The Trikke is a machine you ride and propel by wiggling your body in a way that’s Zen training on three wheels. It puts into direct use the conservation of angular momentum — if you carry a mass through a turn around a center with a radius that decreases while you’re turning, then your linear velocity will increase. You move the Trikke by leaning and ‘S-turning’ your way through a succession of these turns. The Trikke manages to turn all this physics into a fun ride as well as a no-impact aerobic workout (good for aging skeletons).
It was a slow learn for me — took about a month — but skiers, rollerbladers, and almost any kid will get it right away. Adults who’ve forgotten some of the finer points of operating their bodies will take longer, but that’s one of the neat things about this no-pedal, definitely-not-a-scooter, tricycle: it will teach your body, all by itself, to make it go. You’ll learn faster if, unlike me, you keep your mind out of the process.
When you do finally get into the groove, the feeling is beguiling. You move in a sinuous carving motion gently S-curving your way along city streets or park paths on the flat, downhill, and (eventually) uphill at an average 8 mph. It never (not in 8 months, anyway) gets boring. It requires upward of 350 of your calories per half-hour for propulsion, so it’s damn good exercise. It involves 20 or 30 muscles from your neck all the way down to your feet, working in concert, so you don’t hurt or feel exhausted after a workout; you just feel the afterglow of a good generalized energy output.
You also look both weirder and cooler on a Trikke than a penguin on skis, so if you don’t like the idea of getting double-takes (and questions) from almost everyone you pass, that might be a reason not to ride one of these.
Trikke-Tech makes models with air tires and solid polyurethane wheels. For an adult, in normal city environments, I’d say air is the only way to go because of its natural shock-absorption. I have the sporty T-8 Convertible, the smallest adult-sized Trikke with optional air tires. The $500 T-12 is, apparently, the Cadillac of the line; according to Trikke obsessives, it gives the cushiest ride and is best for long cruises. Nevertheless, I’ve found the cheaper T-8 to be fast on its “feet” and very responsive, and it folds up into a package that fits into almost any car trunk.