There’s something majestic about making the movements of a giant pendulum look so easy to control. How a crane driver can make a load hanging from up to hundreds of metres of wire rope stop still in a required place. But how is this possible? I’ll tell you.
In simple terms, to catch a crane swing, the jib has to follow the hook block’s movement to be placed directly above it until the hook block is still.
Read on to see more detail on the different types of crane swing and how to stop them.
Here’s what you’ll find.
- What Is a Crane Swing?
- How To Catch a Crane Swing
- How To Minimise a Crane Swing
- What To Avoid
- Conclusion
What Is a Crane Swing?
A crane swing is the backwards and forwards, side to side, and/or round and round motion of the hoist rope and hook block as they hang down from the jib.
What causes a crane swing?
The swings mainly happen during crane operation. The hoist rope and hook block act like a pendulum. As the crane moves, the weight at the bottom of the rope (hook block and/or load) gets left behind for a moment, then it follows the direction of the crane’s movement.
As the hook catches up with the jib, momentum carries the hook past the plum line. Plum line is the rope’s vertical position, directly under the jib. Or to be precise, under the hoist’s sheeves. The plum line is the natural position where the weight wants to end up and rest at.
When the hook passes this point, it will swing back and pass it again, until the swing eventually slows to a stop, which could take a long time if left.
Centrifugal force is also a factor. As the crane slews round to the left or right, centrifugal force makes the hook swing outwards. It might stay in an outwards position for a while but will eventually swing back in. Think of a swing ride at an amusement park. The spinning of the ride makes the seats stay at an angle away from the centre of the ride.
Wind can also cause crane swings as it blows against the ropes, hook block, and the load, if one is attached. This is made worse when the wind blows against loads that have large surface areas, like shutters or window panels.
What types of crane swings are there?
The hook can swing in different directions, depending on which movements the crane does. Here are the various types of crane swings.
Slew swing
When the crane slews left or right, this causes the hook to follow it and swing left and right.
Jib swing
This depends on which type of crane is used. If a luffing jib moves up or down, this makes the hook swing backwards and forwards. Whereas, a saddle jib has a trolley that makes the hoist rope move. When the trolley travels forwards and backwards along the underside of the jib, the hook then swings forwards and backwards.
Circular swing
This is a combination of both the jib swing and slew swing. It often happens with the centrifugal force when slewing quickly. In this case, the slewing action makes the hook swing side to side and the centrifugal force swings the hook away from the crane, then eventually back in.
A circular swing is the most difficult to stop.
Handbag Swing
A handbag swing isn’t the typical crane swing that people think of. It isn’t commonly known. It’s a term only used by some drivers. A handbag swing occurs below the hook block. It’s when the hook block is still, but the chains (and load if there is one) flicks side to side uncontrollably.
A handbag swing often happens when the slew is tapped/flicked left or right, rather than slewing in on motion.
The problem is that crane drivers only really have control of the hook block upwards. Anything below that often has a mind of its own and can’t be controlled.
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How To Catch a Crane Swing
There are variations of the term in the title, depending on what part of the world you’re from. I usually say catch the swing. But some other terms are, kill the swing, stop the swing, or correct the swing.
Here I’ll talk about the basic principles of catching a crane swing. Later, I’ll run you through different scenarios and ways to avoid or minimise swings.
Stopping a crane swing is about timing. Once the swing is in place, the driver needs to either follow the direction of the swing straight away, or wait for the hook to return in order to follow it back the other way and finish above it.
Here’s how to catch each type of swing.
Slew Swing
Once the slew is in action, the hook will be half asleep and delay in moving. Then it’ll catch up and swing past the plum line. The driver can either catch up with the hook when it has passed, by getting the jib plum above it, or wait for it to return and do the same on its way back.
Jib Swing
Catching a jib swing uses the same principle as catching a slew swing, but rather than moving the hoist rope sideways, you move it backwards and forwards.
Stopping a jib swing can be more difficult than that of a slew swing. Seeing the side-to-side swing of the hook block and ropes is easier to see than the backwards and forwards swing.
There are different methods of catching a jib swing, depending on whether the crane has a luffing jib or saddle jib.
Luffing jib
When the driver jibs down, the hook block moves outwards, increasing the radius from the centre of the crane. And vice versa when the driver jibs up.
