Ram (machine)
A ram is a machine or a tool can be deformed by means of which objects move, or destroy by the ram onto the object discharged leaves. Typical areas of application are driving piles into the ground, for example for pile foundations or for building fences, as well as sheet piles . The ram works according to the principles of energy and momentum conservation . One makes use of the fact that the ram is easier to accelerate than the object in question and usually has a relatively large mass.
history
Ram was originally powered by human power. This is how Franz Josef von Gerstner describes not only the hand- pulling technique that was customary at the time , but also the so-called Viennese percussion mechanism , which he used in 1822 for the foundation work of the Leitmeritzer Bridge. Compared to hand-ramming, the more effective Viennese hammering mechanism was able to drive foundation piles with a significantly higher load-bearing capacity. At the same time, the Viennese striking mechanism was also operated by human muscle power. This changed with the invention of the steam powered ram by the Scot James Nasmyth .
Types
There are basically two types of pile driving:
Blows
The pile is driven into the ground with repeated blows of a hammer. The impact energy is generated by a weight falling onto the pile. The kinetic energy acting on the pile is determined by the mass of the hammer and the acceleration achieved by it. The lifting of the falling weight is done by muscle power, hydraulic fluid, compressed air or explosive gases as energy carriers. The falling weight is raised and dropped onto the pile. To protect the pile, a ram hood (also known as a striking hood or striking plate), which sits on the pile and is lined with wood or plastic at least on the side facing the bear, is hit. The hammer can be designed as a cylinder or more often as a piston. By applying the energy carrier to the hammer on both sides, similar to the way a hydraulic hammer works , the kinetic energy acting on the pile can be increased as well as the number of blows (so-called rapid hammer or, in a lighter version, rapid hammer , up to 600 blows per minute). For heavy pile driving work, hammer rams with a piston weight of up to 10 t and a maximum impact rate of 50 per minute are used.
Steam ram
In the steam ram, the ram is driven by a steam engine. The steam lifts the percussion piston in the housing to its end point, the steam escapes through a valve on the side , and the piston falls down and drives the piling material into the ground by impact with impulse transmission.
Motor ram
A hammer mechanism is driven by a petrol engine. The motor ram is placed on the pile, the hammer mechanism hits the pile directly. There are portable solutions for mobile use.
Pneumatic ram
Functional principle as with the steam ram. With this type of piling, very high piling rates cannot be achieved. These rams are often used, for example, to drive guardrail posts into roads. Alternatively, steel pipes can also be driven with a compressed air ram. See pipe jacking .
Diesel ram or explosion ram
The functionality of an explosion or diesel ram (also known as a diesel hammer or petrol frog ) corresponds to that of a free piston machine . If the piston hits the impact plate, a fuel-air mixture explodes, causing the piston to be thrown upwards again. Explosion rammers, cobblestone rams and post rams that can be operated and moved by one person, such as the legendary DELMAG H2S or the DELMAG Frosch, were audibly and visibly in use in daily road and path construction until well into the 1980s.
Post driver
The post driver is a hand tool that can be used to drive wooden posts, fence posts, etc. into the ground. It is widely used by landscapers.
It is a steel cylinder that is about 1 meter long, has two handles and a lid about 4 cm thick. It weighs 10–20 kg.
Hydraulic ram
Hydraulic rams are hydraulically driven, so they can be used where the use of a diesel ram is not possible, for example for driving steel girders in drilling rigs .
Vibratory hammer
No single blows are generated to bring in the pile, but vibration . Vibratory hammers are mostly driven hydraulically. Imbalances are mounted on a shaft in the ram housing. The rotation of the shafts and the unbalances generate vertically directed vibrations. The ram is placed on the pile. The pile and pile are connected with hydraulic tongs (clamping tongs). This bond transfers the vibrations into the pile. There are high-frequency and low-frequency rams. Since vibration rams can jam the pile, they are in principle also suitable for pulling piles (sheet piling, steel girders). Soil, especially gravel , is "liquefied" by certain vibration frequencies, so that the sheet pile wall sinks deeper by itself under the weight of the dead weight and the clamped vibrator head. In order to facilitate this ramming, to increase precision and the achievable depth, pre-drilling is carried out down to a partial depth (even if the hole closes again, it has a lower density).
Vibratory hammers have been used predominantly since the 1970s. Due to their positive properties, they gradually replaced the diesel and impact hammers that had been used for many decades.
Applications
In addition to the applications already mentioned, there are other possible uses for ramming, for example to break up layers of asphalt or concrete from roads and highways or to compact soil and subsoil.
Battering rams were historically significant to open gates or walls of fortifications through destruction.
Individual evidence
- ↑ Karl-Eugen Kurrer : The technical in the mechanics of FJ Ritter v. Gerstner (1756-1832) , in: Österreichische Ingenieur- und Architekten-Zeitschrift (ÖIAZ), 135 (1990), no. 10, pp. 501–508, here: pp. 504f
- ↑ Ulrich Smoltczyk (Ed.), Gerhardt Drees: Grundbau-Taschenbuch, Part 2: Geotechnical procedures. 6th edition . Ernst & Sohn Verlag, Berlin 2001, ISBN 3433014469 , p. 251 ff. ( Online in the Google book search)
- ↑ according to Duden picture dictionary, road construction board I
- ↑ See e.g. B. YouTube video DELMAG ramming frame H2S
- ↑ See e.g. B. YouTube video Delmag Frog F5
