Group Presentation:

Boom fixings and real mini crane pictures

This post will explore a few methods of fixings and boom development from original sources. The bulldog crane now named 'The Grasshopper' as of now, has to be marketable and innovative. I personally believe that idea number 3 looks like a grasshopper.

Slogans such as "Get the Hopper" and "I need help, I need The Grasshopper" are catchy and have a history of adding lasting appeal to a product and gives it a separate identity, a sort of quirky uniqueness.

fig.1

Above (fig.1) is a picture of a green grasshopper for visual aid. (Idea 3 will be shown at a later date.)

Now moving on to more serious matters...

Below is a crane, it uses a 'cradle' to move the object picked up in the x-direction. The object is picked up using chains and hooks, once secure it is elavated to the desired position.

fig.2

This is an excellent model for us to work from. We can use a inverted T beam for the boom itself. An 'I 'beam will work also but will add unnecessary weight, we will try to avoid it unless the stress calculations require the boom to have extra strength. Remebering idea 3 is supported from both ends and is not wall mounted as this one is therefore should be able to hold considerably more than 500kg.

fig.3

Figure 4. shows how the wheels that allow the cradle to move along the boom are fixed. The wheels are on both sides of the boom. They are fixed in place using a bracket that stops them from moving in unwanted directions or falling off. The wheels can be replaced and the entire cradle removed by unscrewing the bolts. This makes it a separate component from the boom, making it easier to transport.
fig. 4

Talking about portability, the boom will roughly be 4m+ so carrying this around either by man or machine power (landrover defender) is dfficult. So a 'hinge' is in order, and I have one that may suite our needs...wala!

fig.5

We can develop and modify this one to suite our needs. OR the two parts of the boom can be separate but connected with bolts.

Heavy duty materials must be used and an accurate stress test is required to determine most of the positioning of the components and type of fixing required.

This post is designed to develop idea no.3 though a considerable amount of the post can be used for idea no.2 also.

These photos are property of Amardeep Singh Dhillon and can only be used with permission from the owner, me.

Original Design (from meeting 18/03/10)

Initial Design


After discussing each of our initial designs as a group, we came to the conclusion that the best type of crane to meet the specification would be a luffing crane with a counterbalance. A basic schematic of the layout was drawn in order to give a sense of the proportions and scale of the design.

With a 2.6 metre boom at 40 degrees to the horizontal, the total reach of the crane would be 2 metres about the centre of its rotational axis. This allows for an object to be lifted and moved a total of 4 metres from its initial point of pick up. Using a large base, and keeping the main body of the crane fairly low to the ground will lower its centre of gravity and increase stability.


Developed Initial Design #1


The initial design was then developed to include a cable spanning from the counterbalance to the tip of the boom, as well as a support up from the main body. The rotational axis of the crane was moved back slightly on the base to increase stability, thus reducing the required weight of the counterbalance.

It was also decided that a the crane could be rotated via a handle situated on the counterbalance, and also that a hand powered crank would be situated here to operate the winch.

21/03 - Design 3

Design 3 ( The British Bulldog )



This design is a mixture of design 1 and 2 . It is interesting as it is something totally different to what is out in the market. It consists of a boom with supersonic legs and has the load sliding down the boom . The reason why we called it the british bulldog is because the front 2 legs are higher than the back two and the overall design looks like the shape of a dog. This also has marketability.

Advantages

As the struts or legs give more balance to the boom there may not be such a need for a counterweight.

The crane has a sliding system which is quite simple as there is no need for bearings.

The legs can be adjusted causing the boom to change in angle which can reach loads which are higher up with greater ease .

It can be de-constructed within seconds. The legs can be detached and the boom can retract into 2 causing very little space to be used up within the 4 x 4 rover .

bending moment and stress calculations would not be too complex .

Disadvantages

As the load is sliding down the boom, it may hit the ground before the intended point. It is important that the load is kept close to the crane or enough clearence is givin at the bottom.

There is no rotation which can lead to a bit of restriction.

21/03 - Design 2

Design 2





This design has a different approach all together to design 1 and some may consider it to be more 'simple' . It consists of 4 main legs which will be adjustable with 2 rollers on the upper struts which will roll backwards and forwards in the x direction. There will be 2 winches, one to move the rollers in the x direction and one to move the pulley ( load ) in the y -direction. Andy is working on a sliding system for this design.

Advantages

The bending moments and stress analysis is simple to work out.

The legs are adjustable allowing them to reach places which are not each to get to .

There are no bearings involved which means there is less chance of failure within the crane .

No counterweights are needed for steadyness as the crane will be steady.

Disadvantages

Motion is limited. The load can only be transorted in a linear direction rather than at an angle as there are not bearings for rotation.

The cable can get caught with the winch.

As some legs would be shorter than others in certain situations, there can be a danger of tipping or the load sliding down at a faster speed.

21/03 - Design 1 (simplified from original)

Design 1

This is a simplified version of the original design. The design consists of a hand winch placed above the trunk and has a counterweight to allow steadyness within the crane.

The advantages and disadvantages of this design are stated below.

Advantages

Bearings will allow the crane to rotate , therefore there is greater accessibility for different angles.

The base is steady with four adjustable ( anglular adjustment ) legs.

The base does not take up much space and can access areas which are difficult.

Disadvantages

The bending moments and stress analysis will more complex .

The crane would suffer from the possibility of tipping over.

Bearings make the system more complex.