A tilting three-wheeler, tilting trike, leaning trike, or even just tilter, is a three-wheeled vehicle and usually a narrow-track vehicle whose body and or wheels tilt in the direction of a turn.Such vehicles can corner without rolling over despite having a narrow axle track because they can balance some or all of the roll moment caused by centripetal acceleration with an opposite roll moment caused by gravity, as bicycles and motorcycles do. This also reduces the lateral acceleration experienced by the rider, which some find more comfortable than the alternative. The narrow profile can result in reduced aerodynamic drag and increased fuel efficiency. These types of vehicles have also been described as "man-wide vehicles" (MWV).
As with tricycles that do not tilt, there are a variety of feasible choices of how the wheels are arranged, which wheels are steered, and which wheels are driven. In addition, there are a variety of feasible choices for which wheels tilt and which do not.
Because this is an emerging field with many different vehicle configurations, many different individual contributors, and not yet any clearly dominant technology, there is a great deal of potentially confusing terminology in use:
The potential benefits of tilting, compared to the rigid alternative, include:
The drawbacks of tilting, compared to the rigid alternative, include:
As with tricycles in general, the two main wheel layouts are:
Twinned Wheel Rule: In many countries aligned to EU regulations, an arrangement of two wheels on the same axle [not necessarily maintained co-axial], is treated as one wheel provided they are spaced no further apart than 460 mm (18 in) between contact patch centers. This has the effect of allowing vehicles complying with this dimensional limit to be classified as motorcycles. Therefore, such vehicles would be subject to all the technical prescriptions applicable to motorcycles rather than motorised tricycles or four-wheeled vehicles.
Rear-wheel steering tends to be directionally unstable, and so the vast majority of trikes employ front-wheel steering.A notable exception is the Toyota i-Road. In the case of two wheel steering, some accommodation is usually made to account for the different radii of their paths, such as Ackermann steering geometry.
Either the front or rear wheel(s) may be driven, but driving a wheel near its power source is usually simpler than driving a wheel at the other end of the vehicle, driving a single wheel is usually simpler than driving a pair of wheels, and driving a wheel that remains aligned with its power source is simpler than driving a wheel that tilts or steers relative to its power source. Two common drive configurations are:
Less common drive configurations include:
As with tricycles in general, seating may be upright, as on the Piaggio MP3, or recumbent, as on the MEV Tilting Trike. If the vehicle is designed to accommodate a second rider, the seating is usually arranged in tandem to maintain the narrow profile, as on the CLEVER.
The rider may be fully exposed, as on the Tripendo, behind a fairing or windscreen, as on the Piaggio MP3, under a canopy, as on the Honda Canopy, or fully enclosed, as on the Vandenbrink Carver.
Power may come from the rider, as on the Tripendo, from batteries and electric motors, as on the Toyota i-Road, or from conventional internal combustion engines, as on the Yamaha Tricity.
Any number of the wheels can tilt, and advantages to tilting wheels are that the wheels do not need to bear large side loads,and the tires mounted on them can generate camber thrust, which can reduce the need for a slip angle to generate cornering force. Configurations include:
In the case where the two side-by-side wheels tilt, some mechanical linkage is necessary to coordinate their tilting. Implementations include:
Due to the tilting, there is not necessarily any side-to-side load transfer between the wheels in cornering, so the rule of thumb about tadpoles understeering and deltas oversteering does not necessarily apply.If the tilting mechanism has some limitation on tilt angle, then the lateral acceleration the vehicle can experience without rolling over will be a function of maximum tilt angle possible, axle track, and center of mass location.
In all cases, the tilting mechanism may simply be lockable to facilitate keeping the vehicle upright when stopped or parked.Also, passive or active tilting systems cannot simply counter the roll moment caused by gravity, as this has been shown to make a vehicle practically unsteerable, although there is ongoing debate about whether it is truly unsteerable or not.
Enclosures can protect rider(s) from the weather and allow for reduced aerodynamic drag.
