Towing my car AWAYY!!!

The above picture is of a Hydraulic vehicle ramp that provides a simple method of raising a vehicle from the ground, for the easy transport. Getting your car in and out of a trailer will require a ramp. This trailer has a hydraulic tilting bed, where the entire bed can lower into position to form a ramp, and then return to a level position for transport. These types of trailers are extremely useful, but they're also quite expensive.
This trailer has a "beavertail," a downwardly curved portion at the rear of the bed that effectively provides a ramp for your car (This can be used in conjunction with some of the ramp). In some cases it may be necessary to raise the front of the trailer with a hydraulic lift in order to lower the beavertail to the point where the car can be driven on to it.
Once the ramp is in place, the car can be driven on board or it can be hauled on board with a winch. The winch, which can be attached to a secure portion of the car, is usually operated by a motor. And once the car has been raised onto the trailer bed, it must be carefully positioned. Placing the car too far forward or too far to the rear can affect the trailer's stability. And, if the trailer is an open one, care must be taken that the tires are solidly on the bed and not hanging over one side.
Ramp is inclined at a certain angle from the ground. The weight of the produces downwards forces; compressing the inner face of the ramp and the outer face of ramp is under tensile stresses. As the wheel is in contact with the ramp; reaction forces are produced in order to keep the car stable on the ramp. There is strong friction force between the tires and the top face of the ramp that helps the car to be stationary (static friction). Bending moment is also observed about the bottom end of the ramp due to the weight of the car.

Picture Taken by, Ahsan Iqbal, 20-02-2009

Flying with the pros

Long before airplanes took to the skies, birds such as this have been soaring around with a naturally engineered ease. As the diagram shows, there are four main forces acting: Lift, Drag, Thrust and Weight.

For flight to be possible, thrust must be more than the drag. In aircraft this is achieved by expelling gas at high velocities and being propelled by the reaction force. In birds, thrust is cause by the power of the wings pushing air back. A major advantage to the bird is that it has a tiny amount of drag; drag is caused by air resistance to the bird and its extremely streamlined shape lessens this. The skeleton of the bird is also lightweight by using hollowed bones with tiny holes to lower weight which helps to achieve greater thrust.

Birds can glide like the one shown by relying on wing shape, the shape causes a higher pressure of air below the wing by diverting air to a longer route along to the top of it. This causes a greater lift force up than the force of wind down onto it.

Photo by Martin Phipps, March 09
Post by Tom Corbett

Balance: try it with the eyes closed

This simple diagram attempts to show how centre of mass affects my stability while standing on one leg. The white arrows show centres of mass of my bag and body while the reds show roughly the pivot that is my leg.

With centres of mass on either side of the pivot, moments are equal enough for me to stand easily. Switching the bag to the other side along with its centre of mass causes more moments clockwise causing me to lamely fall over. This could also show Moments of Inertia in that I instinctively tried to raise my arms to keep the balance, this put the mass of my arm at a larger radius from the pivot (or axis if that helps you to think about it) thus increasing the moments of inertia and decreasing angular acceleration.

Actually, I'm sure there're some important areas I havent thought about here, if anyone has any suggestions, there's plenty of comment space below. Postpostpost.

Photo by Martin Phipps, March 09
Post by Tom Corbett

A salute to the flag bearer

I saw this flagpole just above the New Street HSBC; the fact that it resembles the beams that we've been working on for the past term and the support used made me put some thought to it. We could model this flagpole as a beam with a uniformly distributed load in the form of its weight and perhaps an extra force on the end for the brass knob. Forces would have to be taken at an angle from the beam which hasn't been done yet during tutorials (I think..) but would be easily managed with simple math.

The support is used to stop buckling along the beam and my guess is that it was set up after the building so that the pole couldn't be built into it. This support is also made of quite a strong metal by the looks making it ideal for its strength against forces acting on it.

A problem could occur if any form of horizontal force affected this pole, it's supported quite nicely vertically but if a strong wind hit the side failure could happen. Then again, this is much less likely since there is so little area for the wind to affect.

Edit: I just noticed what looks like a bit of a spring towards the base of the pole, do you think that this was put in to stop horizontal forces or perhaps just extra support?

Photo by Martin Phipps, March 09
Post by Tom Corbett

My best friend's Umbrella

Picture taken by: Ahsan Iqbal, 09.03.2009


Image taken from: http://en.wikipedia.org/wiki/File:Parts_of_an_Umbrella.svg

Umbrellas are something that I have always taken for granted and never bothered to explore the science behind the curtains. This has been an eye opening investigation on my behalf and hopefully you feel the same.

The umbrella operates on a very simple idea; it is an instrument designed to protect from rain or sunlight. The structure of an umbrella consists of a hollow tube that has a spring running through it, a runner is a part that moves up and down on the tube facilitating the opening and closing of the structure. The upper part of the protective structure consists of ribs that are connected to the top of the umbrella; the stretcher is joined to the runner and acts as the connection between the ribs and the runner.

An umbrella is opened by applying upward force on the runner; this results in pushing the ribs outwards to form a canopy. This action produces tension in the stretcher as well as in the joints at the end of the stretcher. The main issue in constructing an umbrella structure is its apt operation below the elastic limit of the materials used in the construction; so the material returns to its original shape once the runner is released (pushed downwards). Another key matter in the design of an umbrella is the precise rib distribution (hexagonal, octagonal, and so on depending on the size of the structure) about the tube at the center; to balance the weight once the umbrella is opened.

The only external force applied to the structure is that produced by wind; this applies bending moment about the tube and tension in the joints of the stretcher and the ribs alike.