So, to catch a jib swing on a luffing crane, the driver needs to jib down if the block swings outwards and jib up if the block swings inwards towards the crane, in order to get the hoist ropes resting in a plum position. The speed of the jibbing depends on how quick the block moves.
So, let’s say the jib has up to five gear speeds. If the initial jib movement that started the swing was down in gear three, then more often than not, the speed to catch the swing will be in three as well. This might not kill the swing straight away, but it will be near enough.
If the driver takes the crane’s movement the opposite way to the direction of the swing, they will make the swing bigger when the hook returns.
Saddle jib
Catching a jib swing with a saddle jib uses the same science as with a luffing jib, except luffing isn’t possible. Instead, the driver uses the trolley.
When the hook swings outwards, the driver will trolley out to position the trolley above the hook, and do the opposite if the hook swings inwards.
This is easier to do than with a luffing jib, because the trolley moves quicker than what a jib does, so can catch up with the hook sooner.
Circular swing
As stated previously, circular swings on cranes are the most difficult to control.
Because they’re a combination of both a jib and slew swing, the actions shown above to catch each individual swing needs to be done.
When you’re a beginner, you can deal with one swing at a time, but when you get more advanced, you’ll be able to deal with both the jib swing and slew swing at the same time. This makes for smoother, more efficient driving, if done correctly.
How To Minimise a Crane Swing
Stopping a crane swing is an essential skill to have, but if you can minimise the swing in the first place, stopping it at the finish point becomes much easier. As a crane driver myself, I like to work on the swing from setting off from the starting position, all the way to its destination.
There are a few techniques to minimise crane swings. I’ll run through them here:
1. Operate at the slowest speeds.
As I sated before, the faster the crane moves, the larger the swing will be. So, if you’re just starting out as a crane driver, a good option is to use all the slow slew, jib, and trolleys speeds in order to keep a stable hook block and load all the way through the motion.
If you’re on a site that is patient and understanding, this will be fine if you tell them you’re new to driving cranes and need time to get used to it.
But most sites will lose patience with this driving. Unfortunately, politics often takes over. Deadlines need to be met. Site managers pressure crane supervisors, who pressure slinger/signallers. Eventually, crane drivers can take the flack if their driving isn’t up to scratch.
2. Gradually increase, then decrease the speed of the motions.
Let’s say the crane is at 10m radius, and you want to go out to 40m radius. You can start going out at the slowest speed, then gradually increase. Once you’re around 10m away from your target, you can gradually decrease the speed again until at the slowest when almost there. This works with both luffer and saddle cranes.
If you time the speeds right, when you initially head out, the hook will swing out. When it swings back in, you wait for it to swing out again, then increase the speed a little to catch up. The hook might swing again, so you repeat this process with each faster speed. Then you do the reverse when slowing down at the end. Wait for the hook to swing inwards, to drop a speed each time.
The same principle can apply to the slew action. Instead of firing the crane straight around at full speed, you can start off slowly, then gradually increase the slew speed. Once near the target, you gradually slow down again.
3. Move, slow down, then move again.
Whatever action you want to do, whether it’s slew, jib, or trolley, when you start the motion and the hook gets left behind, you can slow down or stop to let the hook catch up. And when the hook catches up to the plum line, you can continue the motion at the same speed as the hook.
This should keep the hook pretty much plum with the jib until your destination. But there will be a small amount of swing to kill at the end.
4. Lower the hoist.
The less hoist rope you have to play with, the harder it is to catch the swing. The swing is quicker and more erratic. So, if the hook block is right up near the jib, you might have some difficulties.
If you have the option of doing so, you can lower the hoist as much as possible. This will slow the swing down, which will make it easier to control.
5. Increase the radius as you slew round.
I’ve spoken about centrifugal force. As the crane slews, the force will naturally make the hook swing outwards.
So, if you need to end up at a greater radius than your starting position, a useful trick is to start increasing the radius just after you start slew action, to stay on top of the swing. Then, if you wish, you can follow the previous trick of continuing to increase the jib/trolley speed.
To summarise:
- Operate at the slowest speeds.
- Gradually increase, then decrease the speed of the motions.
