Vol.06 WOLVERINE RMAX4
CHALLENGERS OF MONOZUKURI
Story of New Model Development
CHALLENGERS OF
MONOZUKURI
Story of New Model Development
Vol.06
WOLVERINE RMAX4
TAKING ON CHALLENGES WITH FLEXIBLE AND BOLD APPROACHES
In the new medium-term management plan, the Outdoor Land Vehicle (OLV) business has been newly established as a strategic business domain. For Recreational Off-Highway Vehicles (ROVs), in particular, Yamaha is aiming to expand its market share mainly in North America.This time we had an interview with the development team of the WOLVERINE RMAX4 about this new model.
The ROV we are focusing on this time is a dedicated off-road vehicle that can run on unpaved rough terrains, grasslands, and sand areas. Unlike an ATV, on which the operator sits in a straddle position like on a motorcycle, an ROV has a steering system similar to that of a car, including a steering wheel and a throttle pedal. Yamaha is a pioneer in this genre.
Our company this time launched a new model in the recreational category, the WOLVERINE RMAX4 (hereinafter referred to as RMAX4), a full-size model that seats four people.
We had an interview with five RMAX4 development team members: four from the RV Development Division, Recreational Vehicle Business Unit, Outdoor Land Vehicle Business Operations, who are project leader UEKI Yuuichi, driving test engineer SASAKI Shun, strength test engineer AYAMURA Yuki, and body designer ISHII Tomoyuki; and another member from the 3rd PT Design & Development Division, Product Development Section, Powertrain Development Center, who is drivetrain designer TANAKA Daisuke.
JAPAN-U.S. JOINT DEVELOPMENT WITH AN EYE ON THE WEST COAST MARKET, WHICH HAD NOT BEEN FULLY DEVELOPED
Approximately 70% of the entire ROVs are sold in the U.S. YMMC, one of our group companies in the U.S., is in charge of the production of Yamaha ROVs. Development is also being carried out in cooperation with our U.S. offices.
ROVs are a form of mobility that can run on rough terrains with their excellent off-road capability and functionality. Although the market in which ROVs can be introduced is limited because of their unique characteristics, including the fact that they cannot be driven on public roads, they are incorporated in the strategic business domain of the new medium-term management plan. This is because ROVs are becoming high value-added products especially in the U.S. market, and the market is also expected to expand in the long term.
“After the pandemic, outdoor leisure has more expanded and become established in the U.S. People are more interested in ROVs, so there is room for further growth. In addition, it’s only been about 20 years since this genre was established. It is expected that ROVs will continue to become larger and their specifications will be improved. This is a market where we can expect increased revenue through the high added value,” says Ueki.
The RMAX4 is also a model aimed at expanding market share in a category that had not yet been fully developed. “The land in the U.S. has diverse terrains. The East Coast, for instance, has many forests and waterfronts. The South has muddy areas, whereas the West Coast has sand dunes and deserts. Conventional models were relatively suited to tight forest trails of the East Coast, but the RMAX4 was designed to be a model for the West Coast featuring vast trails, including sand dunes, and steep hills that can be driven comfortably even with four adult passengers on board,” says Ueki.
As shown in the concept of the RMAX4, “Serious pursuit of outdoor adventure with friends and RMAX at the West Coast,” the RMAX4 was a model aimed at the West Coast market. Although the RMAX4 is a minor change model of the RMAX2/RMAX4 compact, which was highly praised in 2020 for its newly designed 999 cc engine and CVT transmission, the chassis has been extended by 800 mm to improve rear seat comfort while ensuring durability, and the drive system has also been revamped to improve driving performance on wavy roads and steep hills. It is a first full-size model in the WOLVERINE series that could be considered a new model.
TAKING ON DEVELOPMENT CHALLENGES WITH FLEXIBLE AND BOLD APPROACHES
One of the missions in the development was of course to create a new variation while keeping new investment to a minimum. Listening to their development story, however, we cannot help but feel their determination to create the best possible product without giving up until the very end. The same is true at all of our development sites, but in the RMAX4 project, it seems that evaluation criteria were not easy to define and test conditions were carefully decided by trial and error.
