Unless you own or operate large capacity all-terrain or hydraulic truck cranes, you may not be familiar with the attributes of a boom dolly.

Essentially, boom dollies help to support the weight of the crane boom with the superstructure of the machine turned to the rear instead of over the front of the machine. The primary need for a boom dolly is to distribute the weight of the crane over more axles and at an extended length, allowing the crane to be a permitted transport.

Lead photo edited

The primary need for a boom dolly is to distribute the weight of the crane over more axles and at an extended length, meeting permitting requirements. 

The boom dolly will help spread the weight of the boom over the dolly axles and also increase the length of the vehicle or outer-bridge. Outer-bridge is the distance from the first axle of the vehicle to the last. Increasing this distance, in most cases, will result in an increase of gross weight allowed on the road.


Nelson Manufacturing offers tandem, tri-axle and quad-axle dollies that pin to the boom of various cranes, as well as spread-axle dollies for areas where additional length or axle spacing is required.  

Nelson Manufacturing built its first boom dolly in 1962 for a P&H 660TC truck crane, according to Tony Niese, president of Nelson.

“The 1 + 2 axle configuration dolly had a pintle hook to the rear of the crane and supported the conventional crane boom at the front of the dolly,” Niese said. “At the rear of the dolly were storage provisions for counterweight.”

Transportation necessity

Today by far, most boom dollies are made for AT and truck cranes in the 90 to 300-ton capacity, Niese said.

The boom dolly is an essential piece of equipment allowing more cost effective and efficient movement of today’s cranes, according to Chris Holland, president of Holland Moving and Rigging Supplies (HMR Supplies).

“Without the boom dolly, it may be necessary to remove a jib, crane boom and outrigger boxes from the crane,” Holland said. “Today’s boom dollies can be configured to haul counterweights, spreader bars, cribbing, etc. We have worked with customers and allowed them to eliminate a complete fall-off load for the crane. A properly designed boom dolly can be a huge cost-saving piece of equipment.”

HMR Supplies has been making boom dollies for more than 35 years, spanning two generations of the company’s family ownership.

“We have brought our expertise to our boom dolly designs to make them more than just a pair of axles under the crane boom,” Holland said. “Our team works with the customer to build the best dolly for [their needs].”

While there are many types of boom dolly designs, Holland said 2, 3 and 4-axle dollies are seen as the standard but custom solutions are available, including 3 + 2, 2+1, lift axles, special spacing and the like.

HMR Supplies

HMR Supplies has been making boom dollies for more than 35 years. Each boom dolly produced by HMR Supplies is specific to the particular crane in which it will be used. 

“Often, we equip the dolly with split towers, bolsters, air locking mechanisms and a wide array of other customizations,” Holland said.

Boom dollies are also used for self-erecting tower cranes and in some cases for boom trucks.

“People have always employed some variation of a dolly to move heavy things,” said Crystal Dieleman, president of TransWorld Manufacturing. “This just happens to be a dolly with an attachment to hook up to a crane, either coupled to the boom or the back of the crane.”

“Dollies vary greatly,” said Dieleman, “But you can summarize to tow-bar, post/tower and articulating. There are many variations beyond that.”

Gustavo Anzola, sales manager for Greenfield Products, explained that each state has its own rules and regulations when it comes to permitting ATs with a boom dolly.

“A boom dolly for a Grove GMK5250L in Florida may look completely different for the same crane model in Texas,” Anzola said.

Nelson offers standard tandem, tri-axle and quad axle dollies that pin to the boom of various cranes, as well as spread-axle dollies for areas where additional length or axle spacing is required to meet permit requirements.

Strong market

Demand for boom dollies is pretty strong, according to the leading manufacturers of these machines.

“We are anticipating that 2019 will be a strong year for the crane market,” Niese said.

Due to the nature of boom dollies, demand is mostly regional.

“In certain areas of North America, certain cranes can be transported without a boom dolly while in other areas a dolly is needed,” Niese said. “In still other areas such as Michigan, dollies are only needed on certain machines during spring thaw. In this case crane companies work to share dollies between multiple cranes.”

Dieleman also characterized demand in the U.S. as strong.

“Some areas have more strict bridge and weight regulations and therefore dollies are required with smaller capacity cranes so they are more common,” Dieleman said.

Anzola said his company has seen strong demand for the past 12 months, with higher volumes in 2018 than in 2017. Demand is pretty well distributed, he said.

“Most of the Northeastern states don’t require boom dollies so there is very minimal demand out of that region,” he said.

The biggest factor for boom dollies is what region the crane operates in, Holland said.

“Regulations vary from state to state on allowable axle spacing’s and axle weights,” Holland said. “Frost laws have a huge influence on the design of a dolly as the allowable axle weights are reduced.”

Boom launcher create efficiencies

When a boom dolly will not get the axle weights down to the allowable limits, a boom launch trailer can be a good solution.

Nelson Manufacturing President Tony Niese said a boom launch trailer will haul the boom and also remove and install the boom into the crane’s superstructure under its own power.

Greenfield Products’ Gustavo Anzola termed the boom launch trailer market as “niche.”

“The majority of launchers are produced to work with 400-ton capacity cranes or higher,” said Anzola. “Some of the large cranes are not designed to work with a boom dolly and the only way that they can be transported is by removing the boom assembly.”

He said Liebherr’s LTM1450-8.1 and LTM1500-8.1, Grove’s GMK7550 and Terex’s AC500-8 are popular crane models that will use boom launch trailers.

“Typically, if more components than just the boom need to be removed, the machine can do that itself, and the boom can be the last component to be removed,” said Niese. “That being the case, with a boom launch trailer, you can eliminate the need for an assist crane allowing your smaller cranes, and accompanying crews, to be out making money on other jobs instead of disassembling one of your own machines.”

