Holt-Oram Syndrome is a rare genetic syndrome that causes abnormal growth in the upper limbs and heart. With this syndrome only affecting 1 in 100,000 people, vast majority of car brands are likely to not have accommodations for shorter arms (however this accommodation likely applies to much taller people in general as well). This project’s mission is to make driving for a 15 year-old girl with Holt-Oram Syndrome more accessible, providing the function of steering to be more in-reach, and applicable to most, if not all, cars. The goal would involve creating an attachable part that’s easy to install and use across multiple vehicles that allows for more accessible steering.
The purpose of this project is to allow a teen with Holt-Oram Syndrome to learn to drive. The main barrier to this is her inability to reach the steering wheel due to her shorter arms and weaker grip strength. The device also needs to be safe, resistant to unwanted movement, and transferable from vehicle to vehicle.
This will be done by
There are many products that accomplish a similar task as to moving the steering wheel forward however after further research we have deemed that moving the steering column itself forward would be arduous and be non transferable in any way shape or form additionally there are many legal regulations around any sort of modification to the direct controls of the car beyond minor accessibility accessories.
After realizing this we moved towards a mounted ball, peg, ETC, that would mount onto the steering wheel itself and then though it would not be able to convey the controls that are on the steering wheel it would be easy enough for someone to reach around to access blinkers, wipers, and headlights as it would be not in the way additionally it would not be in the way of the airbag because it is quite small in comparison to the wheel.
In addition to end up being a safer easier option for the family it is also easily transferable between different vehicles that have different steering wheel sizes and will require minimal tooling to do so.
This custom design features what is commonly known as a “steering wheel spinner knob” – a steering wheel attachment that allows one-handed, full-rotation turning. This adaptive driving aid provides a secure way to steer with one hand, making driving easier and safer for those with conditions affecting arm or shoulder range of motion, hand grip strength, and/or wrist stability.
This concept design takes the general idea of a ball attaching to the steering wheel by a clamp, but gives an option of extension using discs that interlock. The solid end of the discs has two tiny buttons that would slide into these slots that exist on the hollow end, essentially making a loop of interlocked pieces.
Pros: Easy assembly, easy to adjust length, allows for more secure force to be applied.
Cons: More expensive depending on amount of discs made, unused discs could be lost.
This design is of a clam-shell style clamping mechanism where it would just screw down in using softer screws such as aluminum or brass in addition to some rubber padding on the inside of the clamp would securely clamp down to the steering wheel.
Pros: This would be an incredibly secure form of mounting and would have little issue with longevity
Cons: This would also be more expensive due to the requirement of milling aluminum and addition to the multitude of bearings and clamps to make sure everything stays secure. Also the clam-shell would not work for the most extreme ends of diameter for a vehicle.
Our Selected Concept Design is Concept Design 1 – noting that we are modifying it to have the clam-shell clamp from Concept Design 3.
While all of the designs were approved safe for use, and showcased both similar durability and comfort, this one stood out as the simplest and easiest to use and install – which is a big priority for our family, seeing as how this project is for a 15 year old whom will need to be able to use this adapter across several cars throughout her lifetime. While Concept Design 3 was a touch more adjustable, Concept Design 1 is close capability-wise and also the cheaper to fabricate.
Overall, Concept Design 1 proved to rank the best taking into consideration safety, durability, adjustability, ease of use, ease of install, comfort, and cost across all of the potential Concept Designs.
1. EXTENSION. The bolt within the ball handle is secured by a nut, and is simultaneously securing the clamp onto the steering wheel (alongside the other bolt) and capable of being adjusted to fit a comfortable reach. This longer bolt allows for up to five inches of extension, which can be useful for when the child grows up or is switching over to a different car.
2. SECURE CLAMPING. As stated in the previous detail, the two bolts can be adjusted within the clam-shell clamp’s pieces to be secured as tightly onto the steering wheel as possible. The insulation on the surfaces that clamp onto the steering wheel help prevent damage from the immense pressure that’s applied when securing the clamp. The adjustability of the clamp itself can also be very useful for when the child switches to a car with a different type of steering wheel.
3. COMFORTING/SPINNING HANDLE. We talked with the family about what shape the handle should be for the most comforting use, and we met an agreement on a ball-shaped handle. While the overall outer diameter is to-be-determined, ideally, the size of the ball handles should be small enough to provide a comforting grip when using the steering wheel. The handle’s connection with the bolt’s smooth head provides an even smoother connection, meaning the ball can rotate freely on top of the bolt, allowing for more types of hand motions to be comfortable when rotating the ball.
4. EASY (DIS)ASSEMBLY. With most of the pieces involved being linked with only hex nuts and bolts, the design can easily be put together in a few minutes, and can also be taken apart in that amount of time.
The determination of the materials to be used during the fabrication process was decided by analyzing the following key traits across contender materials:
Density, which affects the weight.
Modulus of Rupture, the measurement of the materials ability to withstand load until failure.
Modulus of Elasticity, the ability of the material to deflect under load and return to it’s original shape after deformation.
Hardness, the measurement of the materials resistance to damage such as scratches, dents, and general wear and tear.
Cost, which affects the materials availability to us for this project.
Aesthetic Evaluation, the determination of how pleasing the material would be be visually.