One of the reasons for this is that ROVs are not products like ordinary cars that run in a specific environment such as public roads. Even though the RMAX4 can run on dirt roads, they include diverse terrains such as rocks, sand, grassland, and steep hills. In addition, customers use the product in different ways, so such a wide variety of expected situations made it even more difficult to determine test criteria. “Target setting is necessary for evaluations, but the answer is not always set in stone. We derived final target values by sharing with the U.S. development team how we felt after test-driving the actual route that customers usually took,” says Sasaki.
For example, when the team was working on the development of the new Electric Power Steering (EPS) that eventually has a significantly increased assist torque compared to the previous model and allows for comfortable operation even in harsh conditions, they continued improving the product thoroughly until the final phase of the development. In close cooperation with the EPS manufacturer, the development team finally determined the specifications of the EPS with selectable High, Standard, and Low modes.
They also went through a process of trial and error to make major improvements to the front-wheel drive switching system, which was one of the highlights of this project. This switching system has a mechanism that limits the differential motion between the right and left axles with a spline engagement, but the spline is subjected to excessive pressure when switching between Diff Lock and 4WD. To ensure the reliability of the system, the development team struggled to choose the design specifications and construction methods for the splines and other switching parts.
“It wasn’t easy to figure out how strong the splines should be. I designed the splines repeatedly to enhance their strength while ensuring their easy switching, but the spline teeth broke many times in durability tests. Even when I finally found some possibility of ensuring the strength of the splines after redesigning them along with careful consideration of manufacturability, another problem surfaced, such as the rigidity around the forks, which I thought had enough margin of safety,” Tanaka recalls.
This gives a glimpse of the team members’ attitude toward the development, in which they placed great importance not just on their own subjective opinions, but also on customers’ perspective. “When establishing evaluation conditions, I analyzed customer feedback and mindset, and assumed how customers would use the vehicle and how many times they would switch the diff lock, based on my own experience in the U.S. market, to set the evaluation criteria,” says Sasaki.
There was another major reason why the development was not as straightforward as it seemed: it was difficult to test and evaluate under identical conditions. In the revamped brake fade evaluation, for example, the team focused on conducting tests under as identical conditions as possible at both the Japanese and U.S. test sites to improve the accuracy of the evaluation. To recreate Japanese hill conditions in the U.S., they prepared master data such as vehicle speeds and temperatures, and then reproduced the conditions on flat roads using a test vehicle with weights loaded so that they could obtain test data close to those in the Japanese conditions.
There are many other stories behind the development. For example, when they conducted Diff-Lock/4WD switching tests repeatedly on a sandy ground simulating a sand dune, the test vehicle kept digging the sandy surfaces with its spinning wheel, causing the test road conditions to change. Since it would be impossible to obtain correct test data on that test condition, Tanaka, Sasaki and other team members dug and filled holes repeatedly with shovels to create the same test conditions.
“We used our brains flexibly on the spot, but also continued testing in a bold manner. That’s what RV development is all about,” says Ayamura. The team’s approach for the RMAX4 development was a perfect example of this.
CREATING A HISTORY OF ROVS AS PIONEERS WHO OPENED UP A NEW GENRE
It's thanks to each member's manufacturing skills that they were able to take flexible approaches.
"Looking back now, it was very reassuring to know that all of the test members had some level of material processing skills such as cutting and welding. No matter who I asked to do a job, he did it at a high level of quality. It was our team's biggest advantage that allowed us to whip up a prototype very quickly," says Ayamura.
Take the newly developed rear differential as an example. In addition to the strengthened gears and case, it was also equipped with a breather. Even for this small breather, the team performed CAE analyses on how the differential oil was drawn into the gears before carrying out a bench test. To evaluate this differential, Ayamura in cooperation with his team members made a wheeled test platform that could tilt up to a considerable angle. He also created a mock-up of the rear seat so that the team could examine the space and the steps in detail.
It can be said that the creative power of each development member was a source of producing new adventure machines. The development team admires the RMAX4 greatly, as Ueki says, "It's extremely revving to ride. It's a model that really suits our company culture." This shows us the team's passion to develop an attractive model that will help Yamaha regain its position in the ROV market.
