The Science Behind Power Cranes
If you have marvelled at a tower crane and asked yourself “how do those things work?” don’t worry, you are not on your own. A feat of engineering, tower cranes have been at the forefront of construction and innovation for centuries, yet knowledge of their mechanics and their functionalities are still reserved for experts and practitioners. To shed light on this industry, NMT Crane Hire study the science behind tower cranes.
Foundations For Tower Cranes
One of the most important aspects in ensuring a crane strays upright is making sure a suitable foundation has been laid. Like any building or skyscraper, a foundation needs to be sewn in order to secure the structure and to prevent any mishaps. Typically, a foundation for a tower crane will be secured with cement (again, like a building or skyscraper) and in certain cases, steel beams will be used for added security to the structure. The usual formatting of a crane’s foundation will consist of the base of the crane being attached to a concrete pad via large anchor bolts. Following on from this step, the pad will be connected to the steel beams, which are reinforced with concrete pillars. This foundation gives the crane a wider base platform, and as it is secured with concrete, this significantly reduces the chances of any tower crane toppling, even in extreme conditions. Modern-day cranes and their foundations are built to withstand winds of up to 145mph, meaning they should comfortably deal with category 4 hurricanes and storms.
Another vital component of a tower cranes structure is the counterbalance. Evidently, tower cranes are not built to just stand up and look pretty; they are responsible for manoeuvring large materials at great heights. When operating heavy materials at height, one of the main concerns is the risk of toppling, and that is why tower cranes are usually fitted with a counterweight. However, the equation for working out how much weight is needed for a specific load is far more sophisticated than one would think. Here is the equation in full to help you determine the appropriate counterbalance weight for your crane:
Step 1: Determine the amount of weight being applied to one end of your crane
Step 2: Measure the distance between the weight and the pivot point
Step 3: Multiply the amount of weight by the distance between the two points
Step 4: Measure the distance of the opposite side of the level (the space which is available for the counterbalance.)
Step 4: Divide the total applied torque (the force which causes the rotation) by the distance of the counterbalance weight.
How Heavy Can They Lift?
As mentioned in the equation above, the amount of counterbalance required depends on the weight of the materials. As cranes are required to lift high and to lift big, just how heavy can they haul? The maximum unsupported height for a crane is around 265 feet, but this height can increase if the crane is attached to the side of a building. With that in mind, the typical tower crane offers a lifting power of around 19.8 metric tonnes. As previously explained, this amount of weight changes depending on the height of the crane, the conditions in which the crane is lifting and a number of other variables, and with a number of safety concerns, it is important to air on the side of caution when deciding how you load your tower crane.