Tilting three-wheeler

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Tripendo recumbent tricycle, a tilting three-wheeler (2F3T)

A tilting three-wheeler, or tilting trike is a three-wheeled vehicle whose body and or wheels tilt in the direction of a turn,[1] and is usually a narrow-track vehicle. Such vehicles can corner without rolling over despite having a narrow track because they can balance some or all of the tipping moment caused by centripetal acceleration with an opposite tipping moment caused by gravity, as bicycles and motorcycles do.[1] 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.[2] These types of vehicles have also been described as "man-wide vehicles" (MWV).[2]

As with tricycles that do not tilt, there are a variety of feasible choices of which wheels are steered, which wheels are driven, and where the three wheels are located. In addition, there are a variety of feasible choices for which wheels tilt and which do not.

Configurations[edit]

Wheel layout[edit]

As with tricycles in general, the two main wheel layouts are:

Steering[edit]

Rear-wheel steering tends to be directionally unstable, and so the vast majority of trikes employ front-wheel steering.[3] 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.

Drive[edit]

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:

  • Drive two tilting wheels in the rear.[4]
  • Drive one tilting wheel in the front. One example is the Rose-Hulman Ragnarök pictured below.

Seating[edit]

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.

Enclosure[edit]

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[edit]

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.

Tilt[edit]

Any number of the wheels can tilt, and advantages to tilting wheels are that the wheels do not need to bear large side loads,[1] and the tires mounted on them can generate camber thrust, which can reduce the need for a slip angle to generate cornering force.[5] Configurations include:

  • one wheel in front and only the front tilts, referred to as 1F1T (i.e. one front one tilts). Notable examples include the Ariel 3, MEV Tilting Trike, Honda Canopy, Vandenbrink Carver, and CLEVER.
  • one wheel in front and all three wheels tilt, referred to as 1F3T (i.e. one front three tilt). An example can be seen in the Rose-Hulman Ragnarök pictured below.
  • two wheels in front and only the single rear wheel tilts, referred to as 2F1T (i.e. two front one tilt).[6]
  • two wheels in front and all three wheels tilt, referred to as 2F3T (i.e. two front three tilt). Notable examples include the Piaggio MP3, Yamaha Tricity, and Toyota i-Road.

In the case where the two side-by-side wheels tilt, some mechanical linkage is necessary to coordinate their tilting. Implementations include:

  • Some form of one or more parallelograms, such as on the Tripendo pictured above and the Mercedes-Benz F300 Life Jet Concept Vehicle pictured below. This has been employed on tadpole and delta trike configurations.
  • Some form a pair of swingarms, possibly connected by some form of bell crank.[7] This tends to be employed on delta trike configurations.
  • Some form of crank, in which case the two wheels are not directly side-by-side.[1] This tends to be employed on delta trike configurations.

Due to the tilting, there is not necessarily any side-to-side load transfer between the wheels in cornering, so the rule about tadpoles understeering and deltas oversteering does not necessarily apply.[8] 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.[8]

Active or passive tilt control[edit]

Tilting may be either passive, as with a bicycle or motorcycle, in which case countersteering is required,[9] or active, where the rider or some other controller actively sets the lean angle directly. An active controller may calculate a desired lean angle from some combination of lateral acceleration and steering input, and it may set a desired lean angle with some combination of mechanical, electrical, or hydraulic actuators.[10] In any case, active tilting system cannot simply counter the roll moment caused by gravity, as this has been shown to make a vehicle unsteerable.[11]

  • Unenclosed vehicles may employ passive tilt control because the rider can still put a foot down when stopped. The rider is responsible for controlling tilt just as they would on a two-wheeled bicycle or motorcycle.
  • Enclosed vehicles, in which the rider cannot reach the ground, must provide come kind of active tilt control, either automatically or under rider control, to keep the vehicle upright when stopped.

