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There are four major methods of foundation repair in the southern part of the United States. They are known as concrete pressed pilings, concrete pressed pilings with insert, steel pressed pilings, and poured concrete piers (Bell Bottom Piers). It should be noted that the Federal Housing Authority has not certified or expressly established “approved foundation repair methods.”

A comparison of foundation repair methods must include the poured concrete piers or Bell Bottom Pier method. It was the first foundation repair method developed to stabilize concrete slab foundations. It was developed in the 1960s and its primary disadvantages are higher cost and longer construction time. However, this method has impressive advantages. It is based on the same construction concept that is used to build support columns for highway overpasses. It is a thoroughly researched concrete slab repair method that is recommended by the vast majority of structural engineers. Large holes are dug under the areas that need foundation support. Concrete is poured into the holes and steel rebar is placed in the wet concrete. When the concrete is dry the building structure can be leveled. The Bell Bottom Piers are extremely strong and will resist all horizontal and vertical soil movement. It is the most permanent foundation repair method available.

In the 1980s a lower cost but remarkably inferior method of foundation repair was developed called concrete pressed pilings. It is probably the simplest and lowest cost of all the methods of foundation repair. It is still used today because in can be completed in a short amount of time and there is no waiting time for the concrete to cure. However, it has major disadvantages. This process uses the weight of the building structure, or a portion of it, to leverage or vertically drive precast concrete cylinders into the ground. The depth of the driving process is limited by both soil conditions and the weight of the building structure. There is a point called the refusal point, which is the point where it takes more force to drive additional piles than it does to lift the building structure. The refusal point is the limit that piles can be driven into the soil because any additional force would raise the foundation of the building structure rather than driving the piles further into the soil. Therefore, the precast pressed pilings, which are driven-in vertically, many not reach bedrock or stable soil. Perhaps the greatest disadvantage of this method is the fact that there is nothing preventing the misalignment of the precast concrete cylinders. There is no way to determine if piles have been driven in the ground in a straight vertical column. If the first pile hits a big rock it could break or become misdirected and continue at an angle. Any of the concrete piles could fracture and break and misalign the entire column. Even if the concrete piles are aligned in a vertical column they have no way to resist future horizontal soil movement, which is very common with any building structure that is experiencing foundation problems. And another potential drawback is that the repair crew may improperly exceed the driving limitation while forcing these concrete piles into the ground and thus severely crack the foundation they are supposed to be stabilizing. This method is an unproven foundation repair method and typically no soil test is performed prior to installation. For these reasons, the concrete pressed pilings method is recommended far less frequently than in the past.

Because of the severe deficiencies of the concrete pressed pilings method, a variation was developed called the concrete pressed pilings with insert method. A comparison of these methods of foundation repair will reveal that they are very similar. The minor difference is that the precast concrete piles have a hole in the center for placement of a steel rod. The steel rod, if inserted during the driving process, will help keep the concrete piles in a vertically aligned column. However, the steel rod will not prevent all potential misalignment problems. The steel rod will help the entire column resist horizontal soil movement. Unfortunately, this new method does not address the other disadvantages mentioned earlier. The depth of the driven vertical concrete piles is still limited by the weight of the building structure. And the foundation of the building structure is still as risk of damage if the repair crew exceeds the driving limitations. In addition, this method introduced a center hole in the vertical column of the concrete piles that will accumulate water. An accumulation of water in expansive soils will put additional forces on the vertical column as well as the foundation.

The steel piling method is the latest version of the pressed piling method. A comparison of these three similar methods of foundation repair will reveal some improvement with the latest version. Steel pilings are stronger than concrete piles and can be driven deeper into the soil. However, the driving depth is still limited by the weight of the building structure and the refusal point. And the steel pilings are thinner than the precast concrete pilings and less able to resist the forces of vertical and horizontal soil movement. And steel piling also share the other disadvantages of concrete piling such as misalignment that cannot be detected and unconnected piling segments that can not resist uplift forces of soil movement.

Martin Dawson is the co-founder of Dawson Foundation Repair headquartered in Houston, Texas. He is a leading authority on repairing failed commercial and home foundations using the time tested and thoroughly researched drilled Bell Bottom Pier method. His company has serviced Texas since 1984, and since 2009 began to expand into other southern states.Article Source:http://www.articlesbase.com/real-estate-articles/comparison-of-methods-of-foundation-repair-1733898.html

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A Brief Personal History -

I joined the golf industry in 1973. I worked for a golf club manufacturer in Chicago. At that time the city had the largest concentration of golf club producers in the country: if not the world. The industry was at the cusp of change going from the traditional process of using carbon steel forged irons and wooden woods to investment cast irons and stainless steel woods. Investment cast irons, and metal woods were both deemed as game improvement products. They made for more forgiving clubs for the average golfer as they had features that carbon steel irons and wooden woods did not.

The reason for the concentration of companies in Chicago partly stemmed from the fact that the Wilson Packing Company was located there. Wilson began making sports equipment as an offshoot of its original meat packing business. When, early in the twentieth century, they decided to manufacture golf clubs they brought clubmakers over from Scotland to produce the equipment. Over the years many who worked for Wilson spun off and started club companies of their own. In addition many support component manufacturing companies also sprang up around the manufacture of the clubs. This included plastic trim parts, and leather golf grips.

