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.

Pimpin'

During a night out a flatmate of mine found this impressive leopard skinned wonder. A pimp cane! It was unfortunately broken beyond ducktape repair and I thought I'd have a look at it to determine how it failed. At first glance it's obviously made of strong, rigid material and shows little outer wear. Compressive loads would usually be put onto the top in the form of a part of somebody's weight, these could cause buckling within the stick perhaps while it pivots at the floor. On closer inspection, the stick contains two layers: An outer layer made from solid wood which is manufactured in two parts, and a weaker, strand like form of inner wood which has been torn out in patches and contains twisted fibres. Although a reasonably thin stick for it's length, the inner wood is built into both ends making the failure less likely to be a buckling. Further to this, the twist suggests that excessive torsion occured.

To fix the strength of the stick it would be best to either make the outer layer as one part, or use a stronger inner material.
Photo taken by Tom Corbett, Feb 2009
Post by Tom Corbett

I should have gone to Birmingham Uni

One local legend has it if an undergraduate student walks under the tower as the bell chimes, he is sure to fail.
Check out the time on the clockface...

Check it out, at 110m this is the tallest freestanding clock tower in the world. It was named after Joseph Chamberlain, a pretty famous politician and businessman, who took the seat of Chancellor at the uni. So famous the Midland Metro named a tram after him ZOMG!

Incidentally, I also went to the college named after him in Highgate, tru story BRO.

The clock tower has a simplistic design, using basic fundamentals to provide the structural support needed.

The base was constructed of approximately 60 cubic metres of solid concrete, sunk nearly 10m below ground to provide the foundational support. This base rests directly on the bed rock below ground for added stability!

There are a few bells located at the top, the largest of which clocks in at 6100kg. One would assume numerous reinforced steel beams would be required to handle the force of such a heavy load and the massive moments from the bell as it chimes.

To confirm, I tried to climb up it to check out and a get a few snapshots of the 6 tonne bell but the receptionist informed me all public access was closed due to several students hurling themselves from the top balcony to grisly deaths.

Probably victims of the aforementioned curse.

The four courses of brick at the balcony allow it to better resist the horizontal wind forces, a common feature across pre-19th century European clock towers. This particular tower is based on one in Siena, supposedly after Chamberlain's admiration of said building.

Fun Fact: this was the inspiration for J.R.R. Tolkien's towers in his work The Lord of the Rings.



Until next time,

H.A.

Hallo!

^ lookit how cute i was!!!! what happened? :( ^

Good evening, my name is Haider Ali, 2nd year Mechanical Engineering. I honestly have no idea why I am still on this course: I despise my modules, lecturers and all my fellow students, except for Basit <3 (he's from Tamil Nadu, tru story <3<3<3).

I have passing interests in mechanics, motorbikes and a bunch of other nerdy stuff, but who cares

Anyway, enjoy this blog, folks, I <3 u ALL!!!!1!1!11!1!!!!1one!!!!!!

a 720 nollie no-comply goes horribly, horribly wrong :(

I am Ahsan iqbal, 2nd Year Mechanical Engineering student at Aston University. I have been fascinated by the way things work and the forces involved in them. This interest made me work harder and get better grades in physics and mathematics and hence I chose Mechanical Engineering as my degree. My interests include experimenting with different ingredients to cook healthy food, watching BBC food, gaming and playing cricket. That is it for now wait for my next blog.

If life deals you a bad hand, cheat

My first case study is this simple card tower. The cards act as supports by transmitting the forces through them, much larger towers can be created and these support the larger loads by spreading force from the weight across a larger base area. The real problem involved comes from the lack of friction in the card's material; friction is needed to oppose the outward movement at the base of the cards. This is solved partly by placing a rougher material under the foundation, preventing the cards from slipping. The card tower is also an example of the weakness of pivots, the smallest force can lead to a total collapse of the tower and a very sad builder, this explains why building foundations are built firmly beneath ground.

To make up for the lack of effort involved with my tower I youtubed the greatest card creations and found this It's interesting to see that he uses a honeycomb like structure to aid the building by decreasing pressure. Engineering at work! It's still cheating though.
Photo taken by Tom Corbett, Feb 2009
Post by Tom Corbett

Hey there! Another one today. This is the powdered fire extinguisher from my flat. Fire extinguishers contain compressed chemicals and if under trauma the nozzle to be damaged there is a risk of injury or damage.  This wall hook for the fire extinguisher is crucial for maintaing a useful height for accessing in case of emergency but also has a problem in that if it fails it could cause an accident.

The red rubber prongs at the top squeeze the neck of the extinguisher unit and there is a small hook at the bottom which works with a recession on the bottom of the extinguisher. Together the prongs and the hook keep the extinguisher from falling.  As most of the force from the extinguisher is taken by the prongs a clockwise moment is in action which must be countered by the screws on the wall mount.

Photo taken and edited by Martin Phipps, 01/02/2009, Studios 51, Birmingham

This is a bar stool from my flat.  They are a great example of moments and compressive force together.  Unfortunately they are completely hopeless.  No back support and poor area of contact with the ground.  The forces tend to be almost always biased wherever I am sat on it, making the stool feel unbalanced, the force applied on the foot rest only make things worse.

Moreover the poor choice of materials make the seat very uncomfortable as the padding is extremely thin combined with reactive force from the stool.  They have been repaired several times within the last 6 months.

At least they make great miniature tables for having dinner on.

Martin

Photo taken and edited by Martin Phipps 01/02/2009, Studios 51, Birmingham

Door Hinge:

Door hinge connects the door with the wall. Door hinge is a simple example of Newton’s third Law of physics, as the force acting on the wall by the door is equal to the force acting on the door by the wall and acting on opposite direction. In this particular case, keeping in mind the general principle of mechanics, door and the hinge are in equilibrium. Perpendicular component of the force acting on the door knob produces a moment about the door hinge. It is easiest to open the door by pushing the door knob as the moment is larger the farther away it is from the hinge. Pushing at an oblique angle to the door is less effective and the door will not open if one pushes towards the hinge.

(Picture taken by Ahsan Iqbal, Date: 03/02/09, Topic: Door Hinge)

Some Introductions

Hello everybody, my name is Martin Phipps. I have been at Aston University for almost 5 years now (long story) and have finally decided to actually study Mechanical Engineering, mainly because of the challenge it provides and the many interesting subjects it covers.

My main interests are Cycling (when I get the chance to), Music, Gaming and Apple; not the fruit, although very nice to eat they are! The computers, iPods etc. I also work for them so I might be a little biased.

Oh and I am from a little place called The Wirral (or if you have no idea where that is think Liverpoooool). I love Brackets.


Hey, I'm Tom Corbett, fellow Engineer and sleep enthusiast. I began my studies following on from a love of Maths and decided to work on something with a lot of versatility; I guess it's appropriate then that I'm now sitting here blogging it up. Mechanical Engineering turned out to be a great area to apply myself and I've thoroughly enjoyed the practicality of it all; hopefully I can use some of this knowledge to analyse some of the more interesting designs out there. Specifically, I'll be looking into forces acting on these objects and how these forces affect them.

Sorry about the poor photo, I was hunting down a good daytime one for ages, they just don't exist! Looking forward to posting again soon.