A design and assembly of the corner wheel assembly using Solidworks

1.1 Introduction:

Since the introduction of cars, there has been a concept of racing.

The main idea behind a race is to discover the peak performance of the race-car; as well as; improving various factors in the build of the race car to improvise its lap times. The assembly consists of sub-assemblies which are made by parts. As the resources in the world is finite and cost is a factor in racing, there is constant need of improvisation of all parts in terms of its design; which involves factors like its strength, weight, structural integrity; sustainability and pricing of each part. A major part of how fast or maneuverable a car is decided by the way the car transfers the power from the transmission to the road.

The point at which this transfer happens is at the wheel, and one of the most important parts of a race-car is its wheels. There is a lot of scope for improvement for the wheels in terms of how its design can be optimized to accommodate a wheel which can be much lighter than and structurally as strong as the wheels used prior to it, if not better.

The wheel was one of the foremost things invented by mankind around 3500 BC and it has since changed the way humans live. The initial wheel was a basic cylindrical log used as ‘rollers’ with cross-bars going across them through their underside to prevent the log to move out from beneath the load, it is also estimated that it took about 1500 years before the next big development happened to the wheel in the form of spokes like in the figure below, one of the biggest breakthrough in the history of the wheels being the usage of iron to make the rims which happened around 1000 BC (refer image below). The modern wheel design was brought in by G.F Bauer when he patented ‘wire tension spoke’ in 1802, further development of which saw it evolve into the spoke wheels we see on bicycles. It was in 1927 that steel welded rims were introduced on the car the Ford model T, prior to which it came with wooden wheels. This was a major step for wheels as it was cheaper to produce and was structurally much more reliable than a wooden wheel. The further development in the field of metallurgy which brought in alloys that further gave rise to alloy wheels which were lighter, structurally more rigid and better heat conductors which allowed for a shaper handling, a lighter automobile which meant a better power-to-weight ratio while still being cost-effective, as durable as steel wheels if not better while also being visually appealing.

Figure a: A solid wooden wheel found in rural Turkey near Konya

Figure b A Primitive steel wheel

1.2 literature review for the parts:

The parts required to build a wheel assembly is rim, wheel disc, hub, tire and the hub-cap.

RIM:

The rim is the part which makes up for the outer boundary of the wheel and connects the wheel disc to the tire and the common materials used for building the rim are carbon steel, iron alloys and magnesium alloys.

WHEEL DISC:

The wheel disc is the part connecting the hub to the rim and is often of the same material as the rim itself for alloy wheels as they are cast from a single block of said alloy itself. Some common materials used for making the wheel disc are carbon steel, iron and magnesium alloys.

TIRE:

The tire connects is the rubber component which grips the car on to the road and also takes the first impact from the road. A tire is made of various components like rubber, high-strength steel and cotton ply, but for the model, the tire has been given, which is the same tire that has been used in the assembly.

HUBCAP:

The Hubcap is a simple component which covers the end of the hub and serves a pure aesthetic purpose. The common materials used for making a hubcap are plastics and also stainless steel at times depending on the kind of automobile.

1.3 Design and Development:

A few concepts were thought of during a brainstorming session and after a lot of discussions and creation of the design selection matrix, concept-1 was used which in essence is a double wishbone system, as this system incorporates a smooth ride, allows a sharp steering while being structurally rigid. It also allows us to change Camber and Ackerman angles which in turn allow the tire’s surface of contact to be modified and hence the grip of the tire to the road can be increased or decreased depending upon the type of the course the car is racing in. The constraints for the whole model in terms of dimension are dictated by the model of the FSAE car given. Similarly, the dimensions of the wheel had to be made fit the tire given.

1.4 Design Analysis and Research arguments:

Wheel:

The requirements of the wheel were to be,

Structurally rigid, should be able to withstand a torque applied to it without deformation.
Light in weight so as to improve power-weight ratio.
Matching the dimensions of the tire provided so as to be a perfect fit.
Cost effective.
Aesthetically pleasing, as wheels are one of the things that grabs most attention from a viewer.

Keeping in mind all of the above criteria, designs were drawn up, a lot of inspiration from F1 cars were taken as they represent the pinnacle of racecars.

Figure c Lotus team F1 rim

As the rim was already provided, the design required work on the wheel disk and the pilot bore. For the design of the wheel disc, a freehand was given so lot of design ideas were considered but the design of a 12-spoke alloy wheel was finalized as it could ensure enough structural strength to handle the torque applied to it without deforming.

Hubcap:

The requirements for the hubcap were,

To be structurally rigid.
To fit perfectly on the axle.
To add to the aesthetics of the wheel itself.

Keeping in mind all the above criteria, the hubcap is a part which exhibits more of form over functionality, a standard hubcap without a lot of complication in the design was chosen. The mounting style was decided to be a simple clip-on fit the axle itself so as to reduce the complexity of the design.

2.1 Final Design:

RIM:
The final design was chosen to be a 12-spoke alloy wheel which was inspired by F1 cars.