In either case, the tilting mechanism may be lockable to facilitate keeping the vehicle upright when stopped or parked.[12]

Countersteering[edit]

Tilting trikes that are forced-tilted, such as the Carver, are tilted without countersteering the control and are not balanced by the operator. Later versions of the Carver introduced automatic countersteer to increase tilt speed and reduce the force required to tilt the vehicle. Other forced-tilted vehicles may incorporate automatic countersteering.[13] A prototype tilting multi-track free leaning vehicle was developed in 1984 that employs automatic countersteering and does not require any balancing skills.[14]

Use of 'extra' wheel[edit]

There is no general agreement on how much, or even what use to make of the third wheel on a tilting trike. Sometimes it does little more than a kickstand with a caster, employed at low speed. These vehicles are called free-leaners and they must be balanced and leaned into a turn with countersteering, just as with motorcycles or other single-track vehicles. Free-leaners can feel more comfortable because the net ground reaction force remains aligned with the midplane of the vehicle and riders to not experience lateral forces, as they do in non-tilting vehicles. Most motorcycles using this technology are scooters. According to the manufacturers' marketing these three-wheelers are more stable, have a better weight distribution and handle poor road surfaces better compared to a standard two-wheeled scooter.

Other tilting trikes use the third wheel to resist wind loads and force a faster lean to set up for a fast corner or emergency lane change. Opinion is divided on how best to control this benefit, and various electric and hydraulic systems have been employed to create specific tilting behaviour, with notable success on the Carver. An alternative is for the driver to control the tilt only, and the chassis steers automatically. This may be easier to learn for drivers.

Examples[edit]

See also[edit]


References[edit]

  1. ^ a b c d Stephen Nurse, Mark Richardson, and Robbie Napper (September 2015). "Tilting Human Powered Trikes: Principles, Designs and New Developments". Australasian Transport Research Forum. Retrieved 2018-10-18.
  2. ^ a b Pauwelussen, J.P. (1999). "The dynamic behaviour of man-wide vehicles with an automatic active tilting mechanism". TUDelft. Retrieved 2018-11-12.
  3. ^ Timothy Smith (January 30, 2009). "This a description of how to build a Rear Wheel Steering Front Wheel Drive Trike". International Human Powered Vehicle Association. Retrieved 2018-10-27. Sharp steering movements throws your weight with the turn and upsets the stability of the trike.
  4. ^ Edelmann, Plöchl, and Lugner (May 18, 2011). "Modelling and analysis of the dynamics of a tilting three-wheeled vehicle". Multibody System Dynamics. doi:10.1007/s11044-011-9258-7. Retrieved 2018-11-15.
  5. ^ Dan Roe (November 4, 2016). "This Professor's Bike Experiments Might Change the Way You Ride". Bicycling. Retrieved 2018-11-05. Camber thrust is the ability of a tire to generate force when leaned over during a turn.
  6. ^ Sahil, Oza, and Malankiya (2015). "Design and Stability of Recumbent Tricycle" (PDF). ResearchGate. Retrieved 2018-11-02.
  7. ^ Ben Coxworth (March 11, 2011). "Deliver-E Trike quietly takes on uneven ground". New Atlas. Retrieved 2018-10-27.
  8. ^ a b Robert Q. Riley and Tony Foale. "The Dynamic Stability of Three-Wheeled Vehicles in Automotive-Type Applications". Robert Q. Riley Enterprises. Retrieved 2018-11-05. The single front wheel layout naturally oversteers and the single rear wheel layout naturally understeers.
  9. ^ Berote, van Poelgeest, Darling, Edge, and Plummer (2014). "The Dynamics of a Three-Wheeled Narrow-Track Tilting Vehicle". ResearchGate. Retrieved 2018-11-02.
  10. ^ Adrian Padeanu (May 2, 2018). "An A-Class-powered three-wheeler with RWD and a body that leaned into bends". Motor1.com. Retrieved 2018-10-27.
  11. ^ O. Dong, C. Graham, A. Grewal, C. Parrucci, and A. Ruina (September 30, 2014). "A bicycle in zero gravity can be balanced or steered but not both" (PDF). Vehicle System Dynamics. Bibcode:2014VSD....52.1681D. doi:10.1080/00423114.2014.956126. Retrieved 2018-11-06.
  12. ^ Adam Ruggiero (March 18, 2015). "Future Of Human Powered Transport Is A Trike". GearJunkie. Retrieved 2018-10-27.
  13. ^ Poelgeest, A; Edge, K. A.; Darling, J. Development of a Steer Tilt Controller for a Three Wheeled Tilting Vehicle.
  14. ^ Mike McCarthy (January 1987). "Bankable future for leaning car". Wheels Magazine. pp. 12–13. Retrieved 2014-11-18.

Bibliography[edit]