Anti-Rollover Omni-Wheel

According to the Fatality Analysis Reporting System (FARS), one-third of all passenger vehicle occupants who lost their lives were in vehicles that rolled over. I have designed an automotive anti-rollover device. I call it AROW (Anti-Rollover Omni-Wheel). This device targets car accident mortality reduction by 10%-30%. Its physics is reminiscent of well-known automotive device ABS (Anti-Lock Braking System). It is mounted over a car wheel. It engages early in a rollover event to remove rollover fulcrum from car wheel tire shoulder and to drain the rollover momentum. It is a simple and low-cost mechanical device with no controls or gears to fail. Two embodiments are provided. The first one is separated from a car wheel. The second one shares a disk with a car wheel. I estimate AROW mass production cost to be around $200–400 per car ($50–100 per car wheel), insignificant compared to a car cost, considering benefits it brings.

With energy denser car batteries and new carbon-based materials coming to the market, car manufactures will try to lower car curb weight. But it will raise the car’s center of gravity due to the high position of passenger bodies (payload), thus jeopardizing car lateral stability. By reducing rollover risk, AROW solves this problem and helps saving energy and slowing down climate change.

On July 3, 2022 I filed a provisional patent application with USPTO (United States Patent and Trademark Office) on this device with title ANTI-ROLLOVER PASSIVE OMNI-WHEEL SIDING CAR WHEEL, Ser. №63/358,147, but I have decided not to pursue a patent for it and just publish its design so everybody can use it. Provisional patent application is just a draft and it is not examined by the USPTO.

Disclaimer: If you decide to implement this device, please make sure to do your own research to see if any similar designs or inventions have valid patents or copyrights.

I include here all design descriptions and drawings. FIG. 5 gives impression on how the device works.

BACKGROUND

According to the Fatality Analysis Reporting System (FARS), one-third of all passenger vehicle occupants who lost their lives were in vehicles that rolled over. Here are fatalities per 100,000 registered vehicles:

- Passenger cars had the lowest rate of 3.69
- Vans were similarly low, at the rate of 3.83
- Pickup trucks at 7.18
- SUVs had a much higher rate of 10.22

Car manufacturers use various solutions to reduce rollover risk. EV manufacturers place a heavy battery pack at the car floor to lower the center of vehicle gravity. Tesla X, which has a rollover risk factor around 7, has a curb weight of 2.5 tons and its battery pack weight is around 0.5 tons — that alone exceeds usual payload (useful load) for this car. Even mini or smart EV models have a 300 lb battery pack that counters the weight of two average people riding such a car. That means more energy goes into moving heavy battery packs around than into transporting passengers. Another solution to lower car rollover risk is an active suspension system that tilts the car toward a corner.

Solution presented here uses a passive Omni-wheel (it does not use torque from a car axle, and it rolls freely, led by the car wheel, over which it is mounted). It engages at an early stage of a rollover event to remove rollover fulcrum from a car wheel tire shoulder and to drain the rollover momentum. Using such an anti-rollover device opens an opportunity for lowering car battery pack weight when energy denser batteries come to the EV market. That alone can save 10–20% of energy used by EVs.

Omni-wheel was invented by J. Grabowiecki, US patent 1305535, a century ago. Since then, it has been used in many applications, even by NASA in vehicles used on other planets and in fancy robots, moving and balancing on a single Omni-wheel. All these are active Omni-wheel applications, where torque from the motor(s) is passed to the Omni-wheel to move the vehicle or robot around.

SUMMARY

Omni-wheel, mounted over a car wheel, has a rigid structure that can withstand a short-term (for a few seconds) load from a car on rare but deadly rollover occasions. In the first embodiment, Omni-wheel has a bulge/padding on one side to provide a gap between Omni-wheel and car wheel. This gap should be at least an inch, measured when an Omni-wheel is mounted, but not on the ground. And the gap can change but should not disappear when the wheels are on the ground or when rollover starts. Radius of the Omni-wheel is a bit smaller than the radius of the car wheel tire when not on the ground. On the ground, the Omni-wheel should touch but barely touch the ground, due to car tire compression at the ground. Almost all weight of the car should be carried by the car wheels. Permanent contact between Omni-wheel and the ground is needed to avoid sudden accelerations in Omni-wheel spinning. Depending on a car tire profile, the radial difference (the difference between the radiuses) of the Omni-wheel and the car wheel can vary from a quarter of an inch to an inch, or even more for heavy car types. This radial difference is approximately equal to the value of the tire compression under the car curb weight. If the radial difference is large, then either the gap between the Omni-wheel and the car wheel or the Omni-wheel width should be increased as well:

1) The greater the gap between Omni-wheel and car wheel, or the larger the width of Omni-wheel, the better lateral car stability. Restriction comes due to safety: Omni-wheels should be hidden under the car body (a solution to this is provided in the second embodiment).

2) The smaller radial difference between Omni-wheel and car wheel the better car stability. Restriction comes from: Omni-wheels should barely touch the ground, and should not carry much of the car weight.