The design started off with the blank rim provided as the boundary of the wheel as shown in the figure below,

Figure d Blank wheel rim

The initial approach was to add extra planes using Add plane function, draw points for a spline through pass through to create a profile in a 3D sketch, on which the revolve feature could be used to create the desired solid profile after which sketches of cuts could be made as per necessity to be further extruded. This approach was time consuming and did not allow for the profile to have a smooth curve.

The final approach was to overwrite the 3D sketch which was used prior to the revolve command in the original rim. This approach allowed the rim to have the spokes with smooth curves and allowed the aesthetics of the rim to be closer to the design idea decided. The final design of the wheel rim is show in the figures below, in different orientations to show the design more accurately.

Figure e Front view of rim

Figure f View of rim

Figure g View of rim

This design was finalized and further finite element analysis and sustainability reports were done on the same and further used on the assembly.

HUBCAP:

The final design was chosen to be a basic hubcap as this part does not actually serve a purpose in the functionality of the car but rather is an aesthetic addition.

The procedure to create the model for this was rather simple as it required an extruded circle with a smaller circular cut through the centre of the larger circle which instead of going through all of the circle, left a small circular disk on one end of the circle.

The final part design is shown in the figures below, in different orientations to show the design more accurately.

Figure h View of Hubcap

Figure i Front view of hubcap

This design was finalized and further sustainability reports were done on the same and used on the assembly.

After the completion of which, they were put together as a sub-assembly for the main assembly of the corner wheel.

2.2 FINAL DESIGN:

The final sub-assembly is visually appealing and neat looking while also being structurally rigid and light in weight; some snips of the sub-assembly are attached below.

Figure j Front view of the wheel sub-assembly.

Figure k Wheel sub-assembly

Figure l an exploded view of the sub-assembly.

3.1 SUSTAINABILITY AND FINITE ELEMENT ANALYSIS:

Solid works provides very powerful tools in the form of Solid works sustainability and finite element analysis as these tools allows a user to further link their solid model from the solid works to the real world. The sustainability tool allows the user to decide upon a material depending upon various environmental factors while the finite element analysis allows a user to see various things like stress, strain and displacement among many others for a given model for different elements which allows the user to make a more informed decision about selection of materials for the said assembly or part.

3.2 MATERIAL SELECTION:

The research done on racing wheels gave us the commonly used materials for a wheel as magnesium alloy, hence that was used as a starting point for a minimum yield stress so as to have the minimum possible displacement under stress, once magnesium alloy was chosen, and similar materials was looked up using the feature which gave us the materials of AISI 1020, Aluminum 1060 and aluminum 6061 to be the closest to the magnesium alloy in terms of its strength, while still being environmentally more viable and cheaper to manufacture, given below are a few comparisons,

Figure m Magnesium alloy against 1060 alloy

Figure n 1060 against AISI 1020

Figure o Aluminum 6061 against AISI 1020

After this sustainability analysis it was pretty clear so as to have the material to be AISI 1020 as it environmentally less polluting while also being cost effective and light all at the same time when compared to magnesium alloy as well as 6061 and 1060 aluminum alloys.

3.3 FINITE ELEMENT ANALYSIS:

Figure p Stress Comparison

A finite element analysis was carried out a fixed geometry being maintained at the outer boundary of the rim, while a torque of 175 N-m was applied on the four wheel bores as seen further below, the same was done to three different studies with different materials being applied to each study as magnesium alloy, AISI 1020, aluminum 6061 and 1060 alloys as per the selection from the sustainability analysis. In figure p a stress comparison is given for all the 4 materials, below which, in figure q a displacement comparison is given where it is seen that the maximum displacement for the rim with the usage of AISI 1020 was acceptable for use in the assembly and hence was chosen for making of the wheel.

Figure q Displacement Comparison

Further in depth analysis was carried out for AISI 1020 for which a torque of 175 Nm was applied for which the displacement and maximum von-misses stress were well under the acceptable range. A few snippets of the same have been attached below. And further on, AISI 1020 was used as the material for the wheel.

Figure r Stress analysis for AISI1020 in depth

Figure s Displacement analysis for AISI 1020

Proof of concept:

4.1 Rendering and animations:

Solid works also possesses a powerful tool in the form of rendering tools which lets a user to project a solid model or an assembly on to various kinds of landscapes and situations with the option of adding a camera to further adjust the focus and the frame amongst many other options. This allows a user to further reduce the space from having a solid part on software to be able to see the parts in a real world scenario. A render of the sub-assembly was created using the same, and snippets of the subassembly in a couple of different scenarios have been attached below. This allows for further better visualization and betterment of the design. It also allows a user to create animations

Figure t A render with a factory setting.

Figure u a render with a snow-trail backdrop

4.2 Animation:

Animations were also created and were added as soft copies.

Citations:

Fig a: https://www.alamy.com/stock-photo-a-solid-wooden-wheel-found-in-rural-turkey-near-konya-76666580.html

Fig b: https://www.pinterest.com.au/pin/304485624792191979

Fig c: https://www.motorsport.com/f1/news/formula-1-pushing-for-bigger-wheels-in-2021-1044392/3115711/