The following is an excerpt from my upcoming book Green Machine and the Mototaxi Junket. Learn about the Mototaxi Junket and read more excerpts here.
Mototaxis are the supreme example of questionable engineering.
Not sure what a mototaxi is? Take a motorcycle. Now cut off the back half. Bolt the front half to a two-wheeled, rectangular frame complete with a small couch. On top of that, bolt another tube frame fit with pleather that extends over the couch and handlebars. Given the pleather colors are usually red, yellow, or blue, it's not that hard to look at. But that's where the good news stops. The bad news starts when you bring up anything of importance.
Let's start with the engine. It's almost a Honda. But rumor among the racers was the die-cast forms used to manufacture this engine were those rejected by Honda. Great start. The manufactured product was a single cylinder, air-cooled four-stroke engine. According to our mototaxi's registration, it was 150cc. Most were actually 125cc. And given how gutless it felt, we weren’t too confident in our registration card’s accuracy. Regardless, it was not a whole lot to work with. The transmission was a party too.
To be fair to our mototaxi, the only transmission problems we had were operator error. In America, the gearing configuration of motorcycle transmissions follows a general pattern: from neutral, (operating a lever with the left foot) you push the shifter down to find first gear. A half step up brings you back to neutral. A full step up brings you to second gear. A full step up from second takes you to third and so on. This was not the case with the mototaxi. Neutral was found at the very top. And each successive gear was down a whole step on the transmission lever. No, this was not complicated. However, all three members of 3 Tired Travelers had experience with motorcycles; all three were licensed in the U.S. to operate motorcycles; Scott and Andrew even owned motorcycles. That's a lot of muscle memory to overcome. So every time we shifted we had to actively think about shifting. When we didn't take this active stance–which happened a lot–we tended to shift in the wrong direction. At least for the first few days.
Worse than the occasional handlebar header due to an incorrect down shift though was our steering. The transmission was on the front half of the taxi–the motorcycle half. A series of chains transferred the transmission’s energy to the rear wheels—on the sofa half. From an intermediate shaft mounted below the diamond-plate floor of our passenger bay, a chain ran to the back left wheel.
That's correct, our three wheel mototaxi was single wheel drive. One could argue this made turning easier. Wheels that lie in the same plane cover different distances through a turn. Having independent rear wheels would accommodate this difference. (So would a rear differential, but that was asking for a lot.) But that also meant our mototaxi pulled to the right.
This wasn’t too bad on winding roads, where the frequency of turns forced you to swing the handlebars back and forth, to work different muscles, to allow perfusion of blood, and to concentrate on the road to a degree that drowned out the burning sensation of fatigue. On straight stretches though, my muscles seared to the surface. All the teams (except Pete, Team Rubber Duckies) had the option to rotate drivers and rest; but no one stopped when the mototaxi was still running. So we all did the best we could. My energy conservation technique was to press into the driver's back rest and lock my right arm, pinning the handlebars into a leftward veer. My arm was a tad long for this to be comfortable though, so I had to shift my weight to the left side of the seat and let the better part of one butt cheek hang free. A less efficient technique was to turn my left hand palm up and curl the left hand grip. I fought fatigue by switching between the two. Other people had similar techniques. One innovative team fastened a length of cord to the end of each hand grip and ran it around their back. The operator could then lean back and trap the cord between him and the backrest, utilizing the friction to maintain a straight course. Whatever clever tricks we used were no match for the mototaxi though. We would all walk away with unsymmetrical muscle gains.
Another asymmetrical aspect of our mototaxi was braking power. Don’t worry—all three wheels were fitted with brakes. Crappy drum brakes, but at least they all functioned. The two rear brakes were even linked so they braked together, more or less. The asymmetry lied in front to back ratio. On a typical motorcycle, the front brake provides about 70% of the stopping power. This is because weight shifts forward as the bike slows. It's hard to say what the ratio was for our mototaxi though. There were two rear brakes and, given the shape of the thing, there wasn’t much of a forward shift of weight. Really, these nuances were irrelevant, because the asymmetry lied not in the position, but in the origin of the braking power. On motorcycles, 100% of braking power comes from the bike. On the mototaxi, I'd estimate 10% originated from the anal sphincter pucker.