To determine the maximum torque a bolt can withstand from a clamp, the k-factor of the bolt’s material, force of the clamp and nominal diameter of the bolt are multiplied together (𝜏 = KFD). While the amount of torque we apply to clamp the steering wheel may not be a high amount, it’s still recommended to choose a material with a higher k-factor like the zinc-plated bolts to allow for the most torque possible. The insulation we’re applying can also help increase the k-factor by behaving as an extra “defense” of the main clamp material.
The padding is a very important part of this design as it allows it to transfer between vehicles, however it also needs to be able to survive extremely hot and sunny conditions. On average vehicles can get up to 150°F in direct sunlight on a very hot day so I need both the adhesive and the material itself to be able to survive both extended direct sunlight also extended compression and its extended heating
Due to liability and safety concerns of Dr. Canfield we were not permitted to fabricate the spinner knob ourselves, however, we were authorized to purchase a spinner knob that matched both our designs and the requirements of this project. After we weeded out options that did not fulfill the base requirements of being safe structurally sound and fit the steering wheel, we then moved on to a few options that more of a variety of sizes and shape. The different shapes that we chose were a post, ellipsoid, and a wheel. The post was because it offered the most extra length to the wheel meaning that her limitation of being able to reach the steering wheel would be minimized by the most amount. The ellipsoid was a compromise between the extra length of a post and the comfort of a wheel. And a wheel offers the easiest time to turn the wheel without rotating your wrist. The ellipse slide was our foremost option and therefore we had two different sizes to verify that the size of the ellipsoid was not an issue more than an asset.
We tested every adapter within the same conditions to ensure a fair and accurate comparison. With the adapter secured on the upper-left side of the steering wheel to accommodate for the teen’s left-handedness, we had her navigate a consistent course: an oval loop around an empty shopping mall parking lot, ending in a designated corner parking spot. This allowed us to benchmark each model’s capabilities regarding: grip, comfort, turning speed, steering control, and the devices overall security to the steering wheel itself.
Firstly tested was a spinner knob adapter, presented in Figure 1. This model proved superior – providing the teen with a secure, comfortable grip for her smaller-than-average hand and the necessary rotational ability to accommodate for her limited rotational mobility due to her fused wrist plates, both complications resulting from HOS. These conditions led to a visible boost in her steering confidence. The trial showed the teen navigating the lot with ease, executing sharp turns and maintaining control with fluid movements. While the original assembly had featured screws that irritated her hand, immediate on-site modification resolved this – resulting in a final mechanism that sufficiently met all of her needs alongside our safety requirements.
Secondly tested was a metal rotary adapter, displayed in Figure 3. In terms of vehicle dynamics, this adapter performed effectively – it fastened securely to the steering wheel, allowing for both smooth handling and precise steering. However, the teen’s smaller hand size due to her HOS made it difficult to maintain a secure grip, leading to a noticeable decrease in her perceived control over the vehicle. Despite being technically successful, in terms of practicality, this adapter simply did not meet our specific needs.
Thirdly tested was a pistol grip adapter, illustrated in Figure 5. We ruled this adapter unfit due to significant design flaws. It provided no rotational support to compensate for the teen’s fused wrist plates due to HOS, making it uncomfortable and impractical for her to use. Alongside this, it was physically incompatible with her vehicle’s steering wheel. Due to this lack of mechanical stability and failure to meet her specific mobility needs, this device was deemed both unfit and unsafe for use.
Lastly tested was a rubber brodie adapter, depicted in Figure 6. This adapter was expected to perform well based on its functional similarity to the first two models; however, its significantly larger scale immediately proved problematic. The increased size made it near impossible for the teen to have a comfortable or secure grip. Also, like the previous unsuccessful adapter, it was physically incompatible with her vehicle’s steering wheel. Due to this lack of both mechanical stability and ergonomic compatibility, this device was ruled unfit and unsafe for use.
The installation of the spinner knob itself is incredibly simple. It is a clam-shell design that only requires A hex wrench to assemble and disassemble when assembling one should place 1/2 of the clam-shell on the far side of the steering wheel (towards the dash) then place the other half that has the spinner knob itself attached towards the driving seat on whatever side your dominant hand is. When tightening the hex screws, one should hand tighten both first and then use the hex wrench after to prevent any stripping or cross threading on the hex screws.
To use a spinner knob safely it first must be affixed properly. There should not be any wiggles or movement when moving or putting pressure on the knob itself; the knob head should spin but that should be it. Secondly, one should gain experience and use a spinner knob before they take it out on the open road. It is recommended one should use an empty parking lot or a wide-open space with no other vehicles or things to run into this should be akin to learning how to drive. Additionally, while using a spinner knob, one should understand that they will not be able to react the same as if they were using a normal steering wheel. For example, it is much harder to turn quickly with a spinner knob than it is with two hands on the wheel at 9:00 and 3:00 And therefore the individual driving should be ready and able in an emergency to grab the steering wheel.
Despite the minor setback and letdown it was to not be able to fabricate our own iteration of the steering wheel adapter, the group and family were very pleased with the research and testing that was done. The daughter took a liking to the spinner knob adapter, and now she plans on using it to start learning how to drive with her mother. The family also looks to seek other ways to gain more of a comfortable reach with car modifications and extra seat movement, something we wouldn’t have been able to do for this project because of legal limitations. We’re glad we were able to reach this outcome, as it would’ve been way more complicated if we took our initial spacer route. One thing that we would most likely change with the approach of purchasing and testing adapters is to make sure the adapters themselves are actually “universal fit” as advertised, as this was an inconvenience with a couple of the adapters we purchased. Overall, this project provided a lot of educational answers all around, even without the greenlight for fabrication.