The company I worked for at the time was the largest club producer in the world making several million clubs per year, and shipped worldwide. During that time my position was that of Purchasing Director, later changed to Director Global Sourcing / Purchasing as the supply side of the industry moved from domestic sources to those offshore.

The Change from wood to Steel –

Metal woods had been around the industry for some time before modern processes made them the game improvement tools they are today. The first metal woods were made from Aluminum, but they were heavy, costly and not as durable or popular as laminated maple or Persimmon woods were at the time. For the purest, Persimmon was the material of choice. Today, Persimmon woods are produced in small quantities, and are still available from some specialty manufacturers arond the country. Persimmon was the precursor of the laminated maple wood head.

Laminated maple heads were the less costly of the two wood types. They used what was called a 2-1 layup. Two thin plies of hard maple were glued together in one direction, and a third ply was glued at 90 degrees to the others. This process was repeated until the desired thickness of the layup was achieved. Driver blocks were thicker and had more plies then the fairway woods (#3,4 & 5) did. The advantage to the laminated wood was stability. Making a head using a laminate produced a very stable and durable finished head. An insert made of any number of materials was placed in the center of the wood's face. This provided a non-wood surface area where the ball was struck. This insert, most often made of ABS cycolac plastic, prevented the wood from failing due to continued strikes. The insert could be held in place by means of adhesive, and the use of screws. The term “hitting the ball on the screws” came from this practice.

For the purest Persimmon was the material of choice. Persimmon is from the same family as ebony. It is a hardwood that in Asia is used for making furniture of high quality. It proved to be of the right density and weight for use as wooden golf club heads. It was also ideally suited, at the time, because the ball could be struck without the use of an insert. They came along late in the game, and only added durability to the heads.

The disadvantages of wooden heads is that there is inconsistency in natural products. Weights are not evenly distributed throughout the product. In golf current thinking is to make clubs with the greatest control and consistency from one to the other. This is done by weighing shafts and frequency matching them to weighing grips and heads for the same reason. The tighter the tolerance, the more consistent and repeatable the equipment becomes. This provided the platform for the modern matal woods when they broke on the scene in the late seventies.

Pittsburgh Persimmon –

As the name implies, at the time there was a mix of the traditional, and the then newly emerging technology. Today the term metalwood sufficies for the entire class. Metalwoods are produced using the investment casting process, also known as the lost wax process. It consists of making a master model of the desired size, shape and configuration of the wood. A mold is then created and wax is allowed to flow in the impression. This produces a wax duplicate of the intended wood head.

Several wax pieces are then affixed to what is termed a tree. This is a group of like pieces in two rows over hollow tubes and an inverted funnel, all made of the same wax. There are usually anywhere from 8 to 12 or more wax molds on the tree. The tree is then taken to a rotating drum much like a small cement mixer. A ceramic slurry is contained in the mixer. The tree is immersed in this mixture to coat the waxes. This process is repeated several more times. Each time using a thicker and thicker slurry mix a shell is built up around the entire tree and head molds. After drying and becomng hard the tree assemblies are place in an autoclave. This melts the wax out of the molds leaving behind a detailed hollow cavity that duplicates the master model in every detail.

The unfilled trees are then placed in a kiln on the foundry floor. There they are heated until they are almost white hot. A nearby electric induction furnace had melted stainless steel to almost 1800 degrees F. Workers with long handled tongs remove the trees from the kiln one at a time and bring them to the furnace. The furnace is tipped, and molten steel is pounred into the empty molds. After the pour the molds are placed in a controlled atmosphere chamber to avoid any unwanted conditions from occurring in the metal as it cools.

Once the molds have cooled the shells are then broken away from the raw steel castings. This is where the term “investment casting” originates. One has to invest in the mold as it is destroyed to retrieve the end product. It is also referred to as the “lost wax” process. The heads are now ready to go into the finishing process.

The finishing process for stainless wood heads consists of welding the sole plate (bottom) to the top shell, and then putting the head through a series of polishing operations to get the desired final appearance for that particular model. If desired a urethane foam compound can then be added to control the final weight, and deaden the sound as the head impacts the ball.

The great advantage that stainless metalwoods have over the older wooden woods is two-fold. They are much more consistent. This is because they are produced from a master model so specifications from one head to another can be controlled and matched. They are also much more durable than the old wooden woods, without the same amount of upkeep being required. Weights can be moved around the head to any desired position to achieve whatever ball flight trajectory is desired.

The trend today is for large heads in comparison to where it all began. The larger heads are achieved by using more exotic metals. Initially a 400 series stainless alloy was used because of its toughness and durability. As heads grew ever larger new metals had to be employed. This was due to the possibility of failure as the wall thickness of the heads decreased as they got bigger. The preferred material to do the job for the oversize heads is Titanium. It has the qualities of lightness, toughness and strength demanded by the larger thin walled heads. Metalwoods have found a permanent home in golf because they are a game improvement product.