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.