We got a question sent to us on our Instagram account [CraneServiceInc] asking why would you rent an all-terrain crane vs a crawler crane. This was a great question because it involves a few factors and schools of thought. In our example we throw out the price of the all-terrain crane and the price of a crawler crane. Technically that does matter, but you will see why I throw that factor out during this article. I will briefly talk about the differences and advantages of each crane class. In this article we will talk about the Terex AC250–1 versus the Manitowoc 2250. Both of these cranes are 300 ton class cranes.
All-terrain cranes had a few advantages, mostly they involve the mobility of this type of crane. First off, the Terex AC250–1 all-terrain crane is highly mobile. We can mobilize this asset to a project in relatively no time. It can roll to a project with only a few trucks and trailers. This is a huge advantage in mobilizing this asset versus the crawler crane. The second mobility advantage this crane has is the ability to crab steer and all wheel steer.
Examples of steer options for heavy machinery.
This allows this type of crane class to be able to maneuver into tight or confined working areas. Where other cranes would have to make a 100 point “k” turn or not be able to get into the spot. Thus having to possible use more boom to get the project done, which then decreases the chart. More on that later. Also, this crane class has large all-terrain tires. This helps the crane be able to maneuver less than desirable terrier, like mud, loose gravel, sand, steep grades, etc. The differentials also can be locked to allow for more grip. It is worth noting that the boom trucks and truck mounted cranes have the lockable differentials too. Here are two disadvantages to using an all-terrain crane. The first is the boom is heavy. It is actually really heavy. So heavy that you can see the boom deflect when the crane is hoisting heavy materials and is scoped out [see below].
Boom deflection on Tadano-ATF22G-5 — a 250 ton all-terrain crane
The more boom you scope out the more your chart potentially decreases. When you increase your boom length you are essentially exposing more of the heavy steel to the forces of gravity. The forces of gravity will pull down on the crane and in turn pull up on the back end of the crane. Once the weight of the boom and the load create a force greater than the force of the counterweight, carrier, etc of the crane then your crane will tip. In some cases, we will remove the jib that is stowed on the boom in order to limit the force pulling against the counterweights. The last disadvantage of the all-terrain crane is once again boom related. The wind can also hinder and decrease the effectiveness of the crane. The dynamic loading that wind places on an all-terrain crane boom can create side loading and various other loadings on the boom that can hinder the crane. In some cases, the wind is so fast that the crane cannot be used safely. In essence the exposed bool acts like a sail. The wind pushes the boom in the direction of the wind. Cranes come equipped with anemometer’s attached at the tips of boom. The anemometer measures the wind speed at the tip of the crane and reports that value to the load moment indicator software in the operator’s cab. You need to boom down the crane once the wind speeds reach the manufacturers allowed speed.
Now let’s discuss the Manitowoc 2250, a 300 ton crawler crane. The advantages of the all-terrain crane almost mirror the disadvantages of the crawler crane. First being the mobility of the crawler crane. Unlike the all-terrain class cranes you can’t just take this crane and move it at a moments notice. Why? Well instead of having a few truck loads to move the all-terrain crane, this crane class requires many truck loads to move. In some cases up to 16 truck loads. This crane class requires more DOT permitting, perhaps more route planning and requires more crew members to get this crane on-site. The mobilization costs for this crane can in some cases be in the six figures. It is worth noting that our largest all-terrain crane the Grove GMK-7550, a 550 ton crane, can also have mobilization costs that are in the six figures. You will however won’t generally see that type of expense in the the 300 ton all-terrain crane that we are using in this example. The crawler crane and rotate the tracks in opposite directions and is able to maneuver into small places too. But it will take a longer time to get into place as it doesn’t move as fast as an all-terrain crane. The advantages of the crawler crane can be seen in the boom too. The boom in a crawler crane in most cases is lattice material. Meaning it has steel beams in “x” patterns along a square boom structure.
Lattice boom from a Manitowoc 2250 crawler crane.
This lattice material is advantageous for a few reasons. Two of which pertain to our article here. One being that since the boom is not a solid structure you significantly reduce the weight of the boom. This allows the chart of the crane to be stronger versus the chart of the same capacity all-terrain crane. This means that this crane is capable of hoisting heavier loads with longer boom out. The Manitowoc 2250 can hoist wind rotors to the ground, but the Terex AC2501 wouldn’t be able to do that. You would need our Grove GMK7550, a 550 ton, all-terrain crane to accomplish the same job. The openness of the boom also allows the wind and air to travel freely through the lattice material while limiting the exposure of the lattice pieces with the wind. This means that this crane can operate in higher wind speeds, and is not affected by the wind like an all-terrain crane is. Now both cranes will experience dynamic loading due to winds, but the affect of the wind is not as prevalent in a crawler crane. You can see where one crane has advantage say in mobility the other crane has a better advantage in long boom or windier situations. To get back to the thesis of this article, why would you buy a crawler crane versus an all-terrain crane? Well you would buy one or the other based on the work you are chasing after, bidding or wanting to complete. If I had a lot of wind clients, clients who required a strong crane for long durations I would probably lean towards getting a crawler crane. Although I can move the crawler crane whenever, I would try to minimize that and try to find long term projects for it. Conversely, if I wasn’t necessarily in the wind industry, had a large service radius and projects that were shorter in duration, then I would go with an all-terrain crane. You can now see that the answer really comes from what type of work you trying to gain [proactive reason] or what type of work is in your service radius [reactive reason]. Both reasons will help you decide which crane to purchase.