PTV Plan-Form-Design Pros & Cons:
Delta Trike VS Tadpole Trike
There are many discussions documented on the World Wide Web regarding the pros and cons of delta trike versus tadpole trike designs. Those many designs are not referenced here. Instead, you are urged to study those documented discussions and make your own conclusions. Many of these discussions are based on the conventional design layout of recumbent delta trikes, designs that typically, if not virtually always, place the front wheel well in front of the occupant. In the delta/tadpole comparisons, the front wheels are closer to the occupant, a layout that has been defined by the biking community to be a more operationally stable configuration. In addition, both of the aforementioned designs have stability concerns during rapid steering and cornering maneuvers in addition to yaw oscillation while the occupant is pedaling. This ‘flip over’ characteristic is similar to the inherent issues with the original 3-wheeled All Terrain Vehicle (ATV) designs. It is well known that the only counter to this instability is two fold, lower the center of gravity (CG) of the vehicle AND utilize vehicle/wheel tilt during cornering maneuvers (similar to Motocross motorcycle racing).
The term ‘velomobile’ has emerged as the current description of a tadpole trike that is fitted with some sort of occupant shell. Some velomobile designs are simply streamlined shells; shells that do not really provide inclement weather protection and/or shells that are quite difficult to either get into (ingress) or get out of (egress). An increasing number of velomobile shells are being designed with weatherproof cockpits, basically hinged canopies, but still ingress or egress is not simple. Clearly, the emerging velomobile market is becoming quite sophisticated and as a result increasingly expensive.
In order to make any kind of valid vehicle design comparison, the critical decision factors that enter into a design evaluation need to be well defined. The following list, albeit not necessarily complete from everyone’s viewpoint, identifies those vehicle qualities that are important (maybe even critical) in any design evaluation. Structural integrity, safety and efficiency are foundations of good design and engineering. Marketability, life cycle management, sustainability, serviceability and beauty are important factors in the quality of a product to serve humanized technology.
1. Safety, is the vehicle designed with the occupant’s safety having been carefully considered and provided for within the limits of such a vehicle’s design constraints?
2. Visibility, does the occupant have the confidence of knowing any and all of the surrounding traffic conditions?
3. Stability, is the vehicle ‘fun and exciting’ to drive or is the vehicle ‘constantly having to be controlled?’
4. Aesthetics, does the body form convey the essence and emotion of personal independent human transportation elegance, structural order, speed, efficiency, ecology, fun and forward thinking as well as sculptural beauty and the state of being cool?
5. Intelligence, does the vehicle have tightly integrated and highly functional ergonomics and electronic controls?
6. Occupant Comfort, can the vehicle be occupied for long periods of time without sacrificing occupant comfort? This includes, ventilation, adequate seat profile adjustment, foot rests, effective occupant restraint, seat anthropometrics and head support?
7. Driving Ergonomics, does the vehicle provide an easily readable cockpit display, simple vehicle controls for steering/braking/lighting, and efficient operation?
8. Serviceability, does the vehicle provide easy access to serviceable items, including lighting replacement, seat adjustment, brake pad replacement, battery charging/replacement (assuming vehicle is or has an electrically powered mode of operation), tire replacement, shock (ride) adjustment, etc?
9. Upgradeability, can the vehicle be technologically upgraded as new and better components are developed and are available? This may include some type of electric /ICE (Internal Combustion Engine) powered hybrid (Propane or LNG) to provide substantially increased driving range.
10. Economics, is the vehicle’s initial purchase economically justifiable and most importantly is the operation, maintenance, and upgradeability of the vehicle economical? This includes how easily important parts (i.e., exterior body) can be replaced due to unforeseen damage due to weather or driving circumstance.
Why the REDBUD™ PTV-G™
The REDBUD™ PTV-G™ has, by design, incorporated a number of features that directly address these ten design issues. The most significant design feature of the REDBUD™ PTV-G™ is the ‘articulated steering’ vehicle design that utilizes both lean and tilt geometry, in both the front and rear sections, to provide extremely stable driving maneuvering and safety. The articulated steering (located immediately behind the occupant) and lean and tilt are accomplished/performed both pneumatically and electronically. Some of the other significant design aspects of the REDBUD™ PTV-G™ are listed next.
The aesthetics of the REDBUD™ PTV-G™ are visually and aerodynamically elegant. The smooth delta trike form provides a significantly smaller (narrower cross-section) vehicle shell frontal area than a tadpole trike plan form, reducing the vehicle aerodynamic drag. The form is not an elongated egg of limited distinctive character but brings the essence of self propelled recumbent motion to the exterior.
