The Kyosho flagship Inferno Buggy has been popular amongst racing buggy enthusiasts around the world. The name “Yuichi Kanai” is synonymous with the “Inferno” as the person who designed the entire series for 3 decades, including the new MP10.
We’ve interviewed Yuichi Kanai, who single-handedly controls quality and design, and does exhaustive performance testing locally in addition to attending many of the most highly competitive races around the world. In the following interview, Kanai discusses his concepts and design ideology behind the creation of the new MP10.
How has the 1:8 buggy racing scene changed since the MP9 was released?
Compared to when the MP9 was released in 2008, aerodynamics has gradually evolved and there are many more high-performance tires available. While speed has not really increased over the last ten years, the number of high-grip courses certainly has. Many 1:8 off-road tracks are sprinkled with sugar water and incorporate carpet sections to produce high-grip conditions, although not as much as the full carpet courses used for electric buggy racing.
Considering these changes, what is the main development concept of the MP10?
Designing a chassis that excels on high-grip surfaces is a priority of the MP10 development. The focal point is the increasing levels of tire grip, and developing a chassis that can best compliment it. Since the MP9 was released 10 years ago, the Inferno chassis has undergone repeated improvements through to the TKI4, but track surface conditions have also evolved with greater availability of good tires and aerodynamics.
There are many improvements I wanted to make to create the MP10, while keeping the best of the TKI4. My standard approach is less is more; so I look to reduce the number parts, even by a single screw. The MP9 was designed for reduced weight, but this wasn’t as important in the MP10 as grip and control become more difficult with a lighter chassis. Even over small bumps and jumps, a lighter chassis will exhibit a more severe response. Therefore, the focus of the MP10 was not to lighten the chassis that is already underweight, but to create a more robust and durable car that’s easy to drive.
There was a car several generations ago called the MP7.5, which most people (including myself) found easy to drive with excellent control. While the MP9 TKI4 is undoubtedly the fastest Inferno ever built, when the settings are not optimized for the conditions, it can become a little difficult to control. Considering how most buggy races run long finals, I designed the MP10 so it’s a little easier to drive.
The body shape is the first thing that catches your attention. What are the main points of the MP10 body?
In designing the body, my aim was to create a shape that produces dynamic performance as well as visual impact. The body for the TKI4 delivers excellent performance in low grip conditions but on high grip surfaces the front window angle is too upright for some conditions and it makes control more difficult. I also wanted to make the body look more aesthetically appealing.
To produce easier handling characteristics I increased the angle of the nose section and balanced this by reducing the angle of the windshield slightly. I also considered adopting a front wing like an electric buggy but after considering the appearance, I decided against it. The side pods on the TKI4 body are rather thick, so to make the MP10 more streamlined and more visually appealing, the height of the side pods is reduced.
It’s a cool looking car isn’t it! Various shapes and materials including polycarbonate were tried and tested for the “wings” at the rear of the side pods in order to increase rear grip. Height was quite low during initial testing, but I found higher wings increase grip and provide excellent stability.
When fully evaluated, the MP10 body exceeds the performance of the MP9 body in all aspects. Stronger downforce is generated, which is especially noticeable as the machine grips the racing surface through corners and delivers improved stability through the jumps. As the appearance is also significantly different, the body may be the most talked about component of the MP10.
In developing the MP10, what were the objectives behind the key changes to the chassis?
The key focus is weight distribution on the chassis for easier cornering and control. In addition to optimizing the weight distribution, major changes from the MP9 include the redesign of various components and the suspension. To increase strength and durability, the diameter of the inside lower hinge pins has increased to φ4.5mm in the MP10 compared to φ4.0mm in the MP9. Additionally, the material thickness around the hinge pin holes of the lower arms has been increased. The redesign of the lower arms removes some of the gussets as compared to the TKI4 arms, but the solid construction of the arms increases its overall strength and keeps dirt from accumulating as much as it tended to do with the older arm design.
The front upper arm changes from an A-arm to an I-arm design, which alters the geometry and makes it much easy to maintain, but most of all it delivers improved control. After rigorous testing it was clear that cornering and steering is significantly easier with the I-arm design.
The anodized aluminum rear suspension mounts are 5mm longer than the TKI4. After increasing by 1mm at a time through exhaustive testing, the additional 5mm was found to be optimal for the MP10.
With the detailed changes to the suspension, the shock towers and geometry have also been reviewed. Benchmarking against the TKI4 and the evolution of the MP9 over ten years, it is clear that the TKI4 runs exceptionally well and it will be difficult to improve on this. With only a slight change, the number of mounting holes for the upper arms and shocks has been reduced to exclude those that were never used so drivers won’t get distracted with too many settings.
The rear of the main chassis has been extended by 2mm compared to the MP9. The amount of milling to reduce the weight of the chassis has also been reviewed because every aspect of the TKI4 design focused heavily on minimizing weight. The objective of the MP10 is increased strength without adding weight unnecessarily. The new lighter side guards and a narrowed rear chassis result in both incrased strength and weight reduction, as well as sharper styling. I tested how far I could narrow the chassis with different mufflers and manifolds. In truth, I wanted to narrow the chassis even more!
To increase the strength of the chassis, the MP10 radio plate thickness is increased to 3.0mm from 2.5mm on the TKI4. Although very rare, there were incidences of the 2.5mm radio plate cracking at its thinnest part, but because it was securely attached at several points, this usually went unnoticed. Although it appears unchanged, this has been reinforced in the MP10.
Many other components have been redesigned for strength and controllability such as the integrated ball link stabilizer for maintenance efficiency, increased steering angle with the new steering plate, and reinforced tie rods. Experienced Inferno drivers will discover many new components when they assemble the MP10 and appreciate the comfort and satisfaction you get when building a Kyosho car.
In the design and development of the MP10, I was able to confirm the great performance of the TKI4. As mentioned earlier, after 10 years of gradual evolution in the MP9, developing a car that was better than the TKI4 was quite difficult. However, in order to create the MP10, I need to develop a machine that exceeds the TKI4. Without question, the MP10 is easier to control and handle through corners. More than anything else, this is the most exciting aspect of the MP10.