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OGK KABUTO Co.,Ltd.
Using CFD (Computational Fluid Dynamics) to Improve Aerodynamic Performance of Helmets for Sports and Motorcycle Racing Games at the Olympics

[Vol. 2] OGK KABUTO develops helmets for athlete cyclists and motorcycle drivers. They undertake CFD analyses in early phase of product development as well as wind tunnel experiments to simulate how inner geometry affects the performance. Having introduced the first aero components in this particular field using highly developed technology, OGK KABUTO aims for further improvement of aerodynamics and minimization of development phase.

Picture 3: WG-1, a helmet for cycling sport

First Aero Components in the Industry that Control Turbulence

Analysis results (Fig 2) of WG-1 (Picture 3) for athlete cyclists indicate that the air flows through helmet interior.

Fig 2: Analysis model. Click to enlarge.

 

Fig 3: The effect of Wake Stabilizer
The device controls air flow around the helmet that occurs while driving (Patent no. 4311691)
Click to enlarge

OGK KABUTO developed Wake Stabilizer, the patent-registered aerodynamic device, in collaboration with universities. Fig 3 shows velocity distribution of RT-33, a motorcycle helmet, with and without Wake Stabilizer. Traditionally, the shape of a helmet was considered round, but researchers pointed out that “round objects are unstable. They will drift off the expected path.” Mr. Kuchino recalls: “just like a no-spin shoot in soccer, round objects with no rotations tend to stray off the motion pattern. The fact surprised us when we heard it for the first time." This led to the development of Wake Stabilizer, which made the helmet surface intentionally uneven. Round helmets are unstable as turbulence occurs at the back. Making the surface uneven means that the turbulence occurrence can be avoided and the entire head is stable when moving forward, allowing the neck to smoothly move without being interrupted by fast speed.

Picture 4: RT-33, a motorcycle helmet

Mr. Kuchino, who actually wore the improved helmet and experienced the enhanced changes, says that it feels nothing like the previous model. Drivers may drive at the speed exceeding 300km/h in some motorsport races. Resistance can be clearly felt when trying to move their necks while driving at 100km/h or more. However, wearing Wake Stabilizer enables drivers to move their necks regardless of the speed. Their users including professional drivers confirmed that they could radically reduce the burden on neck when running through motorways.

“We have applied rectangular shape for our helmets long before it was first used for the back of vehicle body. Although it was seen as unconventional at that time, our competitors now use the same approach to develop products,” says Mr. Kuchino.

Experiment Results Conformed to Analysis Results

Mr. Ota says that the simulation and experiment results are “suprprisingly a close match. Results of wind tunnel experiments often fluctuate but that cannot be helped.” The fluctuations are due to difference in air density, which is determined by temperatures of the day. Analysis results could be affected by changes in voltage that makes the wind tunnel unstable and tilts of helmets that alters air flow slightly. Mr. Ota thinks that CFD simulations can be trusted when identifying the pattern of aerodynamic performance far more than experiments.

Upon introducing CFD software, OGK KABUTO looked at several tools as well as SC/Tetra. The reason why they chose SC/Tetra was because the tool was developed by a reliable Japanese firm. The fact that the tool is used by a lot of major international corporations helped them make decision. Trial seminars were also satisfying. “I felt that SC/Tetra was most operable out of others,” says Mr. Ota. Settings are simple for high-end CFD tool, and a lot of processes including mesh generation can be executed automatically. They were also happy with the diverse range of Postprocessor functions. Mr Kuchino says: “when we use analysis results for PR purposes, I give several requests to analysts to make sure that the images are simple enough for non-experts to understand, and they don’t disappoint me.”

One of the functions Mr. Ota values is wrapping, which is used before conducting fluid simulations of CAD models. During the development, models are often scanned using 3D scanner and converted to STL files. Whereas a considerable amount of STL file adjustment is needed in other tools, SC/Tetra wrapping function enables users to easily generate model data with enough accuracy for analyses, although geometries are slightly uneven. “We need to generate more accurate models with precise geometries for final analysis, but we use wrapping function to generate rough model for prior evaluations. When we want to see the effect of attaching parts with slightly different shapes, we can just wrap the scanned data and start analyzing right away,” says Mr. Ota.
 

CFD-oriented Development Approach First Used for Olympic Models

As the experiment and simulation results agreed with each other, OGK KABUTO found that they can undertake evaluations without actual models. They are eager to investigate the ventilation of helmet interior and air flow further. This cannot be identified in wind tunnel experiments. They expect that SC/Tetra will be useful for examining the details.

The current challenge of OGK KABUTO is the development of helmets for Rio 2016 Olympics. For this, they take CFD-oriented development approach for the first time. As an initial phase of development, they use geometry data to conduct simulations repeatedly. The model they are currently developing is planned to be used for the next season’s leading model. “If we become more proficient with SC/Tetra, the development speed will be much faster in few years’ time. The objective of the company as a whole is to reinforce our strengths, which are high aerodynamic performance and light weight,” says Mr. Kuchino.

SC/Tetra is expected to improve product development of OGK KABUTO dramatically.

​​*All product and service names mentioned are registered trademarks or trademarks of their respective companies.
*Contents and specifications of products are as of June 1, 2015 and subject to change without notice. We shall not be held liable for any errors in figures and pictures, or any typographical errors in this brochure.

Company Details






 

OGK KABUTO Co.,Ltd.
Founded September 1982
Products Helmets and related products for motorcycles, bicycles (for children and adults), and sports
Representative Shuji Kimura, CEO
No. of Employees 87 (as of October 2014)
Capital 20 million JPY
Location Nagata, Higashiosaka-shi, Osaka (Japan)
Website http://www.ogkkabuto.co.jp/english/

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