Greenfield Products Boom Launch Trailer

A boom launcher eliminates the need for an assist crane. 

Safety concerns

Over the past few years, boom dolly safety has been a top industry concern. All of the boom dolly makers have been actively looking into ways to make dollies safer.

HMR Supplies provides drawings, documentation and lists out instructions for specific operations that could pose hazards for its boom dolly owners.

“It’s critical to remember that, while it doesn’t have a motor or isn’t driven, the dolly can move and should be treated with respect,” Holland said. “Most customers are familiar with their operation as most dollies work the same and operate in a similar manner. We will gladly work with any customer to ensure safe operations. It’s important for a new driver to be driven in a controlled environment before going out on the open road. Each crane and dolly acts differently and the driver needs to get familiar with it before hitting high speeds, crowded streets and narrow roads.”

Niese said Nelson takes boom dolly safety very seriously.

“We look closely at each proposed dolly/crane combination and have set criteria that each combination must match for us to move forward with an order,” he said.

Weight distribution is an important aspect of usage and the crane should have a minimum of 60 percent of the total gross weight on its axles and the dolly can only have a maximum of 40 percent on its axles, Niese said. Nelson provides provisions to allow operators to complete the connect and disconnect operations while on the ground. Air locking pins, rocker leveling springs and hand cranks to move rolling towers are all features designed to prevent the need to climb up on the dolly itself, Niese said.

Boom dolly safety has been particularly scrutinized in Canada.

Greenfield Products

Greenfield Products offers five types of boom dollies, Model B2, Model C3, Model W3, Model D4 and Model W4. Pictured is the Greenfield W4 with a Grove GMK6400.

“Nelson has spent a great deal effort to look into the concerns that have been brought up in Canada,” Niese said. “Nelson is an active member of the Crane Rental Association of Canada (CRAC) Boom Dolly Safety Committee as well as the SC&RA Boom Dolly Task Force. We have provided support to the CRAC effort as they have been working to test and analyze crane and dolly vehicle combinations.”

Differing standards

Dieleman said one of the safety issues is that the majority of crane manufacturers design ATs to European standards, which are different from U.S. or Canadian standards.

“Boom dollies aren’t common in Europe so the onus falls to the end-user to select a crane and complementing boom dolly to mobilize their equipment legally and efficiently,” she said. “Then you have the dolly manufacturers who are designing products by U.S. or Canadian standards, and often times the circumstances/regulations are such that the particular crane and dolly combination has never been put together before, and therefore never been tested together before.”

As well, crane owners are required to buy dollies based on fluctuating government regulations.

“While dollies have been used for decades as an effective way to meet bridge and weight laws, it is astonishing to think that boom dollies never really entered the vernacular until recently,” said Dieleman. “There really is a lot going on with a boom dolly and all too often this gets boiled down to a cost-based decision for a non-revenue generating asset. The market is competitive, and therefore margins are tight for these very custom products.”

More importantly, Dieleman said she is not aware of any formal training being offered by a labor union or third-party training program that touches on the subject of boom dolly safety.

“There is no classroom instruction or test questions or any type of certification to become ‘competent’ or ‘qualified’ to even use a dolly,” she explained. “Most jurisdictions would consider a person to be ‘qualified’ to drive a crane and dolly with a simple CDL, but anyone would agree that driving a crane coupled to a dolly is very different from a tractor trailer. When you consider the liability and how high the stakes are, it is shocking that boom dollies aren’t covered in coursework, apprenticeship or training programs along with everything else.”

Custom specializations

Nelson’s most popular boom dolly model is the CBC-30ST, a crane boom carrier, tri-axle with a split boom tower.

“Our tri-axle close coupled dolly is generally used on machines in the 90T-300T range,” Niese said. “On the smaller cranes in this range they are typically configured so that they can haul counterweight on the deck of the dolly. On the larger cranes counterweight is typically not added to this type of dolly due to the amount of boom load.”

Each boom dolly produced by HMR Supplies is specific to the particular crane.

“There isn’t a standard model per se, although we do sell more three-axle dollies,” Holland said. “The important thing to consider when building a dolly is how are you going to use it? Do you want to carry counterweights on it, spreader bars, specialized storage, mats, etc.? Do you have a specific axle weight you need to be at? Special road considerations, axle spacing, castering axles, etc.? It’s critical to have the design discussion up front and not rush the dolly.”


Last year TransWorld Manufacturing produced several boom dollies for the Liebherr LTM 1400, including this 4-axle articulating boom dolly for Bob Hill Crane. 

For example, Holland said that if you know that you can do 80 to 90 percent of your normal work by adding a counterweight to the dolly it normally makes sense to go a little larger in size to accommodate the counterweight stowage instead of having an additional truck, trailer and person haul that counterweight over the life of the crane and dolly.

Last year TransWorld Manufacturing produced several boom dollies for the Liebherr LTM 1400 because that crane model is being phased out in favor of the LTM 1450, which requires a boom launch trailer, Dieleman said.

There has been a lot of interest in TransWorld’s ultra-lightweight dolly line.

“We’ve figured out how to make the lightest dollies on the market without sacrificing strength,” Dieleman said. “With this new design, we have been able to design combinations that will legal a crane where it wasn’t possible before, or maybe keep the owner out of superload permit territory, or just offer an extremely efficient way to travel. With this design, the boom can now transport with y-guys attached rather than having to remove them.”

Greenfield’s most common boom dolly is the closed group 3-axle with 54.5-inch axle spacing. This boom dolly configuration is accepted in many states and the user can typically permit over 60,000 pounds, Anzola said. For West Coast states, Greenfield’s most dominant model is either a 3-axle spread or a 4-axle spread dolly.


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