When one side of a car is raised in the air, the car wheel tire shoulder at the ground starts playing the fulcrum role in rolling the car over. At a certain angle of inclination, Omni-wheel is involved: it removes fulcrum from the tire shoulder and takes over horizontal part of the rollover momentum by sliding, and gravity counters the rest of the momentum (its vertical part). The tire shoulder, which initiated the rollover, drains energy of the momentum through friction by loosening ground traction during sliding. Smaller radius of an Omni-wheel, compared to the car wheel tire, and rubber tread over the Omni-wheel rollers provide some shock protection before car shock absorbers are involved. And rubber tread on the Omni-wheel rollers is needed to allow compression of car tires on car braking.

In an alternative embodiment, Omni-wheel and car wheel share the same disk. It withstands greater load from a car during rollover than the first embodiment, and in mass production it costs less (with the car wheel cost accounted for). Omni-wheel is hidden under the car body due to a deep borehole in the shared disk. Cars can have either regular car wheels or wheels, whose disks are shared with Omni-wheels, just like some cars can have either wide low-profile wheels/tires or high-profile narrower wheels/tires.

DRAWINGS — FIGURES

FIG.1 Omni-wheel
FIG.2 Side view of Omni-wheel
FIG.3 Front view of Omni-wheel disk
FIG.4 Omni-wheel mounted over a car wheel
FIG.5 Anti-rollover process
FIG.6 Disk shared between car wheel and Omni-wheel

DRAWINGS — REFERENCE NUMERALS

10 Omni-wheel disk
12 Holes for mounting bolts
13 Hub
14 Groove on the disk for bearing cylinders
15 Bulge for padding Omni-wheel from the car wheel
20 Omni-wheel hoop/ring
22 Braces holding a bearing cylinder
23 Braces holding a roller
30 Roller
33 Rubber tread on a roller
40 Bearing cylinder
50 Car wheel and tire
60 Axle
70 Ground level
80 Rollover momentum
90 Drifting direction
100 Disk shared between car wheel and Omni-wheel
105 Groove for car tire
110 Borehole in shared disk

DETAILED DESCRIPTION

FIRST EMBODIMENT — FIG(S) 1, 2, 3

Omni-wheel in its center has disk 10 which is mounted on a car through hub 13 and is bolted in through the holes 12. The Omni-wheel is mounted on a car wheel side, and bulge 15 on the Omni-wheel disk provides at least 1" gap between the car wheel and the Omni-wheel. There is a groove 14 at the rim of the disk 10 for rolling bearing cylinders 40. Bearing cylinders are attached to the hoop/ring 20 with braces 22. Braces 23, on the outer side of the hoop/ring 20, hold rollers 30, which are covered with rubber tread 33.

Radius of the Omni-wheel should be a bit smaller than the car wheel tire radius, so that Omni-wheel barely touches the ground and does not carry much of the car load during normal drive. That ensures bearing cylinders 40 barely spin, and here is why:

Since Omni-wheel and car wheel travel the same distance, velocity on their perimeter is the same. But since the Omni-wheel radius is slightly smaller than the car wheel tire radius, the Omni-wheel angular velocity is a bit greater than the car wheel angular velocity. Thus, angular velocity of the hoop/ring 20, which is the angular velocity of the Omni-wheel, is a bit greater than angular velocity of disk 10, which is the angular velocity of the car wheel, on which the Omni-wheel is mounted. This small difference is picked up by bearing cylinders 40, and that is how their low spinning is ensured. Bearing cylinders 40 do not need to withstand fast spinning, but they need to be designed to withstand short-term (for a few seconds) load from the car on rare occasions, when rollover starts.

Rollers 30 barely spin, if spin at all, usually. Thus, the requirement for them is the same: withstand short-term load from the car on rare occasions, when rollover starts. There is no fast-spinning requirement for the rollers.

Omni-wheel hoop/ring 20 should be very rigid to withstand tearing stress that comes through disk 10 from the car leaning on Omni-wheel when rollover starts.

ALTERNATIVE EMBODIMENT — FIG 6

Alternative embodiment differs from the first embodiment only by disk 100 that is shared between a car wheel and an Omni-wheel: 105 is the groove for the car tire, and 14 is the groove for Omni-wheel bearing cylinders 40. When the Omni-wheel and the car wheel tire are mounted, the assembly looks like in FIG.4. This alternative embodiment withstands greater load from a car during rollover than the first embodiment can withstand, and it costs less (with the car wheel cost accounted for) in mass production. The Omni-wheel is hidden under the car body due to a deep borehole 110 in the shared disk 100. Some cars can have interchangeably wider low-profile car wheels/tires and narrower high-profile car wheels/tires. They can also have/adopt a shared-with-Omni-wheel disk as a safer alternative.

OPERATION — FIG(S) 4, 5

Sample dimensions used in FIG(S) 4, 5 show how to estimate the center of car gravity raise when rollover starts. Actual vs. sample dimensions depend on car width and on tire profile. There are two rules of thumb:

1) The greater the gap between Omni-wheel and car wheel, or the wider Omni-wheel, the better lateral car stability. Restriction comes from safety: Omni-wheels should be hidden under the car body.

