Inside HUNT: Revolutionising Bicycle Rim Design through FEA (Finite Element Analysis)

Today, we're taking a closer look at how we use Finite Element Analysis (FEA) at HUNT to enhance bicycle rim design with Ollie Mant, our Test and Development Engineer who completed his MEng in Mechanical Engineering at Swansea University (you can learn more about Ollie here) and Paddy Brown. Paddy earned his MEng in Mechanical Engineering from the University of Sussex and rode for the HUNT road team before becoming part of our engineering team. Together, they use FEA to make our rims lighter, stronger, and more durable, ensuring you get the best ride possible.  

Keep reading as we delve into how FEA is transforming our design process and improving your cycling experience. 

Lets start off with who you both are and what you both do here at HUNT.

Ollie MantMy role is Test and Development Engineer at The Rider Firm, working under both Hunt and Privateer Bikes. I have an MEng in Mechanical Engineering, with a Year in Industry, from Swansea University, I joined the company after I finished my degree. 

Paddy Brown – My role is Development Engineer at the Rider Firm. I gained a Meng in Mechanical Engineering at University of Sussex and whilst there, I rode for the HUNT road team and on graduation I joined the engineering team.

Could you briefly explain what Finite Element Analysis (FEA) is and why it is important in the design process of bicycle rims? 

FEA is a computational method used to simulate a product and how it is affected by stresses. Historically, in engineering in general, prototypes would have to be made and then tested in the real world, which is a timely and costly process. The use of FEA saves this; it allows us to simulate what happens in the real world, so we can reduce costs and development time. In addition to rims, we have also used it to simulate stresses in the hub flange when we have found issues around these areas.  

 

What are the primary benefits of using FEA in the design and testing of bicycle rims? 

As previously mentioned, FEA saves time and money in developing a rim and allows to assess multiple different versions of rims, before we look to even have a rim made. FEA also allows us the potential to save mass through assessing where in a product material is needed more so and areas where it is less critical through the stress distribution. As a result, it has the potential to save weight in a product, whilst keeping it just as strong, if not stronger. 

The mesh is applied to the products being tested, with the fineness of the mesh being increased to focus on areas of importance. Left is the spoke hole for a "spoke pull through" simulation, right shows a rim impact simulation. Red areas are high levels of stress (Von Mises) when the load is applied and blue shows areas of low levels of stress.

How does FEA contribute to the overall safety and performance of bicycle rims?

FEA allows us to understand how the stress we apply in the simulation is distributed through the product. With this we can help reduce the stress seen in areas that are particularly high in stress and build in safety factors with the aim to improve the strength and the durability of the rim. This is to ensure it meets our stringent testing regulations in the real world, which are designed to ensure the rim developed is fit for purpose and ultimately safe for the rider.  

 

Can you provide an example of a design challenge that was successfully addressed using FEA?

The new HUNT XC Wide V3 was developed using FEA with the aim to address an issue we had seen in other rims. We had found there is a stress raiser in the spoke bed and under use we could see the nipple being pulled through the spoke bed in certain occasions. A model in FEA was used to assess the stresses in the lower portion of the rim in different iterations of profiles to determine the best solution to the issue. It was found that going to a wider spoke bed, reduced the stress in the spoke bed by ~9%, whilst ensuring the mass of the product is kept within the project guidelines.  

How does FEA testing compare to traditional physical testing methods in terms of accuracy, cost, and time efficiency?

We are always trying to understand better how FEA and real world testing match up better, so we can reduce the cost and time to bring new products to market. For something like spoke stresses and stresses on hubs, this is relatively easy to model and predict, thus the relationship between simulation and real world are comparable and thus highly time efficient.

A direct impact to the upper portion of the rim is something that is significantly harder to model as there are many factors to take into account which is very difficult. For example, the tyre, how it reacts to the impact and then subsequently the effect it has upon the rim. Additionally, the spoke configuration, and even material, has a large impact on the overall strength of the wheel. With this, we use our impact test rig as the base of the FEA model and we simplify the model and take assumptions – something that is done across the board in engineering.  

As a result we do sometimes find, the outcomes of FEA modelling do not necessarily reflect real world testing and that is where we have to go back to the drawing board. This is why we have development validation plans and design development processes in place so we can ensure the product output from the design process meets our test requirements both in lab and, crucially, under our amazing test riders. 

Regardless of how the impact test FEA modelling and real world test align, the process is significantly quicker than testing 100 odd rims.

FEA developed rims

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In what ways does FEA enable more innovative and complex designs that might be difficult to test physically?

When we design a product and use FEA to assess it, we create what is called a design study. This study allows us to critically assess the effects of individual and combined changes, such as a radius or the thickness of different sections. This process also allows us to try unusual things too, which may not necessarily spring to mind straight away, like non-uniform thicknesses. With this in mind, you would have to make potentially 100’s of unique moulds to manufacture each individual rims designed to see the affects – an extremely timely and costly process. The effects of each design change will not always be obvious through the means of testing either. On top of this, we would not have any quantifiable stress data, which is significantly more precise than generic impact energy. 

 

How do the results from FEA testing translate to real-world performance for cyclists?

Ultimately, they will help to make a better product, whether it be helping to improve the durability of the hub, improve the resistance to spoke pull through or improve the strength in the upper portion of the rim. It will provide a product that is more durable so the rider can ride harder, faster and have more fun.

 

How do you ensure the FEA models are accurate and representative of real-world conditions?

This is the fun part of creating the FEA model. It is easier for us to consider the tests we do within the lab for this part as it already replicates high stress riding situations in a simplified form. We have to consider all the forces that the product undergoes in the test , calculate the forces/stresses and then apply it to the model. The spoke pull through test is a relatively easy model to recreate in simulation form: create a rim profile, apply a load to a given area and then apply a stress which is equal to that of the test (300kgf – for reference that’s over twice what the recommended spoke tension is on our wheels).

 

We hope that this give you an insight into how we use advanced modelling technologies such as FEA to develop our range of high-performance wheels. To learn more, sign up to our newsletter and get notified of new journal posts, interviews, videos and new product launches!

July 08, 2024 — Jacob Rubio