Steering requires that the axle(s) of the front wheel(s) form a finite angle with the axle(s) of the rear wheel(s), i.e. not be parallel. This misalignment may be accomplished in a variety of ways, and usually the front wheel(s) rotate about a steering axis relative to the rest of the vehicle and the rear wheel(s). One notable exception, already mentioned above, is the rear-wheel-steered Toyota i-Road.
Some Tilting trikes are forced-tilted, such as the Carver, where the countersteering is not controlled by the operator. Some versions of the model introduced automatic countersteer to increase tilt speed and reduce the force required to tilt the vehicle. Other forced-tilted vehicles may incorporate automatic countersteering.A prototype tilting multi-track free leaning vehicle was developed in 1984 that employs automatic countersteering and does not require any balancing skills.
A larger range of tilting three-wheelers has appeared in the recent years and use manually controlled countersteering like a motorbike, such as the Piaggio MP3 or Yamaha Niken.
One vehicle variation is to control the steered wheel(s) indirectly by tilting them, along with the vehicle body, and this system is known as free to castor [FTC]. The directional control of a FTC wheel is not particularly strong, as demonstrated by the wheels on a shopping cart, and the castored wheel(s) will turn due to any applied side loading. If the steering axis is not vertical, however, the directional stability above about 10 mph (16 km/h) is very strongly controlled by the dynamic forces. If the castored wheel is attached to the front of a narrow tilting vehicle the castor will automatically place itself on the correct steer angle for the tilt and the speed of the vehicle. A system can be used below 10 mph (16 km/h) to improve slow-speed performance where the steerable wheel(s) are progressively captured to the vehicle tilt action as vehicle speed decreases.
An anti-lock braking system (ABS) is a safety anti-skid braking system used on aircraft and on land vehicles, such as cars, motorcycles, trucks, and buses. ABS operates by preventing the wheels from locking up during braking, thereby maintaining tractive contact with the road surface and allowing the driver to maintain more control over the vehicle.
A recumbent bicycle is a bicycle that places the rider in a laid-back reclining position. Most recumbent riders choose this type of design for ergonomic reasons: the rider's weight is distributed comfortably over a larger area, supported by back and buttocks. On a traditional upright bicycle, the body weight rests entirely on a small portion of the sitting bones, the feet, and the hands.
A tricycle, sometimes abbreviated to trike, is a human-powered three-wheeled vehicle.
Steering is a system of components, linkages, and other parts that allows a driver to control the direction of the vehicle.
A sidecar is a one-wheeled device attached to the side of a motorcycle, scooter, or bicycle, making the whole a three-wheeled vehicle. A motorcycle with a sidecar is sometimes called a combination, an outfit, a rig or a hack.
A single-track vehicle is a vehicle that leaves a single ground track as it moves forward. Single-track vehicles usually have little or no lateral stability when stationary but develop it when moving forward or controlled. In the case of wheeled vehicles, the front and rear wheel usually follow slightly different paths when turning or when out of alignment.
Suspension is the system of tires, tire air, springs, shock absorbers and linkages that connects a vehicle to its wheels and allows relative motion between the two. Suspension systems must support both road holding/handling and ride quality, which are at odds with each other. The tuning of suspensions involves finding the right compromise. It is important for the suspension to keep the road wheel in contact with the road surface as much as possible, because all the road or ground forces acting on the vehicle do so through the contact patches of the tires. The suspension also protects the vehicle itself and any cargo or luggage from damage and wear. The design of front and rear suspension of a car may be different.
The caster angle or castor angle is the angular displacement of the steering axis from the vertical axis of a steered wheel in a car, motorcycle, bicycle, other vehicle or a vessel, as seen from the side of the vehicle. The steering axis in a car with dual ball joint suspension is an imaginary line that runs through the center of the upper ball joint to the center of the lower ball joint, or through the center of the kingpin for vehicles having a kingpin.