2) The smaller radial difference between Omni-wheel and car wheel the better car stability. Restriction comes from: Omni-wheels should barely touch the ground and should not carry much of the car weight.

FIG.4 shows Omni-wheel during mounting on axle 60 over car wheel with a tire 50, when the wheels are still above the ground 70. Sample dimensions at FIG.4:

- Omni-wheel radius is 0.5" smaller than the car wheel tire radius
- Rubber tread on the roller is 0.5" thick
- Roller (including tread) has a diameter of 3"
- Gap between Omni-wheel and car wheel is 1"

FIG.5 shows rollover in progress at the moment when the tire shoulder, which is still on the ground 70 and acts as the fulcrum, is about to lose the ground, and the fulcrum is about to shift to the Omni-wheel. But because Omni-wheel rolls freely in any horizontal direction, it will steal the horizontal part 90 of the rollover momentum 80, and the gravity will counter the rest (the vertical part of the momentum). The tire shoulder, which initiated the rollover, drains energy of the momentum through friction by loosening ground traction during sliding. By loosening ground traction, it reminds of ABS (Anti-Lock Braking System) that prevents wheel locking.

Let’s see how high the car’s gravity center can rise. Distance between the fulcrum point and the Omni-wheel ground contact point is about 2.5" (it comes as a sum of the roller radius 1.5" and 1" gap between the wheels). Let’s assume that the roller rubber tread is squeezed from 0.5" thickness to 0.25" thickness under the car weight at the ground. Then the difference between the car wheel tire radius and the Omni-wheel radius at the ground will increase from 0.5" to 0.75" (the increase of 0.25" is equal to the compression of the roller tread). All these numbers and numbers for the ratio below are shown in FIG.5. Let’s assume distance between car wheels plus one width of a tire is 5', then we can find that right side of the car is raised by about 1.5' based on the ratio:

0.75" / 2.5" = 1.5' / 5'

For any other car size and another tire profile, sample values should be replaced with the real values, and the ratio explained above can be used to estimate the inclination of the vehicle. Now, since the center of gravity is in the middle of the car width, it raises by not more than half of the calculated 1.5', which is 0.75'. Thus, Omni-wheel limits sample car center of gravity raise by 0.75'. If there is a need to reduce this value, it can be done by increasing the gap between Omni-wheel and car wheel, or / and by increasing the width of the Omni-wheel (which is equals to the diameter of the roller with tread).

CONCLUSION, RAMIFICATIONS, AND SCOPE

Passive Omni-wheels, mounted over car wheels, add to the car stability. This application has nothing to do with active Omni-wheel applications where Omni-wheels are the car wheels. Passive Omni-wheel is a simple and reliable mechanical device which can be designed for any car model and any tire profile. It has no controls or power transmission gears to fail. It opens an opportunity for car manufacturers to reduce car curb weight, thus improving car energy efficiency. With energy denser batteries and with new carbon-based materials coming, the Omni-wheel solution for car stabilization can meet the demand for reducing car curb weight. Currently, for example, Tesla X has a curb weight of 2.5 tons and it uses a battery pack that weighs more than 5 passengers with a luggage, thus, energy spent to carry a car or a battery pack itself is way more than energy used for moving passengers. And since only a fraction of electricity is green (60% of electricity produced in the US is by methane or coal burning and 20% by uranium fission), lowering the weight of cars and of car battery packs seems to be the best way to lower the carbon footprint of transportation. One of the side effects of lowering car curb weight is raising the center of gravity of the car with passengers, due to the high position of passenger bodies. Thus, lowered curb weight might increase rollover risk for a loaded car. That is where a presented anti-rollover device comes to rescue.

CLAIMS

These are free for everybody to implement:

1. Anti-rollover device for a car, comprising an Omni-wheel mounted over a car wheel
, wherein said Omni-wheel has smaller radius than said car wheel tire
, wherein said Omni-wheel barely touches the ground when said car wheel tire is compressed under said car curb weight
, whereby low spinning of bearing cylinders of said Omni-wheel is achieved due to small radial difference between said Omni-wheel and said car wheel tire
, whereby, early in a rollover event, said Omni-wheel removes the fulcrum from said car wheel tire shoulder, starts sliding, and drains energy of the rollover momentum through said tire shoulder friction by loosening ground traction
, whereby gravity brings said car back to the ground.

2. Anti-rollover device for a car, comprising an Omni-wheel and a disk shared between said Omni-wheel and a car wheel
, wherein borehole in said disk is deep enough to hide said wheels under a car body
, wherein said disk has two grooves at its rim
, wherein the inner groove of said two grooves is for a tire and the outer groove is for said Omni-wheel
, wherein said Omni-wheel has smaller radius than said car wheel tire
, wherein said Omni-wheel barely touches the ground when said car wheel tire is compressed under said car curb weight
, whereby low spinning of bearing cylinders of said Omni-wheel is achieved due to small radial difference between said Omni-wheel and said car wheel tire
, whereby, early in a rollover event, said Omni-wheel removes the fulcrum from said car wheel tire shoulder, starts sliding, and drains energy of the rollover momentum through said tire shoulder friction by loosening ground traction
, whereby gravity brings said car back to the ground.

DRAWINGS