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The Raised Front: The Physics and Forms (Part IV)

By now you are introduced to all the facts about what a wheelie is and how many types are documented. Saying this doesn’t mean that this is all there is to wheelies. In the past articles, it was mentioned how the most types of wheelies can be performed in two forms. Also learning about the beginner, intermediate and professional wheelies doesn’t just cover the universe of wheelies. In this article, we will go even beyond the types and difficulty levels rather than do Dexter’s lab analysis of the word wheelie.

A wheelie is a case of dynamic equilibrium which is controlled by the following factors:

  • Throttle input rotates the rear wheel of the motorcycle and maintains instantaneous momentum when the motorcycle is moving.
  • Foot Braking is done to counter either tip-off or the dropping of the front wheel.

A wheelie generally takes place in two steps:

I] When the wheelie is to be initiated,

  1. Inertia forces with throttle feed being maximum and minute input of foot braking
  2. Specific wheelies that have a transition stage amongst them have other variable forces.

II] Once the wheelie is achieved, the next step is to sustain it.

  1. Balancing the moments over the pivot which essentially is the rear wheel when the wheelie is in action.
  2. Inertia force which is governed by the throttle feed and the foot braking as per requirement, primarily acting on the rear wheel during a wheelie. The front-wheel acts like a counter mass in that state.
  3. Forces due to gyroscopic effect.
  4. Dynamic factors at random (unevenness of road surface, specific wheelie conditions, aerodynamic drag, eccentric cases such as the asymmetry of the motorcycle in question, handlebar placement in specific wheelies).

In the picture above you can see how wind as one dynamic factor can influence a rider performing a wheelie when the rider is either facing the wind or is in its flow.

In the picture above, you can see how wind can be a significant factor when it is hitting the cross-section of a bike while in a state of a wheelie. Imagine the balancing effort required by a rider in say a No Hands Motorcycle Wheelie!

We at MotorbikesIndia.com went all guns blazing with Protosign Designs Private Limited to design this world exclusive research so that our readers can understand how aerodynamic drag effects a Basic Straight-Line wheelie as an example. The above photos are the engineering and scientific analysis known as CFD (Computational Fluid Dynamics) used by 2-wheeler designers globally to figure out the effect of air on a motorcycle cutting through it. This is the same analysis which is an important part of motorcycle development for any company trying to design high-speed machines like Ducati Supersport, Suzuki Hayabusa, or the tarmac shredding Kawasaki Ninja H2 way before deciding to manufacture it.

Moving on, in the real world actually a motorcycle is not engineered to be on a single wheel. In terms of the physiology of a motorcycle, the factors which continuously bar it to attain a state of wheelie are as follows:

Center of Gravity: Physics says the lower the mass concentration of an object, the more stable it is. Remember how you could almost never knock down that inflatable clown to the ground? The same principle is applicable to a different class of motorcycles which are purpose defined. Lower the center of gravity, the more stable the bike is which in turn makes it tougher to be pulled in a condition of a wheelie. Since you are trying to take a body out of a stable condition to execute a wheelie, the forces of gravity would always try to bring a body to its most stable position which is the 2-wheeled riding position.

In the photo above you can observe 4 different classes of motorcycles with different riding positions which would give an idea of where the center of gravity would roughly lie for each kind along with the rider in the equation.

Above you can see how different classes of motorcycles have distinct ground clearance and variable center of gravity position as an attribute to its design which is purpose-specific.

The shape of the pillion seat: As per earlier mention in the article, http://www.motorbikesindia.com/a-weapon-to-throttle-sfr-bike-cosmetic-functional-mods-part-i/ where the rider’s sitting position is actually shifted onto the seat more or less, not having the right seat support would cause the rider to lose abdominal grip resulting in a crash. A good seat angle also contributes to the angle of the wheelie. One can imagine how it’s next to impossible to perform a No Hands Motorcycle wheelie on an enduro or a dual-sport motorcycle. Notice how flat the seat contour is.

Asymmetric Exhaust Systems: Conventionally, a motorcycle’s geometry isn’t symmetric. It means that most bikes don’t have a 50:50 weight distribution if you divide the bike from a top view in two halves. Close observation will show how an exhaust for a good 90% motorcycles is onto one side only. Since exhausts do have some weight in them, in a wheelie condition they tend to pull a bike towards them.

Wheelbase: The math for this is pretty simple, the longer the wheelbase of a motorcycle, the more difficult is it to pop a wheelie. Conventionally, the longer wheelbase makes a motorcycle much more stable and straight line-oriented. This also means that the bike is much more anti-wheelie oriented in nature. One can see why drag bikes always have a long wheelbase. On the other hand, the shorter the wheelbase the more wheelie friendly the motorcycle is. Notice how bikes such as the Kawasaki KLX 450R or a Triumph Daytona are much more wheelie happy than a Honda Goldwing or a Harley Davidson CVO.

Tire Width: The difficulty experienced by a person balancing a wheelie on say a Hero Splendor’s rear tire (80 mm tire width) might not meet the eye of a regular. Just to compare don’t you think that balancing a wheelie on a bike like TVS Apache RTR 160 4V (110 mm tire width) which is a 30 mm wider would be easier? Easier here stands for the fact that leaner the tire, more translatory motion is it likely to experience and slip in a condition of wobbling. On the other hand, wider the tire, lesser is the chances of side by side moment of the bike (averts snake path for a bike) making it better at producing a more stable wheelie than the thinner tire contender.