Countersteering is used by single-track vehicle operators, such as cyclists and motorcyclists, to initiate a turn toward a given direction by momentarily steering counter to the desired direction. To negotiate a turn successfully, the combined center of mass of the rider and the single-track vehicle must first be leaned in the direction of the turn, and steering briefly in the opposite direction causes that lean. The rider's action of countersteering is sometimes referred to as "giving a steering command".
A three-wheeler is a vehicle with three wheels. Some are motorized tricycles, which may be legally classed as motorcycles, while others are tricycles without a motor, some of which are human-powered vehicles and animal-powered vehicles.
The CLEVER is a type of tilting three-wheeled motor vehicle that was developed in a collaboration between the University of Bath, BMW and a number of other partners from across Europe. CLEVER is designed as an alternative to conventional means of personal urban transport. The narrow body endows it with some of the manoeuvrability and congestion avoiding capability of a motorcycle, whilst offering comparable weather and impact protection to a car. Carbon emissions are reduced as a function of low weight and a small frontal area. The narrow track width requires that CLEVER tilts into corners to maintain stability; thus it is fitted with a Direct Tilt Control (DTC) system that uses hydraulic actuators linking the cabin to the non-tilting rear engine module.
Bicycle and motorcycle dynamics is the science of the motion of bicycles and motorcycles and their components, due to the forces acting on them. Dynamics falls under a branch of physics known as classical mechanics. Bike motions of interest include balancing, steering, braking, accelerating, suspension activation, and vibration. The study of these motions began in the late 19th century and continues today.
A handcycle is a type of human-powered land vehicle powered by the arms rather than the legs, as on a bicycle. Most handcycles are tricycle in form, with two coasting rear wheels and one steerable powered front wheel. Despite usually having three wheels, they are also known as handbikes.
Bicycle and motorcycle geometry is the collection of key measurements that define a particular bike configuration. Primary among these are wheelbase, steering axis angle, fork offset, and trail. These parameters have a major influence on how a bike handles.
A scooter is a motorcycle with an underbone or step-through frame, a seat, and a platform for the rider's feet, emphasizing comfort and fuel economy. Elements of scooter design were present in some of the earliest motorcycles, and motor scooters have been made since at least 1914.
A motorized tricycle, motor trike, or motortrycle is a three-wheeled vehicle based on the same technology as a bicycle or motorcycle, and powered by an electric motor, motorcycle, scooter or car engine.
The Yamaha Tricity is a tilting three-wheeler motor scooter made by Yamaha Motor Company. It is part of Yamaha's LMW offering along with the Niken.
A narrow-track vehicle is a vehicle that leaves a narrow ground track as it moves forward. Narrow-track vehicles may have lateral stability when stationary but usually lean into turns to prevent falling towards the outside.
The Yamaha Niken is a 845 cc tilting three-wheeler motorcycle, manufactured since 2018 by Yamaha Motor and sold worldwide.
Passive tilt control. The 3Ws with an additional degree of freedom that allows the driver to tilt the vehicle during turning are categorised as passive tilt-controlled 3Ws. Active tilt control. Real-time computation of cornering force and gravitational force, acting at the CG, needs to be carried out to evaluate the required tilt angle during the automatic control of actuators.
"Twinned wheels" means two wheels positioned on the same axle, which are considered to be one wheel, whereby the distance between the centres of the areas of contact with the ground is equal to, or less than 460 mm.
Sharp steering movements throws your weight with the turn and upsets the stability of the trike.
At slow speeds, the single rear wheel does the steering.
Camber thrust is the ability of a tire to generate force when leaned over during a turn.
The single front wheel layout naturally oversteers and the single rear wheel layout naturally understeers.
as is the case with passive tilt control, an additional stabilisation mechanism is required at very low speeds and when stationary.
[Note, the uncontrollability at zero gravity is only true for the linearized inverted pendulum. The arguments precluding control are heavily dependent on the linearity of the system, and the non-linear inverted pendulum in zero gravity seems to be controllable. Indeed, simulations by Philip James ... demonstrate that with appropriate wiggles of the base, a constant average acceleration of the base can be maintained while holding the pendulum angle in a bounded range.]