Ensuring a high level of transportability and assembly
while maintaining a conventionally solid structure

The new 55t class TK-G series is compactly designed for effective work even in narrow locations

Development Story 06


Together with the solid structure inherited from the conventional TK series, user merits such as excellent transportability and assembly were added. The new 55t class telescopic crawler crane model for the TK-G series is ideal for handling operations in narrow locations, such as urban areas.

Toru Nakazawa
Manager, Telescopic Crane Development Group, Crane Engineering Department, Design & Development Engineering Division, Global Engineering Center
Organizing a development system for creating outstanding products
Joined the Kobelco Construction Machinery in 2003. As an electrical design engineer, he has successively occupied various posts in development for products such as the “Panther-X 250” rough terrain crane. “As I led the project, I concentrated on creating a work environment that encouraged members of the development team to focus on their work.”

Takafumi Kubo
Telescopic Crane Development Group, Crane Engineering Department, Design & Development Engineering Division, Global Engineering Center
Endeavoring to enhance the transportability and assembly of the machine
Joined the company in 2016. In charge of customization, he focused on the field of design. “I joined the project from the midway, but I had the opportunity to absorb a variety of knowhow. I hope to apply it in future development projects.”

Mitsuaki Iguchi
Hydraulic Component Development Group, System & Component Development Department, Design & Development Engineering Division, Global Engineering Center
Responding to a customer’s sensible needs with technological prowess
Joined the company in 2015. “For this project, I was primarily focused on developing the winch. I attained the development of braking that directly linked to an operator’s sensation, and improved user-friendliness in terms of maintenance.”

Yuki Kitamura
East Japan Service Group, Crane Customer Support Department, Crane Sales & Marketing Division, Marketing Business Unit
Reducing the actual on-site voices to the final product
Joined the company in 2007. He was involved in concept work at the initial stage of this project. “I proposed ideas that reflected the voices of our customers, all the way down to details like the positions of grease feed ports.”

Yuya Morimoto
Crane Marketing Group, Sales Administration Department, Crane Sales & Marketing Div, Marketing Business Unit
Bringing potential needs to light and acting as a bridge for the development team
Joined the company in 2011. “Up until that point, I was responsible for production engineering wherein I supported the enhancement of manufacturing environments for factories both at home and abroad. Using my experience as an advantage, I came up with development ideas that matched market needs.”

In 2017, the company released its new 75t class TK750G, adding a new model in the TK-G series. The model featured Kobelco’s crane technology, maintaining the conventional solid structure and power, achieving the smallest transportation width of less than 2.99 m. The model proved ideal for basic construction work and also as a support machine for such work.

In June 2018, there was the long-awaited appearance of the 55t class TK550G which inherited the concept of the series. In addition to the firm structure that is the characteristic of the TK series, the model featured a combination of high transportability and assembly. About one year after the introduction of the TK750G, this machine responded to the market needs that differed from the field of the 75t, garnering attention as a machine that maximizes mobility in narrow worksites including city construction work.

Tackling and resolving a jigsaw puzzle of complex issues

TK750G, which was developed prior to the TK550G, maintained the attractive features of the conventional TK series while clearing the 2014 exhaust regulations. Moreover, by achieving a compact body with the smallest transportation width of 2.99 m, it eliminated the need to file for a “special vehicle traffic permit” for trailer transportation. Eliminating the complex paperwork and the lead time to obtain the permit itself resolved the issue of operational time loss.

Shortened by 0.1 m compared with conventional machines, the model has a 3.7m turning radius of rear tail. With the crawler retracted, the body width is at its smallest 2.99 m, allowing it to self-mobilize into narrow construction sites.

For the development of the TK550G, the basic concept remained the same; add value such as transportability, while succeeding conventional features for operating in severe construction sites centering on basic construction work. However, the development did not simply involve scaling down from 75t to 55t. Engaged in the formation of the development concept from a marketing viewpoint—transmitting market needs into development division—Yuya Morimoto recalls the significance of developing the new 55t class model.


The TK550G did not just feature the smallest transportation width. With the crawler retracted, the smallest width was also 2.99 m, allowing to enter narrow construction sites on its own power. With the Tokyo Olympics in 2020, redevelopment business in the urban areas are likely to continue, and several narrow construction sites are expected. That means there are plenty of opportunities for the TK550G which is even more compact than conventional machines. The vehicle width may have become smaller, but the number of opportunities is growing even larger.

