upright, Resembling a two wheeler (diamond frame) but with two wheels at the back and the rider stradling the frame. Steering is through a handlebar directly connected to the front wheel like a Baby tricycle;
delta, is similar to an upright, with two wheels at the back and one at the front, but has a recumbent layout. One or both rear wheels can be driven, while the front is used for steering (the usual layout). Steering is either through a linkage, with the handlebars under the seat (USS) or directly to the front wheel with a large handlebar (OSS); dark knight sequel and tadpole, a recumbent design with two steered wheels at the front and one driven wheel at the back. Rarely, the front wheels can be driven while the rear wheel steers. Steering is either through a linkage and a www.babycenter.com tie rod to the plates of the spindle assemblies (USS) or with two handlebars, each connected to a steerer tube (usually through a bicycle headset, with the handlebars acting as stems) and a tie rod between the plates of the spindle assemblies (OSS).
The tadpole trike, which is rapidly becoming the most popular design, is often used by middle-aged former bicyclists who are tired of the associated pains from normal upright bikes ("wedgies" or "DFs" [diamond frames], as they are called in many recumbent forums). With its extremely low center of gravity, aerodynamic layout and light the joker weight (for trikes), tadpoles are considered the highest performance trikes.
Not all trikes fall into one of these three classes. For example, some early pedal s used two wheels in tandem on one side and a larger driving wheel on the other. Another design is an in line three wheeled vehicle, with two steered wheels: one at the front and the other in the middle or at the rear. It is not unusual for Baby tricycles to have front and rear wheels of different sizes.
Riding
Adults may find upright Baby tricycles difficult to ride because of familiarity with the counter-steering required to balance a bicycle. The variation in the camber of the road is the principal difficulty to be overcome once basic Baby tricycle handling is mastered. Recumbent trikes are less affected by camber and, depending on track width and riding position, capable of very fast cornering. A few trikes are designed to tilt into the corners much as a bicycle does, and this also renders them more comfortable on cambered roads. They are discussed as tilting three wheelers (TTW's).
In the case of delta Baby tricycles, the drive is often to just one of the rear wheels, though in some cases both wheels are driven through a differential. A double freewheel, preferably using no-backlash roller clutches, is considered superior. A jackshaft drive permits either single or two-wheel drive. Tadpoles generally use a bicycle's rear wheel drive and for that reason are usually heath ledger death lighter, cheaper and easier to replace and repair.
Recumbent trikes often brake one wheel with each hand, allowing the rider to brake one side alone to pull the trike in that direction. This has led to a geometry (also called centre point steering) with the kingpin axis intersecting the ground directly ahead of the tyre contact point, producing a normal amount of trail. This arrangement, elsewhere called "zero scrub radius" is used to mitigate the effects of one-sided braking on steering. While zero scrub can reduce steering feel and increase wandering it can also protect novices from spinning out and/or flipping. The alternative is to use standard Ackermann steering geometry, perhaps with both front brakes operated by the stronger hand. While the KMX Kart stunt trike with this setup allows the rear brake to be operated separately, letting the rider do "bootlegger turns", the standard setup for most trikes has brakes for each side operated by each hand.
In the UK, upright Baby tricycles are sometimes referred to as "barrows". Many trike enthusiasts ("trikies") in the UK belong to the Baby tricycle Association, formed in 1929. They participate in day rides, tours and time trials. Massed start racing of upright Baby tricycles is limited to one or two criteriums such as in Bungay, Suffolk each year.
An often-noted problem with recumbent trikes, much debated by trikers and recumbent riders of all kinds, is their poor climbing ability: the rider can't get out of the saddle and stand up on the pedals to climb hills. Trikers argue that they make up the time lost going up hills by going much faster on the downhill side because www.tricycle.ie of the low, aerodynamic riding position. In fact tadpole trikes hold most of the current human powered vehicle speed records. More germane to trikes climbing ability is their weight: Trikes are always heavier than bikes of the same quality. In fact, the lightest commercially made tadpole trikes, at around 30 pounds, are easily twice the weight of an upright bicycle of the same cost and quality. Deltas are even heavier.
Trikes strongest suits are cornering, stability, comfort, rider stamina and terminal velocity. They also have some not so obvious benefits: the rider doesn't need to uncleat at stops (which also makes for quicker getaways), the ability to ride and climb at very low speed and the upright position giving a much more pleasant view of the world around. Shortcomings that potential tadpole trikers should realize center on the low riding position which makes the who lyrics them difficult to mount (grab handles are often available) and makes them hard to see in traffic, so flags and blinking lights are often used. Visibility concerns become minimal on bike trails and off-street riding.
Manufacturers
Makers of upright trikes include George Longstaff, Higgins, and Pashley Cycles in the UK. Italian company Di Blasi make a folding upright trike, which folds to a compact 68 x 28 x 62.5 cm. There are also many inexpensive, mass-produced upright trikes available through mass-market retailers. They are generally heavy and of uneven quality, but are perfectly suitable for occasional, low-demand riding, especially by those with mobility problems.
Makers of recumbent trikes include KMX; Hase (who make the Kettwiesel delta, improbably named after the British children's programme Catweazle); Inspired Cycle Engineering, who make the Trice range of tadpole trikes; AVD, who build the record holding Burrows Windcheetah or Speedy, a design exhibited in the Metropolitan Museum of Modern Art (MoMA); Australia's Greenspeed, one of the oldest manufacturers; Michigan-based WhizWheelz, which makes 10 models, including a sub-US$1000 model tadpole and a tandem; and Big Cat HPV which builds the 6 Catrike models in Florida. The largest manufacturer of recumbent trikes is Sun Bicycles who make both tadpole and delta trikes. The deltas are built from designs licensed from Gardner Martin's EasyRacers, the premiere maker of recumbent bicycles. Sun bicycles are factory-made in Taiwan and are among the least expensive trikes of good Baby tricycle quality.
In the past trikes have been associated with homebuilders as manufactured trikes are extremely expensive due to the small order numbers and the high quality of hand-built construction. Most good quality adult trikes cost at least $US2000 and the best can easily exceed $US3500 (though several moderate quality trikes in the $US999 to $US1600 range have been introduced recently). |
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发表于 2008-5-29 15:50
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