Glass Roofs

Picture taken by: Ahsan Iqbal, 09.03.2009

The above pictures are of a glass roof for the entrance of the car parking in Birmingham City University. This glass roof consists of a number of beams supporting the glass structure. At the top of the glass structure there are 4 long flat metal beams; the ends of which are joined to another metal beam that is then connected to the side. There is also a thin beam running across perpendicular to the long flat beams giving rigidity to the structure.

The weight of the structure is supported by additional two beams going diagonally across forming an X-shape figure that will actually help to give stronger support at the center; as the center of gravity lies at that point. The weight of the structure produces tension in the supporting metal beams, the wind adds on to this tension by producing a bending moment.

The accurate management of possible torsion and bending stresses produced by the wind is a key factor in the success of such a complex structure. The key elements of the design are: material strong enough to withstand the stresses produced, construction method of support to provide rigidity to the structure and durability of the structure as damage or destruction can have serious effects.

Ladder Science!!!

Picture Taken By: Ahsan Iqbal, 15/02/2009

Hello again guys, this week I am going to talk about a step ladder that has two extendable lengths for more convenient storage, the lengths can be slid together for storage or slid apart to maximize the length of the ladder. It also has a small horizontal platform at the top. The ladder is hinged in the middle to form an inverted V, with stays to keep the two halves at a fixed angle providing support each end and helping it not to tip over. The ladder is in static equilibrium as the sum of all the horizontal and vertical forces acting on the ladder is equal to zero and the moment about at any point along the ladder is also zero. The most interesting thing is the friction at the ends of the ladder. Friction force is large enough to prevent it from slipping.

Material selection plays a major role in the structure of the objects under stress. In the case of ladder, material used is aluminum that is light weight, soft, durable and malleable metal. Aluminum is able to withstand the extensive stresses on the structure of ladder and hence is makes it safe for use.

Bus Shelter

An open bus shelter manufactured from (mainly) iron, the one wall and two supports must be strong enough to support the large roof above, though this is helped circumvented by the main body of it being manufactured of a light cheap plastic with an iron "skeleton". It also needs to be strong enough to, for example, handle extra weight through snowfall, etc. Because of the relative large size, most of the force is exerted on the two foremost supports; this helps to spread the compressive force away from the main body.

The structure itself has foundations sunk below ground to provide added stability against strong winds. The 6 seats are affixed using 4 large wall brackets, essential to handle today's morbidly obese generation.


H. Ali.

Crumple Zones

Another simple study today: crumple zones on cars. Quite an understated safety feature in my opinion, these vitally protect passengers during a crash by helping to avoid complete stops by the car. These zones, found on the front and rear of vehicles, are designed to buckle for low loads. They use a less rigid material than the steel shell surrounding the passengers so that buckling can easily occur across it. During a crash, buckling in the crumple zone absorbs energy and diverts it down the side of the car, away from those in danger. The Force is spread over time in this way, lessening deceleration to protect passengers. Similarly, in trains crumple zones are used extensively across every carriage, the front end uses a long crumple zone to reduce strain, causing more plastic deformation, and preventing fracture.

Photo taken from blog.johnath.com
Post by Tom Corbett

Crane

A crane is a lifting machine equipped with a winder, wire ropes or chains and sheaves that can be used both to lift and lower materials and to move them horizontally. It uses one or more simple machines to create mechanical advantage and thus move loads beyond the normal potential of a human.
In order for a crane to be stable, the sum of all moments about any point such as the base of the crane must equate to zero. In practice, the magnitude of load that is permitted to be lifted (called the "rated load") is some value less than the load that will cause the crane to tip.
The moment created by the boom, jib, and load is resisted by the pedestal base or kingpost. Stress within the base must be less than the yields stress of the material otherwise the crane will fail.
Cranes, like all machines, obey the principle of conservation of energy. This means that the energy transferred to the load cannot exceed the energy put into the machine. For example, if a pulley system multiplies the applied force by ten, then the load moves only one tenth as far as the applied force. Since energy is proportional to force multiplied by distance, the output energy is kept roughly equal to the input energy. In practice output energy is slightly less, because some energy is lost to friction and other inefficiencies.

Picture by: Ahsan Iqbal, 08/02/2009

Window hinges

Hi again second one of the week.  Here is one can be annoying at the same time is there for our safety.  Ever noticed how many of the windows in student accommodation have limits. Its obviously there to stop us from falling out of the window and to stop us from dropping things out the window (at least that was what I was told). They all have different mechanisms to limit the degree of 'openage' in the case of my flat there is a simple sliding piece of metal and a hinge. The system is fairly well lubricated too. When I want to open the window, the sliding hinge slides down and the middle hinge supports this. What is a nice feature of this system is the fact I can open the window to many different degrees and it will stay there. This is due to the middle hinge being attached as low down the frame as possible. If you think of the first bit of a sine wave (bear with me here) the gradient begins low then high then low again at the first peak. Well the clever window designing people decided to only limit the window to open within that first low gradient and thusly the window's inertia will always be under 'control'. I may be horribly wrong here so please any corrections are welcome.

Martin Phipps

Photo taken and edited by Martin Phipps in my Flat.

Heavy Hanging Light

Hi guys n gals,

Bit of a mystery for me so any ideas would be great. As we can see from the image to the left there is a rather heavy piece of glass being supported by 3 chains separated by approximately 120º each, thusly dividing the counteractive force by 3. So far so good.  This will easily help with the tension on each chain so they don't snap. Problem is why are they all connected to the same point at the top, surely this would be best having 3 separate connections with the ceiling putting less stress on the ceiling. Maybe there is a plate-like fixture behind the ceiling which is fastened to the connecting points spreading the force out over a larger surface area. Any suggestions?

Martin Phipps

Image taken & edited by Martin Phipps in Docevita Café, Aston University.