Transmissions for Total Dummies

meshed gears

It's said that if you ask a stupid question, you'll get a stupid answer. That's not really true: ask a knowledgeable person a stupid question and you'll probably get a smart answer that gently corrects your (question's) stupidity. You know, like asking Neil deGrasse Tyson, "How many days are there in a light year?" On the other hand, if you ask a stupid question – or even a smart question – of a person who knows nothing, you shouldn't get an answer at all; just some form of "I don't know." That is, unless you're asking an eHow contributor like Victor Fonseca (three-time winner of the DotD, so far). All bets are off then, like the time Vic attempted to answer the question, "How Does a Car Gearbox Work?"¹

Given that a gearbox, whether in a car or not, is a part of a transmission, you would expect Fonseca to start off by explaining what a transmission does: it converts the rotation of one device (the power source) into the rotation of some other device through the application of toothed gear pairs or groups. That's not what Vic says, though: he says,

"The modern automotive gearbox is essentially just that: a figurative box of gears that are activated when the gear selector, or gearshift, is activated. Each category of speed has a corresponding gear designed to give the automobile the maximum amount of torque and speed."

That whole "maximum amount of torque and speed" flies in the face of logic, of course, since the whole purpose of the gearbox is to maximize either torque or speed, which have an inverse relationship. But not according to Victor...

...who goes on to describe both automatic and manual transmissions in loving – although not necessarily correct – detail. Take, for instance, Fonseca's conceptualizations of a manual transmission:

"For a manual transmission, when the clutch is engaged, the gearshift can be placed into any desired gear."

...and an automatic tranny, aka a slushbox: "The automatic transmission selects the appropriate gear ratio and spins the main drive shaft accordingly depending on how much the driver is engaging the accelerator. When the brake is engaged and the car decreases speed, the counterweights in the automatic transmission housing slow, changing the gear ratios and slowing the main drive shaft." We weren't aware that the typical car has a drive shaft that isn't the "main drive shaft," although we suppose that AWD and various flavors of 4WD have "non-main" shafts. Be that as it may, Victor's is still a completely stupid "answer" to the question.

The reason we say "completely stupid" is, well, that not once does Fonseca mention the simple machines known as gears. Not once does he say anything about gear ratios or their use to change rotation speed and direction. Not once does he mention how one might engage reverse without changing the direction of rotation of the engine's crankshaft. No, the closest this expert's political science degree lets him come to actually explaining how a gearbox works is this utter rubbish:

"The higher gears, or speed gears, intersect with the drive shaft farther away from the gearbox [sic]. This is due to simple physics. Rotating the drive shaft requires a great deal of power and torque; therefore, the lower "starter" gears are located closer to the gearbox and engine"

While that segment contains an element of truth for manual transmissions (it has zero to do with an automatic) it's clear that Fonseca merely performed a copy-reword-paste of this information without understanding it. Had someone with minimal knowledge of simple machines edited this (instead of a journalism major), he or she would certainly have wanted to know why the "speed gears" aren't constantly engaged with the "drive shaft." Victor doesn't know, doesn't say, and presumably didn't care as long as he got his fifteen bucks. That's the very definition of a Dumbass of the Day.

¹ The original has been deleted by Leaf Group, but can still be accessed using the Wayback machine at archive.org. Its URL was    ehow.com/how-does_4909837_car-gearbox-work.html

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