By incorporating a wide pedaling crank and placing the front wheel between the occupant’s legs, it was possible to significantly improve the frontal visibility (windshield is lower between the left/right pedal crank ‘bulges’).
A front hood provides feet/leg and storage space covering and access to the drive train and the electric motive power subsystems, part of the serviceability of any vehicle.
The REDBUD™ PTV-G™ incorporates corrugated nylon tubing molded into the body shell to create a structural frame that will absorb energy in case of a critical driving situation. In addition, a padded headrest and seatbelt support structure, similar to what is incorporated into a NASCAR driver seating restraint, provides increased safety for the occupant. Finally, the REDBUD™ PTV-G™ utilizes joystick vehicle controls thereby removing the ‘steering wheel-to-driver impact’ safety issue typical to automobiles.
The TFT LCD color display within the cockpit, mounted just below the bottom of the front windshield, provides access to all of the critical vehicle parameters, such as speed (color changes based on whether the REDBUD™ PTV-G™ is accelerating, cruising or braking), current gear ratio, electric motive power consumption, headlight and turn indicators, and options as may be added. All of this intelligence is easily accessible through the joystick controls. These electronic aids are critical to maximize driving comfort while providing driver enhanced ergonomics for vehicle control.
The recumbent style of seating provides significant occupant comfort and efficient anthropometrics for pedaling power. In the case that the occupant wishes to utilize human power (pedaling), the pedal crank is mounted at approximately mid chest level to promote maximum comfort and is consistent with positive human ergonomics. If human power is not being utilized, the occupant can simply rest their feet on the floor pan beneath the pedal crank. The head and body restrains are easily adjustable for the occupant’s body profile. Reverse to ingress into, for egress from the REDBUD™ PTV-G™, the joystick is simply tilted back, clamshell door is folded up, and driver steps out and stands to walk, closing the door for a secure compartment. Ventilation ducts provide fresh outside air into the front and rear of the cockpit. Hinged side windows provide air flow and hand/arm access to the outside. All of the three wheels of the REDBUD™ PTV-G™ have adjustable air ride suspension components.
The REDBUD™ PTV-G™ fits through a standard residential door and can be stored in a small floor space by lifting the nose, pivoting on the rear wheels allowing the rear wheels and body tail to become the three point floor rests. This provides apartment dwellers in congested cities the ability to maintain independent transportation which can be used similar to a bike.
The design of the front and rear wheel assemblies provides easy serviceability. The front wheel assembly can be lowered to allow a simply wheel change. The rear wheels are easily serviced by simply removing the hub T-nut. In neither case is it necessary to manipulate the hydraulic braking components (I.e., the rear brake rotors are attached to the hub axle and the front brake rotor is attached to the front drive assembly and not to the front wheel itself). The brake caliper ‘pads’ are simply exchanged via a single engagement pin. The rear section of the REDBUD™ PTV-G™ is essentially an ‘open frame’ design with simple and easily removable frame covers. As mentioned earlier, the front hood allows accessibility to the front drive train and forward lighting system for servicing. All of the electric motive power battery capacity is mounted in the rear section.
A long-term commitment has been made to provide an upgradeable extended driving range REDBUD™ PTV-G™ design. The natural separation of the REDBUD™ PTV-G™ into two sections (front and rear) provides the ability of incorporate differing drive train components. One such concept is to utilize an 80 to 125 cc ICE operating on either Propane or LNG to extend the driving range by a factor of five. Simple ‘hardware store’ types of Propane containers would be utilized with a spare being carried within the rear section for emergency use. In addition, as electric motor technology improves, the front drive train can be replaced to improve REDBUD™ PTV-G™ efficiency and performance. This type of upgradeability is critical to extending the lifecycle of urban commuting vehicles.
The economics of ownership of a REDBUD™ PTV-G™ have been carefully analyzed. Many of the components are standard bicycle or motorcycle types of components. The REDBUD™ PTV-G™ frame is fabricated from simple 4130 high strength tubing and sheet metal components that can be easily replaced. No welding of components are utilized anywhere within the vehicle frame. This design approach can significantly reduce the initial costs and allows the REDBUD™ PTV-G to be containerized and reassembled at its final destination. In addition, the REDBUD™ PTV-G™ is customizable to maximize the comfort of the occupant. This is not a one size fits all, but, it is a one size can be made to fit 90% of adult normal occupant body sizes. For example, the choice of the front wheel size (20 to 24 inch tire diameter) is dependent on the ‘inseam’ (clothing size term) length of the occupant. The rear wheels are typically 27-28 inches in diameter.