Displacement of an engine: Though this motorsport is much more about the rider than the machine the higher displacement and torque received by the rear wheel, the easier it is to perform a wheelie. One must have come across automobile magazine covers and articles where the rider is performing wheelies on a bike. What is to be very carefully inferred is that they tend to for maximum times do this on a heavier cc bike, Examples can be anything above 150cc. People are awed by it but don’t tend to realize that it isn’t the capability of the rider altogether in that case always but a big effort by the bigger torquey engines. When was the last time you saw a journalist perform a wheelie on a 100 cc bike? Also, if this still needs some proof, one should check the Ducati Wheelie Control (DWC) system, how it works and why is it needed in a bike such as Ducati Panigale. V4. This also begs the question of why small 100-125cc bikes don’t have such systems?

Now, to round up the two forms, there are two different forms of a wheelie:

Straight Line Wheelie: This form of wheelie is regarded as one where the whole act of wheelie is potentially in a single direction, Even if it might look like that the motorcycle’s tire is not maintaining one specific line but weaving to and fro about a mean line, the form is considered a straight line only. This is much simpler of both the forms in the context that you are just combating the force of gravity pulling the front wheel back to the ground.

Check out this amazing video of Flamingo Straight-Line Wheelie performed by Rohitesh Upadhyay who has just bagged a set of world records for India.

Our friends from Protosign Designs Private Limited prepared this simulation of a Basic Straight-Line Wheelie for us to help better explain our rider about all kinds of effects that a rider and the bike experience together.

Circle Wheelie: This form of wheelie is much difficult and takes time to learn. This form of wheelie is performed in a circular path. The bike’s motion in a circular fashion creates a centripetal force towards the locus of the circle. The act of maintaining the counter mass to balance a wheelie and then turn the whole bike using the unsteerable rear wheel is more than a challenge. In this particular case the amount of angle that the side of the motorcycle would be inversely proportional to the terminal velocity.              

Angle in Circle is the angle formed between the bike’s central axis and the surface. Leaner the bike is (lesser the angle) towards the surface, more velocity would the biker need to sustain the circle wheelie.

Terminal velocity for the circle wheelie is a point post in which the centrifugal force will throw off the biker off the bike.

Have a look at this video of Flamingo Circle Wheelie performed again by Rohitesh Upadhyay.

Protosign Designs Private Limited was generous enough to prepare this simulation of a Basic Circle Wheelie to help understand all kinds of effects on a rider and the bike.

If you wish to trace how much centripetal force is being experienced by a rider doing a circle wheelie, use the equation below:

F=MV2/R                                                 

F: Centripetal Force

M: Mass of the bike

V: Velocity at the instant

R: Radius of the Circle made by the bike

Hence, we can summarize both types of wheelies with this chart:

Combination Wheelies: If you thought Professional wheelies were the final stage of it all then you are sorely mistaken. In tournaments, you are not just judged on the basis of the type, form, or difficulty level of a wheelie but also how are you able to perform different combos. Here, we have Rohitesh Upadhyay, a two-times world record holder from India demonstrating a set of combination wheelies.

To give a fairer idea, SFR judging criteria is something like ice skating, gymnastics or even dancing where you are not just judged on what you can do but also how effortless you are in transition from one trick to the other. Now, combos need not always be of a specific set but are always as per rider who is to perform it. Saying this, there are more than a million permutations and combinations one can attempt.

Finally, this concludes a dimension of Sportbike Freestyle Riding (SFR), Sportbike Freestyle Riding (SFR) is professional motorsport which is to be practiced as per specific safety norms. This includes everything from proper safety gear, motorcycle modifications, a controlled environment, and a lot more. Practicing or even mere imitating an SFR trick on a public road without legal consent is a punishable offense.

Also, a shoutout to Protosign Designs Private Limited, do check out their page on LinkedIn and Instagram. They are into rendering amazing Mechanical Engineering solutions and specialized 3D printing services.

LinkedIn: https://www.linkedin.com/company/protosign-designs-private-limited/

Instagram: https://www.instagram.com/protosign_designs/

Stay tuned to the SFR junction for other such informative and exciting takes on this amazing motorsport. Stay safe and ride on!

Disclaimer: This article was prepared or accomplished by it's author in their personal capacity. The opinions expressed in this article are the author's own and do not reflect the view of Motorbikes India or it's owners.

The views and opinions expressed on this web site are soley those of the original authors and other contributors. These views and opinions do not necessarily represent those of Steve Gerweck, the GERWECK.NET staff, and/or any/all contributors to this site.

About Gaganbir Singh

Gaganbir Singh is an avid automobile enthusiast with an experience in freelance auto journalism. Having chaired SAE (Society of Automobile Engineering) collegiate chapter during his graduation, he has had the chance to experience the genre hands-on. Interested in mechanics of how things work, he has spent considerable time working with some of the most esteemed names in the auto industry. Currently self-employed and exploring the palindrome by managing the best set of Sportbike Freestyle Riding extreme athletes of the country is his USP. Safety is a great deal of importance to him in the automotive spectrum.

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