6.4. Resonance Concept

So, basically what to do here is, so this is a setup of the double acting steam hammer, you can see two cylinders one is the upper cylinder, other one is a lowest cylinder. Now in the upward stroke what you do is, you supply air into the lower cylinder. So, when you supply into this, this is a lowest cylinder, when you supply air into the lower cylinder, the hammer which was earlier in the lower cylinder will be pushed up into the upper cylinder. So, the hammer is pushed up into the upper cylinder, the air which was already there in the upper cylinder will expel out to the exhaust. So, the air which was already there in the upper cylinder will be expelled out through the exhaust. So, basically what you are doing here is you supply air into the lower cylinder. So, that will push your hammer upward into the upper cylinder and the air which was already in the upper cylinder will be released through the exhaust, now your upward stroke is complete.

The double acting hammer consists of two cylinders (upper and lower). During the upward stroke, air is supplied to the lower cylinder, pushing the hammer into the upper cylinder. This causes the air in the upper cylinder to exit through an exhaust. This process is essential for achieving the hammer effect, which is the hammer's purpose, as it allows the hammer to strike with precision by altering the air pressure between the two cylinders.

Imagine a seesaw where one side goes up when weight is added to the other side. The double acting hammer operates similarly; adding air is like adding weight to the lower side of the seesaw, causing the hammer to rise and strike.

So, what are you doing the downward cylinder? You supply air through the inlet into the upper cylinder. So, when you are supply air into the upper cylinder, the hammer which was already there will be pushed into the lower cylinder. And air which was already in the lower cylinder will be expelled out through the exhaust. So, now that completes a downward stroke, so alternatively you are supplying air into a upper cylinder and the lower cylinder, so that you can have the rising and falling.

For the downward stroke, air is supplied into the upper cylinder, which pushes the hammer back down into the lower cylinder. This motion expels the existing air in the lower cylinder out through an exhaust, completing the full cycle of movement. The ability to alternate air supply between the two cylinders creates a continuous motion of rising and falling, which is fundamental to the hammer's function.

Think of a person's arm moving up and down to hammer a nail. When they lift their arm (simulating the upward stroke), the weight of their arm is pushed up. When they bring it down (downward stroke), it drives the nail into the wood, much like how air pressure drives the hammer.

So, another important thing we need to know with respect to double acting hammer is in this most of the blow energy is the derived from the steam energy. Both for the upward stroke as well as for the downward stroke, the blow energy is derived mainly from the steam energy. So, 90% of the blow energy is derived from the action of air or the steam. So, that is why, for the double acting hammer we need not for a heavier hammer. We can go for lighter hammers, smaller in size and you can go for the shorter stroke or shorter height of fall.

The double acting hammer derives most of its striking energy (90%) from steam or compressed air. Therefore, it doesn't require a heavy hammer; instead, lighter hammers can be employed. This design allows for a more compact and efficient hammer because the energy generated is sufficient to drive the hammer even with a reduced weight.

Consider a balloon filled with air. When you let it go, the air rushes out, pushing the balloon across the room. The air pressure provides enough force to move it, just like steam or compressed air does for the hammer, allowing it to work effectively without extra weight.

And this hammer is basically designed for lighter conditions, lighter conditions in the sense. So, it is basically designed for light to medium weight piles and for soil with normal frictional resistance. So, very tight clay, hardened clay with very high frictional resistance, so we are not supposed to use these double acting hammers. Because these double acting hammers are designed for lighter conditions, that means for light to medium weight piles and for the normal soil with normal frictional resistance.

Double acting hammers are optimized for use in light to medium weight piles and soil types that offer normal frictional resistance. They are not suitable for extremely hard soils, like tightly packed clay, as the high resistance would hinder their ability to operate effectively.

If you try to drive a nail into a concrete block with a lightweight hammer, it doesn’t work. Similarly, double acting hammers need the right conditions (lighter piles and easier soil) to function properly.

So, these double acting hammers, they basically have a very high blow rate, if you look into the blow rate, you can see that the blow rate will be 95 to 300 blows per minute. So, it is very high when compared to the single acting hammer. So, such a high blow rate may can easily damage the concrete pile. So, that is why it is not recommended for the concrete pile.

Double acting hammers have a blow rate ranging from 95 to 300 blows per minute, which is significantly higher than single acting hammers. Due to this high frequency of blows, they could potentially damage more delicate structures like concrete piles, making them unsuitable for such applications.

Think of how a fast-paced drummer could overwhelm a delicate musical piece. Similar to that, the rapid strikes of a double acting hammer could cause more harm than good when trying to drive a concrete pile.

So, let me summarize what we discussed, so your use of steam energy in driving the ram allows use of shorter stroke and compact hammer than single acting hammer. So, when compared to single acting hammer these hammers are more compact smaller in size, lighter in weight and they have a shorter stroke. And they are designed for lighter conditions, they can deliver a blow rate of 95 to 300 blows. This lighter ram and highest striking velocity maybe suitable for driving light to medium weight piles into soil having normal frictional resistance.

The use of steam energy in double acting hammers enables smaller, lighter designs with shorter strokes compared to single acting hammers. They deliver high blow rates suitable for specific conditions, particularly for light to medium weight piles in normal soil types.

Consider a sports car designed to be lightweight for speed and agility, just like a double acting hammer utilizes its lighter structure for efficiency in driving piles.

So, we cannot recommend this hammer for a tough soil condition with very high frictional resistance. And not always preferable for concrete piles, as I told you high blow rate can result in damage of your concrete pile, which is basically weaken tension. So, it is not recommended for concrete pile but you can use it for steel piles.

Double acting hammers are not suitable for tough soil conditions with high friction or for driving concrete piles due to their high blow rates, which could cause damage. They are better suited for applications involving steel piles in less resistant soil.

Just as a race car may not be the best choice for off-roading, the double acting hammer is specialized and not suited for every type of pile-driving scenario.

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