However, all of them would not be possible unless the team could make the machine more compact and lightweight, while maintaining the strength and power of conventional machines. In short, they were asked for the simultaneous resolution of a three-way deadlock: rigidity, size and weight. The development project leader, Toru Nakazawa looked back on the situation.


In the first place, we’re talking about contradicting elements such as rigidity and light weight, or open space and the laying of hydraulic piping and various cables. Given the constraints of a scaled down version of the TK750G, it was like attempting to solve a very difficult jigsaw puzzle. However, these birth pains are what we engineers live for. With that our motivation, we decided the optimal solution for each issue.

Applying the “user hands-on approach” which only Kobelco would be capable of

Kobelco Construction Machinery has consistently adhered to serving “user hands-on approach”. This was reflected at every turn in this development project. For example, construction sites around cities are located in narrow areas, providing little space for assembly. Standing on the front line of service on a daily basis, Yuki Kitamura had caught the needs in the field and was sure that there was high demand for the TK550G in the outset of the project.


The TK550G was easier to assemble/disassemble than the 75t class. It could enter into small spaces on its own mobility with its boom up, and could be ready for immediate operation without a large space for assembly nor a support machines. The mobility of the machine with reducing time, labor and labor cost is just what is asked for in the field.

In addition, the rear tail of the body was shortened this time, reducing turning radius to 3.7 m. Shortening the rear portion required a small and heavy counterweight, which was resolved with filling materials. This further accelerated mobility at the construction work.

The spirit of valuing the convenience and operability of operators in the field is also shown in the winch’s tuning. Mitsuaki Iguchi, a hydraulics professional, showed his strength in this field.


To ensure consistent braking stability, a wet-type winch was used. In particular, attention was given to a brake response, basing much on the opinions of the operators and repeated trial and error to achieve a response timing that would allow comfortable and stable operation.

Creating a superior product through communication and collaboration between divisions

The members of the TK550G development team were young, and gathered from various fields. According to Takafumi Kubo, who was involved in the field of machine design, said “The seriousness of responsibility promoted the growth of each individual in the development team.”


Special attention was focused on to the convenience of the operator, positioning the hand grips for easy operation when elevating and maintaining the machine, and also details such as the position and width of steps.

The TK550G was also equipped with a toolbox for storing work tools and maintenance parts. To create this toolbox, 2 m width was presumed, allowing the box to be horizontally laid when loaded on a transportation truck. A full-scale model of the box was made of cardboard and many opinions were gathered from various individuals. Taking into consideration convenience as well as the rigidity when the lid was opened, the lid was structured at a 1:2 division. A quite openness corporate climate made it possible for young members to work without anxiety and promote these detailed functions.

A toolbox for storing maintenance tools and accessory parts. To ensure convenience and rigidity, the lid is separated into two parts.


We could get immediate replies to any questions or problems because we had the TK750G development staff in the same section. Sharing the knowledge and fruits of the predecessors allowed the young team to cope with new development themes and lead to the success.

Nakazawa, who was the project leader, also focused his efforts on maintaining an environment that would allow each individual to concentrate on development. Normally, for example, the respective developer is engaged in the various examinations throughout the development process from drawing up examination points, watching over the examination itself to handling the final analysis. Needless to say, this process was quite a burden for an individual.


For this project, information was shared with the examination section at an early stage and role was clearly divided. By entrusting the examinations and report drawing to the examiners as much as possible, the development team was able to focus on the analysis of test results, to perform deeper inspection. There were some problems on negotiations with each department, however, as a development team that went beyond each department, each of them did their best in their respective fields, creating an opportunity and culture in which we worked as “one to support the manufacture of an even better product”.

The TK550G was born on a development stance of responding to customer’s needs by placing value on the voice from the field and a corporate culture of “creating a superior product” supported by teamwork beyond departments. This combination resulted in the birth of this outstanding Kobelco Construction Machinery product. The company has received excellent evaluations from customers who did a test drive of the machine. They have provided opinions such as “smooth movement seems possible even in small limited spaces” or “applications are likely to grow with the use of items such as the optional winch.” As construction demands grow in urban areas, the TK-G series will be more widely used by customers.

Development members gathering in front of a TK550G prior to shipment. The group was formed by young members who would be responsible for future development projects.

The appeal of the TK series

* The contents described above is based on the information at the time of issuing (January, 2019).