connections could be used as they require no spanners or wrenches or other hand tools, this reduces weight and may increase speed of assembly.

• No need for a counter balance/ anchoring as required by models such as the jib crane.

• Wheels would not be considered due to the type of terrain the crane would be required to operate on (often not plane or rubble).

• Adjustable leg stands could allow the height of the gantry crane to be altered depending on how uneven the terrain is found to be (fitting a spirit level into the model can assist in assuring balance of the glide rail is achieved before the load is lifted).

www.ghequipment.com.au/products/cranes/portcranes.htm
www.aluminiumcraneco.com/portable-gantries-gantry-crane.htm

Jason Harries - Initial Design

My train of thought was based on the idea of simplicity and for that reason I researched into the history of cranes and got some ideas from the Ancient Romans.

Pentospastos

This was a simple crane design that used a simple triangular frame and a block containing three pulleys which is attached to a manual winch. With this formation it could could lift over 1000kg.

The general design is simple and depending on the material used it could withstand the forces required of it.

However the design will not allow it move the load too far, so the design must be altered if it is to fullfill the required result.

Also places to peg the support cables may be hard to find in a disaster scenario.

Polyspastos

This is a crane of simlair design to the Pentospastos but on a larger scale. This one has multiple lines coming from the winch to pulley block which gives it the ability to lift more weight.

This design has the same flaws as the first one, and to lift the larger force either a large human force would be needed or a mechanical force would be needed to turn the winch.

The designs do not completely full fill the required specification but the idea can be modified so that it can perform as needed.