Lifting Gear and Weak Link

Lifting Sling/Strap Material

The lifting Slings we intend to use are made out of a material called high tenacity polyester yarn which is renowned for its hardwearing properties. Widely used through out industry and construction due to their low weight, flexibility and ease of use. These lifting slings are also relatively cheap with an example of lifting capabilities and prices from lift safe solutions below;

For our Gantry crane, it is recommended that we supply our product with straps capable of lifting 2 tonne to ensure durability through use and be at least 6m in total length to ensure it can deal with awkward loads.

Source: www.liftsafesolutions.co.uk

Bow Shackle Material

When deciding which material would be best suited to use for our bow shackles, it came down to two options, high tensile or stainless steel. High Tensile steel would offer us extreme durability and strength at a relatively low cost; however from our design specification, it is clear that the crane will be used in disaster areas, it is therefore accepted that the crane must be durable in all weather conditions. This therefore lead us to turn to using stainless steel Bow Shackles, which still offer great strength yet also offer good corrosive resistance. An example of the load capacity and price for an ideal Bow shackle can be seen below.

Source: www.s3i.co.uk

D ring limits to fail before 1.2 tonnes to prevent damage to crane.

With our D-rings also being manufactured from stainless steel it is accepted that it is more likely that the crane will fail before any of the lifting gear. As a result of this it has been seen as a good idea to implement a safety device within the design to ensure the protection of the main crane assembly, this will ensure longer product life and serviceability, key for our design success. To this end, we have proposed that all our D-rings, which connect the load to the pulley system be designed to fail when it is loaded with more than 1.2 tonnes, a safe loading limit with enough leeway either side of 1 tonne to ensure safe operation of the crane. 

Bearings for use in Gantry Crane

The bearings that we have opted to use are known as barrel roller bearings. We have opted for this design as they are known for their ability to cope with high axial loads and have the ability to cope with misalignments which may happen when loading the crane on planes which are not perfectly level, which is a realistic situation as the crane will be used in undulating terrain.

The requirements for our bearings are as follows, take a min load of 262.5kg each, have an inside diameter of 20mm, outside diameter of 47mm and a width of 14mm.

As a result the Gantry system will require 8 of these bearings for the running gear on the top beam of the gantry. 

The Bearing shown below is manufactured by a company called Shaeffler, a German company specialising in bearings for use in industry.

The bearings that we have opted to use are known as barrel roller bearings. We have opted for this design as they are known for their ability to cope with high axial loads and have the ability to cope with misalignments which may happen when loading the crane on planes which are not perfectly level, which is a realistic situation as the crane will be used in undulating terrain.

The requirements for our bearings are as follows, take a min load of 262.5kg each, have an inside diameter of 20mm, outside diameter of 47mm and a width of 14mm.

As a result the Gantry system will require 8 of these bearings for the running gear on the top beam of the gantry. 

The Bearing shown below is manufactured by a company called Shaeffler, a German company specialising in bearings for use in industry. 

A priced example, £20.13 per unit.

Minutes of Group Meeting 6/12/11

The group met today to present and discuss the work which we had done over the past week, select a concept and to allocate tasks for the coming week. Attending were:

·         Dave Brown

·         Ross Catchpole

·         Rich Brennan

·         James Golding

·         James Flanagan

 The group agreed on a system by which to score the concepts which were drawn out, considering each category and weighting it as to how important the factor was in our design. Each idea was then given a score between -3 and 3 for each category, and the concept with the highest score will be developed to become our final design. To clarify, portability was defined as how easily the crane could be broken down and moved, and mobility was based on the range of positions the load could be deposited in. It was also agreed that the weak link and carrying handle concepts will be incorporated into the design.

	Weighting (multiplication factor)	Gantry Crane	Tripod with Adjustable Legs	Tripod with Rubble weighted Base	Spider Crane
Portability	4	2	0	-1	1
Mobility	3	0	1	-1	1
Cost	4	2	1	0	-1
Ease of Manufacture	3	2	0	1	-1
Ease of Use	2	1	0	-1	1
Total Score		24	7	-6	2
Position		1	2	4	3

The Gantry Crane concept was the clear winner; however it was felt that it was not perfect and 

improvements could be made. These mostly related to stability and adjustability and were agreed on. They have been incorporated into the design sketch which will also be uploaded to this blog.

James Flanagan presented the research which he had done into materials (which will also be uploaded) and it was decided overall that aluminium was the best choice to make the crane out of due to its corrosion resistance, ease of working and good strength to weight ratio relative to its price. Titanium and composites were both superior in their strength to weight ratio however their price, both as raw materials and the increased cost of manufacture related to working with them, made them a less than ideal choice for the design.

Ross Catchpole is to look into joint designs suitable for the chosen concept this week and discuss them with Dave Brown to draw into the design in time for the group meeting next week, due to the huge number of possibilities available when all concepts were considered in research this week.

Tasks to be done and presented and the next group meeting:

Ross Catchpole – Research harnesses and Load connections suitable for the crane

Dave Brown – Sketch Final Design (with joints in)
                        Start CAD of design

Rich Brennan – Start stress analysis of design and determine required second moment of area.

James Flanagan – Assist with stress analysis and CAD.
Find strength values for different types of aluminium and their limitations.
Research coatings.

James Golding – Research winch and pulley systems suitable for crane. Include electric winches and their power sources.

The next whole group meeting will be on 12/12/11. 

Minutes of Group Meeting 28/11/11

An initial group meeting was held to issue tasks to all of the group members, discuss some initial concepts and create the blog on which to post our work.

Those attending were:

·         Ross Catchpole

·         Richard Brennan

·         Dave Brown

·         James Golding

·         James Flanagan

It was decided that the following people will carry out the following tasks and present their work/findings to the group on 5/12/11 at the next group meeting, as well as posting it on the group blog.

James Golding - Submit Gant Chart onto Blog
                          Submit Group roles to Gareth
                          Research winch / lifting systems and their pro’s and con’s

James Flanagan – Research into material types. Justify choices of materials for different components of possible concepts.

Richard Brennan - Research current crane systems and consider what calculations will be required with different concepts.

Ross Catchpole - Costs of crane system case studies
                            Consider costs involved with tender
                               Research joint types for possible concepts

Dave Brown -      Sketch Concepts and consider pro’s and con’s of each
                           Research size and weight restrictions on crane

The decision was made during the meeting to move the project forward quickly in order to allow maximum time to analyse the design and solve any problems we are to be faced with.