- Move, slow down, then move again.
- Lower the hoist.
- Increase the radius as you slew round.
What To Avoid
Crane driving is a safety-critical job. One false move or a lack of judgement could be fatal to machinery, property, and materials. But most importantly, life.
Here are some things to consider avoiding doing in relation to catching a swing on a crane.
1. Avoid catching the swing in an unsafe direction
When you’re waiting for the hook to swing a certain way so that you can follow it, best practice is not to try to catch the swing in the direction of an object or person, if the load is the same height as that object or person.
You might overshoot the movement, which could make the hook and/or load collide with the object or person. Or you might catch some of the swing, but not perfectly. Then the jib would be in a plum line that is too close to the object/person. The hook, load, or even lifting accessories could continue swinging and make a collision.
I made this exact mistake when doing my crane driving training at a construction college, using a saddle-jib crane. We practised using 1t concrete blocks attached to the chains.
The crane was situated next to what was a former aircraft hangar. A long unit of racking was set up about 2 metres from the hangar. My task was to slew one of the concrete blocks, similar to the one here, towards the building, then trolley in to run the block towards me, between the rack and the hangar.
Because I’d been doing well until that point, I got over-confident. I took the concrete block round towards the hangar faster than I should have done, let the block swing out towards it, then tried to kill the swing in one, toward the building.
I misjudged it and made the concrete block hit the hangar, which made a hole in the corrugated metal wall.
I wasn’t reprimanded. In fact, no harsh words were said. The college just repaired the hole. When I looked, there were lots of holes repaired on that wall, so it must’ve been a common theme and I was just another one on their list to make fun of.
The thing is, in a controlled environment like that, you might get away with it. But when you get out into the real world, it could cause huge financial costs, serious injuries, or loss of life.
What can be done instead?
- You could kill the swing in the opposite direction of your target, if the target is near a person or object. Once the hook block is steady, you then very gently take it to where it needs to be.
- If you’re a reasonable distance from the required destination, you can use one of the methods stated earlier. Slow down when approaching the location until there is almost no swing.
If there is still a swing, you could still catch it in the direction of the danger, if you’re far enough away and going slow enough. Then you gently tap the hook over the last little bit.
- I possible, you can kill the swing toward the potential danger if the hook and/or load is high enough to miss it if you misjudge the movement. That way, no collision is possible and you can tidy the swing up and hoist down when the hook is steady.
What else can you avoid doing when catching a swing?
2. Avoid getting overconfident
I’ve already told you what happened to me when I got overconfident. Like they say, complacency is the enemy of safety. It’s the same with driving road vehicles. When we get too confident, we take risks that we shouldn’t. Sometimes we get away with, other times we don’t. It’s a numbers game.
3. Avoid bowing down to pressure
As already mentioned, some site personnel don’t have patience. They’re under pressure themselves, so they filter that pressure on to other people.
If you feel like people are pushing you to drive the crane in a way that you’re not comfortable with or faster than your skill set, keep your cool and continue to operate the crane in a way that you feel is safe.
You’re in charge of the machine. It’s your ticket on the line. And it would be you facing the sack or a court case if something bad happens.
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To summarise:
- Avoid catching the swing in an unsafe direction.
- Avoid getting overconfident.
- Avoid bowing down to pressure.
Conclusion
As with everything, quality crane driving and efficient swing killing comes with experience. When you first start learning to drive cranes, you might only want to do one motion at a time. That could mean – when picking up a load, for example – hoisting up, then slewing to get in line, then jibbing to get to the destination.
You should then progress to two motions. So, for example, jibbing/trolleying and slewing together.
Eventually, you’ll confidently use all three motions at the same time. Then you’ll be able to minimise crane swings easier. This will actually make for smooth crane driving if done properly.
Hopefully, this article has educated you all about crane swings.
You now know:
- what a crane swing is
- what types of crane swings there are
- how to catch the crane swings
- how to minimise crane swings
- what to avoid doing when driving a crane
Ultimately, safety is the one thing you need to keep in mind at all times. This involves concentration, awareness, calmness, and patience.
When you first start driving a crane, you’ll have more swings than Tarzan. But don’t worry. Follow these tips, and you’ll soon be a master of your machine.
Now go catch those swings.